Q: The number of display devices seem a
Bird Line Sections and Meters
Using MB-1 with Analog Sensors
Q: What is the maximum distance the external
7-Segment Display modules and external Bar Graph module can be placed
from the control head?
should be limited to two feet.
Explain MB-1's different Power Measurement Modes
- In Amateur Radio applications, it is useful to
be able to measure peak power, average power, and
instantaneous power in numerical form. (After all,
the newest breed of advanced power meters are
digital meters.) Most of the digital RF power
meters on the market can not measure all three of
these modes. For example, the PowerMaster has only
one digital power mode - namely peak power. And
while the other digital RF power meters on the
market claim two power measurement modes, an
experiment is proposed below that tests those claims
when using those meters in a typical operating
On a properly tuned transmitter, the
peak power should be close to key down power, or
slightly higher due to the ability of the
transmitter's power supply to recover during
syllables or code elements. But peak power tells you almost nothing
about your talk power. A meter that provides a
numeric readout of peak power only will not give you
an accurate indication of talk power. (In fact,
a peak reading meter will give you approximately the
same reading with your compressor on and off even
though there may be a significant increase in talk power
with the compressor is turned on.) To measure talk
power, you need a meter that measures average power
over a reasonable interval (more on that below).
And why instantaneous power? Instantaneous power is
most useful during transmitter, amplifier, or
antenna tuner adjustments where it is desirable to
have the meter's readout respond "instantaneously"
as adjustments are made by the user. Meters that display only peak power in numeric form
can give a
sluggish numeric response due to the peak hang time, especially for larger
peak hold time settings. You can approximate a real
time response using a peak reading meter by temporarily
changing the meter's peak hold time setting setting to
a small value, but this can be inconvenient, especially
if you are not directly next to your meter.
- MB-1 can measure peak, average, and
instantaneous power simultaneously, and can also
display all three modes simultaneously if desired.
Some additional comments on average power and
instantaneous power measurements:
Peak power is straightforward, but some comments on
average and instantaneous power are warranted
because these terms are sometimes used imprecisely.
- Average power: An important parameter for
average power measurements is the period of
time that the signal is averaged. This depends on the application,
but to be meaningful for Amateur Radio, the period should be at least as
long as a few syllables for voice, or as long as a few dits and dahs for CW -
let's say from a couple of tenths of a second to several seconds.
As its name implies, instantaneous power
measurements are a series of "snapshot" measurement in
with a rapid update rate. For the most responsive
measurement, the meter should follow the real time
signal being measured precisely with no hang time or
To determine if a meter can measure average power or
instantaneous power as defined above, consider the following experiment.
If the meter has an "Average" mode, select it. With the meter
inserted in line, tune up into a
dummy load with a known key down power
level (for example, 100 watts). Then using a keyer, send a
series of dits at various speeds. The generated "dit" signal should have an
approximate 50% duty cycle. Therefore, after a short time,
the average power reading displayed on the meter should read approximately 50% of the key down power.
Then send a series of
dashes at various speeds. The generated "dashes" signal should
have an approximate 75% duty cycle. With the dashes applied, after a short time, the
meter should read approximately 75% of the key down power. If the
measurement from the meter
under test bounces erratically without converging, or if
the measurement deviates significantly from the
expected values, then the meter under test is not providing a useful
indication of average power as defined above.
If the meter under test can measure instantaneous
power, the majority of the measurements from a keyed
CW signal (dits or dahs) should read either the key
down power (100 watts in this example) or 0 since
the keyed CW waveform is alternating between these
two power levels. (Since keyed CW has a finite rise
and fall time, an occasional measurement may occur
at the transition, sometimes yielding an
intermediate value.) If the meter under test
reads neither 0 nor the approximate key down power
for the majority of its measurements, it is not
measuring instantaneous power as defined above.
To measure instantaneous power, MB-1 samples
the signal at a very high rate (up to 500 times per
second) and displays the measurement for the display
interval set by the user.
To measure average power, MB-1 accumulates and processes all samples
in a .3
second to 8 second sliding window (depending
upon how the user has configured MB-1's averaging filter) to arrive at an average
If you agree that the criteria in the above
experiment are reasonable for Amateur Radio
measurements, you will find
that the digital displays of the other popular digital power meters display neither average power
nor instantaneous power as defined above.
What benefits will I see with MB-1's Digital
- When displaying instantaneous or average power
with a constant power level applied, you will see a
stable measurement with virtually no jitter.
Likewise, if you key power on and off multiple times
with the key down power set to a fixed value, you will
see the same measurement (within a very small
delta). If you do A/B comparisons between MB-1
and the other digital meters that are capable of
displaying instantaneous or average power on the
display head, you will see the differences in both
stability and repeatability.
Before giving a meter credit for having good
stability, try this test. Apply power from a stable
source and note the reading. With power still
applied, change the power level a small amount and
see if the meter reading responds to the change as
it should, or if it holds the reading. If you
observe the latter case, the meter may be
incorporating hysteresis to achieve apparent
use the term "Measurement Cycle". What is that?
- A measurement cycle is the basic processing unit of the MB-1 software. Each
measurement cycle includes adjustment of the Programmable Gain Amplifier to
maximize the resolution for the current sample, acquisition of the
measurements from the forward and reverse coupler ports, processing of those
measurements (e.g., digital filtering, SWR Trip processing, etc.), and
finally display of the measurement values on the display devices
using the selected display update rates.
This process repeats indefinitely unless interrupted by a user request,
such as when a menu button is pressed to change a
meter setting. Depending upon how the meter is
configured, the MB-1 Measurement Cycle time can
be less than 2 milliseconds.
What is the significance of 15 bit low range resolution?
- At the lower power ranges where resolution is more critical, 15 bit
resolution provides smaller step sizes, and therefore better resolution. Since
the maximum (full scale) digital output of the MB-1 Amplifier/D-to-A chain
is 32,768, 1 count represents a signal whose voltage is 1/32,768 of the full
scale voltage (the voltage generated by the coupler when full scale power is
applied). And since MB-1 operates its A-to-D chain at the voltage level
and not the power level, the one part in 32,768 becomes one part in (32,768)2 when determining the smallest
power step size that can be resolved.
consider a coupler with a full scale power rating of
10,000 watts (a value
used others when discussing this topic). When calibrated with MB-1, such a
coupler would generate the maximum count (32,768) at full scale.
Therefore, the smallest power
level that can be detected by MB-1 occurs when the A-to-D chain generates a
single count. This corresponds to 10,000 * (1 / (32,768)
2) , or 9.3 microwatts. (In reality, because of the A-D noise
floor, a more realistic number is 50 microwatts.)
You may make the valid observation that this
value is somewhat meaningless since MB-1 display
devices show only two significant digits after the
decimal point. That's a valid point, but when the software
is working with microwatt power per step, on a carefully calibrated
coupler, you can have confidence that low power readings, when rounded to two
significant decimal points, are meaningful.
To address this loss of
resolution problem at low power levels,
some of the other meter manufacturers offer multiple
couplers for the same bands that primarily differ in
their sensitivity. MB-1's
15 bit resolution makes this unnecessary.
You use the term "Averaging Window" for Average Power Measurements. What
does that mean?
- For average power measurements, you can set the averaging window from .3
seconds to 8 seconds. You can think of this in terms of filter response and
time constants. The digital filter time constant for average power
measurements is set to one fifth the averaging window (resulting in the averaging window being equal to
approximately five time constants).
Therefore, if you apply a step function such as a 100 watt key down signal, if
the averaging window is set to 5 seconds, the average power
value will read to within 1% of the final value (100 watts) approximately five seconds after it is
Why no temperature
- Some other meters that incorporate "logarithmic
detector" chips in
their design can benefit from
temperature compensation. The MB-1 is essentially immune to the type of
temperature drift encountered in those designs.
