Hi:

When listening to a broadcast station using an analog receiver you just tune back and forth near the station frequency
until you hear it, but that does not work for military radios where most of the time there is no transmission.  Hence
the need for frequency or wavemeters like the BC-221 and the LM series to set them on the assigned frequency.  The
calibration books for these meters were machine generated for each serial number unit.  This was long before computers.
The later FR-149B/USM-159A Frequency Meter uses a long 35mm film strip and an optical readout to get the 0.01% accuracy,
and again is custom made for each serial number meter.  But the need for them has almost gone away with the advent of
synthesized radios.  But there must still be some analog radios in use since the manual for mine has a date of March
2006.  Note they are accurate signal generators (to set receivers) and have a hetrodyne capability to set transmitters.
http://www.prc68.com/I/USM159.html

When working at a microwave company we used cavity wavemeters where at resonance there was a suck out.

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

-------- Original Message --------

I have a General Radio Type CAG-60098-A Precision Wave Meter made for Navy
Department - Bureau of Ships according to the nameplate.  According to
Wikipedia that would date it between 1940 (when bureau of ships was
created) and 1966 (when abolished).  It has an inductor in sort of a
"hockey puck" labeled 16-50 kc that plugs into a socket on the front panel.
Inside is a very nicely made variable capacitor with a vernier drive.  It
has been a while since I had it apart, but there is a diode in series with
the meter and not much else as I recall.  The meter scale is 0-200
(microamp?) and the capacitor scale is 0-75 with no other marking.  I have
no manual, but I assume there were other inductors for different frequency
ranges with a calibration chart to interpret the 0-75 reading.  It must
have been made to test transmitters by tuning for peak reading on the meter
and determining the frequency from the dial reading.

a different Alan (KE7AXC)

On Sun, Feb 12, 2017 at 5:47 PM, Alan Melia alan.melia@btinternet.com
wrote:

On 12 February 2017 at 06:08, Scott Stobbe scott.j.stobbe@gmail.com wrote:

How about the diffraction grating? Natural ones have probably existed
billions of years, but they were made by man in the 18th century. These are
still in use today in instruments like optical spectrum analyzers.

The wavemeter must have been around a long time too. These are still used
at THz wavelengths.

Dave.

Hi

Ok, so how does that make a BC-221 a wave meter?

Bob

Hi

If you look at a typical BC-221 in use, it goes from “calibrated” in a nice warm hut to the back
of a jeep. It heads out to an ice cold flight line and the switch turns the batteries back on again.
It bumps in and out of a batch of B-17’s setting each one up for the day’s net frequencies. You
would be doing very well to hold 50 ppm under those circumstances. That was indeed adequate
for the purpose.

Bob

Hi

The GR is a classical wave meter that works off of a tuned circuit and a broadband
detector. The BC-221 works on an entirely different principle and has no ability at all
to run in the mode that the GR operates in.

Bob

The BC-221 was mentioned in a Time-Nuts thread from December, 2015.
Copying from my post in that old thread:

Back in the early 1970's I took my BC-221 and added a TTL divide by
1,000 (or 2,000 or 4,000 or 8,000) external circuit to generate very
precise audio test tones from the RF oscillator. The BC-221 had two
output frequency ranges: LOW: 125 to 250 kHz HIGH: 2 to 4 MHz  By using
the appropriate range and divide ratio I could generate 15.625 Hz to 4
kHz (and multiples) with very smooth continuous tuning and great
accuracy (typically better than 0.005%). This was very useful for
adjusting and measuring audio filters and circuits, such as 2125/2295
Hz AFSK terminal units I was using on 2 Meter AM and with SSB rigs for
HF FSK. I could tune up my filters built with 88 mH telephone surplus
toroidial inductors. I could also use the audio source to compare by
ear the beat note between harmonics of my divided-down 5 MHz commercial
surplus precision oven oscillator and RF signals (such as during the
ARRL Frequency Measuring Test).  The anti-backlash gear mechanism,
large dial with high resolution interpolation scale, and well-built
variable capacitor were difficult to find in other commonly available
radio related equipment. In my opinion the BC-221 was a technically
beautiful precision instrument. It was the time-nuts tool of choice for
several decades!

