Vintage Frequency Measurement
Hi
Maybe I’ve been wrong for the last many decades …
To me a wave meter is a tuned circuit device that tells you the frequency by a resonance
peak. They are a very common old school item for microwave frequency measurement in
a teaching setting.
https://www.britannica.com/technology/wavemeter
Bob
On Feb 12, 2017, at 12:16 PM, Robert Atkinson via time-nuts time-nuts@febo.com wrote:
In a word,Wavemeters. Classic US onwas the BC221 with built in 100kHz crystal calibrator
http://radionerds.com/index.php/BC-221
British was the "Class D"http://www.royalsignals.org.uk/photos/classDno1.htm
For UHF and Microwave it was Lecher lines or cavity wavemeters.
Robert G8RPI.
From: Scott Stobbe <scott.j.stobbe@gmail.com>
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Sunday, 12 February 2017, 6:08
Subject: [time-nuts] Vintage Frequency Measurement
I was inspired recently coming across a Lampkin 105 frequency meter, as to
how frequency measurement was done before counters.
Certainly zero-beating a dial calibrated oscillator, would be one approach.
Is there a standout methodology or instrument predating counters?
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So far all the answers are about high-end expensive equipment. There were
also low cost frequency meters. I have one 40 years ago that was not
expensive. It wa a simple "frequency to voltage" circuit that drove an
analog meter. It was made just before the digital multimeters came out,
maybe in the 70's Sold for well under $100. I think these were the most
common type. The others being described here were WAY behind the
hobbyist's budget
On Sun, Feb 12, 2017 at 5:39 AM, Dan Rae danrae@verizon.net wrote:
On 2/11/2017 10:08 PM, Scott Stobbe wrote:
I was inspired recently coming across a Lampkin 105 frequency meter, as to
how frequency measurement was done before counters.
Certainly zero-beating a dial calibrated oscillator, would be one
approach.
Google BC-221 and you may get some idea of how those worked. I just wish
I could find the one hidden in my garage :^)
Dan
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--
Chris Albertson
Redondo Beach, California
Also Motorola and Schomandl had similar instruments-I have one of the latter here I'm still trying to get a replacement meter for. The Gertsch and Motorola instruments were very similar to look at but not identical. The Schomandl was distinctly different with its tall vertical design.
DaveB, NZ
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Mike
Garvey
Sent: Monday, 13 February 2017 2:36 a.m.
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Vintage Frequency Measurement
Look at (Singer) Gertsch Frequency Meter. This was standard measuring
equipment in our (spectroscopy) lab in 1975.
Mike
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of
Neville Michie
Sent: Sunday, February 12, 2017 05:20
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Vintage Frequency Measurement
Back in the early sixties I worked in a lab adjusting filters for line
transmission.
We had numerous oscillators, built to be boat anchors, and CROs set up
for X-Y display.
The lab had 100hz, 1kHz, 10kHz standards wired in.
We were expert at recognising lisajou figures. We might have several
oscillators running together, and we could establish almost any
frequency with precision.
Calibting an oscillator would not have been difficult.
Cheers, Neville Michie
On 12 Feb 2017, at 5:08 PM, Scott Stobbe scott.j.stobbe@gmail.com
wrote:
I was inspired recently coming across a Lampkin 105 frequency meter,
as to how frequency measurement was done before counters.
Certainly zero-beating a dial calibrated oscillator, would be one
approach.
Is there a standout methodology or instrument predating counters?
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
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and follow the instructions there.
I am surprised no-one mention the 3-beat method, which was fairly common for
Hams with comms receivers. You put the BFO on and adjusted so the main slow
beat modulated the level of the output tone. You can judge zero beat to much
better than 0.1Hz that way probably near as low as 0.01Hz. (1E-9 for 10MHz
!!)
Lissajous figures are not ideal either but don't require a comms receiver,
(but do require a 'scope with X-Y facilities :-)) ) a better technique
certainly for fixed frequencies (stand comparison) uses Z-mod on the scope
or a running "toothed wheel" display see Radio Laboratory Handbook by
Scroggie.
Ah and the BC-221......
Alan
G3NYK
----- Original Message -----
From: "Bob Albert via time-nuts" time-nuts@febo.com
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Sunday, February 12, 2017 5:00 PM
Subject: Re: [time-nuts] Vintage Frequency Measurement
First you need a standard, a crystal oscillator. If you want serious
precision, you'd have one in an oven. Zero beat that with WWV. Then make a
very stable VFO and calibrate the harmonics against the crystal. Assume
linear calibration on the VFO between check points.
The military LM and BC-221 were very good units. I had one. The check
points in the calibration book were too far apart but there were others
that weren't documented that would make for more precise calibration.
I also built a frequency meter that was amazingly accurate, from a GE Ham
News project printed back in the early 1950s. It used a VFO that went
between 100 kHz and 101 kHz for its full range, adjusted by a micrometer
dial (military surplus). Its harmonics would be zero beat with the
unknown. Using a successive number of harmonics would identify the
harmonic number and the scale could be interpolated to within much less
than 1 kHz over the HF range.
Of course, zero beat was hard to identify so you could use an oscilloscope
lissajous pattern (if you had an oscilloscope, which I didn't). What I did
was turn up the volume and listen to the beat. When it got down near zero
the sound of the AGC surging would tell me the frequency of the beat and I
could adjust to make it stop surging.
When I got my hands on a Beckman counter I was in heaven.
Bob
On Sunday, February 12, 2017 4:01 AM, Neville Michie
namichie@gmail.com wrote:
Back in the early sixties I worked in a lab adjusting filters for line
transmission.
