[Amps] Alpha Input SWR

[Gary Smith]

Hardy,

I'm also driving an old Alpha but don't 
know how similar our amplifier input 
circuitry is. I too have a K3 with 
internal tuner. I have no aftermarket 
tuner in line and at the antenna end, have 
5 vertical antennas all switched via a 
remote Ameritron RCS-8V.

If I run barefoot, the SWR to the K3 is 
different than if I go through the amp. I 
must first use auto-tune on each band with 
each antenna I switch to. The memory in 
the K3 retains all SWR settings and I 
never have to re-adjust until I once again 
use (or turn off) the amp. This change 
means I have to use auto-tune again but 
after doing this, I'm fine again. Your K3 
should be the same. If I do not use the 
auto-tune after making a change, I will 
get fold-back issues, with terrible output 
and it just isn't graceful.

73,
Gary
KA1J

> My K3 has a real problem driving the 8410. Even with the matching network it 
> has a problem I can't seem to understand.
> The SWR on 12 m is over 3:1.
> Hardy N7RT
> 
> ----- Original Message ----- 
> From: "Peter Voelpel" <dj7ww at t-online.de>
> To: <amps at contesting.com>
> Sent: Friday, January 09, 2015 7:26 PM
> Subject: Re: [Amps] Alpha Input SWR
> 
> 
> > What is bad about SWR <2?
> >
> > 73
> > Peter
> >
> > -----Original Message-----
> > From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Hardy 
> > Landskov
> > Sent: Samstag, 10. Januar 2015 03:09
> > To: Charles Henry; ed at w0yk.com; amps at contesting.com
> > Subject: Re: [Amps] Alpha Input SWR
> >
> > Charly,
> > Changing the length of coax to the input will not change the SWR. Look at 
> > a
> > Smith Chart.  Only dealing with the tube's capacitance along with the 50 
> > ohm
> >
> > resistor to ground with a suitable matching network will lower the input
> > SWR. I wish Alpha and whoever is the designer of amps now would  match the
> > input to every band but they don't. It's not that much more money to do it
> > right.
> > I am going to sell this 8410 because of that reason. What a piece of junk.
> > 73 HNY to all....  Hardy N7RT
> >
> > ----- Original Message ----- 
> > From: "Charles Henry" <k4vud at hotmail.com>
> > To: <ed at w0yk.com>; <amps at contesting.com>
> > Sent: Friday, January 09, 2015 3:15 PM
> > Subject: Re: [Amps] Alpha Input SWR
> >
> >
> >> All I have been able to do is to cut and try the length of the drive coax
> >> from the radio RF output to the amplifier input.
> >> Sri forgot the lengths and never got 1:1 anyway.   Charly
> >>
> >>> From: ed at w0yk.com
> >>> To: amps at contesting.com
> >>> Date: Fri, 9 Jan 2015 08:44:18 -0800
> >>> Subject: [Amps] Alpha Input SWR
> >>>
> >>> What experience can anyone share for reducing the input SWR on Alpha
> >>> amps?
> >>> On some bands the input SWR is 1.6:1 or higher on our 86A, 87A and 91B
> >>> amps.
> >>>
> >>> Thanks,
> >>> Ed W0YK
> >>>
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