[Lowfer] Poor LF propagation lately?

[Bill Ashlock]

Alan,

 

This is interesting! Are you saying that our LowFer "Winter Season" has everything to do with the drop in AT noise level at the receiving end during this period? That could be verified by looking at yearly plots of strictly noise levels in the US. Anyone know of available plots? If you are correct, why then do the BC stations such as the one at 183.0K come in so strong during the winter months here in Andover that their modulation products frequently mess up the watering hole at 185.3? I'll have check my records but I think I have measured up to 1000uv/M of carrier at 183K during this time - but nothing close to that in the summer months.

 

Best regards,

Bill
 
> From: alan.melia at btinternet.com
> To: lowfer at mailman.qth.net
> Date: Fri, 27 Mar 2009 17:20:17 +0000
> Subject: Re: [Lowfer] Poor LF propagation lately?
> 
> Hi Both, I cannot resist my usual comment that there is not a "season" for
> LF propagation.....only a season for comfortable listening. In fact
> Trans-Atlantic propagation on 136kHz and 500kHz has been good over the last
> few weeks that is a greater distance that you are probably shooting at (?)
> Some of the best conditions across the Atlantic have been achieved in
> summer.
> 
> There is very little of the excess night-time absorption due to
> procipitation of hot electrons from CMEs and Coronal Hole flows, and in fact
> the amount of disturrnabnce has been low. there may be one or two
> possibilities that account for poorer than normal conditions over
> intermediate ranges. One iis that I suspect, but have no expert back-up,
> that during a long quiet spell such as we have been havingover the last 18
> months the E-layer which is responsible for night-time skywave signals seems
> to become increasingly transperent at these frequencies. This effect is more
> noticable at less-than-maximum ranges where the signal is entering the
> ionosphere at a higher angle.
> 
> A second possible cause is that the conditions are fairly stable. The
> ionosheric shell is not being casued to ripple so much by solar wind impacts
> and thus when the fading conditions are unfavourable you can get partial
> canellation for long periods. This is often worse in periods of low
> absorbtion because the higher mode (hop count) paths arrive at higher
> strength. This effect is noticable on long paths like T/A but is not quite
> so serious.
> 
> Daytime skywave is probably about 8 to 10 dB lower that it was when the was
> more solar activity and dB lower than summer-time
> 
> Steve Dove's grabbers and plots may not be telling a true story at present.
> I find his plots of DCF9 and HGA22 have shown drops in sensitivity that are,
> to my mind confirmed by the drop in the average level of the daytime noise
> plot. Last nights plot is particularly telling as an obviously local source
> of noise normally 10 to 12dB above the base-line slid off the bottom of the
> plot in the post midnight (UTC) period. I have noticed these periods over
> the last month or so when Steve's plots do not seem to align with conditions
> in the way they did for a lot of the last year. Making reliable measurement
> over years in a way that they can be compared accurately is fraught with
> difficulty and Steve does a great job in trying to keep the plots in line.
> 
> Interesting stuff this LF :-))
> 
> Best Wishes
> Alan G3NYK
> 
> 
> ______________________________________________________________
> Lowfer mailing list
> Home: http://mailman.qth.net/mailman/listinfo/lowfer
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Lowfer at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html