Longpath African Loggings
 

BOTSWANA 4930, 1615-1622, VOA Feb 1 on their new 60mb frequency. Interview with a NASA official discussing the upcoming space shuttle flight, and the issues with the heat shield tiles and integrity of the insulation on the booster fuel tanks; questions from phone callers in Kuwait and elsewhere. VOA ID at 1630 and into news. Good signal at one hour past local sunrise. A short MP3 with VOA ID can be heard he http://www.guyatkins.com/files/voa_botswana_4930.mp3 (Atkins-WA)

SWAZILAND 4760, 1609-1615, TWR, Mpangela Ranch Feb 1 Presumed, with male in unid. African language (listed as Tshwa in WRTH). The pace and tone of the talk sounded like a sermon; hymn or religious song at 1615. Best on SW antenna during near-grayline condition. Fair-good level, and strengthening slowly. Slight co-channel interference from presumed AIR Port Blair. (Atkins-WA)

ZAMBIA 4910, 1558-1605, ZNBC Radio 1 Feb 1 Best reception so far this winter of Zambia on longpath. Nice fish eagle IS at 1558, drums at 1600, and announcer with 'ZNBC' and mentions of Zambia in unid. language. Into a tribal chant or similar by male, followed by a choral hymn, and into possible news items 1605. Fair to good signal at tune-in, and still fair at 1635 recheck-- 1 hour past local SR and 1/4 hour past Lusaka SS. Best on Southwest Beverage. (Atkins-WA)

Guy Atkins
Puyallup, WA USA
mod. ICOM IC-756Pro & mod. ICOM R-75
Kiwa MAP / ERGO / DSP-59+
450 & 700 ft. Beverage Antennas

Just FYI for those who ponder the term "Long Path"

See URL:
http://www.k4lrg.org/Training/Tech_N...Long_Path.html

Great pictorials on the subject

--
Caveat Lector (Reader Beware)

This is excellent reading; thanks for pointing out the link.

I do have "issues" with the second illustration, though. 14 longpath F1/F2
layer hops to get from transmitter to receiver is not a proven fact. The
author's modelling program is necessarily based on classic propagation
theory, but doesn't address the possibility of signal "ducting" between the
layers.

If so many multiple hops are required, why don't we hear echoing and
experience severe signal fading on HF on a regular basis? The multiple
arrival angles of the signal at the receiver would strongly suggest this.
However, experience shows that longpath reception is no more prone to fading
& echoes than a path of one or two hops. In fact, almost all longpath
signals I've encountered have a smooth, and often rapid (10-20 minutes) rise
in signal strength, and then a gradual decline, without major fading or
fluctuations as you would expect in the classical model.

I'm inclined to believe that ionospheric ducting is more the norm than the
exception, as theorized by Yuri Blanarovich a few decades ago.

Much more on this subject can be read in two excellent, detailed (& lengthy)
articles on tropical bands propagation, written by John Bryant and David
Clark for Fine Tuning's "Proceedings" in the early 1990s. I was on the
editorial staff through those years and was fortunate to be have access to a
lot of the background information Bryant and Clark used in their articles.

73,

Guy


"Caveat Lector" wrote in message
news:g0PLd.8213$bu.2150@fed1read06...
Just FYI for those who ponder the term "Long Path"

See URL:
http://www.k4lrg.org/Training/Tech_N...Long_Path.html

Great pictorials on the subject

--
Caveat Lector (Reader Beware)

Guy Atkins wrote:

This is excellent reading; thanks for pointing out the link.

I do have "issues" with the second illustration, though. 14 longpath F1/F2
layer hops to get from transmitter to receiver is not a proven fact. The
author's modelling program is necessarily based on classic propagation
theory, but doesn't address the possibility of signal "ducting" between the
layers.

If so many multiple hops are required, why don't we hear echoing and
experience severe signal fading on HF on a regular basis? The multiple
arrival angles of the signal at the receiver would strongly suggest this.
However, experience shows that longpath reception is no more prone to fading
& echoes than a path of one or two hops. In fact, almost all longpath
signals I've encountered have a smooth, and often rapid (10-20 minutes) rise
in signal strength, and then a gradual decline, without major fading or
fluctuations as you would expect in the classical model.

I'm inclined to believe that ionospheric ducting is more the norm than the
exception, as theorized by Yuri Blanarovich a few decades ago.

Much more on this subject can be read in two excellent, detailed (& lengthy)
articles on tropical bands propagation, written by John Bryant and David
Clark for Fine Tuning's "Proceedings" in the early 1990s. I was on the
editorial staff through those years and was fortunate to be have access to a
lot of the background information Bryant and Clark used in their articles.

I'm more of a believer in ducting myself, rather than hops.

dxAce
Michigan
USA