Re: [IRCA] Intriguing DXing locations

[Nick Hall-Patch <nhp@xxxxxxxx>]

At 23:04 5/3/2010, you wrote:
>Those would indeed be great, and away from all forms of RF noise.
>
>I was also wondering how close they were to the ocean; my understanding is
>that going even a few hundred yards or so inland puts a significant damper
>on TA/TP signals - can any TA/TP veterans confirm/correct this?
Hi Kevin, 

I suspect that the amount of loss is somewhat dependent on the ground conductivity of the inshore land, the frequency of the signal, and the arrival angle of the signals, but only really have data for the second of those suppositions.  The others are based on the supposition that a low arrival angle signal from over the ocean will lose strength more slowly over highly conductive land (salt marsh) compared with poorly conductive land (rock) the further it travels.   A high arrival angle signal, on the other hand, presumably will not be as affected by ground conductivity so one might assume it will be nearly as strong inland as at the shore.   

As for the second supposition, a few years ago, John Bryant and I did some simultaneous signal strength recordings at the shore and points up to around two kilometers inland at Grayland, and found that the loss was highest for higher frequency signals,  and varied from 1 to 12 dB depending on how far inland one was (but signals were almost always best right at the beach).   It didn't seem to be a linear decay, rather there seemed to be reinforcements and cancellations of signals at different points,  so one might luck out and hit a "pretty good" spot further inland, so one shouldn't out of hand reject a site a little ways inland.   Randy Seaver wrote a good article years ago about this,  entitled "Sea Gain" which is IRCA reprint T062, and some of our results did seem to have some theoretical underpinnings (Randy had found some academic work on the subject).    Unfortunately, both John and I were pretty busy at the time, and never really finalized any conclusions on the subje!
 ct...."more study is needed"  (I'm sure Mike of the Grayland motel would be OK with several weeks of rental from  DX researchers.....).

best wishes,

Nick




*****************************
Nick Hall-Patch
Victoria, BC
Canada 


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