Topband: one-way propagation

[ZR]

Having operated in Western and Central Europe a few times over the years on 
160-40M from average to better stations Ive observed something else.

With the typical 5-7 hour time difference the East Coast hears EU well 
before sunset in the winter and its hard to impossible to attract a QSO. 
This is the prime evening time in EU where activity is highest adding to the 
across the band din making weak signals poor copy. Also there is band 
sharing with commercial and other stations that drops down considerably as 
the evening progresses. Some of those signals are wide with TX generated 
noise.

As it approaches EU bed time the consumer noise generators are shut off, 
more hams are in bed and the bands "seem" to open to NA.

A good part of EU is also under the auroral curtain at times which adds to 
the band noise and signal attenuation.

Whatever real or imagined propagation anomalies exist just add to the 
problem.

The only cures I know of are running a remote TX a lot closer to EU; or a 
tube with handles and a 10dB+ boost over 1500W such as he who is often 
complaining about others comments on here.

Carl
KM1H


----- Original Message ----- 
From: <k9la at frontier.com>
To: <topband at contesting.com>
Sent: Monday, December 03, 2012 1:09 PM
Subject: Topband: one-way propagation


> Jim K9YC asked about other possible mechanisms besides atmospheric noise 
> to account for one-way propagation on 160-Meters. For the record, I also 
> believe atmospheric noise (and even man-made noise as experienced by the 
> PT0S ops) is a big player in these observations. By the way, I also would 
> like to extend a big THANK YOU to the PT0S ops, especially for their 
> topband effort.
> One-way proapgation was an interesting topic in the AM broadcast industry 
> in the 1970s (I do not know if it still is). The issue was tied to 
> allocation of frequencies and the difference in loss depending on whether 
> it was an east-to-west path or a west-to-east path. John C. Wang of the 
> FCC measured signal strengths of 18 MF broadcasting stations (540 – 1630 
> KHz) at 4 receiving sites throughout the continental US to compare the 
> measurements to the CCIR model.
> Subsequent analysis of this data by Douglass D. Crombie of the Institute 
> for Telecommunication Sciences in Boulder found that for paths between 200 
> km and 3000 km, the east-to-west path loss is some 9 dB greater than in 
> the west-to-east direction. Further analysis shows this is highest for 
> frequencies above 830 KHz. The data did not show any such difference on 
> north-to-south paths and south-to-north paths.
> The second-to-last sentence in the previous paragraph suggests that the 
> ionosphere, being immersed in the Earth's magnetic field, is anisotropic – 
> in other words, the ionosphere looks different for RF going east-to-west 
> versus west-to-east. But if you run ray traces with Proplab Pro (it 
> includes the effects of the magnetic field and electron-neutral 
> collisions) for both directions, you will see no significant difference – 
> at least I have not for my runs). We have to watch it here, though – the 
> model of the ionosphere in Proplab Pro is a monthly median model (as it is 
> in all of our propagation prediction programs) – so it does not capture 
> the day-to-day variability, which may be involved in these observations.
> So I believe there is a possibility that there are other mechanisms at 
> play to give us one-way propagation. Unfortunately, as far as I am aware, 
> we do not understand them.
> Carl K9LA
> _______________________________________________
> Topband reflector - topband at contesting.com
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