You know it's springtime... RE: FM DX.

[ehenness@natick-amed02.army.mil]

Peter George explains e-skip:

>     VHF-FM skip is not so much "rare", per say but VERY SPORADIC.  It
>is called "E-skip" and is very prevalent during the months of May through
>early August.  There have been MANY theories about FM and low band VHF-TV
>E-skip.  The 11 year solar cycle may play SOME role in "E-skip" occurances,
>but the main culprit of "E-skip" lies in the more occurance of 
thunderstorm
>activity happening in the summer months.  Most E-skip openings provide 
long
>distance reception of low-VHF TV (Channels 2-6) and FM (88-108) in the 
order
>of 700-1500 miles from the transmitter to you.

It's also known as tropospheric ducting, where the storm activity creates a 
path (or 'duct') for the signal to ride along.  

A few examples:  Once, while travelling up I-84 right at the Pike, I 
flipped the radio to 92.9 to see if WBOS was in range in Sturbridge.  I got 
92.9 from Atlanta (WSB-FM?) while driving at 60-65 for about 20 minutes (by 
then, I was well within range of the stations on FM-128) and WBOS did not 
break cleanly through until I was within 495... 

My father is a retired cop, and the town in southern CT he worked for used 
39.58 MHz as their primary frequency.  In the summer, more often than not, 
they'd get skip from Wisconsin cops in their cruisers routinely.  I can't 
recall whether the WI cops had the same PL or my dad's department used 
carrier squelch.  Any time there was storm activity somewhere between 
Connecticut and Wisconsin, the band would open.  At the low frequency, it 
happened more often than on broadcast band FM, although the base stations 
were probably using no more than 100 watts.

And sometimes, amateur radio operators get tropospheric ducting on 2 
meters. This means the maximum useable frequency has gotten as high as 148 
MHz.  The distances are a bit shorter, though, usually not much farther 
than Pennsylvania or New Brunswick or Nova Scotia.  This is due both to the 
lower power used (vs. broadcast FM) and the frequency.

Ed Hennessy

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