[MRCA] How to zero beat with accuracy

[B. Smith]

     Many  MRCA members may not be familiar with zero beating and I 
thought I would pass this info (posted below)  written by KB6NAX on for 
information. The technique published below will allow you to achieve 
zero beat within cycles. This technique is very helpful when calibrating 
an older frequency counter or any device that uses a 5 or 10 Mc time 
base and you are using WWV as a standard. Its kind of tricky and you 
have to juggle the levels back and forth between your WWV reception and 
the output of the time base.
      Both signals  have to be coupled into a suitable receiver.  A 
Technique that I have used is to put a good antenna on the receiver for 
WWV and then feed or couple the output of the 10 mc time base via a 
attenuator direct into the receiver antenna input via a " splitter" Vary 
the attentuator for best results. In the past I have also had good 
results with using a single wire antenna feeding the receiver and just 
coupling the time base output by placing a output "wire" from the time 
base near the receiver antenna wire and varying the coupling.   Play 
with it.   Often for best results I will use the WWV transmission on 20 
Mc when I am calibrating a time base of of 10 mc.  Always observe the S 
meter and listen to the audio at the same time.
Z


-------------------------------------KB6NAX Post via Boat Anchords 
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Zero Beaters,

This has been a great discussion of technique for calibrating receivers, 
VFO's, sig gens and the such.  But I was wondering when someone would 
mention the S meter method.  As you approach zero beat the S meter 
starts waving at you when you are within about ten Hz of zero beat.  
That is plenty close enough for calibrating sig gens but a bit closer is 
needed for carrier insertion for exalted carrier AM or SSB reception.  
That's when the pumping (waxing and waning) of the noise level is your 
last and best hope for obtaining an error free zero beat, if possible 
with the limitations of instability and drift to contend with.  The only 
remaining problem with a "perfect" zero beat is whether you are exalting 
or canceling the carrier, i.e., phase aiding or phase canceling the 
carrier.  The bottom line is that a "perfect" zero beat is not really a 
very practical solution in most cases. Conceivably one could build a 
phase discriminator into a setup and feed the output to a volt meter or 
oscilloscope and tune for optimum phase match as indicated by a DC 
voltage.  Splitting Herz by the hairs, no?


Arden Allen
KB6NAX
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