Date: Wed, 9 Jun 2010 10:14:09 -0400
From: "Carl" <km1h@jeremy.mv.com>
Subject: Re: [Amps] Peter Dahl / Harbach SB-220 transformer
Directly grounding the grids increases the stage gain which may lead to
instability on the highest bands.
## It works good on 80-40- 20-17-15-12-10m. Heck, it even works very good
on SB-220's... that have been modified for 6m. [those are ones you modified for
6m]
This also adds more stress to the bandswitch.
## why would it stress the band switch more ? grnding the grids just means
20-25w
less drive required... or conversely... with the same drive... = way more power
out.
Adding another 100-150W wont sound any louder at the other end.
## It's WAY more than that. Besides.. with the grids directly grnded... you
can stuff 4-400-A/B/C's into it.
later... Jim VE7RF
Carl
KM1H
----- Original Message -----
From: "Pete Smith" <n4zr@contesting.com>
To: <amps@contesting.com>
Sent: Wednesday, June 09, 2010 6:24 AM
Subject: Re: [Amps] Peter Dahl / Harbach SB-220 transformer
> Strikes me as the only good way to get more out of an SB-220 - avoids
> stress on the bandswitch and tune cap due to higher voltage. I wonder
> if anyone has ever combined this with directly-grounded grids, which
> W8JI and others advocate for increased power gain.
>
> With the original grid circuitry, my SB-220 gets just about 1.2 KW out
> on 80 and 40, decreasing to about 900 watts on 10, all with 100 watts of
> drive.
>
> 73, Pete N4ZR
>
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