[AMPS] Amp Tuning (was 3-500Z Grid Current Rating)

[Pete Smith]

At 03:12 PM 5/4/1999 -0400, Dick Green wrote:
>
>> I've found with my Henry that using the old "dip and load" technique
>always
>> leads to the best operating condx
>
>snip...
>
>> With modern gear there sometimes is a tendency to simply tune for max
>output without paying
>> close attention to the grid/plate.
>
>snip...
>
>Thanks, Dave. I'm glad somebody finally said this. I've seen a lot of posts
>here about tuning for max output, and I've never been able to reconcile that
>approach with the old "dip and load" technique I learned with my first tube
>transmitters back 15-16 years ago.
>
>These days, I use a hybrid approach with my SB-220. I have an external power
>meter positioned on top of the amp case, very close to the fixed Ip meter
>and multimeter, and I set the multimeter to Ig. That way, I can see power
>output, Ip and Ig at the same time. After setting the drive level, I dip the
>plate (making sure output peaks as well), advance the load control for max
>output, and repeat until there is no further increase in output. While doing
>all this, I keep one eye on Ig to make sure it stays within safe limits,
>reducing drive and retuning when Ig is too high. After this, when operating
>SSB, I try to remember to advance the load control slightly for improved
>linearity, dropping output maybe 5% (recommended by KM1H.)

IMO, this is definitely the way to do it.  The only caution I would add is
that grid current can soar pretty high when running full drive with loading
that is still short of optimum.  That tends to argue for running reduced
drive when first tuning, to be nice to the tubes.  You will have to repeak
when applying full drive, though.

On my SB-220, I've found that presets (cardboard behind the knobs, with
settings marked) work fine without retuning on 80-40, and usually on 20.
On 15 and 10, some tweaking is indicated because the tuning is much fussier
there. 


73,  Pete N4ZR
Loud is good


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