>At 03:37 PM 2/21/99 -0800, Arne Gjerning wrote:
>>Is this an EIMAC tube or RCA? Can not find this nubmber in EIMAC catalogs
>>I have. Does it have descriptive number or EIA 4 digit number?
>It's an Eimac
>It's a cross between the 3CPX5000A7 and the 3CX15000A7. It's specs in most
>regards are the same as the 5000. But its current curves ressemble the 15000.
>As Terry(W6RU) has already stated it's a pretty easy tube to build around.
>Medical Pulls are fairly cheap. N8RGR is the man to talk to if you want to
>obtain an example.
>The draw backs of this tube. The filament is of the Oxide Coated
>Unipotential type. 15 Volts at 14 amps with a 6 Minute warmup time and no
>one rebuilds them. Secondly they have a fairly high output capacitance
>(36pf) So even though they have a max freq spec of 110Mhz your not going to
>match them up with a pi-network on 10 Meters.
? At QRP levels, this is undoubtedly true because RL would be abnormally
high. Increase the anode current to normal, RL drops to a reasonable
level, and a match is easy. One of the greater old-wives' tales of
amateur radio is that adding another tube doubles C-out which renders
the amplifier unusuable on 10m. However, when a second tube is added,
RL is cut in half, and that doubles the C needed for C-tune. Thus, it is
not the anode-C / Cout which causes a match prob. on 10m, it is the ratio
of Cout to RL.
>The complete specs for this tube are up on an FTP site setup by G8WRB.
? Got a url?
>design of the tube is fairly old itself. 1968 is the date on the data sheet.
? ... sounds to me like an enlarged 8877 design.
- later, Bob
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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