[TowerTalk] slightly OT - Wattmeter suggestion?

[K8RI on TT]

On 4/21/2011 12:40 PM, Jim Brown wrote:
> On 4/21/2011 9:20 AM, Tom Osborne wrote:
>> Why would you need a peak reading meter for tune up?
> I routinely do initial tuning of the antenna at low power, then turn on
> the amp and carefully tune the amp for maximum output with a series of
> dits. This puts less stress on the and and power supply than keydown,
> and while it works with an averaging meter, a peak reading meter makes
> this easier.  A peak reading meter also makes it easier to tweak the amp
> on the fly as you QSY for S&P during a contest.

I tune both the amp and exciter into a dummy load.
I switch the input of the tuner to my antenna analyzer and adjust for 
R=52, X=0, then switch back to the rig and go on the air.
I can typically run +/- 40 KHz on 40 meters without repeaking/tweaking  
anything.  That's probably less than many would do, but I'm kinda 
picky.  If I wasn't I could probably cover most of the bad without 
retuning. <:-))

> Tuning for max output is especially important with triode output stages,
> because it minimizes distortion (that is, harmonics and splatter).  When
> you hear a broad signal, it's a sign that the lid running it either
> doesn't know how to tune his amp or set his audio levels, or both.

Tetrodes may be tuned a bit differently depending on how hard they are 
being run. Initially it's max out, and then max screen current.  Or to 
make matters simple, just tune for minimum AC power to the amp for a 
given drive.  In any case, follow the manufacturer's instructions.

There are a number of amps out there that are way over rated and most of 
the older amps (prior to the 1500 PEP out rule) are more than a bit 
short on voltage and/or iron in the power supply leading to over driving 
or over working the PS...or tubes as the owner tries to get the 
*current* legal limit out. <:-))

73

Roger (K8RI)


> 73, Jim Brown K9YC
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