Topband: one-way propagation

[Peter Sundberg]

Last weekend was (finally) a return of over-the-pole conditions in my QTH,
similar to what we experienced frequently in 2009 and 2010. I could hear
western NA stations ALL day here, some with very good signals despite full
daylight at my end. They did not fade out until sunrise over there >14.00
GMT. 

Everyone I heard was coming in via SP, true beam heading across the pole.

I called many stations, repeatedly for long periods of time. Some signals
were peaking 559/569 in the rather slow QSB. Not even a QRZ in return,
except for VY2ZM, we worked at 1014 GMT.

One way propagation? No, I don't think so. I think that the fact I was not
heard was just the difference in noise levels at both ends. Probably adding
to that, the NA stations heard were using receive antennas that were
pointed anywhere BUT to the North pole.

On moonbounce I experience one way propagation very often. But then I can
mathematically explain why, it has to do with so called spatial offset and
a 45 degree Faraday rotation. No mystery, just a sound explanation because
of geometry. 

There are times during strong auroras when I can hear European stations on
low bands pretty well in the evenings but they can't hear me. Again, at
those times I am sure it is due to the noise level a the other end. If
signals are depressed by aurora up here at 65.4 N then the crud on the band
is also depressed. So I hear stations at S3-5 levels very well. But they
are probably seeing the normal >S7 evening time noise background, masking
my signals completely. 

However, in contests, like the first night of CQ WW CW a couple of weeks
ago, it was frustrating to operate on 160m in the aurora. Even when doing
S/P it was difficult to work stations in northern Europe, although I heard
them very well at S2-3 levels.  

So, I don't think that there is a magic situation where one-way-propagation
exists on HF, it should be fully reciprocal. In my opinion it's rather a
result of different noise situations at both ends.

73 de Peter SM2CEW 



 

At 22:08 2012-12-04 , Mike Waters wrote:
>I've often thought that some "one-way propagation" is simply due to the
>differences in antennas. For example, two stations with the same power,
>ambient noise level, etc. are receiving on Beverages pointed at each other,
>but their TX antennas have different takeoff angles and/or patterns. For
>example. station A with an NVIS antenna (like a low horizontal loop) might
>hear station B who is transmitting on a vertical, but maybe not vice versa.
>
>73, Mike
>www.w0btu.com
>_______________________________________________
>Topband reflector - topband at contesting.com
>