Jim Reid wrote:
>I use an Alpha-Delta-4 switch with which I select between
>my Ten Tecs and Yaesu transceivers, and previously the
>950SDX
Well, if the Alpha-Delta has 40 dB of isolation then:
100 Watts = 50 dBm
This means that 10 dBm still gets to the Yaesu front end. 10 dBm is 10
mW. Enough to blow it up? I doubt it but who knows.
> As I understand, you are to tune up using
>pretty high power, then back the drive back such that
>you actually will output only 1500 watts peak on SSB;
>this method is supposed to get you max linearity and
>lowest IMD products. So I have been tuning up at
>around 3kW into the Bird load.
Actually, I don't think this is really the appropriate way to do it. You
should really tune up at your operating power. Perhaps I'll start flames
coming at me or a debate, but I would think an amp is optimized for a
particular output power when you tune up AT THAT POWER level. The tune
and load settings for 1500 Watts are different from those of 3KW. So you
are actually operating your amp somewhat mistuned in this fashion.
Rich Measures is one of the big promoters of tuning up at high power.
What I think Rich's point is that you don't want to tune up your linear
at 100 Watts out and then turn up the input to 1500 Watts out. That will
certainly cause mis-tuning. I will say however, if you want to tune up
at 100 Watts out, fine. Just then re-tune when you bring your power up
to 1500 Watts out. Tuning at low power will get you in the
neighboorhood, but the final tune positions for high power operation are
definitely different. I've confirmed this.
The optimum load impedance of the tube will vary with drive level as the
plate current which is a component of the load impedance figure varies
with drive. So IMHO, the opitmal load for the tube at 3 KW is definitely
different than 1500 W which means if you tune for the 3KW situation, yet
operate at 1500 W you aren't operating with maximum gain, efficiency and
I think as well, linearity.
The amp should really be tuned up at the desired output power level.
73,
Jon
KE9NA
--------------------------------------------------------------------------
The Second Amendment is NOT about duck hunting!
Jon Ogden
jono@enteract.com
www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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