Date: Wed, 13 Oct 2010 07:18:21 -0700
From: "Jim W7RY" <w7ry@inbox.com>
Subject: Re: [Amps] TUNER
EXCEPT when you get to the higher bands. (10 and 15. And sometimes 20). You
need a way to cancel out the reactance. At least you do on a pair of 4CX800
Russian tetrodes.
73
Jim W7RY
### agreed. Alpha achieves that by switching in a tiny bit of uh in
parallel with the grid to chassis resistor.
## On these 8170/8171 tetrodes, they use a small roller inductor in parallel
with the 450 ohm resistor. That
cancels out the XC from the C between control grid and cathode.
If you don't do this,,, you will have SWR on the input, between xcvr and input
of amp.
Jim VE7RF
--------------------------------------------------
From: "Jim Thomson" <jim.thom@telus.net>
Sent: Tuesday, October 12, 2010 11:19 PM
To: <amps@contesting.com>
Subject: [Amps] TUNER
> Date: Tue, 12 Oct 2010 18:04:53 -0400
> From: "Roger (K8RI)" <sub1@rogerhalstead.com>
> Subject: Re: [Amps] TUNER
>
>
> I wonder how one of these tuners, or input boards would work with a
> passive grid input on a Tetrode.
>
> 73
>
> Roger (K8RI)
>
> ## what for ? The xcvr 'see's flat swr anyway. You either have a 50
> ohm passive grid R
> or a 200 ohm resistor.....and a 4:1 un-un. On the big boy tubes
> [handles] they use a 450 ohm
> resistor and a 9:1 un-un. In all cases the xcvr is happy, and no tuner
> required.
>
> Jim VE7RF
>
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