[Amps] Autotuner for Amp Input

[Gary Schafer]

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 at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Jim Barber
> Sent: Thursday, October 07, 2010 1:23 PM
> Cc: amps at 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 at 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
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