Way back in 1964 I worked in a two-way shop part-time while in college.
We also sold and serviced Amateur Radio gear. The other techs and I built a
receiver set-up for doing frequency measurements out of two similar short
wave receivers. One receiver was the master receiver for WWV (or other
frequency of interest) and the other was used for picking up the oscillator
under test. The master receiver had a cathode follower on its VFO which fed
the secondary receiver's mixer. ( The secondary receiver's VFO was disabled)
One of the receiver's last IF stage was coupled to the vertical input of
an oscilloscope and the other was coupled to the horizontal input. It was
very easy to watch the Lissajous pattern on the scope and set a very good
zero beat. It was very easy to see beat notes of 0.01 Hz. or better if you
wanted to sit there that long and watch it. With a 10 mhz. reference that
would be 1/2 cycle at UHF, probably close enough for most applications.
It was also very cool to watch the permutations of the atmosphere on the
signal from WWV. We could also look at any HF frequency besides WWV on 10
Mhz. Back then WWV had standards all the way to 25 Mhz. Then there is CHU.
Also usable for ARRL's FMT.
Maybe I'll put another one of these together. (Solid state this time) It
was cool.
One potential problem was the oscillator under test being picked up by
the wrong receiver. An external antenna with a coax feed usually has enough
isolation.
Now GPS and WWVB are probably easier to do if you got the bucks.
Then www.buylegacy.com has had some HP "GPS Receiver Discipline Clock
Frequency Reference" unit for $249.
The Old Fart,
Al, K9SI
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