Hams need more headroom to make up for inadequate cooling (Oh my. I dont
like all that noise, how can I quiet it down?) and lack of understanding how
to tune a tube with a fussy grid. Mindless QSY's without watching the grid
meter dont help.
Carl
KM1H
----- Original Message -----
From: "Paul Christensen" <w9ac@arrl.net>
To: <amps@contesting.com>
Sent: Wednesday, September 05, 2012 6:04 PM
Subject: Re: [Amps] Alpha &&DX Conversion
Vic,
Valid point but the FCC- registered efficiency was 58% and is typical of
an FM broadcast GG design. The AEL FM 2.5K is a GG design and not
tetrode-based as were the more common FM broadcast transmitters.
Paul, W9AC
----- Original Message -----
From: "Vic K2VCO" <k2vco.vic@gmail.com>
To: <amps@contesting.com>
Sent: Wednesday, September 05, 2012 5:57 PM
Subject: Re: [Amps] Alpha &&DX Conversion
Paul,
Don't forget that the FM transmitter was probably running class-C which
might be 75% efficient compared to the 60% or so available in class
AB1/2.
On 9/5/2012 2:48 PM, Paul Christensen wrote:
"I will tell you why i run a 2 tuber, you put in 25 watts in and do
1500 easy not
push a one tuber to do 1500 out. it all comes down to what you can
afford. bill 73"
This may be an interesting point of reference. During my college years,
I worked at a
3KW FM station in Rockford, IL as its chief engineer. The transmitter
was an AEL
FM-2.5K (FCC type accepted to 2.5KW output) and used a single 8877 to
produce
2500-watts output at 104.9 MHz. All day long, every day, 365 days a
year. A
three-bay circularly polarized antenna brought ERP to 3KW.
If a 77Dx is running intermittent amateur-class service but under high
duty-cycle modes
like RTTY at 1500-watts output (the U.S. legal limit, for example), I
think its
reasonable to assume that a 8877 is already operating with sufficient
headroom of
roughly 1KW. For what purpose do any of us need more than 1KW of
headroom from our
vacuum tubes when producing 1.5KW?
Paul, W9AC _______________________________________________ Amps mailing
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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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