30,000 watts? Are you kidding me or what?
- The data types and software algorithms used in
the MB-1 software max out at approximately 32,000
watts, so it was decided not to artificially limit
the measurement range to a lower number. A high
power coupler, when calibrated in accordance with
the manual, should work properly. Also, with the Generic Meter Application feature,
depending upon the analog sensor and type of
application, the maximum full scale value of a target parameter
can be just about any value, so the larger range has
value for those applications.
But to answer the question - has MB-1 been tested at
30,000 watts? Only with the
- Q: What is the SWR
- Many of the popular digital power meters do not provide a stable
SWR indication for time varying signals such as SSB. This
is especially true if the meter incorporates a rapid response display device such as
meter or bar graph. Since the SWR is
independent of signal level, this behavior is usually a limitation in the
meter, and not a result of the SWR changing with the time varying signal.
MB-1 can provide a stable SWR value for time varying signals. This is accomplished by using digital filtering on successive SWR
samples. When the algorithm determines that it has arrived at an accurate
SWR value, the digitally filtered value of the SWR is displayed.
In most cases, even
short duration signals, such as a whistle, a lip smack, or even the keying
noise from most microphones PTT buttons, will display a stable SWR value and
hold it long enough for you to read it comfortably.
Note that this is not a simple "display hold" feature. For example, if,
while sending a CW signal, you change the SWR of the load, you will see the
new SWR displayed on MB-1.
Q: What is the "Snap
Measurement to Constant Signal" Feature?
- You can configure the meter to snap (lock) the average measurement
to what would have been its final value when a steady state (constant)
signal is detected. An example will help explain how you might use this
Assume that you have configured the meter to display average power on one of
the display devices such as the analog meter. Assume also that the averaging
window has been set to a long window (e.g., 8 seconds). If you
place your equipment in a tune mode (which generates a constant signal),
it will take approximately 8 seconds for the average measurement to reach
its final value. If you have the snap feature on, as soon as the software
detects that the level of the input signal is constant, a user configurable
timer will be started. After that
timer elapses, the average value will lock or “snap” the average measurement
to the current steady state power level that is being applied. This
allows you to view the actual average power for
normal operational conditions such as a voice or CW
signal, while giving you a quick, stable response to
a constant signal, as would be encountered when
tuning your transmitter.
will find this feature useful if you have remotely located an analog
meter next to one of your stations away from the control head. Since you can only display one parameter
at a time on an analog meter, choosing to display the average power value with the snap feature
provides you the advantages discussed above. You can turn the snap feature
off completely if desired.
Digital Filtering for Instantaneous values? That
doesn't make sense.
- The Forward and Reflected power measurements are
processed in parallel as a both a snapshot values
(the true instantaneous values), and as filtered
values. When the signal is varying, the snapshot
values are displayed. When the software determines
that a steady state signal is present, the filtered
versions of the measurements are displayed. When a steady state signal is
as during tune-up, this almost completely removes
any jitter from the displayed values and results in
extremely stable and repeatable measurements.
How Does the Peak Hold Algorithm work?
- Each time a measurement is processed, the
software checks the value of the current peak power,
and if it is higher, the peak power is updated to
the new value. The peak hold timer is then reset.
Assuming that the no power measurements exceed that
last peak power measurement for the peak hold
interval, the peak hold timer will time out, and the
new peak power value will be set to the current
power level, regardless of its value. For SSB, for
instance, if the peak hold is set to 1 second, and
you stop transmitting, the peak power will drop to 0
within 1 second or less, depending upon when the
last voice peak occurred with respect to the end of
I have a coupler that I want to do a custom
calibration with but I don't have an accurate
- You can place the MB-HF-1 coupler in tandem with
the coupler you are calibrating and measure the DC
output voltage from MB-HF1 to set your calibration
points. The procedure is described
here for Bird Line sections, but this approach
will work for any coupler.
How do I know if my coupler will work with MB-1?
- After you have used the coupler calibration
setup routines a few times, you can do a reasonably
quick calibration with your coupler and simply try
it out. If you want to do some stand-alone testing
of the coupler first,
Q: Regarding Support for multiple couplers, do all the couplers have to be the same
- No. Each coupler is calibrated independently with its own calibration
table. You can mix HF, VHF, and UHF
frequency range does the MB-1 cover?
- There is no restriction. If you have a Bruene type coupler with DC outputs that meet
the interface requirements, you should be able to interface it to MB-1.
Q: What are the coupler
- MB-1 can adapt to a wide range of Bruene type couplers.
For couplers whose full scale power produces a DC
voltage greater than 6 volts, resistive dividers (15 turn
provided in the MB-1 Amplifier/Mux chain to scale the voltage down to
prevent overdriving the
Amplifier/A-to-D chain used in the meter. For best resolution and accuracy, the coupler should put out
a DC voltage of 6
volts or more. This is not a problem for most
couplers. MB-1 will work with coupler with lower sensitivity but at a
reduced resolution. For a more detailed discussion,
see the section on
Q: Can I use the
LP-100 Couplers with MB-1 ?
- No. The LP-100 couplers provide voltage and current samples instead of
forward and reflected DC outputs voltages, which are found in Bruene type
Q: How is the MB-HF1
Bird 4391A RF Power Analyst is used.
Q: Can I integrate the MB-1 into an Antenna Tuner and use the MB-1 for power
and SWR measurements instead of the tuner's meter?
- For a manual tuner - Yes. Just connect the coupler connections
from the tuner to one of MB-1's four coupler ports. To use an analog meter
when integrating MB-1 with your tuner, you have two choices. You can use
MB-1's internal analog meter (or any other external analog meter you have
connected to MB-1). Or you can drive the Antenna Tuner's analog meter as an
external Panel Meter from MB-1. Just use the standard MB-1 procedures for adding and
calibrating external couplers and Panel Meters. If you integrate MB-1with
your tuner, all of MB-1's features, such as SWR trip and Min/Max are available.
For an Automatic Antenna Tuner - Not Recommended. This is not recommended
for Automatic Antenna tuners unless you are sure that the input impedance of
the coupler ports (300 K), when placed in parallel with the tuner's
measurement circuitry, will not affect the tuner's operation.
You do not have a setting for band correction for 1.25 meters. Can I
calibrate my 1.25 meter coupler and save the settings for a band I am not
- Yes. The 160 meter - 70 cm titles used by the software are just place
holders for separate sets of band correction factors stored in the EEProm
Can the meter read powers lower than the lowest calibration I calibrated the
coupler at, or higher than
the highest calibration point I calibrated the coupler at?
- Yes. This is accomplished by using the calibration data for the
lowest or highest power level at which the coupler was calibrated. The meter
can also read power levels higher than the full scale value for which the
coupler was calibrated at as long as the input voltage at the coupler input does not saturate
the MB-1 Mux/Amp. The
normal calibration routine includes steps to ensure that saturation will
not occur at or below the full scale power.
Q: While experimenting with the Band Calibration feature, I switched between
the Reference Band and a Band that I performed frequency correction on while
keeping the frequency and power of my transmitter constant. As expected,
when I switched bands using the Band menu, a different power value was
displayed. But if I take the ratio of these two power measurements, it
does not agree with the real time band correction value being displayed in
the Correction field of the Band Menu.
- That is because the Correction Factors, which are calculated during
calibration, and applied during operation, are done at the voltage level, not
the power level. If you take the ratio of the square roots of the
two different power measurements, this should equal the real time band
correction factor value that you are seeing displayed in field 2 of the Band menu.
