[time-nuts] Vintage Frequency Measurement

Wes wes at triconet.org
Sun Feb 12 19:15:14 EST 2017

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.

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