Erik,
About all you can conclude from the WSPR readings is the relative
difference between antennas. If you want to compare two horizontal
antennas, place them end to end. The radiation at the end is at a
minimum and the antenna will not interact.
As for comparing a vertical with a horizontal antenna, or two verticals,
the only thing one can say is at that particular time and distance for
propagation, one antenna is better than the other. That may not be true
for other propagation conditions, so be careful when generalizing.
As far as two horizonal antennas oriented in different directions, you
would expect greater signal strength in directions broadside to the
antenna. That directivity may be useful in actual use, but is not a
valid comparison between the two antennas.
73,
Don W3FPR
On 11/21/2017 8:40 PM, Erik Basilier wrote:
I hope my interest in WSPRLite antenna comparisons doesn't lead this thread too
far off topic, but I have further thoughts on how to orient the two antennas
being compared.
Frank, who is much more experienced with this comparison system, suggested that
two horizontally polarized antennas should be oriented end-to end, due to
parasitic interacton between the antennas. I questioned whether the end-to-end
configuration would be free from interactions. Be that as it may, but while
thinking about configuration choices, I came up with another reason why
end-to-end would be the right thing to do.
Suppose we are comparing two omnidirectional antennas such as verticals. Even
if the receiving stations are unevenly distributed in different directions, the
comparison based on received reports should be fair. If instead we are
comparing two horizontal dipoles, that are not pointing in the same direction,
and receiving stations are not distributed evenly in all directions, the
antenna with fewer receivers in the main lobes would likely be at a
disadvantage. If the feed system is the part that is different between the two
ontennas, one could compensate, as I suggested, by swapping antennas for each
feed system, but the time taken allows the conditions to change, so one would
probably have to go back and forth a number of times to gain confidence in any
observed difference in performance. Close to the coast receiving stations would
be largely missing in roughtly half of possible compass directions, and
unidirectional antennas would be affected more than a dipole with its bid
irectional pattern. Much seems to depend on the proprietary algorithm used to
composite a single performance number for from the WSPR received s/n rations at
multiple receiving stations. What is the balance between the number of good
reception reports vs. the distance for each one? When we talk about difficulty
in comparing one vertical and one horizontal antenna, I suspect that similar
considerations may account for result being inconsistent or difficult to
interpret.
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