[AMRadio] Home brew AM

Patrick Jankowiak recycler at swbell.net
Mon Oct 4 20:32:27 EDT 2004

I would say that the fidelity was pretty good compared to a 
BC-610, mostly because the audio amplifier was of exceptional 
quality and so lightly loaded.

The power at carrier was pretty low, only about 80 watts, and 
when we were done tweeking, we were getting about a 340 watt PEP 
signal out of it.

Running the power low, with low voltage and current allowed the 
rare tube to stay cool.

As for power, I imagine the BC-610's carrier is much more powerful.

The modulator amplifier is rated at 175 watts and is an Altec 
1570B, using two 811A's in class B push pull with the grids 
driven directly from cathodes of some beam power tubes, the 
schematic of this unit is here:


It has 10 tubes, and operates with 930VDC on the 811A's.

I use two of these amps in my stereo.

best regards,

From: "Brian Carling" <bcarling at cfl.rr.com>
Subject: Re: [AMRadio] Home brew AM

How does that compare to the performance of say the 250TH final
stage in a BC-610?
It sounds like you are running at lower power.
Also how many tubes do you use in the cathode modulator?

On 2 Oct 2004 at 20:12, Patrick Jankowiak wrote:
 >> Cathode mod works very well on a 250TH. We are getting 80-90
 >> watts carrier no problem at 2200V. For the details:
 >> http://www.montagar.com/~patj/cathmod01.htm
 >> Patrick

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