[Amps] PASSIVE NEWORK CATHODE INPUT

[Jim Thomson]

Date: Wed, 19 Sep 2018 02:03:09 +0200
From: "Peter Voelpel" <dj7ww at t-online.de>
To: <amps at contesting.com>
Subject: Re: [Amps] PASSIVE NEWORK CATHODE INPUT

<Of course it works on the GS35b and also flawless on Henrys 8K ultra.

<With 3KV on the GS35 anode gain is slightly more then 11dB.

 

<73

<Peter 

###  The passive input on the henry 8 k ultra is a dogs breakfast at the best of times. 
The 3CX-3000A7 is already 50 ohms.   So what are they trying to match ?   You also
have  38 pf  between the grid and the cathode..which is directly in parallel with  the drive.
Put a 38 pf cap across  a T connector at the input of a dummy load and see what  happens. ,
esp on the upper  20-10..and also 6m bands. 

##  They cut one too many  corners on the 8 K ultra.   The cold sides of the relays they used
to pad both tune and  load would burn up.  Blower used is the wrong unit.   You always end up
with some swr on the input of the 8K  ultra.   Then they tell you not to use the auto tuner in the xcvr..
as it will try and  track..and fails.  There are several other issues with the 8 k ultra.   The entire  B+  supply
is right out of a 1954 hand book.
The suppressor /  plate choke setup was another dogs breakfast... that finally got sorted out on the
very last production units made. 

##  JA6TAY  got the  relay switched  PI nets down to a fine art on his latest production  runs of his now
available  commercially made   3x3  160-10m amp.  

##  You want some flywheel action  with a tuned input..and a passive input  wont provide that. 
With any   PI  tuned input, that   38 pf of grid to cathode C is simply absorbed into the  C2 cap  on
the pi tuned input....ditto with any other  GG  triode. 

Later.... Jim   VE7RF