----- Original Message -----
From: "DF3KV" <df3kv@t-online.de>
To: <amps@contesting.com>
Sent: Thursday, May 19, 2011 10:49 AM
Subject: Re: [Amps] PA efficiency
It depends on the circuit layout, the type of tube and the anode voltage.
** Of course it does
The Eimac datasheet of the 4CX250B shows 48% at 1KV, 57% at 1.5KV and 60% at
2KV. Circuit losses still must be deducted from those figures.
** That is an obsolete tube that is both cheap and has poor IMD.
Most commercial made ham amps loose already efficiency on 10m.
** Dont blame it on the tube or the PS.
I don´t think that 58% efficiency from a GG amp on 2m is that bad and a
difference of 150-200W to the optimum will not work any additional station
in a contest.
** Its decent for a first attempt with a known good tube. I certainly
wouldnt want any extra of loss in the tank unless I didnt mind retuning
during a long transmission. With the 3CX1000A7 amp its rock solid under all
conditions and the only time Ive retuned it is to see if anything has
changed over the years....it hasnt. I cant say that about some other amps
Ive operated elsewhere in contests.
Carl
73
Peter
-----Original Message-----
From: Carl [mailto:km1h@jeremy.mv.com]
Sent: Donnerstag, 19. Mai 2011 16:06
To: DF3KV; amps@contesting.com
Subject: Re: [Amps] PA efficiency
The idea is to not use a tube on 2M that is already at or close to its
maximum frequency for full output spec.
In this case if it is an efficient tube designed for GG linear service to
start with and is rated for say 250MHz then it should be capable of the same
efficiency as on 20M. An 8877 is a case in point and also a 400MHz rated
3CX800A7 which still is over 50% efficient on 432 and is 60%+ on 222MHz.
My 3CX1000A7 2M amp has no problem making 61% on 2M subtracting the excess
drive.
Carl
KM1H
----- Original Message -----
From: "DF3KV" <df3kv@t-online.de>
To: <amps@contesting.com>
Sent: Thursday, May 19, 2011 6:35 AM
Subject: Re: [Amps] PA efficiency
> You might have a hard time to reach even 60% efficiency from a VHF/UHF amp
>
> 73
> Peter
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Jim Thomson
>
> If I built an amp that I thought had 68% eff.... then found out it was
> really only 48%... I'd go nuts. Not good enough.
>
> later.. Jim VE7RF
>
>
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