> Excellent food for thought, Tom --- I never would have
> thought of it that
> way before...
There are things in the electronics world that are not
perfectly bilateral. For example a lossy impedance matching
network isn't precisely bilaterial.
I've been considering the chance the ionosphere is that way
for a long time and haven't found much evidence the signal
only travels one way.
For example VK3Zl and myself have been working a few times a
day on 160 for almost ten years. In that time we have had
3948 QSO's.
Of those 3498 QSO's in the log, there isn't a single clear
case of one way propagation. There are very clearly times
when Bob has to switch to another antenna from the normal
antenna, there are very clearly some times when a
horizontally polarized antenna from my end is a few S units
(whatever dB amount they really are) better or worse
compared to the vertical, there are times when the noise at
one end or the other is high, or when I catch him in a fade
on an transmission while I'm on a peak or the opposite.
Similar things happen with JA's or other directions.
But in the past several years there hasn't really been a
case when factors like using the wrong antenna or varying
noise levels or just bad timing don't account for the
feeling things are unbalanced.
I think the reason these feelings are widespread on 160 is
do to several factors, some of which you just hit on...
1.) ERP is critical and few cases are likely to have
stations with the same or similar ERP as the fellow they are
working
2.) Noise levels are all over the place and we generally
base RST on our perception ratio of signal to noise rather
than actual uV into a standard antenna. As a matter of fact
I would venture to guess not a single person uses a
standardized uV/m field intensity in reports. I know in the
summer here my background noise even without obvious
lightning crashes can be 5-15db louder than winter, so that
skews my outgoing reports. Bob averages 2 S points better in
my report compared to his during our summer, and it balances
back up in my winter when he has noise. Of course I have no
idea what an S point is for Bob or anyone else, but I know
for me it is really just a dB or two unless I am looking at
a meter!!!
3.) 160 has slow fading. The period of fading is very often
a few dozen seconds to a minute or more, making it very easy
just to have bad timing. One person hits the peak, and the
other hits the null. I had this exact thing this morning
with a JA. While his signal was good, when he actually
transmitted it always wound up being in the declining slope
of QSB. I of course transmitted back through luck on the
peaks until I forced the time enough to delay the cycle so
he was on the peaks.
4.) Most people don't transmit on the same antenna they
receive on. I notice difference in fading time over a
distance of a few thousand feet. I certainly notice a
difference between Beverages and a high dipole. There is
even a difference between a vertical array and a Beverage
near each other even though they are both vertically
polarized antennas. Why would anyone always expect the
receiving antenna to always have the same fade timing or
rate or even absolute level as an entirely different
antenna?
5.) There are cases of noise or QRM that come and go. Since
reports are often if not nearly always based on what we
perceive or feel, why would expect that not to change?
I certainly can't say there isn't ever such a thing as true
one way propagation, but the most supporting arguments don't
seem to have much more than "feelings" as a supporting
backbone. So I guess it is all a bit like religion. What I
see after spending years of carefully looking at several
thousand contacts makes me think it is more just random bad
luck or timing, noise, unbalanced stations at each end, or
the wrong antenna rather than the path only working one way.
I think if it was a very frequent large effect it would have
showed in a few of 5922 QSOs, and so since it did not I
think it is possible but greatly overblown. It's much easier
to blame mother nature than accept the fact it is because we
don't have enough choices of antennas available, or the
timing is bad. A complex answer with lots of variables (some
being unpleasant to our ego) is always harder to sell than
simple three word covers everything excuse.
But that's just my opinion. :-)
73 Tom
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