The SB-220 has a decent spaced load cap, either version. Ive run up to
5:1 many times with no arcing using a CW cut 80M dipole on 75 or the
same antenna on 17 and 12M. When the bands are wide open the cable loss
doesnt mean much. It requires tuning up carefully at about half power in
the CW position. Then increase drive, retouch the controls and then
switch to SSB and dont touch anything.
SWR is overblown IMO on HF.
Carl
KM1H
----- Original Message -----
From: "Steve Katz" <stevek@jmr.com>
To: <amps@hidden-valley.com>; <amps@contesting.com>
Sent: Monday, March 02, 2009 5:33 PM
Subject: Re: [Amps] SB-220 and load mismatching...
>I don't see how you could hurt the tubes operating into a mismatch. If
>you hurt anything, it's more likely to be the load capacitor.
>
> I used to operate the SB-220 into a 4:1 VSWR or so on 80m quite often,
> since that's the normal band-edge mismatch for a midband tuned 1/2WL
> dipole on that band! Never had a problem, never even arched the
> capacitor but that was a concern.
>
> WB2WIK/6
>
> -----Original Message-----
> From: amps-bounces@contesting.com
> [mailto:amps-bounces@contesting.com]On
> Behalf Of Jeff Carter
> Sent: Monday, March 02, 2009 2:27 PM
> To: amps@contesting.com
> Subject: [Amps] SB-220 and load mismatching...
>
>
> Hi all,
>
> It has recently come to my attention that folks are running amps into
> unmatched loads. Nobody seems to be worried about VSWR very much.
>
> I've got a SB-220 that I've never run into anything but a 1:1 match.
> If I understood correctly back during college, if I'm running 500W out
> into even a 2:1 that means I've got something like 50W on the line
> coming back at me, yes? I'm using RG-8, and the line loss is
> negligible for the length and frequency involved.
>
> My question is, how forgiving is the SB-220 of VSWR mismatches? What
> is the maximum mismatch that you personally have run or seen run with
> this amplifier? The reason I'm asking is that I've got a 80m dipole
> that presents high SWR on other bands (of course) but if the SB-220
> will let me get away with it, I'd like to try it.
>
> What I *don't* want to do is screw up these brand new tubes.
>
> Thanks,
>
> Jeff/KD4RBG
> _______________________________________________
> 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
|