I forgot to add. This amp is a 160 - 10m job so we're really gonna
have some big Farads sittin' there, aren't we?
73, Alek.
At 09:04 PM 29/08/2010, Alek Petkovic wrote:
>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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>
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