We had numerous oscillators, built to be boat anchors, and CROs set up for
X-Y display.
The lab had 100hz, 1kHz, 10kHz standards wired in.
We were expert at recognising lisajou figures. We might have several
oscillators running together,
and we could establish almost any frequency with precision.
Calibting an oscillator would not have been difficult.
Cheers, Neville Michie
On 12 Feb 2017, at 5:08 PM, Scott Stobbe scott.j.stobbe@gmail.com
wrote:
I was inspired recently coming across a Lampkin 105 frequency meter, as
to
how frequency measurement was done before counters.
Certainly zero-beating a dial calibrated oscillator, would be one
approach.
Is there a standout methodology or instrument predating counters?
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
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and follow the instructions there.
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On Sun, 12 Feb 2017 17:16:18 +0000 (UTC), you wrote:
In a word,Wavemeters. Classic US onwas the BC221 with built in 100kHz crystal calibrator
A couple of years ago, I got a BC221 from an estate; had to recap the
homebrew power supply the late ham had built for it, but the BC221 worked
fine and after all these years I could still zero beat the reference
crystal against WWV, using the S-meter when the beats got too slow to hear.
Absolutely beautiful dial mechanism on those critters.
Totally OT: I once sat radio in a P2V "Neptune" that was being ferried back
to Alameda for update; still had the ART-13/BC-348 combo with an LM freq
meter.
--
Gary Woods AKA K2AHC- PGP key on request, or at home.earthlink.net/~garygarlic
Zone 5/4 in upstate New York, 1420' elevation. NY WO G
To put BC-221 things in perspective, the 1 Mc/s reference crystal was
adjusted, according to the manual, to within 5 c/s...
Things have come a ways since!
Dan
On 2/12/2017 12:51 PM, Bob Camp wrote:
Hi
Maybe I’ve been wrong for the last many decades …
To me a wave meter is a tuned circuit device that tells you the frequency by a resonance
peak. They are a very common old school item for microwave frequency measurement in
a teaching setting.
https://www.britannica.com/technology/wavemeter
Bob
As I said before, there were cavity wavemeters used in industry. I've attached
a couple of pictures that show some in action. In both photos I (with the tie)
and my partner are working on a prototype IMPATT diode power amplifier for the
AIM-54C Phoenix Missile. This used 16 matched IMPATT diodes in an X-band
cavity. At this point it is actually a free-running, pulsed oscillator. In the
final usage it was injection locked to a three diode oscillator which in turn
was driven by a single diode that was locked to a GUNN oscillator. These were
all connected via a five-port circulator. The GUNN was phase locked to VCXOs at
about 100 MHz, multiplied 96 times to X-Band.
Since this was free-running the frequency measurement accuracy of a cavity
wavemeter was adequate. In photo 2 the wavemeter is the grey cylinder with the
black top just in front of the lab notebook. In operation it was tuned and
caused an amplitude notch that was detected with a waveguide-mounted diode.
In the other photo there is another wavemeter on the test station behind me
among some waveguide attenuators and phase shifters. Maybe of interest to
frequency nuts is the transmitter-receiver unit from the production AIM-54A
missile. It is just "above" the bend of my elbow. There were seven, pie shaped
VCXO circuit cards in a temperature-controlled chassis. Maintaining frequency
accuracy under launch shock and the vibration from hanging on the wing of an F14
at Mach 2 was lots of fun.
Wes
Hi
That’s not the accuracy of the crystal mind you. That’s how close you do the zero
beat to something else that is more accurate. The crystal is out in the open and it
drifts quite a bit as the unit warms up or changes temperature due to being moved
around.
Bob
On Feb 12, 2017, at 6:11 PM, Dan Rae danrae@verizon.net wrote:
To put BC-221 things in perspective, the 1 Mc/s reference crystal was adjusted, according to the manual, to within 5 c/s...
Things have come a ways since!
Dan
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Hi Dan yes that is 5e-6 about all an unstabilised (temp) AT could hold for
any period. I guess there were no WWV or MSF signals around then. When a
good source was available off-air it was possible to do better than that. In
service it was probably "dont waste time trying to better the minimum
requirement. The transmitter you are looking for wont be that accurate or
stable"
In 1960s I saw several BC-221s in the racks at the Rugby LF and HF stations
acting as standby frequency sources (VFO) for rapidly running up a
transmitter on an unusual frequency (not a normal route) for which they did
not have a crystal available.
Alan
G3NYK
----- Original Message -----
From: "Dan Rae" danrae@verizon.net
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Sunday, February 12, 2017 11:11 PM
Subject: Re: [time-nuts] Vintage Frequency Measurement
To put BC-221 things in perspective, the 1 Mc/s reference crystal was
adjusted, according to the manual, to within 5 c/s...
Things have come a ways since!
Dan
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Well 5 cycles per second is more than accurate enough. That translates to a 150 Hz error at 30 MHz, definitely negligible for the uses of all these gear. There was no official Time Nuts group at the time, although many of us had the spirit. Yet the capability of the BC-221 far exceeded its specification if you could receive WWV.
I noted immediately that zero beat of WWV at 5 MHz was not as precise as at 15 MHz. In those days there was even a 30 MHz WWV but it got shut down a long time ago. And there were CHU and JJY.
Bob
On Sunday, February 12, 2017 4:02 PM, Dan Rae <danrae@verizon.net> wrote:
To put BC-221 things in perspective, the 1 Mc/s reference crystal was
adjusted, according to the manual, to within 5 c/s...
Things have come a ways since!
Dan
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.