For example, assume that you have done the reference band calibration on 80
meters, and that you have also performed band correction on the 6 meter band
during calibration. For this discussion, assume that the coupler is more sensitive
on the 80 meter band (for a given power, it will produce a larger DC
output voltage when the operating frequency is in the 80 meter band than it
will when operating on the 6 meter band for a given power level). In this case, you would expect to
have a positive correction factor (the ADC value measured when operating on
the 6 meter band needs to be adjusted upward to give the corrected power
Repeat your experiment as follows: Take a coupler that has been calibrated
as above, apply a signal on the 80 meter band, and then change the band on
the MB-1 Band menu without changing the transmitter power or frequency.
You should see that the power reading displayed by MB-1 with the band set to 6
meters is a larger power value.
Using some numbers, assume that you measure 20 watts on the 80 meter band,
and measure 21.22 watts when you switch the band to 6 meters using the Band
menu. In this case, the correction factor (which will be displayed on the
Band menu on Line 4 of the LCD) should be = sqrt (21.26) / sqrt (20) = 1.031.
If you have performed band correction at more than one power level on a
given band, the power correction factor will be recalculated for every
measurement using interpolation of the available band correction factors. Therefore, if you vary the power between two or more power
levels that you performed band correction on, you will see the value of the
displayed correction factor change to an intermediate value as you vary the power.
Of course, the idea here is to give you the correct value when you
actually do switch your transmitter to another band. Hopefully, the
above explanation will help you understand how band correction is accomplished by the
What is the OEM Calibration Table Update Utility used for?
- MB-1 comes with a factory loaded calibration table for the MB-HF1.
We hope to include calibration tables for other
popular couplers as well.
Couplers in this
table are assigned an OEM code that can be used to
simplify coupler setup if you are interfacing to one of the supported couplers.
The calibration tables for OEM couplers are loaded into the "OEM" section
of EEProm. These OEM coupler tables can be easily loaded into one of
MB-1's four coupler tables (coupler 1 - coupler 4) during coupler setup by specifying only the OEM code (see User's Manual).
- The OEM Calibration Table Update Utility allows you to get the latest set of
calibration tables from the MeterBuilder website by downloading a data file.
That data file is then used to update the OEM table section of MB-1's EEPROM using the
OEM Calibration Table Update
utility developed by MeterBuilder.
MeterBuilder will update the OEM calibration tables as we add support for additional
couplers. The calibration tables will also be updated if we improve the
existing calibration tables for any reason (for example, by adding
additional band correction points at more bands for previously supported OEM
codes including the MB-HF1 coupler).
Of course, for maximum accuracy, you always have the option to do a full custom calibration on any
Bruene type coupler, including the ones supported in the OEM tables. However, the factory
loaded calibration tables simplify this process since you only have to specify the
correct OEM code during calibration (thereby eliminating the need to do the
point-by-point calibration). If you use the OEM setup procedure, the only additional adjustments required are the FWD and REFL side panel
trim pot adjustments, which need to be adjusted at a single power point as
described in the User's Manual.
Q: If my coupler's FWD-to-REFL tracking is poor, can
I calibrate each port independently to get accurate
reflected power values?
- Yes. You can view this as analogous to the BIRD
mode of operation where you reverse the slug to read
Simply calibrate the FWD port of the coupler using
one of MB-1's four coupler ports, and calibrate the
REFL port of the coupler using a second MB-1 coupler
port. Connect both the FWD and REFL DC outputs from
the coupler to the FWD port of the two MB-1 coupler
ports being used. Leave the REFL input of each of
the two MB-1 coupler ports unconnected. Turn
the REFL port trim ports on each of the two MB-1
ports being used in this mode to their maximum CCW
(minimum sensitivity) setting.
To use a coupler configured this way, use the
coupler menu to select the MB-1 coupler
connected to the coupler's FWD port to read FWD
power. Use the coupler menu to select the MB-1
coupler connected to the coupler's REFL port to read
- Of course, analogous to the BIRD mode of
operation, this requires that you calculate the SWR
manually (easily done with this
online SWR calculator).
But in many cases, when you are reading REFL power,
your primary concern is minimizing the REFL power,
with a lesser emphasis on its absolute value.
The power rating on the coupler label is different
than the value listed in the Specifications. Which
The more conservative values in the
Specifications section are correct. The label will
be changed in the next run.
Bird Line Section and Meters
Q: What advantages does an MB-1/Bird Line section
arrangement have to a Bird type 43 wattmeter?
- With a Bird meter or one of the retrofits, your
accuracy will only be as good as the calibration of
the slug, and then, only for a full scale
reading. Additionally, conventional wisdom is that
the accuracy for used slugs, unless purchased from a
reputable source, is essentially an unknown. If you
calibrate your Bird slug using the MB-1 calibration
feature, you can achieve 2% tracking with your
measurement reference for nearly the entire scale
(approximately the top 98%), even with a slug
that is significantly out of calibration.
Therefore, you can essentially make your MB-1/Bird
element combination as accurate as your reference.
This can be achieved because of MB-1's multipoint
calibration feature. A description of how the MB-HF1
coupler can be used as a reference is given
- Resolution is also significantly better. Take an
element calibrated at 100w FS with MB-1. On a Bird
meter movement, the scale gets compressed at
the higher end. For example, you can probably only
resolve the 98-100w segment on a Bird analog meter
(the last two tic marks) to 1 part in 2 or maybe 1
part in 4. With MB-1, the same 98-100 watt range can
be resolved to one part in 42.
Finally, your will be able to us all of MB-1's
advanced features with your Bird line section.
Can I use the Bird line section to drive MB-1, and
then drive the Bird 43 analog meter with MB-1?
- Yes. While the MB-1 display devices will give
you more resolution, the Bird analog meter can be
used as one of MB-1's external analog meters after
being calibrated with the Panel Meter calibration
feature. This makes sense, for example, if you want
to locate an external meter at a different operating
location than where your MB-1 is located. Of course,
in this configuration, the Bird analog meter can be
used in conjunction with any coupler, not just the
Bird elements and line sections.
Can I use a Bird slug with MB-1 for a different
frequency range than for what it is specified?
- I do not know if
a big mismatch in the nominal frequency range and operating
frequency can cause any damage to the slug, so I
will not comment on that aspect. With that caveat,
measure the open circuit voltage at the frequency
and full scale power you intend to use the slug at. If the
DC voltage is at least 1 volt, it will work. Lower
full scale voltages will work as well, but at decreased
Q: How does
the software control analog meter movements?
linear movements, the level required to drive a given meter movement to full scale
is determined during setup and then saved in EEProm. This data is used in conjunction with other user-defined information, such
as the values of the full scale ranges,
to map a measurement value from the coupler (or other input devices) to an analog meter reading.
For nonlinear analog meters, up to 50
different calibration points are supported (for up to two nonlinear scales
per meter). Typically, as few as 20 points can do a good job, depending upon the
meter scale. This mapping is also saved in EEProm, and used together with the user-defined
ranges and full scale values to map a coupler measurement into an analog meter reading.
Cross needle meters have separate calibration
tables for both directions of travel (50 points each
for the forward and reflected directions) as do
single needle nonlinear meters with two nonlinear
scales, such as a power and SWR scale.
Q: What is "AutoRange
- When an analog meter is in the auto range mode, if the measurement
value rises such that it exceeds the full scale value of the current range, the software
immediately autoranges to an appropriate higher range.
This ensures that the meter always provides an
in-range reading. However, when the signal decreases such that
the new value is now in a lower range, the meter needs to "down-range"
to maximize resolution and accuracy of the new value. When this occurs, an AutoRange recovery
timer starts, and keeps the range set to the higher range until this
timer elapses. This prevents the meter from rapidly hunting between
two or more ranges for quickly varying signals such as CW and voice. You can think of this as
somewhat analogous to the "fast
attack" "slow decay" response on an S meter. MB-1 has an
adjustable AutoRange Recovery Timer. Without the ability to customize this
time interval to your preference, you may find that
a single (compromise) value is too short or too
long. You may also find that a single value may be
suitable for some operating modes but not others.
Q: What is "Soft" Overrange?
- Software controlled analog meters usually restrict the deflection of the
pointer to the meter's full
scale value to protect the meter movement. While this protects the
meter movement, unless the meter has some type of
overrange indicator, you cannot distinguish a full scale reading from an overrange condition,
including an extreme out-of-range condition. Not
having some type of overrange indicator is not a
good idea because while it may protect your meter
movement, it may prevent you from recognizing an
abnormally high power condition.
With MB-1, during analog meter calibration, the
you to define a soft overrange
value, which is the maximum allowed meter
deflection beyond the full scale reading that the needle
will be allowed to traverse when an overrange
condition is present. You can define a range between 0% to 100%
beyond full scale deflection. Typically an
additional 5 - 10% needle deflection above full
scale works fine to provide an easily identifiable
overrange condition without risking any damage to the
meter movement. MB1 provides an overrange LED
indicator on the control head as well, but soft overrange is
particularly useful if you locate an external analog
meter away from the control
head where the overrange LED may not be readily visible.
On a Crossneedle meter, sometimes one needle is
within range, and the other is above full scale. Is
- Yes. Each needle on a crossneedle meter has its
own soft overrange limits. What you are seeing
simply means that one direction is within range, and
the other direction is overrange (being limited by
the soft overrange feature). When this condition
occurs, If you have the AutoRange feature enabled,
it will likely be the REFL needle that will be out
of range since the AutoRange feature will keep the
FWD needle within range. You will see this only
under a high SWR condition.
To read a valid SWR on a
crossneedle meter, both the FWD and REFL needles
must be within range. Otherwise, the intersection of
the two needles will not accurately represent the
I have the analog meter set to AutoRange, but I
sometimes see an overrange Reflected value.
Shouldn't AutoRange kick in to the next higher
- No. For a crossneedle meter, AutoRange is
controlled solely by the value being read on the FWD
power scale. The REFL power range must track
the FWD range for the SWR values to be valid.
Unless you are running with a very high SWR,
you will not encounter this problem.
Q: Why 12 power
ranges for Analog Meters? That seems excessive?
- Many amateur analog power meters have three ranges (e.g., 20 watts, 200 watts, 2000
watts). Other common arrangements use a base of 10 (10, 100, 1000
watts), 3 (30, 300, 3000 watts), or 5 (50, 500, 5000 watts). If you
want a meter that supports all of these popular ranges, you can do it with
It should be pointed out that the 12 scale capacity applies to linear meter
only. For single needle nonlinear meter scales, MB-1
supports up to three power ranges and 1 SWR range. For Crossneedle
meters, up to three power ranges are supported for each of the
two directions (forward and reflected).
Q: When in Auto range on the analog meter, how do I know what range I am in?
- There are two methods: If the Panel Meter menu is being displayed on
line 4 of the
LCD, the current range is shown as part
of the menu information. Alternatively, since the 7-segment modules
can display configuration information as well as
measurements, one of the 7-segment display
can be programmed to show the current full scale range of the analog panel
Q: Where can I get
additional analog meters?
- There are typically several hundred analog meters available on
at any given time. Any DC meter with a full scale
rating of 1 mA or less will work. For details on
determining whether a particular Panel Meter can be used with
Q: Can I use a remote digital display analog panel meter in place of a conventional
(needle) analog meter movement?
- Yes. However, recognize that these panel meters are really just analog
with digital displays. Therefore, you will get some jitter on the reading.
As long as you realize the limitation, feel free to experiment. A more
detailed description is given
far can I locate a panel meter from the base unit?
- Use shielded cable, and you should be able to extend an external analog
meter up to 150
feet from the Control Head. If you have a bad RFI problem, you will have to
take measures to reduce the RFI, such as adding cable ferrites to the
Will extending the distance between an external Panel Meter and the Control
Head require recalibration?
- For short runs, no. For long runs, maybe. The resistance of meter movements is usually low (a few hundred ohms),
so adding a few ohms of cable resistance due to a long run can
have some affect on the calibration. But a complete recalibration is not
necessary. Use the DISPLAY function to exercise the Panel Meter's
calibration verification test with the extra cable connected. If the meter
still reads full scale at the highest calibration check point, no adjustment
is required. If the meter reads somewhat below the full scale deflection point
at the highest calibration check point due to the added resistance, simply
adjust the corresponding Panel Meter calibration pot on the left side of the
case until the needle reads full scale. If the meter is a crossneedle meter,
repeat this process for the REFL power needle as well.
Can I use MB-1 with components of an existing SWR or power meter?
- Yes. You can use either the coupler components, the meter movement, or
both from an existing power meter. Feed the coupler inputs from the existing
meter into an MB-1 coupler
drive the meter movement in the existing meter from an MB-1 panel meter port. The coupler and meter movement in
your existing equipment need
to be disconnected from their internal meter circuitry, but you can use a
multi-pole double throw switch to switch the leads from MB-1 back to
their normal internal connections to allow the meter to operate stock.
Q: I calibrated an external Crossneedle meter correctly but the SWR readings
are slightly inaccurate.
- Keep in mind that for crossneedle meters, MB-1 does not attempt to
display an SWR value. After it calculates the FWD and REFL power levels, it
simply drives the FWD and REFL needles respectively.
Therefore, for crossneedle meters, MB-1 is relying solely on the meter face
SWR curves to provide accurate SWR readings at the intersection of the
FWD and REFL needles.
- If the crossneedle meter was calibrated correctly, but the expected SWR
readings are not displayed correctly at the intersection of the Forward and
Reflected needles, then the meter face on the external meter you are
using has a calibration error in the SWR curves. MeterBuilder has
confirmed this problem on a few of the popular crossneedle meters. Usually
the errors are small, and would not be easily recognized without the types
of utilities that MB-1 provides to confirm calibration.
- The source of the problem is easily confirmed by running the MB-1's
simulator at a constant SWR (use any virtual power coupler, except virtual
coupler 7 which applies up to one SWR unit of variability). Set the Demo
mode for the ST2 mode
(step mode 2), which will hold each simulated sample for approximately 5
seconds. Jot down the forward and reflected power values for one of the snapshots.
Plug these numbers in to the
online SWR calculator, or use some other
calculation. If the independent SWR calculation matches the expected SWR
value that the simulator is running at, you have confirmed that MB-1 is
driving the forward and reflected needles to the correct power points, and
therefore, there is a calibration error in the SWR
curves on the meter face you are using.
You can also confirm this problem independent of MB-1. Simply apply a DC
voltage through resistors to the forward and reflected connections on the
crossneedle meter under test to position the needles statically (you can use
the variable 0 -5 volt source on the rear panel of MB-1 to aid in this
test). Again, use the
online SWR calculator
or another independent SWR calculation
to determine if the forward and reflected power values are consistent with
the SWR value indicated at the intersection of the two needles.
Are there any special restrictions when using MB-1 with a high accuracy
"taut band" analog meter or with a Professional Grade analog meter?
- No - as long as its full scale drive requirements are 1 mA or less.
