In short I agree.
It is not a good idea to put in a extra tube in any comercial amp.
You would probably need so many parts, that it would be a better idea to
homebrew a new amp.
I have a nice one tube AL-80B an concluded that a homebrew 4CX1500B amp is
required to have a clean 1kW+ signal.
This will be built with a spare place for an extra tube, if that is ever
required (limit in LA is 1000w).
I don't agree that you necessarily would need a new blower.
With two tubes the back pressure would be 1/2, so the air flow for each tube
can be the same as for one.
About s-meter reading, I have never measured an s-meter that is 6dB for each
degree.
Typically it is 20-30dB between s1 and s9, instead of the 8x6dB=48dB it
should be.
A s1-3 signal will typically increase by 1-2degrees with 3dB power increase.
73 de LA6MV
Helge
-----Original Message-----
From: Robert & Linda McGraw K4TAX [mailto:RMcGraw@blomand.net]
Sent: 8. september 2003 06:00
To: Wt8r@aol.com; shr@medinaec.com; amps@contesting.com
Cc: rickn@netdoor.com
Subject: Re: [Amps] Ameritron AL-1500
In a short answer NOPE! These amps are marginal in all aspects at the 1500
watt power level.
To explain: the PSU is not capable of handling the extra current of a 2nd
tube. It would require a new plate transformer and the space to mount it.
New diodes which would have some 2X the current rating of the present ones.
A 2nd filament transformer will be required and the space to mount it. Most
likely even the power switch is under-rated too not to mention the RF
switching components. On the RF side, the tank circuit components are the
wrong values as the input Z will be about 1/2 of the present design value
and much too under-rated in terms of current handling ability for a 2nd
tube. The cooling requirements will double so the present blower is
inadequate. The plate current meter range is inadequate as well as the grid
current meter and the relative output power measuring circuit.
But if it all worked, it would net you only 1/2 S unit increase on the other
end.
To that end, one could invest say $1000 in parts just doing the mods and
adding parts and after all said and done, should one try to sell it, they'd
be lucky to get $500 to $750 total because it is a modified HB, butchered
and hacked amp.
73
Bob, K4TAX
----- Original Message -----
From: <Wt8r@aol.com>
To: <shr@medinaec.com>; <amps@contesting.com>
Cc: <rickn@netdoor.com>
Sent: Saturday, September 06, 2003 9:20 AM
Subject: Re: [Amps] Ameritron AL-1500
> >
> > At 12:11 PM 9/5/2003 -0500, you wrote:
> > >Has anyone ever successfully added a second tube to an AL-1500? What
> > >changes would be needed to make the power supply sufficient?
> > >Rick KD5MGK
> >
>
> Rick--
>
> What does a General class operator intend to do with a modified
> amplifier that runs 4 KW+ input anyway? Judging from the callsign, my
guess is
> that he intends to run it from a 120 VAC wall plug.
>
> Obviously Rick hasn't the foggiest idea of what he is talking
about.
> This is one of the dangers, both to Amateur radio and his person, of
> inexperienced people playing with things they know nothing about.
>
> Perhaps this is some of the great technological treasure trove that
> W5YI was talking about bringing into ham radio through his NO-CODE
program.
>
> 73 de
>
> Dave, WT8R
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
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