[Amps] grid resonance

[R L Measures]

On Aug 7, 2006, at 9:23 AM, Bill Turner wrote:

> ORIGINAL MESSAGE:
>
> On Mon, 7 Aug 2006 10:09:32 +0100, you wrote:
>
>
>> Me neither, because it's so difficult to understand what a dip  
>> actually
>> means, except in the very simplest cases.
>>
>> The GDO is deceptively simple instrument. The trick is to tell  
>> when it
>> stops being simple, and starts being deceptive.
>
> ------------ REPLY SEPARATOR ------------
>
> A GDO "deceptive". I could not disagree more. Assuming the GDO is
> designed properly, what is says is happening really is.
>
> In all fairness, I have seen one GDO which had its own dip at a
> particular frequency, apparently due to a resonance within the meter
> itself.

Correct.  By coupling the dipper to nothing and sweeping each range,  
the false dips are found.  Once the false dips are noted, they can be  
ignored.  In a well-designed dipper, false dips are few and slight too.

> Aside from that however, when it shows a dip, there is most
> assuredly a parallel resonance present, or at least a circuit which
> will absorb power at a particular frequency such as an antenna.

Indeed.  To measure an antenna's 1/4 wave resonance, inductively  
couple the dipper's coil to a short across the feed point, and to  
measure an antenna's 1/2 wave resonance, couple the dipmeter's Tune-C  
- through a 5pF or so C - to the antenna under test. - note - Trio- 
Kenwood dipmeters have this built in.
>
> Bill, W6WRT
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R L MEASURES, AG6K. 805-386-3734
r at somis.org