(For those not familiar "taut band" meters, these types of meter
movements are found in high
end equipment, such as the type of analog meters used in some of the Bird
Wattmeters. The armature of the meter movement is suspended by fine wire,
essentially reducing the needle friction to nearly 0, which results in extremely
What are the rules that determine whether I have to calibrate an external
Panel Meter as Linear or Nonlinear?
- If your meter face has at least one nonlinear scale, you must calibrate
the Panel Meter as a nonlinear meter, even if it the meter face also has one or more linear scales on it. In
this case, you will simply treat the linear scales as a special case of a
nonlinear scale. To simplify setup, when asked to specify the number of
points you wish to calibrate the linear scale with, specify 1.
Q: I have a nice large analog meter with a single linear scale that reads 0
- 10. But since the
scale starts at 0, how can I display both power and SWR on this single
- Assume that you have a linear scale that ranges from 0 - 10. When calibrating
this meter with the MB-1 setup routines, specify the meter scale as
"Linear". Set up the Power scales as desired (for example three power scales
at 10, 100, and 1000 watts). During the SWR portion of the setup, you will
be asked to specify the starting value of the SWR scale as 0 or 1. Since the
meter has only a single scale that starts at 0, specify 0. Set the SWR range
(full scale SWR value) to 10. The software will use this information to set the
resting position of the needle to 1 when the meter is
displaying SWR. With this approach, in addition to your three power scales of 10, 100, and 100
watts, you will also have an SWR scale with a range of 1 - 10.
- Admittedly, an analog SWR meter with a scale that starts at 0 is unconventional, but
without this feature, any 0-based analog meter
would be ruled out for use with SWR measurements.
Q: Can I mix and
match Couplers and Panel Meters?
- Yes. Any coupler can be used with any of the five (max) panel meters
that can be connected to MB-1. And the same applies in the opposite
direction (all four couplers (max) can be used with panel
meters that have compatible ranges).
Take a simple example. Assume that you have a single coupler connected to
the output of your amplifier, which feeds a single antenna. Assume
further that you have two transceivers at different locations in your shack,
both feeding the amplifier through a coax switch. With this configuration, you could locate the MB-1 meter near transceiver 1, and use
the internal crossneedle meter when using that station. You could also
connect another crossneedle meter, or conventional (single needle) meter to
MB-1, and locate that meter near the second transceiver. This gives
you remote display capability.
To simplify switching between stations, you could configure the settings for
station 1 into one of MB-1's configuration sets, and the settings for
station 2 into a second configuration set. Simply select the appropriate
configuration set, and MB-1 will change its configuration to drive the
appropriate panel meter using the same coupler. In this simple example, both
configuration settings would be identical, with the exception of the panel
meter. But you could also change any or all of the other meter parameters to suit your
needs and save them in a configuration set. For example, one configuration set could be set up to display Peak
Power at the transceiver 2 panel meter and the other configuration set could
be set up to display average power at the transceiver 1 panel meter.
What is the big deal about a linear scale crossneedle meter?
- Other crossneedle meter scales are nonlinear to account for the
nonlinearity of diode detectors and other nonlinear aspects of the coupler
used with the meter, most notably the
square law relationship between coupler output voltage and power. This results in a highly compressed scale
at the high end of each range resulting
in poor resolution. A crossneedle meter with linear scales does not
have that problem.
Another problem with some nonlinear crossneedle
scales is the occasional need for multiple scales, even for x10
scales, since the degree of the nonlinearity differs between
the x1, x10, and x100 scales. This further
complicates the reading of such scales.
Can the included crossneedle analog meter be used for RF Ammeter and Generic
- Yes. When an RF Ammeter coupler of Generic Meter application is selected
(vs. an RF power coupler), and a crossneedle analog panel meter is selected, the software automatically disables the reflected
needle on the crossneedle meter (which has no meaning for non-power applications). All other analog
meter functions are available, including AutoRange and overrange detection
(including soft overrange). The following measurement modes are available
for display on the analog meter for non-power applications: TUNE
(instantaneous value), PEAK, AVERAGE, MIN/MAX captures of these measurement
I want to use an analog scale that does not start at
0 for a Generic Application. Can MB-1 calibrate
a scale like this?
- Yes. As an example, see this
Application that has an analog meter with a
temperature scale that ranges from 70 degrees
Fahrenheit to 170 degrees Fahrenheit. Although this
scale is used with a Generic Meter Application, the
same approach can be used to get a similar "expanded scale" for power and
RF ammeter applications as
For the temperature example, during setup, specify
the meter type as Nonlinear. (Even
though the meter movement and scale in this example
are linear, this must be done because the scale does
not start at 0.)
Set the Full Scale value to 170. Set the number of
lineup points to 17. This will give you calibration
points at 10, 20, 30, ... 150, 160, 170.
All calibrations points must be set,
even though we are not interested in those values
below 70. Therefore, we do need to calibrate the
"don't care points" below 70 degrees. To do this,
offset the mechanical zero bias of the meter so
that it reads off scale below the smallest value
of 70). For calibration points of 10, 20, ..
60, advance the front panel pot slightly starting
from the most CCW position of the pot, keeping the
needle below the first valid point on the scale
(70). Do this for all remaining "phantom points".
You must advance the needle forward slightly after
calibrating each of these phantom points since the
software integrity checks require the ADC value to
be monotonically increasing for all of the
calibration points (including the "don't care"
Once you reach the calibration points for 70 degrees
and above, calibrate the meter in the normal
fashion, simply dialing the needle to each
calibration point, pressing the SELECT menu
button to save each calibration point. In this
example, after calibration, any value from 70 - 170
will read correctly. Any value less than 70 will
read off scale below 0 (which provides a somewhat useful
under range indicator).
Can MB-1 be use to validate (or generate) the SWR curves on Crossneedle Meters?
- Yes. When driving a crossneedle meter, MB-1 displays the FWD an RF power
without regard to the SWR value. If the FWD and REFL power
scales are calibrated properly, the intersection of the FWD and REFL needles
should read the correct SWR value. Since the simulator has a
programmable SWR range of 1.1 to 9.9 in steps of .1, you should be able to
drive any crossneedle meter (FS of 1 mA or less) across its full set of SWR
curves. After programming an SWR of interest (Demo mode menu Setup), the
best way to do this is to set the simulator to the SWEEP mode, which causes
the FWD needle to repeatedly sweep from 0 to its full scale value, with the
REFL needle tracking based on the programmed SWR values. If an SWR curve
under test is correct, the intersection of the swept needles should exactly
trace out the SWR curve.
- SWR curves can also be created with MB-1. The following discusses two
different approaches using MB-1:
- 1. Using the Simulator - In this case, use the STEP1
mode of the simulator, which selects a random FWD value, upper bounded by the
full scale vale of the associated coupler (and the corresponding REFL
power based on SWR), and holds the reading for about 5 seconds before selecting the next
random power level. Apply a mark on the scale at the intersection of the
needles for a number of points until you have a range of points extending
from low power levels to high power levels.
- 2. Using a Real Coupler Port - Select a real coupler port (1 - 4)
whose Full Scale value is the same (or a multiple .(01, .1, 10, 100, etc) of
the Full Scale FWD power of the crossneedle meter. Drive the FWD and REFL
ports of the selected coupler with two potentiometers. (You can use the front
panel pot port on the rear panel RCA jacks for one of these.) This will
allow you to arbitrarily dial in any FWD and REFL power levels. If you dial
in a series of FWD, REFL power levels pairs corresponding to a particular
SWR value, the intersection of the needles will define the locus of points
for that (single) SWR curve. You can mark the scale with an arbitrary number
of points. Usually, eight points are adequate for each SWR curve, but if the
meter face is very large, you may need more. (You will also
notice that some of the SWR curves have more curvature than others and these
may require a larger number of points.)
