Kelley,
Once the termination is set for a given frequency, it should not require
adjustment until the soil has gotten much drier or wetter. However, some
Vactrol models have very poor temperature stability, so you may find that
they need regular adjustment.
Using a Vactrol accomplishes two things: 1) it lets you change the
termination to tweak the F/B at different frequencies -- mainly above 160M
using the published dimensions; and 2) it lets you change the termination to
compensate for unusual or varying local ground conditions. A single fixed
resistor works acceptably in most cases.
FYI, relatively stable signals that are useful for adjusting the termination
include WWV at 2500 kHz, CHU at 3330 kHz, AM broadcast stations in the
1600-1700 kHz band, and W1AW transmissions around 1818.
73, Gary
K9AY
_______
I just finished building a K9AY antenna this weekend. I used a vactrol in
place of the fixed resistor. I spent a little time this afternoon listening
to a AM broadcast station some 60 miles to the east of my QTH. Setting the
antenna to the NE, the station came in around an S7 or so on my FT-1000D.
Moving to the SW, I could adjust the vactrol so the station was in the S1 to
S2 range and I could hear another station on the same frequency that wasn't
apparent when set to the NE.
My question is, how should I set the vactrol? Once set for a band, does it
need to be adjusted?
Thanks,
Kelley - WØRK
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