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[AMPS] Tuning of amps - 3cx800s,etc..

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Subject: [AMPS] Tuning of amps - 3cx800s,etc..
From: (km1h @
Date: Sun, 15 Mar 1998 16:17:10 EST
On Sat, 14 Mar 1998 23:05:20 EST KA2YKC <> writes:
>One question I have been meaning to ask........
>Can someone please clarify "Loading" ??

In basic terms it may be defined as the method of extracting optimum
power transfer from the tank circuit into the actual load.

>When I turn my LOAD counterclockwise (CMDR HF2500),  the grid current 
>quickly with little drop in output pwr (as recommended). Am I 
>increasing or
>decreasing the loading of the antenna ???

It all depends on your dial calibration; there is no industry standard.
You will have to look inside at your load cap and see. Going toward
minimum C is considered increasing the loading. Very confusing.
In your case you are increasing the loading and yes...that is the proper

>I think I am increasing the loading (even thought the dial is going to 
>lesser #), However, I think I read somewhere (maybe an Ameritron 
>manual) that seemed to contradict this (or their var. cap works in the
>opposite direction - increased loading shows higher dial #) . 
>I interpereted an earlier post as saying not to drop the grid by 
>adjusting the
>load, rather decrease the drive from the exciter. 

Forget about grid and plate for a moment. The idea is to watch the RF
Wattmeter and tune for maximum, go thru maximum about 10% by increasing
the loading. The actual Ig is not important at this point EXCEPT to
monitor AND make sure that the maximums are not exceeded during the
tuning process. You will find that the 3CX800A7 amps run at full output
with Ig well below rated maximums. Typically 15-30 ma for a pair and not
the 50ma each that is "allowed".
Excuse me if I oversimplified things a bit.

>Sometimes I wish I was born 20 years earlier so I could have been 
>taught tubes
>rather than solid state when I was in school .
>Thanks for the free education. 

And I still get confused with solid state! Born too damn early!

73  Carl  KM1H

>73 Eric
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