[GreenKeys] Questions on troubleshooting an antenna

[Web Williams]

I tried the same thing several years ago, and wound up with the
same results. Moving the coil up away from the base was the
solution. You do need to try to get the correct coil length for
the lowest frequency you plan to operate, and have no additional
coil, which will cause resonance and RF radiation issues. Also,
keep in mind that you mentioned a gutter being in close proximity.
Any large bodies of metal within 1/2 wavelength of your antenna
will cause tuning issues. In other words, at 40 meters, it's best to
keep large pieces of metal at least 66 feet away. This may not be
possible in your case, so you will be forced to be creative in
your mounting choices to do as best as you can. If the gutter is
off the tip of the antenna, it will not effect tuning as much as if
you had gutter running parallel to the antenna. If your gutter is
within 1/4 wavelength and parallel to your antenna (within 33 feet
at 40 meters, for example), you're going to fight with the antenna
to overcome mutual coupling, detuning, and signal pattern skew
issues. You would do better to put the vertical on your rooftop
and spread your radials around on top of your shingles. Guy the
antenna tubing with non-conductive (phyllistran or weed-eater twine)
and see if that doesn't cure what ails you.

As a "last resort", you might want to try one of the screwdriver
mobile antennas mounted over the top of your radial field and
see how it does. You can use as long of a whip as is desired.
The design effectively removes stray inductance as an effect of
it's design, giving you one less thing you'll have to compensate for.
If you still have metal in the near-field of the antenna, the screwdriver
antenna will never tune correctly, and at least you'll know the likely
problem, which is most likely metal in the near-field. (Which could
also be wire or copper plumbing inside the walls of your home.)

It would be best to get your antenna out in the open.

> There is an aluminum rain leader about 6' away from the coil. At 5W do
> you think there is any coupling effect?
The power level you are using has nothing to do with the tuning of
the antenna. Either it's tuned, or it's not. If the antenna is tuned
properly, you should see nearly the same (if not identical) SWR at
5 watts as you do at 100 watts or a kilowatt. (Unless something
is arcing.)

My personal advice is to get one of the MFJ SWR analyzers. They're
worth their weight in gold if you're going to do any serious antenna
experimentation. A grid dip meter is OK, but won't give you nearly
the amount of information/feedback as an MFJ analyzer. (Or an AEA
VIA or CIA HF meter, as well as other similar brands/designs.)

Best of luck, 73, -Web (WY3X)