Bill Byrom N5BB

On Sun, Feb 12, 2017, at 08:31 PM, Bob Camp wrote:

This reminds me.

Many years ago the Titan Missile sites around here in Tucson were being
decommissioned.  The people at Davis Monthan AFB who maintained them were going
to be out of work but had an opportunity to bump into something else on base if
they got some more training.  I and a coworker, who had quit a tenured position
at the U of A, were both teaching part time at the local Jr college.  The AF
approached the college to request a class be developed to help their people
prepare for the new work.  The college in turn approached my PhD friend.  He was
happy to do the lecture part of a course but wanted nothing to do with teaching
lab work.  He asked me to share the job with him.

I don't remember all of the particulars but I do remember that after each lab
session the AF folks removed all of the lab gear from the work benches and
locked it away in storage cabinets before wiping down the benches and mopping
the floors.  This included unplugging an HP-5245L and tucking it away.  I
admonished them about this practice and actually taught them about crystal
aging, etc and the need for time for stabilization. This was years before GPS.

I had one woman Sgt confess to me that when she went to a silo to check some
frequency or the other, she was supposed to use a piece of equipment that took
hours to stabilize.  From the sound of it it was some WWVB phase comparison
equipment.  Instead of this process, she grabbed the frequency counter from the
lab, threw it in the PU and hauled it 50 miles to the missile site, plugged it
in and tweaked the widget using the counter.  I had visions of a Titan Missile
targeted to hit Vladivostok landing on Tokyo instead.

Wes Stewart

2/12/2017 7:31 PM, Bob Camp wrote:

On 02/12/2017 01:08 AM, Scott Stobbe wrote:

Hi Scott.  That Lampkin 105 is a sophisticated design.  I did
some research that you might be interested:

For the 2015 November ARRL Frequency Measuring Test, I fired up
my old Lampkin frequency meter.  For their 100th Anniversary,
QST was encouraging the use of “vintage” equipment for the FMT,
and the Lampkin was designed in the 1930s.

I (AA8K) did surprisingly well, coming within 322 Hertz on 40
meters, 202 Hertz on 80 meters, and 18 Hertz on 160 meters.

The Lampkin 105-B was designed by Guy Forest Lampkin BSEE, who
got his first ham license in 1924.  In 1933 he was selling the
model 102, that was checked with the Federal Radio Commission
and commercial laboratories to be within 3 to 15 cycles at 1,712
kc.  He was also selling a “foundation unit” of the Precision
Micrometer, Band Spread condenser, Special Isolantite coil form,
Temperature compensator, Adjustable pad condenser, and complete
circuit details for $14.50.  Lampkin Laboratories moved from 146
West McMillian Street, Cincinnati, Ohio to 8400 Ninth Avenue
N.W., Bradenton, Florida 33506 in 1935.  It was incorporated in
1942.  Precise Power Corporation had acquired Lampkin
Laboratories in 1971/Oct.  At that time Lampkin Labs had 17
employees and wasn't advertising their 107B Digital Frequency
Meter because they were selling as fast as they could make them.
The last known address was 12297 US Highway 41 North,
Palmetto, Florida 34221.  Voluntary Dissolution 2007/April/27.

The 105-B is a fascinating design, able to measure frequency to
0.0025%.  Signals can be measured from 100 KHz to 175 MHz.  It
works similarly to the later World War II BC-221 frequency
meter.  It can receive, or transmit the internal oscillator
2330-2670 KHz.  A diode generates harmonics that can beat
against the signal to be measured.

