[TowerTalk] FW: Moxon rectangles

[Tom Rauch]

is a cracking signal, being well up on the vertical.
Checking with the MFJ
analyser, I was shocked to find it resonant at around
20.25Mhz- this would>>

Clive,

I spoke against including a "resonance" function in the
MFJ259. The reason is you cannot measure resonance of an
antenna through a length of feed cable unless you know a
great deal about the feedline.

All those who think they are measuring resonance of an
antenna when they measure zero X at the end of a
transmission line without understanding special
qualifications are assuming incorrectly. The only exception
would be if the antenna was 50 J 0 at resonance, in which
case the feedline could still introduce false zero X
crossings.

We should ignore the "resonance" readings for now because
they may or may not be accurate.

be consistent with the reflector acting as a director, but
with very poor
efficiency. So, we took the whole thing down, and double
checked everything,
finding no errors. Now something even more puzzling.
Checking further HF
with the MFJ, I find sharp "resonances" around 63 and
106Mhz, being roughly
the third and fifth harmonic of an in band 21Mhz resonance,
but which does
not occur at the fundamental frequency, as described
above.>>

Doesn't surprise me, since you are trying to measure
resonance at the end of an unknown transmission line.

I have some nice fibreglass spreaders for the final job, but
there's clearly
no point in proceeding until I can make the prototype work.
Oh yes
everything checks out FB in EZNEC which indicates that the
dims. ARE
correct, but the &^%$£*** thing just doesn't want to play>>>

Do you have dielectrics at work that are not in the model,
perhaps insulated wire??  Do you have other things not
included in the model bothering the antenna?? Something in
the surroundings? Maybe element insulators with wire loops
around them? Do you have proper feedline dress and proper
decoupling for common mode RF (a balun if needed as
influenced by feedline length and dress)?

73 Tom