Bill Orr recommends around 13 pf per meter for the input capacitor. At 160
meters that would be 2080 pf.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Alek Petkovic
> Sent: Sunday, August 29, 2010 8:07 AM
> To: Fuqua, Bill L; jeff millar; Amps@contesting.com
> Subject: Re: [Amps] Using automatic tuner for Amp input
>
> 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
> > >_______________________________________________
> > >Amps mailing list
> > >Amps@contesting.com
> > >http://lists.contesting.com/mailman/listinfo/amps
> > >_______________________________________________
> > >Amps mailing list
> > >Amps@contesting.com
> > >http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> >http://www.qrz.com/db/vk6apk
> >http://www.qrz.com/db/vk6ap
> >
> >
> >_______________________________________________
> >Amps mailing list
> >Amps@contesting.com
> >http://lists.contesting.com/mailman/listinfo/amps
>
>
> http://www.qrz.com/db/vk6apk
> http://www.qrz.com/db/vk6ap
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|