[AMPS] RF Chokes

[km1h @ juno.com]

On Fri, 27 Mar 1998 15:34:40 -0000 "Geurts, Gerard" <ggeurts@amp.com>
writes:
>G3RZP wrote:
>
>> I didn't think we could find a subject with so much agreement 
>between
>> everybody!
>> 
>> This suggests the inputs are technically correct................
>> 
>> 
>> I have this nasty idea that I'm going to have to build a GDO. 
>> 
>> BUT  is it possible to test using a resistor plate to ground (of 
>same
>> load
>> resistance as the plate wants to see), no DC, a VTVM with a good RF
>> probe at
>> the plate and feed in at say 5 watts from the antenna end and check
>> that the
>> volts at the plate are correct when tuned up? Do it on all bands of
>> course.
>> 
>> Not as easy as dipping the RFC with a gdo, but easier than building 
>a
>> GDO to
>> do the job.
>> 
>> Comments?
>> 
>> 73
>> 
>> Peter G3RZP
>> 
>Or test using a resistor plate to ground, no DC, RFC not connected or
>maybe even not present. Measure return loss at antenna port, tune
>circuit for desired frequency, connect RFC. The only thing you should
>see is a change in the tune capacitor setting, especially at the lower
>bands. Could be done with an antenna analyser, TX and SWR meter or 
>(and
>that is by far the easiest way to do it) with a Network Analyser. 
>Works
>fine for me.
>
>Gerard, MoAIU / AA3ES

All good info Gerard and Peter. See, there are alternatives BUT a GDO is
such a useful device for anyone working around RF...without the benefit
of an HP equipped lab...should have one.

Peter, the last time I checked, CIRKIT on ur turf was still selling a
fine GDO kit. 

On this side of the pond GDO's are showing up quite regularly as older
hams die off and new ones cant figure out how to attach a PL-259. 
Check the various Internet swap groups, HF swap nets and flea markets.
For amp use even the old Heath and Eico types are more than adequate. I
use a 1950's era Measurement Corp Model 59 ( still has the National Radio
ID tag) and the one I built in 1956 from a 1949 CQ article works just as
well.  

73  Carl  KM1H

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