Ken Smith wrote:
In article m,
Too_Many_Tools wrote:

I have a well stocked test bench at home containing a range of analog,
digital and RF test equipment as I am sure most of you also do.

Well the question I have is how do you handle the calibration of your
equipment? What do you use for calibration standards for resistance,
voltage, current and frequency?


For frequency, you can use WWV. You need:
A short wave radio with an audio output.
Perhaps an audio filter tuned to about 1KHz.
A generator you wish to calibrate near the WWV frequency.
A frequency counter that is not too far off.

Procedu
Tune in WWV.
Put wire on generator and set it to WWV-1KHz
Listen for tone and move stuff around until it sounds good.
Feed tone into the filter.
Place the counter on the output of the filter.

The number on the counter is X Hz away from 1KHz when the generator is XHz
off from WWV-1KHz.



This works if you only need about 1 part in a million. The movement of
the ionosphere makes wwv useless for real calibration. This was, of
course, wonderful when we had nothing else. It is far better to get
a gps standard (they are used on cell sites and show up on ebay) and
just use it for the timebase all the time. Alternately, use a Rb
source. They were also used in cell sites and are available easily.
They cannot move more than about a part in 100 million and they make
excellent time bases for frequency counters.