When operating SSB, I don't get as much bounce in
the needle as I expect to.
- If you have the Analog Meter AutoRange feature
enabled, the meter will typically operate in the
range determined by your peak power. For example, if
you are using the internal crossneedle meter on
MB-1, which has three forward full scale ranges (20
watts, 200 watts, 2000 watts), and if you are using
a 100 watt transceiver, since your peak power will
usually exceed 20 watts, the meter will typically be
in the 200 watt range for most of your
transmissions. (The AutoRange feature up-ranges to
the lowest in-range scale, and stays
in that range for an interval determined by the
AutoRange Recovery Time.) When you also take
into account the inertia of the meter needle, and
the fact that SSB average power may be 20% or less
of your peak power, the needle will typically spend
most of its time in the lower end of the scale in
the above example.
If you want larger deflection, simply turn the
AutoRange function off, and pick a lower value
manual range. (The Soft Overrange
feature will protect the meter movement). In the
example above, if you were to choose the 20 watt
manual scale, the needle will show a much larger
deflection with a 100 watt SSB signal. Of course, in
this case, you are using the needle indication as a
relative indicator only, but this technique is
useful for giving you more resolution (deflection),
and with some experience, you will see what your
"normal" signal looks like on that scale. If your
signal then changes for some reason, or if you want
to see the impact of modifying your transmit audio
level on your signal, you will be able to see
changes more easily with the analog meter set to a
lower power manual range.
Seven Segment Displays
Q: I want to display just three parameters on the internal
7-Segment Displays. Can I turn the fourth module off?
Any or all of the internal 7-segment LEDs as well as the external
7-segment LED modules can be turned off completely by setting the Display Mode to
"OFF" using the 7-Segment Display menu.
Q: How do I modify the 7-segment displays if I want to change the colors of
all or some of the 7-Segment Displays?
- The LEDs are plugged into 40 pin sockets, and are easily replaced.
is the AutoMax Full Scale Bar Graph function?
- This feature forces the bar graph to instantly adapt its full scale value to the largest
value in 1 watt increments. Therefore, the bar graph always has the maximum sensitivity and
resolution and can never be out-of-range. A larger signal will automatically
increase the full scale value. If you reduce your power (e.g., go barefoot
after operating with an amplifier), a push of the AutoMax reset button
will reset the auto full scale value to 1 watt allowing it to adapt to the new (lower)
power level. The current full scale value is
displayed in the rightmost section of the bar graph when that area is not
occupied with bar segments. You can also configure
any of the 7-Segment LED modules to display the Bar
Graph's current full scale value.
In addition the MB-1's Min/Max feature, this allows
you to effectively monitor the max value of a second
parameter if desired using the Bar Graph. Regardless
of the parameter the Min/Max feature is processing,
or even if the Min/Max feature is not enabled, the
maximum value of whatever parameter you are
displaying on the Bar Graph will be displayed in the
right most section of the Bar Graph - a handy side
effect of how the AutoMax feature works.
the Bar Graph is in the "TUNE" mode, the persistence of the Bar Graph
display for quickly varying signals seems too low.
- The TUNE mode displays a series of true instantaneous values, and is
capable of being updated several hundred times per second depending upon the
Bar Graph's update rate. Artificially increasing the
persistence would necessarily compromise the Bar
Graph's high update rate.
For high speed signals such as CW, you can set the Bar Graph display update rate to a lower value using
the SPEED menu. Or you can turn the "sticky bar" on. The sticky bar
can be used for any measurement type the Bar Graph is capable of
displaying, including instantaneous power. Since the sticky bar
"hangs" for the user selected interval, it will be easy to see. So
if, for example, you are sending high speed CW, the sticky bar will readily
indicate the maximum power of the CW signal.
For SSB, you will
find that if you display AVERAGE power on the Bar graph
instead of instantaneous power, and use a relatively small averaging window (e.g.,
.6 seconds), you will get a nice smooth response for
SSB. This is also a good way to see the effect on average power of using a
compressor or speech processor.
The specification for your Bar Graph update rate is
> 300 updates per second. Any rate much above 30 can
not be tracked by the eye.
- The high update rate comes into play when you
are displaying an instantaneous value on the Bar
Graph (e.g., Forward Power, Reflected Power,
Delivered Power) with the sticky bit on, and
therefore, the sticky bar is serving as a peak
indicator, even though the parameter being displayed
on the bar graph is an instantaneous value.
The high update rate allows the sticky bar to
capture the largest value of the monitored signal at
a sample interval of approximately once every 3
milliseconds. At a slower bar graph update rate, for
example, 20 updates per second, the sample interval
increases to 50 milliseconds, which could easily
result in a short duration peak being missed.
is the SWR Warning feature?
- The SWR warning feature is totally separate from the SWR protection
feature, and has its own user-defined threshold against which the SWR is
continuously compared. An SWR level that exceeds the warning threshold will
cause a front panel "SWR Warning LED" to light. The LED will turn off as
soon as the SWR falls below the threshold. One advantage the Warning feature
has over the conventional Alarm Trip function is that the indicator responds
instantaneously to excursions around the threshold (the trip delay setting
is ignored), and does not have to be
reset as is typically required for an alarm trip condition.
The feature can be used in place of the SWR alarm feature if you do not need
the relay protection, or the two features can be used together.
is the Alarm Auto-Reset Feature?
- This feature will automatically reset an SWR or
Low/Hi power alarm trip condition after a
user-specified interval has elapsed.
is the Alarm Conditional Auto-Reset Feature?
- This feature is similar to the Auto-Reset feature described above. The
difference is as follows. With the Auto Reset mode, after an alarm trip
condition occurs, the trip condition will unconditionally
reset when the user defined reset interval expires. This
is the mode you will probably use with RF power applications, since the
relay contacts are most often used in series with the PTT function to disrupt power transmission upon
detection of a fault, and those same contacts must be activated again for the
transmitter to be operational.
For a conditional Auto Reset, after the user interval expires, the
software continues to compare the monitored measurement(s) against the fault thresholds,
and will only reset the alarm condition when none of the measurements
are outside of the user defined thresholds. This may be useful for
actually controlling a measured parameter when
using MB-1 with analog sensors. For example, assume that
the MB-1 alarm relay contacts are controlling a heating element that is
being monitored by a thermistor that has been configured for use in a Generic Meter
application to measure temperature as shown
that the high level fault threshold is set to 100 degrees. Power can be
applied to the heating element through one of the normally closed MB-1 alarm
contacts. When the 100 degree threshold is reached, the relay contact will
open, removing power from the heating element. Because of thermal lag, the
temperature detected by the thermistor may still exceed 100 degrees even
after the auto reset interval expires. However, with the Conditional Auto
Reset mode, the trip condition (and relay) will not be reset until the
temperature, as measured by the software, falls below the high temperature
threshold. Since you also have control over the AUTO RESET interval, when
used with the Conditional Auto Reset mode, you can probably obtain a
reasonably tight set point if you are trying to control the measured parameter
within some range.
If you are willing to add some additional circuitry to the MB-1 alarm contacts,
you can build a system that actually controls the amount of hysteresis of a
measured (and controlled) parameter by
using both the high level and low level alarm thresholds to toggle an
external control relay. For example, using with the temperature
application above, the toggle function could be designed to power down the heating element
when the high trip point is reached, and to reapply power when the low trip
point is reached.
is the SWR Alarm Snooze Feature?
