G'day Bill,
I just did a few calcs. We are gonna use the LDG 100AMP tuner in a gs35B amp.
Let's assume it's 100 ohms. We need a cap whose Xc on 3.5MHz = 25 ohms. Xc =
1/2.pi.f.C, So C = 1820pF.
Forgive me mate but that sounds like a bloody big capacitor to have
sitting on the input at 10m.
Even with 50 Ohm tube input impedance, we are looking at 900pF sitting there.
Did I do something wrong or is this all ok?
Thanks and 73,
Alek.
At 02:15 AM 29/08/2010, Fuqua, Bill L wrote:
>You can make it work as long as you shunt the input of the amplifier
>with a capacitor with a reactance of 1/4 or less of the input
>impedance. This will provide the charge storage needed to smooth out
>the sinusoidal wave from and the antenna tuner will still match the
>impedance. I prefer a Q of 10 or better myself but if you chose 1/4
>for 80 meters you will have a Q of 4 on 80 meters and on 10 meters
>it will be 32 with out switching capacitors.
>
>73
>Bill wa4lav
>
>________________________________________
>From: amps-bounces@contesting.com [amps-bounces@contesting.com] On
>Behalf Of jeff millar [jeff@wa1hco.net]
>Sent: Saturday, August 28, 2010 11:31 AM
>To: Amps@contesting.com
>Subject: [Amps] Using automatic tuner for Amp input
>
>What do people think of the amplifier by Bill W4NFR shown in the
>latest QEX? It
>uses an LDG tuner on the amplifier input instead of a set of filter/matching
>networks for each band. It seems like an innovative design.
>
>jeff, wa1hco
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