[AMRadio] AM amp from 807's

[Brian Carling]

On 17 Jan 2002, at 12:40, Bruce - KB6LWN wrote:

> 
> I realize the maxfreq of the 807 is 60 Mc, but perhaps
> with some good layout planning and some finnageling of
> lead/component dressing, and maybe some extensive tube
> and stage shielding and cooling (ala tin can chimneys)
> it can be op'd on 50.4 Mc without too many parasitics.
> Plus, I've read that if the plate/screen potentials are
> reduced to 90-95% of max, the max operating freq goes
> up just a little bit.
> 
> So...  Basically, I figure we're looking at tuned input
> and output circuits, the proper matching of these stages
> to the set (2 or 4) of 807's (or 1625's), some filter
> stages to clean things up a bit, and a PS (700vdc plate,
> 300 vdc screen, both variable), and some metering, for
> an amp that I should be able to sit beside the HT-40
> on the desktop, and would provide somewhere in the area
> of a fairly clean 200-300 watts.  Anyone concurr ?

Hi Bruce - Interesting proposal. If it were me, I think I would try to get some 6146es 
instead of 807s. They will be a lot easier to control. There are a number of designs oput 
there for amplifiers using this tube. Four would get you about 300 watts input on
6m, but if you want to use them in AM  you would need to run about 75 watts
input for 300 watts p.e.p. - that would get you about 50 watts of RF out.
Still not much but plenty for the magic band. We have a great net here in central FL on 
50.4 MHz and I quite often check in to it.

There are other nice choices for inexpensive tubes you will find under tables at 
hamfests, that will work better than 807s at VHF. Your mileage may vary. I will be 
interested to see other responses here. You might also do well to run your idea past the 
larger group on the Glowbugs E-list.

I see you are in the Shreveport area. I am planning to come there soon on business. Any 
chance of an eyeball QSO?

73 - Brian, AF4K