- The snooze feature allows you to temporarily bypass the SWR alarming
functions, and would be useful, for example, when you are adjusting a tuner. After
the snooze alarm elapses, SWR protection automatically resumes. When using the Low Power Trip function, the snooze alarm is also
useful for preventing the alarm from tripping prior to applying a signal that you
expect to never fall below the preset lower power threshold you have defined. The snooze
interval is adjustable.
is the SWR Alarm Low Power Level Bypass?
- This feature allows you to define a minimum power below which SWR
values will not be computed, and below which the SWR alarm will not trigger.
Based on the coupler you are using, you may find
that the SWR values for power levels less than a
certain threshold may be inaccurate. This feature can also be used to prevent
low level induced power from nearby stations from falsely triggering the SWR alarm.
- Q: What is the "SWR
- The digital filter algorithms that process the SWR measurement keep
track of the quality of the SWR calculation. Whenever a change in the SWR
value is detected, the digital filters that "stabilize" the SWR reading go
into an acquisition phase to determine the new value.
The software prevents SWR values calculated during this acquisition interval from updating the SWR Min/Max function and
from being used by the SWR alarm trip function.
- Since the display algorithms
have access to this information as well, the initial
software design blanked out the SWR displays) whenever the SWR filters were in
acquisition interval. We didn't like that approach because it prevented the
display from providing a real time
response of the SWR value when it was undergoing a legitimate change, (for example, when
making adjustments with an antenna tuner). Therefore, the current
design always displays the SWR, either using the filtered (most accurate) value, or
the best "current value" if the filters are still in their
acquisition phase. Since this will sometimes cause suboptimal SWR values
to be displayed, we thought there might be value in providing an indicator
to inform the user when the software was in it acquisition phase and
had not yet reached its optimal value.
- The green LED on the DISP/Set-Up
switch (top right switch) labeled SwrCh will illuminate when the software is in the SWR acquisition interval. During
the "best current" value of the SWR will be displayed.
The "SWR Changing" indicator may flicker occasionally, especially for time varying signals
such as SSB. This is normal, and is the result of a compromise between the
filter accuracy and response time. In most cases, the MB-1 algorithms will lock on to the correct SWR value and
display it in a fraction of a second. The software should
not have to enter another acquisition interval until the SWR changes.
While probably of limited value
to an end user, we left this feature in the product
and set the default setting for this option is OFF.
Feel free to experiment with it if you are curious
about how it works. This
indicator can be
turned ON or OFF using the Averaging Filter menu.
Q: Can the Alarm functions be used with RF Ammeters and Generic Meter
- Yes - The alarm functions can be used in conjunction with the low level and
high level trip point thresholds. Of course the SWR trip point
threshold and SWR warning
feature are not applicable to RF Ammeter couplers and Generic Meter
applications, and are therefore ignored in these cases.
Explain Configuration Sets.
- Configuration sets allow you store up to
five user-defined "sets of
settings". Just about every meter configuration parameter, including
the measurement modes,
the selected display devices, ranges, peak hold times, auto-modes, and Alarm trip thresholds are saved
in a configuration set. If you have two or more rigs located in different parts of the
shack, you may want to customize a configuration set for each station. For
example, one of two configuration sets could be used to automatically
select the settings corresponding to the coupler and panel meter that you
have located at each station. Control of items such as the
External Hi Visibility
Display modules is also easily accomplished by storing their settings in configuration sets. Two
special configuration sets, the Factory Default Set and the Startup Set
are also accessible via one button access.
Therefore, in total, there are seven configuration sets.
- And for additional offline backup, all EEProm settings, including the
data stored in the Configuration Sets described
as well as the coupler calibration tables and panel meter calibration tables, can be backed up
to a PC file and restored from that PC file using the PC-based utilities included with MB-1.
Why don't you have an option to restore the settings that were in effect at
- If you use an approach that automatically restores those options that
in effect during power down, if you inadvertently changed a setting, or
intentionally changed a setting that you intended to use only temporarily,
but forgot to set it back to its original value, those settings will be restored
the next time the unit is powered up - probably not what
you intended. MB-1 requires a positive user action to modify and save the startup set
(long press of Menu Button 1). Therefore, you decide when to define (and
save) the startup set. Any subsequent changes you make to any of the meter
settings will not disturb the startup set (unless, of course, you decide to
save it with another long press of menu button M1).
Using MB-1 with Analog Sensors
is the Generic Meter function?
- MB1's calibration features can be used to measure
a variety of parameters other than those related to
Amateur Radio using a variety of analog sensors and
transducers. To use MB-1 with an external sensor or
transducer, the following conditions
must be met:
- - A DC voltage related to the parameter to
be measured is either available or can be derived
(for example, with an appropriate sensor or
transducer). The relationship between
the voltage and the parameter does not have to be
- - The DC voltage source representing the parameter can share a common ground with
- The DC voltage has a positive polarity.
- The DC voltage increases monotonically as
a function of the parameter being measured.
- - The magnitude of the derived voltage is at
couple of hundred millivolts. (To realize the full
15 bit resolution of MB-1, the derived maximum voltage
generated b y the sensor
should be >= 6.14 volts.)
If the available sensor output does not satisfy all
of the above requirements, it is probably possible
to design an interface circuit to overcome the
limitations. Some examples are given in the
Programmable Meter for Analog Sensors
- User's Manual.
setup of a Generic Meter application, you perform
the calibration by setting the parameter to be
measured to a known value, and then save the
calibration data at the corresponding point.
This can be done at a single point if the
parameter-to-voltage relationship is linear and
passes through 0. If that is not the case, the multipoint
calibration capability of MB-1 can be used to save a series of points that
characterizes the parameter-to-voltage transfer
function. In this case, interpolation is used to calculate the
intermediate measurements from the
available set of calibration points.
here for more details.
Can I use the AutoRange function with a Generic Meter function?
- Yes. The analog meter's AutoRange function and
the Bar Graph's AutoMax function are both applicable
to RF Ammeter and Generic Meter Applications. For
example, the Generic Application example shown
in the User's Manual is a simple voltmeter
application with a 5 volt full scale value. If
instead we programmed and calibrated the
voltmeter for a full scale value of 200 volts, the
internal crossneedle meter (which is programmed from
the factory with three auto ranges of 20 watts, 200
watts, and 2000 watts), could then be used to read
the voltage, and would have two applicable scales: 0
- 20 volts, and 0 - 200 volts, which would
based on the current value of the voltage being
measured. The internal panel meter (or an external
panel meter) could also be reprogrammed with full
scale values of 2, 20, and 200, which would give us
three AutoRange scales of 0 -2 volts, 0 - 20 volts,
and 0 - 200 volts.
AutoMax feature of the Bar Graph works the same
with Generic and RF Ammeter Applications as
for Power Meter applications, namely the Bar Graph's
full scale value automatically adapts its full scale
value to this highest encountered measurement value.
Q: I have an application that uses a Wheatstone
bridge to make a sensitive measurement. Can I
interface the bridge output to MB-1?
- Yes. The only requirement is that negative
output of the bridge must be referenced to MB-1's
Have you tested MB-1 with all of the analog sensor
examples shown in the Generic Meter User's Manual?
- No. But for each example, we have programmed the transfer function
(from the spec sheet, or the transfer function that
was calculated in the example) into MB-1 using the Voltage/Pot
arrangement suggested in Fig 4 of the
Generic Meter User's Manual.
We then verified that
the displayed MB-1 measurement results tracked the
transfer function. Please keep the extent
of this testing in mind
if you decide to experiment with the sensors used in
is the Demo Feature Used?
- The Demo mode feature started out as a development tool, providing a
simulation framework for generating some of the more complex measurement conditions that
would be difficult to generate reliably using real equipment. The simulator
also was a useful tool for running longevity tests on the software and hardware.
