Could it be that one of the major concerns when contemplating working 160 m
dx is location, location, location,...?
Obviously, if the noise level of location A is higher than that of location
B, less dx will be worked from A--you won't hear the weak signals. If the
number of openings to one location is less than to others (for example, the
number of openings from southeast New Mexico to Europe is much less than
the number from the east coast to Europe), less dx will be worked from the
location having the lesser openings. And don't forget the effects of
ground conductivity.
Also, low power and a poor antenna will not provide a signal strong enough
to be copied by a station experiencing strong QRN or overcome the
absorption on the very long paths.
Modeling will not help when trying to develop a receiving antenna system
for a city lot--too many unknown variables. But experimenting is
relatively easy, and it has shown me that some simple to make and install
receiving antennas are much better than my transmitting antenna for receiving.
My lot is 120' x 120', with the house right in the middle. Power lines
overhand my property all across the back. I have had success using tuned
loops (from 6' to 8' in diameter, make of 1" hardline)--they have too much
high angle response but are usually much better than my transmitting
antenna on receive. EWEs also work, but are harder to rotate than loops.
A 100' piece of wire, 2' off the ground and 6" from a concrete block fence,
fed with coax and no matching, has helped me work several X stations I
could not copy on any other antenna (works pretty good from 80 through 15 m
also). The coax antenna, used so successfully by W0CM, gives better S/N
ratio (and less, but still useable, sensititivy) when mounted 2' off the
ground when compared to 10' off the ground. A 100' piece of wire, matched
and terminated and lying on the ground, has also been used. Three loops,
mounted in different parts of the yard and pointing in different
directions, plus one or two low wires, each instantly selectable by a
switch at the operating position, have helped me confirm 134 countries on
160 m during the past six years--certainly not spectacular by east coast
standards. Going from 100 watts to 400 watts was a big help.
I hasten to add that directivity and S/N ratio of all antennas are
preserved only if I disconnect my transmit antenna from its feed line while
receiving. The transmit antenna is a bent piece of wire (nothing vertical,
nothing horizontal), some 160' or so long, fed against ground--highest
point about 50'.
You can't make a crop with the seed in the barn.
Paul W5DM A ham since 1937
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