Bill Orr recommends around 13pf per meter for the capacitance at the cathode
of a GG amplifier.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Jim Barber
> Sent: Thursday, October 07, 2010 1:23 PM
> Cc: amps@contesting.com
> Subject: Re: [Amps] Autotuner for Amp Input
>
> This has no doubt been covered here before, but is there a "shotgun"
> equation or rule of thumb for this? (minimum Q for adequate flywheel
> effect)
>
> In the past I've started with a pi input network with a Q of 4, (based
> on an approximation of the tube operating parameters) but primarily
> because that's about the highest I could use and get reasonable input
> VSWR bandwidth on amateur bands. I'd like to accomodate "flywheel
> effect", but haven't been able to find any reference so far beyond
> cut-and-try.
>
> I can see where using an autotuner (L network) would be a crapshoot,
> since Q isn't part of the matching criteria and (generally speaking) the
> algorithms basically cycle through the relay combos until a match is
> found.
>
> So... With regard to my current YC156 project, I could summarize by
> asking if with an assumed input impedance of around 25 ohms, (mostly
> resistive) would a pi-net with a Q of 4 be an adequate flywheel?
>
> BTW & OT:
> I ended up ordering (2) guaranteed YC156 pulls from Tom, WA8WZG. Thanks
> to all that offered the suggestion(s).
>
> Thanks,
> Jim N7CXI
>
>
> On 10/7/2010 10:55 AM, Bill, W6WRT wrote:
> > ORIGINAL MESSAGE:
> >
> > On Thu, 7 Oct 2010 07:40:50 -0700 (PDT), Lee Buller<k0wa@swbell.net>
> > wrote:
> >
> >>
> >> Have any of you used the method? Seems to have worked for the author
> of the
> >> article in the Handbook.
> >
> > REPLY:
> >
> > The LDG autotuner does provide a good impedance match, but the only
> > question is whether it provides sufficient Q to provide the "flywheel"
> > effect needed for SSB operation. If you are going to be operating only
> > CW, RTTY or FM, whatever Q it has is probably enough.
> >
> > I wish I had a more definitive answer.
> >
> > 73, Bill W6WRT
> > _______________________________________________
> > 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
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|