perhaps the law of diminishing returns?
the amp may be only able to accept a certain drive input before the power 
tubes max out?
not sure why this issue is only happening on 40M, but if you have to reduce 
drive level to 65 watts to get 1K out, i'm not sure what the issue is 
really.
just a characteristic of the amp I would say.
If there was anything going on with the controls, it would be evident on 
other bands as well.
going above the minimum drive level for the power output you want, or the 
max power of the amp will create big distortion.
you'll sound like those good old boys on 27.025
the thing is, even though it's a question, and a bit of a pain to have to 
tweek a bit, if you can get your desired max power output on 40M, with 
minimal drive, then just go with it.  I think a bigger issue would be if you 
couldn't obtain max power output or something like that.
73
Colin, V A6BKX
----- Original Message ----- 
From: "Michael Ryan" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, September 14, 2010 9:06 AM
Subject: HeathKit SB-220 HF Amp tune up strangeness


> Hi all:=20
>
> I use an LDG Electronics TW-1 to manually tune my antennas and HeathKit =
> SB-220 HF Amp.=20
> My tune up procedure varies on 40M then on the rest of the bands. What =
> is actually happening is, my TW-1's pitch, in the continuous tone mode, =
> doesn't max out on 40M. When it does, the results are as follows:=20
> 100 =3D 837 and when I reduce my drive, the power increases.=20
> Its quite common to see 65W =3D 950.=20
> In order to achieve 100 =3D 950 to 1KW, CW, I have to advance my plate =
> and load controls short of Max, according to my TW-1.=20
> What can account for this? Could my plate control be damaged and I'm =
> actually advancing the control too far, possibly out of the 40M range?  =
> I'd like it on par with the rest of the bands, Max pitch =3Dmax power =
> out.=20
>
> 73:=20
>
> Michael DE VO1RYN=20