[time-nuts] Vintage Frequency Measurement
kb8tq at n1k.org
Sun Feb 12 21:26:36 EST 2017
Ok, so how does that make a BC-221 a wave meter?
> On Feb 12, 2017, at 7:15 PM, Wes <wes at triconet.org> wrote:
> On 2/12/2017 12:51 PM, Bob Camp wrote:
>> 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.
> 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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