[Lowfer] A bit of a problem with trimmer caps

[WE0H]

So back to the drawing board huh??? I think I will go back to finishing the
copper pipe variable cap then since it appears at this point that the air
variable caps could be a problem whether it is a big sucker like my Johnson
cap or the small trimmers. Just when you think it is all figured out Murphy
steps on your toes.

Mike>WE0H
http://www.we0h.us/lf

-----Original Message-----
From: lowfer-admin@mailman.qth.net [mailto:lowfer-admin@mailman.qth.net]
On Behalf Of: The Loop Master> Wild Bill Ashlock
Sent: Thursday, February 06, 2003 11:47 AM
To: lowfer@mailman.qth.net
Subject: RE: [Lowfer] A bit of a problem with trimmer caps

Mike R says:

>So I believe your cap will increase in value being submerged in oil; >it
>will also have a higher voltage and current rating. Do you think a >new
>spotlessly clean cap submerged in oil would have lower losses than >a dry
>new cap???

>How about an inductor; would the inductor maintain it's dry value Q if
>submerged in oil??? Would it still be subject to outside influences as >far
>as lowering its Q say if it was moved near some lossy object like >a human
>body or would it not be influenced so much???

Geeez Mike, where did this new 'Engineering approach' come from?  You're
scaring me! <G>

>On your thoughts about the sagging current during wet conditions, well >we
>both know that I still don't have the data you asked for last >summer,

So get to it Mr Engineer; Dam the fun stuff! <G> Actually, in my case, this
trimmer capacitor issue has to put to bed before I can run any more tests
for ground losses under varying conditions. I'll disconnect the trimmer on
the test loop amp, for now, and use a sealed 10 position switch that selects
from a group of small-valued silver mica caps. It was interesting to see the
test loop beginning to show signs of the daytime 'current dip' after being
'rock stable' for days, but I thought this was due to the higher
temperatures we were getting. I installed the solid state relay in the final
for the big loop so that should be running tonight - just in time to make a
comparison of the two loops during the snow storm that arrives later
tonight!!


>but I can verify that my current also drops a bit during wet >conditions.
>Is some if it the cap being lossy, don't know, but it will >drop anyhow cap
>loss or not.

Yah, this is where one really has to be careful to control the variables.
The wetness/high humidity can cause any number of other current-lowering
effects. My equation for wet/dry ground losses is now in question. I was so
surprised to find the test loop, only a few feet off the ground, indicating
almost no increase in Rac when the ground became really wet. This was before
I completed the final for that loop and was measured with the Rac meter
(which of course, is kept dry). When initially connected to the new
transmitter the current was constant for days under all kinds of wet/frozen
conditions. The big loop used to indicate a fairly large quick dip in
current each day, as soon as the morning sun was exactly the same angle in
the sky. Now I'm wondering if this was actually the moment the sun reached
the final, melting the frost on the trimmer.

Great fun!

Bill