Sorry, I confused you all and remembered the wrong device. The valves
are E55L Pentodes. (E88CC is a doube triode, sort of ECC88 then they
ran out of numbers! )
The E55L presumably belongs to the EL55 family, 6.3V heaters, power
pentode Octal base - Its all coming back to me now, the only time I
ever used valves was back in teen years in the early 1970s
Circuit is :
Grid2 connected to anode and decoupled to ground.
Input to each Grid1 from antenna connection via a 270 ohms stopper on
each valve.
Grid3 connected direct to cathode, 100 ohms from each valve to common
output point, DC choke to gnd so the 100R acts as both cathode load and
RF stopper / attenuator.
Three of these blocks in parallel. 250V supply, positive grid bias
applied to all 3 valves at comon input point adjustable 0 - 2V.
This was described to me as a sort of cascode circuit but all internal
to the one pentode structure - looks more like normal pentode operation
to me.
FETs are much easier to understand - wonder if a solid state version has
been produced yet ?
Andy
-----Original Message-----
From: Walter Blanchard [mailto:[email protected]]
Sent: 2001-03-12 21:27
To: [email protected]
Subject: LF: Active antennas at LF.
In the 1960's I had an active aerial using an 807 as the
front-end - with
600v on it too!
Later modified to use an E186F instead. Why are they using
double triode
E88CC?
Can't possibly have the slope and overload characteristics of
an E186F.
Walter G3JKV.
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