[AMRadio] Home brew AM


Brett gazdzinski Brett.gazdzinski at mci.com
Thu Sep 30 12:03:10 EDT 2004


That would be hard, but not impossible.
You would need to read up on mod transformer construction,
find something to use as a core, and wind loads of wire on it,
keeping in mind the very high voltages that it would have to withstand.

You can buy mod transformers, peter dahl makes new ones, ebay, etc.
Old surplus is best, old military rigs, broadcast rigs, old ham
rigs...

I am using mod transformers that were built by RCA in the 1940's
for some sort of ship board radio for the Dutch navy I have been told.

Without any mod iron, you would have to go to some sort of
screen modulation with large tubes.

Brett
N2DTS


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of GGLL
Sent: Wednesday, September 29, 2004 7:55 PM
To: Discussion of AM Radio
Subject: Re: [AMRadio] Home brew AM


Hello people, I agree with the nice look and smell of "glass" AM. Few years 
ago, I made my CW/AM transmitter, with an 807 plate/screen modulated, 50
watts 
CW, 40 watts AM output. Started with a triode/pentode  oscillator/doubler
VFO, 
then converted to solid state oscillator/buffer, followed by a tube driver 
(6BQ5) and finally the 807 to a pi tank output.
Making my own plate modulated transmitter (200..300 watts out) is a buzzing 
idea in my mind since a couple of months. But here the most difficult item
to 
get is the modulation transformer, does someone know a method to build it by

myself?.

Many thanks in advance
Best regards
Guillermo - LU8EYW.

Brett gazdzinski escribió:
> Steve,
> What do you need, everything?
> 
> Here's a partial list of what you need:
> 
> 3 Chassis 17x3x14,
> 3 panels 19x10.25?,
> 3 sets of side supports,
> Power transformer to give 1500 volts at 500 plus ma,
> Choke at 500 plus ma, two is better, swinging for the modulator,
> Rectifiers (I like the k2aw? bricks),
> Modulation transformer,
> Bleeder resistors,
> Big relay and time delay relay for step start if you go that route,
> 4 Tube sockets,
> Filament transformers,
> Killowatt plug in tank coils and its socket and swinging link,
> Push pull grid coils for the bands wanted,
> Push pull grid tuning cap (150 to 200 pf per section, low voltage)
> Modulator grid drive transformer 8 to 10,000 ohms roughly at 20 or more
> watts,
> 2 Neutralizing caps,
> 4 811a tubes,
> Grid leak resistor (big wire wound pot works well),
> Insulated shaft couplings,
> Plate tuning cap, dual 100 pf 5000 volts or better,
> Meters for grid current, mod current, plate voltage, plate current,
> 
> A large pile of wire, high voltage wire, screws, nuts, knobs, connector
> strips, line cord, switches, lights, panel bushings,fuse and holder or
> breaker, 
> spacers, ceramic standoffs, rf connectors, etc.
> 
> I could give you some stuff, and sell you some stuff most likely, and
> MIGHT be able to get you a mod transformer.
> 
> Brett
> N2DTS
> 
>  
> 
> -----Original Message-----
> From: amradio-bounces at mailman.qth.net
> [mailto:amradio-bounces at mailman.qth.net] On Behalf Of
StephenTetorka at cs.com
> Sent: Wednesday, September 29, 2004 9:52 AM
> To: amradio at mailman.qth.net
> Subject: [AMRadio] Home brew AM
> 
> 
> Thanks for the replies.
> 
> The 812/811 combo was sorta what I had in mind.
> 
> Getting the components shouldn't be too hard if I keep searching.
> 
> Let me start here...anyone have any suitable parts?
> 
> About the E class...read a few things about it...sounds most
> interesting...but MOSFETS don't have the fragrance of warm vacuum tubes on
a
> chilly winters evening nor the soft orange glow cast through the rig
> perforations onto the shack walls to keep one company...nor the humming
> vibrations of pumped RF being piped to the outside antenna.
> 
> 73
> Steve WA2TAK
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