Richard Clark wrote:
This should have been foreboding (resonance so near by?).

Well, it stretched from one end of my apartment to the other. It just happend
to be slightly short of a 20m folded dipole.


You say instructions, but instructions for what (to what end, to what
purpose)? Why trifilar? This is suggestive of a voltage BalUn, which
is not going to give you the choking action you need to reduce noise
problems.

It from a book "Simple, Low-Cost Wire Antennas for Radio Amateurs" by
Coan and Orr.


When I hooked it up to the antenna, I found that the resonant frequency
shifted to 14mHz. My guess is that the feedline now is part of the antenna.
However at 7Mhz it is totally dead. So dead that a signal that reads S5 on
my receiver using a 2m JPole hung from the near end of the folded dipole
as an antenna does not move the s-meter at all. The null extends from
around 6950 kHz up to around 7300.

This still sounds like the vagaries of propagation. Do you keep logs?

It's not needed. I have two coaxes going outside, one to the folded dipole,
one to the J-Pole. If I tune in a station in the "dead" range (7.0-7.3mHz),
using the J-Pole as my antenna that reads s-5, when I switch to the folded
dipole, it barely moves the s-meter at all.

Your lead out to the antenna could have a short/open in it.

Possible, but at 14mHz, it comes in great, far better than the J-Pole.

I presume
you use your tuner, however of late I have been given the impression
that SWLers of this generation sneer at it in favor of the magic
BalUns they chase on the Internet (given you are a frequent poster
here, I give you the benefit of the doubt).

It was an experiment. I was hoping to use the antenna to transmit too, and
can't run twinlead out to it. So the compromise was the Balun at the far
end of a coax. I can't say if it worked at all, I never got far enough to
try.


The electrical properties are unrelated to the pattern properties. We
speak of nulls in a pattern.

My bad, I was speaking of a null, as in a frequency range with zero
(or close to it) signal.

If you are referencing a null in tuning, then that would occur at
either resonance, or anti-resonance (broadly speaking). If this is
your intent, then, yes, "nulls" would represent impedance matching
issues which in turn would put a block to signals. A tuner is a
design tool for this situation.

Thanks, that's easy to try. Would it work on the near end of the system?
radio - tuner - 10 meters of coax - balun - 300 ohm feedline - 300 ohm
folded dipole.


Solve your problems one at a time.

Thanks. that's a good idea.

Some of the 10mm rods were broken into pieces in shipping. Does that affect
their performance? Can I just use the pieces as they are?

Magnetic performance is impacted by air gaps. In some situation this
is an asset where saturation is an issue. Super glue the pieces for
the closest fit.

Sorry, I wasn't clear. Someone on another mailing list said that breaking
a ferite rod could magnetize it. I don't want to glue them together
again, I would use the pieces as they are.

Maybe a better question would of been to start from the begining and ask "I
have a 300 ohm twinlead folded dipole resonant at 15mHz, with an aprox 6 foot
twinlead feed line. I need to feed that with 10-15 meters of 75 ohm coax.
How do I get that to appear resonant to my transmitter on 14 mHz, and hopefully
7 and 28 mHz and get some signals in and out?".

Thanks and 73,

Geoff.

--
Geoffrey S. Mendelson N3OWJ/4X1GM
Those who cannot remember the past are condemned to misquote it.