It became apparent that the simulator could
be a useful feature in the product as well. The
simulator generates pseudo random values or other
pre-defined output sequences that are processed by
the software just as real measurements would be
processed. The simulator has been wrapped in a Demo
mode feature, which allows you to generate six
different types of pseudo measurement signals. Once
the simulator is running, the MB-1 features can then
be selected, and will respond to the simulated
measurements in an identical fashion to a real
signal with the same characteristics. This is
probably the best way to familiarize yourself with
all of MB-1's features, and in fact, the Demo mode
is used in the "Quick Start Guide" walkthrough
section of the User's Manual to get you quickly up
The demo feature has other uses as well. If you have added additional
analog meters to MB-1, the Demo mode can be used to help validate the
calibration. Last, the Demo mode can be used to determine optimal parameter
settings to suit your operating preferences for functions such as peak hold
time and auto range decay time without running live.
External Display Devices
Does the sticky bar feature also work with the
external bar graph module?
Yes. The sticky bar operates in an identical
fashion to the sticky bar on LCD's Bar graph.
Do you provide an enclosure for the External Display
No. The intent is for you to provide your own enclosures for
the external display modules.
These can be mounted in accessory enclosures, such as a speaker
enclosure if room permits. Mounting these modules is relatively
However, the displays are totally configurable, and you can activate
them all, or a subset of them to meet your needs. Different users will have different preferences,
and those preferences may change for different operating conditions
(e.g., contest, Field Day, Club Activity, antenna being used).
One reasonable setup is as follow:
Display instantaneous forward power and instantaneous reflected
power on the analog meter. Display Average Power, Peak Power,
and SWR on three of the four 7-segment displays. This gives you a
good overview of you operating conditions. Displaying the selected
coupler on the fourth 7-segment LED is useful if you have more
than one coupler connected to MB-1. With these settings, peak
power will provide you with a good indicator of whether your
amplifier is operating normally, and average power will provide a
good indication of your talk power. Most other meters do not allow
you to display both peak power and average power in numeric form
simultaneously. By monitoring only peak power, your compressor or
other audio settings could be significantly misadjusted, and you
might never notice. On the other hand, the effect of such
maladjustments would be obvious on the average power display.
- Processor, memory tests, and peripheral chips.
- Display devices (LCD, panel meters and panel meter drive
circuits, Internal 7-segment LED displays, External 7-segment
displays, External Bar Graph Module)
- Coupler inputs and Programmable Gain Amplifier/A-to-D Chain
- Front Panel Switches including Switch LED indicators
- Front Panel Hi Precision Pot
- RS-232 Transmit/Receive
- Piezo Sounder
- Alarm Relay
These should catch the majority of assembly errors.
Q: Why no PC features?
Some of the other popular meters available on the market require a PC to
control or configure some of their features. A primary design goal
of MB-1 was to provide a meter that could be controlled entirely without being tied to a PC. When it came time to
consider what "add-on" PC features might be good candidates for
a product , the choices came down to bits and pieces of what some of the
other popular meters already offer in their PC-based applications. While
some of these features are clearly useful, we opted to not be a "me too" meter
in this area.
What is the Min/Max Feature?
This feature is similar to the Min/Max feature found in the
Digital Meter. MB-1 allows you to define one of several parameters, which is
then processed by the Min/Max function. Looking for a dropout, a power spike,
or variations in your SWR? Select the appropriate parameter to
process with the Min/Max
function. MB-1 will monitor that parameter
indefinitely (or until you reset the min/max values), and will capture
that parameter's minimum and maximum values. The Min/Max values can
be displayed on any of MB-1's display devices.
The Min/Max function can process the following measurement
Q: Why would I
- FWD (instantaneous) Power
- Peak Power
- Average Power
- Delivered Power
- Reflected Power
- RF Current
- Generic Measurements (using analog sensors)
This feature allows you to display the number
measurement cycles per second and the number of Bar Graph updates per
second that the meter is currently processing. This tool was useful during the software development
cycle since it allowed us to continually monitor the performance as
features were developed or as changes were made. As a user, you may find this tool useful as well. It can be
used to see what the performance impact is of processing various
measurements, activating the various display devices, and modifying the
display update rates.
To display the metrics, bring up the SPEED
menu. Wait approximately ten seconds without pushing any additional
buttons. Then press the DISPLAY button. The metrics will
be displayed on the LCD. (The 10 second wait time prevents processing
cycles from being used for servicing the switch requests,
which would negatively impact the metrics.)
Q: I am skeptical
of the advertised Performance Numbers and the numbers displayed by
The most demanding claims made in the specifications
the measurement rate of MB-1, and the peak capture and
dropout capture intervals. Here is an experiment you
may be able to run.
- While it is difficult to
reliably generate a very short controlled pulse, you may be
able to reliably generate a repeatable 3 ms RF dropout
to an implementation "quirk" in the VFO design of some
modern transceivers. When tuning across a band on some transceivers,
the VFO implementation is such that some switching takes place at
discrete frequency points. If you place the transceiver in the
transmit mode, as you "roll through" these frequency
switching points, you will see a momentary power loss of a couple of milliseconds.
I observed this on a Mark V transceiver. Some of the frequencies at which this occurs
(in kHz) are:
3522.65, 3603.60, 3685.60,
3767.40, 7126.15, 7208.00,
You can determine if your
transceiver exhibits this behavior, and if so, what the
dropout duration is by placing a scope on the FWD coupler DC
input and capturing the voltage dropout corresponding to the
If the dropout interval on your radio is sufficiently
short to test the dropout response of MB-1, you can run the
Configure the Min/Max feature on MB-1 (on any of the 7 segment displays, the LCD,
the Bar Graph, or the Panel Meter) to capture Min/Max instantaneous
power. This corresponds to the TUN option in the Min/Max menu.
(If you are using the Bar Graph or Panel meter, since these
devices can only display one parameter at a time, set the Bar
Graph or Panel meter to display Min power captured by the
Min/Max function.) Apply power to a dummy load. With power applied, reset the Min/Max value (long
press on the Min/Max button.) Your display device should show
Min/Max values both equal approximately to the current key down power.
Continue to transmit, and change the transmit frequency so that you
make an excursion through one of the frequencies where your
transceiver has a short duration drop-out as discussed above. MB-1 should be able
to capture this event consistently (by showing a min power
of 0). In order to consistently
measure a single event whose duration is 3 ms, the
interval corresponding to the measurement update rate would have
to be smaller than the duration of the event. This corresponds
to a measurement update rate of > 333 measurements per second.
Another way you can observe this is by setting the Panel
Meter to display instantaneous power (TUN choice in the Panel
Meter menu). Place the panel meter update rate (via the SPEED
menu) to its highest setting (9). Apply power and change the
frequency to traverse through the transceiver dropout frequencies. You will
see a momentary dip on the needle corresponding to the short
term power drop out. (You will not see this dip on other digital
power meters that have an analog meter.)
The numbers displayed in the Performance Metrics correspond
to the actual update rates being measured by the software.
MB-1's update rate is much faster when measuring time varying signals
such as SSB or keyed CW. As MB-1 becomes popular, I'm sure
others will put it through its paces with regard to the
Can I use the EEPROM Backup/Restore utility to clone all MB-1
settings, including Coupler Calibration tables and Panel Meter
Calibration Tables? Yes. All settings and calibration tables are stored in the User
Data section of EEProm. Use the EEPROM Backup/Restore utility to
do a backup from the source meter using the EEPRM-BKP-U
option. Then using that backup file, do a restore to the
destination meter with the EEPRM-RST-U option. You
will still have to adjust the trim pots on the cloned meter.