Jim the Alpha 76 is the most popular and most straightforward rig of the old
Alphas.
It runs three (in some cases two) 8874 tubes. It is easily converted to run
a pair of 3CX800's. The only problem here is the cost of the 800's.
The rig has a open-frame T/R relay and covers 160 through 10 meters with the
exception of 12 meters. Plate choke resonance is a problem here and many
operators burn their plate choke at the top and bottom trying to make it
work on 12 meters. The fix for that is fairly inexpensive and involves
switching the RF choke in a similar fashion to the newer Alpha rigs. I
re-wind the plate choke to its original specs except a tap-point is
fashioned about one-third the way up from the cold end. A cam is mounted on
the bandswitch indexer to trigger a micro-switch which energizes a small
open frame relay located near the choke. A capacitor shorts out the lower
third of the choke on the high bands and the rigs works on 12 meters. I
don't have field kits available.
Kits will be available soon for the 3CX800 upgrade...I want to see a few
more working first.
A more deluxe version of the 76 is called the 78. It features a vacuum T/R
relay for QSK, preset band segments on four bands, and a light-weight
Hypersil transformer.
The 374A is the same story except two tubes. A couple of minor differences
also.
I haven't converted a 78 or 374A for 3XC800 service yet but it appears to be
do-able.
The Alpha 77 is the mother of all desktop kilowatts. Most were shipped with
only one tube and I sell kits and instructions regularly to add the second
bottle.
You can run RTTY all day at the legal limit with this one but it's not very
portable.
73, Dick
>Return-Path: jhenders@tdrss.wsc.nasa.gov
>X-Sender: jhenders@zianet.com
To: <amps@contesting.com>
>Date: Tue, 11 Mar 1997 05:42:10 +0000
>To: n4uq@mindspring.com
>From: Jim Henderson <jhenders@tdrss.wsc.nasa.gov>
>Subject: amp conversions
>
>Hi Dick:
>
> I read the Alpha 374/76 note on the amp reflector, not exactly sure
>if it originated with you or Dan. But I would like to know a bit about the
>old amps, as I cant find the reviews in the old mags.
>
> I have a venerable L-4B, but it wont do 160. Was thinking of picking
>up an old Alpha, but cant find out much; except the 8874s are expensive/hard
>to find. I see there is work afoot to convert them to newer tubes. Could you
>point me in the right area to find out about the original amps as well as
>the possible conversions? I see they revolve around the 3CX800, but the note
>mentioned problems with these as well. How about the Svetlana?
>
> Any info surely appreciated.
>
>73 de Jim, KF7E
>ex:5X1XX, 7Q7JH, ZM7AH, ad nauseum
>
>
>Jim Henderson
>jhenders@tdrss.wsc.nasa.gov
>jhenders@zianet.com
>
>
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