The variable condenser has a precision-machined tubular stator
and a tapered, conical rotor.  They are made from steel and
brass and copper plated.  The parts are proportioned such that,
due to the differential thermal expansion, the temperature
coefficient of capacity is a few parts per million per degree
Celsius at all positions of the rotor.  The rotor is moved in
and out of the stator on a micrometer screw.  The large dial and
turns counter give a dial band spread of 8,000 divisions over 42
feet!  The inductor is wound on a six-ribbed form of
polystyrene.  Since the thermal expansion of polystyrene is
greater than copper, as coil temperature increases, the turns
are pulled from circular to hexagonal, and the average diameter
of the coil decreases.

Thermal design is utmost in the Lampkin MFM.  In addition to the
L/C circuit, the vacuum tubes and circuitry are mounted on the
rear, with the chassis cut-away to keep it from heating the
front where the L/C and calibration crystal are mounted.  Wires
connecting the L/C and crystal are very small diameter to reduce
the thermal path.  Even the power transformer is bolted to the
outside of the cabinet.  The 7.5 MHz calibration crystal (no
oven) is held against the front panel.  There is a glass
thermometer mounted to the front panel.  It is custom-marked
with a correction factor for that specific unit.  I left the
Lampkin turned on from October, but the temperature soon
stabilized.  The metal 6J7 tube has the Bakelite cap removed, to
eliminate changes due to moisture absorption in the Bakelite.

Striking features of the Lampkin are:  The very smooth tuning
with almost zero backlash.  Turning the dial clockwise lowers
the frequency, but that is because the micrometer screw is a
right-hand thread and moves the rotor into the stator,
increasing capacitance and lowering frequency.  Increasing
frequency moves the micrometer post outwards through the center
of the dial, like Pinocchio's nose growing.  The outboard
transformer looks clunky at first, until you realize why he did
it.

Modifications.  I replaced the 1 ampere line fuse with a 0.5
ampere for additional protection.  (I have been wary of
unattended equipment ever since an un-fused Radio Manufacturing
Engineers receiver monitoring RTTY autostart almost burned our
house down in the 1960s.)  Measuring frequency requires table
look-ups and correction math.  Since I did not have the original
manual with calibration data, and the end-stop was nowhere near
000 on the counter dial, I decided to calibrate it myself.  At
the same time, I added ferrite inside the coil to drop the
oscillator frequency down into the 160 meter band.  Using my
OpenHPSDR, I calibrated by noting the Lampkin dial reading for
every 100 Hertz on the HPSDR.  During the FMT, I used a Collins
75A-4 receiver in AM mode and adjusted the Lampkin 105-B to
zero-beat the signal.  Using the Lampkin dial reading and
looking it up in the table, I could interpolate for the
frequency between the two calibration values.

During the test, I noticed that the Lampkin was varying because
the line voltage was changing.  The next time I will build the
recommended line voltage regulator using two 0C3 (VR-105) tubes
and a 60 Watt ballast lamp.

I uploaded my mods, photos of the inside, and a scan of the
manual to mods.dk.  I tried to ftp and email the manual to
BAMA/eDebris without success.

See attachments

Hi Mike,

First of all, Wow what an interesting read, thanks for sharing some of the
history and your experiences with the 105. A second thanks for uploading
the manual, which I found to be a great read, as with most old test &
measurement product manuals, they are far from just marketing fluff.

Bare with me, I'm not well versed in early radio history, but, I also found
it neat they choose to crystal calibrate on the 3rd harmonic of the VFO to
help prevent injection lock and for increased sensitivity (but that may be
true of all frequency meters of the era, don't know).

Based on the manual, the thermometer is thermally mounted to crystal
holder, allowing one to temperature compensate the crystal calibration
point. I didn't see a mention as to what crystal cut they used. I would
guess it is one with a flat tempCo with no turning points for the linear
thermometer scale to be used effectively.

Attached is a plot taken from the manual, the VFO stability strip-chart

On Mon, Feb 13, 2017 at 12:24 AM, Mike Naruta AA8K aa8k@comcast.net wrote: