Topband: dipole height

[N4IS]

Hi Rick
>>
I had full size 160M dipoles (not inverted vees) up at 9 meters and
18 meters for about six months and did a lot of A/B'ing of them.
On receive, there was never any difference in audible S/N ratio.
>>

This result is 100% sure to happen. Any time you have more than one resonant
antenna, they will couple with each other. A-B test on 160m is very
difficult to be done properly when one antenna is resonant. There is several
ways to feed a resonant antenna, one of them is driving with another
resonant antenna, like a 2 elements yagi, any element close to 1/2 waive
reradiate the energy it receives from the other element.

The situation with small receiver antennas is worst, If you want to compare
a RX antenna like EWE, Flag or small vertical array with a low dipole, the
interaction will be so intense that all antennas will receive the same
signal noise. The dipole must be at 300 to 500 Ft far from the RX antennas
to reduce the interaction. To eliminate the interaction 1000Ft is necessary.
It is just electro magnetism law. Elevated radials does the same with RX
antennas. 

Does not matter if you are receiving or transmitting the integration works
at the same way, that's the way any yagi works on RX and TX with the same
gain.

RDF is the key point to improve signal noise, not gain. Vertical or low
dipole has very or none directivity, so low RDF or directivity does not
improve signal noise.

Unfortunately, physically detuning any resonant antenna is a must for a good
reception on 160m using external RX antennas, You cannot see but it is
there. Detuning or neutralizing a resonant antenna means change the
dimension to avoid the resonance, it has nothing to do with the feed
impedance of the antenna or structure. Shorting  the end of the coax cable
is just not enough to detune the antenna, only makes it a little longer or
shorter.

Regards
Jose Carlos
N4IS