Topband: strange conditions

[Bill Tippett]

>Date: Sat, 30 Dec 2006 12:38:07 -0500
>From: Jon Zaimes AA1K <jz73 at verizon.net>
>Subject: Re: Topband: strange conditions
>
>Yes, the spotlight effect does happen, but there are many variables.
>
>Ambient local noise is a major factor. I can see this on my 
>hour-long commute from work in northern Delaware, in a heavily 
>populated area, to my home in rural central Delaware. Much of the 
>travel is along an expressway (Del. 1) with few power lines 
>immediately adjacent. The base noise level over my ride can vary 
>from S0 on the open road to S9 or more in densely populated areas, 
>or where there may be significant power line or industrial noise. In 
>the S0 areas I can often hear DX stations that base stations are 
>not. My car is a VW diesel with zero noise floor (www.aa1k.us).
>
>I have also observed increases in DX signals from particular "hot 
>spots" such as atop a 150-foot tall bridge across the Chesapeake & 
>Delaware Canal -- although not as pronounced on 160 as on higher 
>bands. But notably on 160 when crossing a few stretches of highway 
>with tidal marsh from Delaware Bay tributaries alongside. The 
>increase can be several S units here.
>
>Wave angle is another factor. In some directions I have had both 
>long and short Beverages available, and models show the longer ones 
>favoring lower wave angles and the shorter ones favoring high 
>angles. While the longer ones tend to be better for most DX, under 
>some conditions and some paths (particularaly around sunrise/sunset) 
>the short ones take over. Sometimes the vertical TX array is better 
>than the Beverages, sometimes not.
>
>And the "spotlight" does move around. W3BGN, who is about 100 miles 
>NNE of me, and I have observed this over the years -- a particular 
>DX signal will sometimes peak at Steve's and I can't hear it, and 
>vice versa, and it may see-saw back and forth.
>
>Stew Perry W1BB's age-old advice to have as many RX antennas as 
>possible still holds. Sometimes the one you just built is the only 
>one you can hear that needed DX on.
>
>Speaking of Stew, good luck to all in the contest this weekend, and 
>a Happy New Year to all.
>
>73/Jon AA1K