[ARC5] Zero Beat Question

[Richard Knoppow]

    If my reading of the handbook is correct there is a small speaker to 
hear the calibrator on. You should be able to hear the beat from  the 
generator signal as you tune through the calibrator signal. While 
hearing the exact zero beat may be difficult (depending on the speaker) 
you can come within whatever is the lowest tone the speaker will put 
out. Tune on either side of the zero and put the generator in the middle 
and set the dial there. You will be within perhaps 50hz.
     Polarad was a pioneer in making UHF and microwave generators and 
service equipment for radar and television.  If you know the civilian 
equivalent model number please let me know and I will search for its 
instruction book. Polarad had a very good reputation for quality.
     Not defining zero beat is from just assuming everyone knows what it 
means. Well, everyone does not know and its just this sort of basic 
stuff that drives you crazy when its missing.
     I think the output may be of the wave guide beyond cut-off type 
also used on some Hewlett-Packard VHF and microwave generators.

On 7/7/2016 6:54 PM, Robert  Eleazer wrote:
> I suppose that what you can do is to tune in the marker signal to the
> full 1000 cycle tone and then tune it a little more to get the tone
> lower, creep up on it from one side.  Then set the calibration mark
> there.  You may be off by maybe 500 HZ or less.  For the radios that the
> signal generator is intended to calibrate 2 to 3 KHZ is considered to be
> adequate.
>
> The SG-297 is indeed made by Polrad.  It has output with either no
> modulation, FM 150 HZ, FM 400 HZ, and FM 1000 HZ.  When you are in
> calibrate mode there is no modulation.  Deviation can be set at 10 KHZ,
> 20 KHZ and modulation "volume" adjusted as well.  It also has fixed
> crystal controlled outputs associated with various radios' IF's.
>
> The mechanical inner workings are fascinating, with direct oscillator
> outputs controlled by a probe that goes into the oscillator tank and a
> fine tuning feature for that probe as well.  It also has an amplified
> and adjustable output.
>
> By the way, the first thing I picked up to look up Zero Beat was the
> 1965 edition of the ARRL handbook. The results were disappointing; they
> use the term Zero Beat without defining it, referring to it in the
> context of a regenerative detector.
>
> Thanks!
>
> Wayne
> WB5WSV
>
>
>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL