Palomar 90A

[n8yoh]

I am looking for someone that knows how (or if it is worthwhile) to modify this amp to work on 80 meters.  It works well on 40-10 but it seems that the bulk of a.m. traffic is on 3.880-3.885.  I have been looking for a good b.a. but every time I find one on e-bay, they go for crazy $. 

N8YOH
flash1van@hotmail.com

Gordon Sage

[N3DRB The Derb]

probably not. If the tube r TV sweep tubes you'll cook them in short order.

[WQ9E]

Gordon,

As Derb stated not worth it for AM as it uses a couple of sweep tubes and a fairly minimal power supply so it isn't going to offer much help on 75 AM.  Given what I have seen at hamfests, these amps seem popular with the CB types so you might be able to convert it into cash towards something worthwhile.  If you stay within its power capabilities, the Heath SB-200/201 series are probably the best "bang for the buck" amplifiers to own and operate and can be found in the sub $300 range at most hamfests.  These amps will be able to provide around 150 watts carrier output with traditional "full carrier" AM (as long as you don't go for an Old Buzzard award) and will work even better with controlled carrier AM as produced by the Drake 4 line, DX-60, etc.

Rodger WQ9E

[Opcom]

for AM.. yes if you don't cook the power supply, take the total CCS plate dissipation, divde by2, and that's about all you are going to get from it carrier wise.

If you want to use the amp long term, you might do better to put in 6550's or 6CA7's, or 829's if any will fit. At least you can get them, they have good dissipation, and they will work OK on 80M. The cheap $12 6CA7's from Russia work pretty well and are skinny. I have re-done a couple small "10M" mobile linears to use 6146's. I collect them (mobile tube linears), so when the sweep tubes are not handy, I usually convert. I don't mind less power, I like things in my collection to be functional even if I do not use them.

I see several outrageous claims of power for that amp - 400 watts! What tubes and how many does it use?

[N3DRB The Derb]

your plate iron and your power dissipation of your tubes determine how much carrier power you can get out of a given amp.