[AMRadio] Home Brew

Brett gazdzinski Brett.gazdzinski at mci.com
Tue Sep 28 20:13:39 EDT 2004

Mostly depends on what you can get your hands on.
These days, you have to design around what you can get at a reasonable

As far as tubes go, one or a pair of 813's works VERY well in the RF deck,
Pair of 811a or 812a tubes will also do nicely.
A 4-125 will work well at 2500 volts.

High voltage gets expensive, and the 811/812 tubes work from
1000 volts up to 2000.
813 likes 2000 but works lower.
The 4-125, 4-250, and 4-400 tubes like higher voltages.

A rice box makes a good RF exciter, and will drive 813's, 812a's, 4-125, etc
no problem.

For a modulator, KT90 tubes, 811a's, 813,s, 4-xxx will work,
The zero bias triodes are easy, no bias, drive the grids with
an 8 ohm to 6000 ohm output transformer using some solid state audio amp.

Choices are driven by what mod iron you can find, power transformers,
chokes, etc.

I have a homebrew pair of 813's in pie net 160 to 10 meters
Driven by a 4x150 (4cx250b) AB1 mod deck, I have a
Push pull pair of 812a's modulated by 811a's, and a pair
Of 4D32 tubes in pie net 40 meters only.

The old Bill Orr books have lots of good building stuff in them.


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of StephenTetorka at cs.com
Sent: Tuesday, September 28, 2004 3:50 PM
To: amradio at mailman.qth.net
Subject: [AMRadio] Home Brew

Hello All:

I'd like to build my own AM transmitter.
Tube style; more than 200 watts.

Sure a heck of a lot to choose from...but I'd like to hear what you think.

OR...if someone knows of a home brew for sale....

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