Recently I sent a message to this reflector asking for mods on the Drake
L-4B. I got a couple of responses. One from Carl KM1H, and one from Jeff
KQ4HC. Thank you gentelmen for your thoughtfull responses.
At the same time I mentioned that I had owned an Alpha77Dx , and that I had
run it with both 1 and 2 8877s in it, and that I current own an 87A. I
mentioned that I would be glad to share my oppinions on these amps with
interested persons.
I have had a significant ammount of interest expressed in my views on
the Alphas. Although I had originally intended to spare readers of the
reflector my personal views, The number of requests for information
warrants a mass reply.
My observations, which includes some responses to specific questions, are
as follows;
1. I bought the 77Dx with one tube, and a kit necessary to install a
second, from Don Payne. He used to advertise in QST with the slogan "If you
want the finest" The amp was $5300. The kit to convert was another $450 w/o
a second tube
2.The amp preformed beautifully. I immediatly enabled it for use on 10
meters.
It tuned smoothly and easily, was not critical of adjustment, and never
arced over once, even with some bad tuning,and some poor ant matches.
3. The amp would put out 1500 watts easily, and 2500 watts, cw key down
equally easily as measured by a Bird 43 watt meter with a 5000H slug.
Neither output level required 100 watts drive.
4. If you have seen an 77Dx you know the construction is first class. They
are built like a battleship, thats all there is to it.
5. Value is another question. The amp was worth every penny to me, but one
can obtain a very good , manually tuned, legal limit amp, that will outlive
us all for considerably less.
6. I live in S.L.C. Utah, Eimac has a manufacturing facility here, Getting
a second 8877 was easy. Because I wanted at the time, the extra power
capability, I put the kit and the second tube in. (relativly easy,I have
step by step instructions}
7.Again , the amp preformed beautifully from the beginning. Plate current
was double what the meter showed. (the meter only reads one tube) You have
heard that a 2 tuber will do 5000w out. My experience 3000w key down rf
out,with about 75 watts drive, approaching 5000 watts out on peaks
sideband, regardless of the drive. One must remenber that the power
transformer in a 77Dx is rated at 4.4KVA. At 66 percent conversion rate of
available power, 3000 watts out key down, is just a little better than what
one would expect. The Dynamic range of the power supply allows higher peaks
in sideband service. but not key down.
8.Im a cw man. I dont get very excited about the difference between peak
and average power. I will not discuss the decibel here. I will say that
running high power at the levels the two tube version is capable of makes a
noticeable difference.
9.I never had a tube problem in the 1st 100 hours of opperation. After than
I developed a grid to filament short in the 8877 supplied by Alpha. I
popped in a gold plated es tube from Eimac, and no problem, back in
business. I have had good luck with the 8877s. Ive run them in 3 different
amps including one on 2 meters. They are rugged, they dont focus as well as
a 3CX800A7 as used in my 87A, but the 8877 will focus well enough.
10.Conclusions, The Alpha 77Dx is a beautiful, rugged , sweet amplifier to
own and operate. If I had it to do again, I would not convert it to two
tubes. I would rather have a taller tower, and full size antenna. This
leads to the story on the 87A which I will post in a few days.
Thanks again for the responses, and interest shown. 73s
Dave, K7SX
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