[AMRadio] RF Amp

Brett gazdzinski brett.gazdzinski at verizonbusiness.com
Wed Dec 6 08:50:02 EST 2006

I think the 405 TL's will require a LOT if filament
power, that's for sure!
I also think they like very high voltages, over 3000, which
will make things tend to be huge, very large plate tuning caps,
KW plug in coils wont do for that power level, loads of spacing,
and huge tubes make for a HUGE RF deck!
And it's a VERY BAD idea to use parts below the power rating.
Tubes like the TL, TH, and 4-125/250/400 series don't like low 
voltages, the efficiency falls way off.
Look at the Globe King 500, a 4-250 at 1800 volts, 540 watts 
in for 300 watts out.
Run that tube at 3000 and you could likely get 600 watts out. 

You will also need a very large high voltage modulation transformer,
but if you get it built, you will likely be heard, even without
the antenna hooked up!

About 350 to 375 watts of carrier is the legal limit if
you modulate 100%, and you can do that with a pair of
811's or 812's...

If you get it built, we are going to monitor you closely, and
if you go over 1501 watts pep, you will be in big trouble....

Besides the power and voltage, all push pull triode 
setups are the same. You can take any push pull rf deck
and just scale it up to fit the filament voltage, plate
voltage and current, drive power...


> -----Original Message-----
> From: amradio-bounces at mailman.qth.net 
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of Rick Brashear
> Sent: Tuesday, December 05, 2006 5:08 PM
> To: AMRadio at mailman.qth.net
> Subject: [AMRadio] RF Amp
> I am thinking about putting a couple of 450TL's in push pull 
> for the low 
> bands only. 
>     * Has anyone here had experience with that configuration? 
>     * What would you suggest for a driver?
>     * Do you think a couple of 250TH's would do to modulate it?
> It's just in the thinking stage right now, but I have some pretty big 
> iron I'd like to make use of and at least one 450TL and one 
> extra 250TH.
> Thanks for any advice...
> Rick/K5IZ
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