[Amps] 1:9 un-un for grid driven tetrode

[paul at paulbaldock.com]

A much simpler solution would be to use a 50Ohm resistor, no un-un, and more
drive power. I don't know what the tube(s) is you are trying to drive, but
for example a pair of GU74B's would require about 50W drive in to 50Ohms and
give 2KW PEP out.

- Paul KW7Y


-----Original Message-----
From: Amps <amps-bounces at contesting.com> On Behalf Of jim.thom
jim.thom at telus.net
Sent: Saturday, October 23, 2021 9:43 AM
To: amps at contesting.com
Subject: [Amps] 1:9 un-un for grid driven tetrode

A buddy is trying to get a 1:9 un-un to work on his grid driven tetrode.
Terminated in a  450 ohm globar,  SWR is  1:1   but only up to aprx  20 mhz.
Above  20 mhz,  it rapidly all goes to hell....reaching  2.5:1   at 29.00
mhz.   ( this on the test bench)

He needs the  1:9  un-un to work from  80-10m.   What's the trick here ?
 What  is the ideal material to wind the trifilar onto ?

Once eventually installed into the amp, a small  coil is wired in parallel
with the 450 ohm globar to  cancel out the XC from the tube,  but that is a
normal procedure, and will not alleviate the high swr issue on the upper
bands.

Jim   VE7RF
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