>I'm planning to use these two tubes in a homebrew GG 80-10 mtr amplifier.
>I've collected about all the parts, now I just need
>get started.
>Another question. I built a 20 mtr monoband GG YU-158 and connected
>the filament to the cathode via 1000pF 3KV capacitors with a B&W
>FC-15 in series with the fils.
The heater should be connected to the cathode to prevent a potentially
fatal cathode-heater arc during a glitch. When this precaution is taken,
a bifilar filament-choke is needed to keep driving RF out of the 5V
transformer. Also, neither side of the heater transformer should be
grounded, and a glitch diode needs to be connected from the neg-hv to
chassis gnd.
>I was planning to do this capacitive coupling
>on the two tuber, but according to the ARRL HBK, this is not
>good practice.
Why not? I would couple with two capacitors, one to each cathode, plus
c. a 10-ohm film R in series with each cathode. [the resistors would
de-Q the vhf resonant circuit set up between the two tubes, dc balance
the cathode-currents, and create RF-NFB]
>I don't particuarly trust everything said in the ARRL
>HBK, however. What do you think?...
I think we ought to do our own thinking wherever possible. The ARRL gets
some things right and some things they get right later. Getting things
right took way less time when George Grammer, W1DF was Tech Editor of
*QST*. The current crop of *QST* powers-that-be have a relationship
with business that invites comparison with the current George and Dick
show in Washington, D.C.
Editorial Opinion: Except for 2m moonbounce, two 8877s is not a cost
effective way to get more suds. Compared to 2, 8877s, a single 8171 will
make up to 4x more suds for less money. Also, the 8171 is not as
delicate since there is no gold plating to worry about boiling-off. //
My Web site has info on tetrode design.
cheers
>>From: Richard <2@mail.vcnet.com>
>>To: "Ed McKie" <kb5gt@hotmail.com>, " AMPS" <amps@contesting.com>
>>Subject: Re: [Amps] Defective 8877's ?
To: <amps@contesting.com>
>>Date: Fri, 12 Jul 2002 03:41:00 -0700
>>
>>According to Dick Ehrhorn, the problem with the 8877's heat dam material
>>existed for a short period. I would try them before I rejected them.
>>What brand of amplifier?
>>
>> >
>> >I have two 8877's in unopened boxes with 1990 code dates. I've read and
>> >heard that these tubes made at that time were subject to some type of
>> >manufacturing problem. Are these tubes OK, or should I get some others
>>with
>> >later code dates?
>> >Thanks,
>> >Ed, KB5GT
>>
>>
>>- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
>>www.vcnet.com/measures.
>>end
>
>
>
>
>_________________________________________________________________
>Chat with friends online, try MSN Messenger: http://messenger.msn.com
>
>
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
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