[AMRadio] New Transmitter


Mike Sawyer w3slk at uplink.net
Mon Nov 27 10:46:04 EST 2006


Jack,
    Did you mean 572's or 872's? 572's are triodes and 872's are mercury 
rectifiers. I suspect you meant 572's. The 572 are ok but I'm here to tell 
you that the 813 is a damn near indestructible tube! I have seen plenty of 
572's that have crapped out from abuse of some sort or another. But I have 
yet to see an 813 that has crapped out. Take it from me, they are a very 
hearty tube and you can get them cheaper than the 572's.
Mod-U-Lator,
Mike(y)
W3SLK
----- Original Message ----- 
From: "Jack Schmidling" <jack at schmidling.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Monday, November 27, 2006 10:35 AM
Subject: Re: [AMRadio] New Transmitter


Jim Wilhite wrote:
> In my 1964 handbook there is a One-Band Kilowarr Amplifier that uses a
> pair of 813s.  It is grid input and would be easy to modulate using 811s
> or 572Bs.

That brings up something that is confusing to me.  I have been reviewing
specs to get familiar with the more popular tubes out there as they were
just numbers to drool over back when I was homebrewing.  I never got
beyond 807's.

Anyway, I looked into 872's because that is what is in my SB200 and was
surprised to find that the plate dissipation is considerably higher than
an 813.

So, why would one not modulate 872's with 813's?

I guess I should forget about the higher voltages.  Too many senior
moments these days.

js

p.s.  The D104 works great with the new Mouser cartridge.

-- 
PHOTO OF THE WEEK: http://schmidling.com/pow.htm
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