Topband: getting ready for CQWW

w7dra at juno.com w7dra at juno.com
Sun Nov 6 23:37:30 PST 2011


 one thing about using my contest station only a couple times a year,
everything has to be checked and fixed..........

in running 5 watts output without modern instrumentation, i chose to
measure what i could measure accurately, input power to the final tube
(6W6). not being able to check SWR at this level, i stoked up the ol'
worm warmer (single 211 PA) and configured the antenna tuner for a full
voltage feed, tapped down the tuner coil to where i had a 1:1 SWR. this
did require an extra variable cap in parallel with the one in the tuner.

now to set power, as there is no  intrinsic power adjustment, so i dipped
the final, link coupled to the link coupled antenna tuner, and added
resisters to the 6W6 plate circuit. 

at about 190 volts on the plate i had about 40 mills plate current, so
assuming a 70% efficient plate tank........................5 watts output

I do have a second method of checking output power, as i have an EICO
725, which measures 4 watts on the x1 scale and 5 watts on the x10 scale

at this (or any other) power antennas are vital, i plan to use the
station 120 up 130 over  1/2 wave inverted L, with a 5/16 wavelength
counterpoise connected to the bottom of the antenna tuner coil.

running QRP means less worry about receiving

a jpg of the rig is available upon request

mike w7dra
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