[AMPS] Henry 8K at 1500 watts Out -- Warning Long

[Radiodan W7RF]

Ian, you wrote

"On the other hand, to get closer to optimum IMD you'd need to tune and
load for maximum output at the highest drive level, then increase the
loading (which usually improves IMD but notably does not give the
maximum possible output or efficiency) and then reduce the drive without
touching anything else."

I normally load "heavy" to reduce grid current after full output tune. Power
out suffers only 25-50 watts.
This must be where the improved IMD comes from.

73, Dan Magro W7RF, (member SCDXC, SCCC)
Manufacturers Rep & distributor for HENRY Amplifiers.
www.radiodan.com <http://www.radiodan.com>     RFpower@radiodan.com
<mailto:RFpower@radiodan.com> A trip to our web site is worth the click!




> -----Original Message-----
> From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
> Behalf Of Ian White, G3SEK
> Sent: Tuesday, December 08, 1998 11:58 PM
> To: amps@contesting.com
> Subject: Re: [AMPS] Henry 8K at 1500 watts Out -- Warning Long
>
>
>
> Radiodan W7RF wrote:
>
> >Ian,
> >
> >You wrote,
> >>
> >> Therefore if you tune up at full power and then reduce the
> drive without
> >> touching the output network again, you're simply driving the operating
> >> point a smaller distance along the *same* load line. The load line
> >> itself doesn't move, so I don't think the loaded Q of the
> output network
> >> changes with drive level either.
> >
> >I always notice a difference in tuning for for a given maximum at any
> >particular level.
> >Normally, when I tune my 3K Premier with 10-20 watts drive for
> maximum power
> >at this level, inevitably there will be a slight retune needed
> at full 100
> >watts drive.
> >Looking at your last statement, what's different? Is it the small plate
> >voltage drop causing a different plate load impedance at the full drive
> >level that makes for the change in tuning?
>
> When you tune-up the PA for maximum RF output, you're presenting the
> tube with a load line that optimizes the efficiency. When you change the
> drive level and re-tune for max, you're RE-optimizing it. Maximum
> efficiency at the new drive level will require a different load line, so
> you'd expect to need to re-tune a little.
>
> The normal procedure is to tune up at low drive first, and then increase
> the drive, because that obviously involves less stress on the PA - the
> tuning and loading are already close to the correct settings before you
> apply full power.
>
> On the other hand, to get closer to optimum IMD you'd need to tune and
> load for maximum output at the highest drive level, then increase the
> loading (which usually improves IMD but notably does not give the
> maximum possible output or efficiency) and then reduce the drive without
> touching anything else.
>
> 73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
>                           'In Practice' columnist for RadCom (RSGB)
>                            http://www.ifwtech.demon.co.uk/g3sek
>
> --
> FAQ on WWW:               http://www.contesting.com/ampfaq.html
> Submissions:              amps@contesting.com
> Administrative requests:  amps-REQUEST@contesting.com
> Problems:                 owner-amps@contesting.com
> Search:                   http://www.contesting.com/km9p/search.htm
>
>


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm