Unusual "Picket-Fence" DXing?

[Bud50]

I love radio- it can be so unpredictable at times! But how many times have you been at a marginal edge of a station you're listening to and stopped to hear another station picket-fencing in while you're moving? A couple months ago, I was on foot, doing some clean-up on a ridge near home, about 15 miles north of Mobile, AL in an area just west of Axis, AL. I was using a little FM receiver from a Radio Shack/Realistic "Silent Play" kit. (I picked up some of these for pennies a few years ago and use the transmitters sometimes, to relay audio to my reciever of choice, when I can't sit & listen. The little companion FM receievers are HOT!) Needless to say, as I walked, I heard another station "picket-fencing" with the blues music I was listening to on 92.1 WZEW. I stopped, then "fine-tuned" my position until I got the other station in- and it was mentioning stations in Birmingham, AL! It was fairly cool, not cold, but a pleasant afternoon to be working outside. I'll bet the warm sun and cool temps did a little inversion layer propagation! (This is also what we call "mountaintopping" on VHF/UHF/SHF Ham radio, but here in Alabama, we just have some hills and high bumps....!)

I couldn't just stand there- I was losing daylight and hoof it back to the truck. Needless to say, this was an enjoyable surprise to my working afternoon!

Has anyone else "picket-fence DX'ed"?

Bud

 

[rbrucecarter5]

My theory on this phenomenon is that the multiple bays on the transmitting tower produce a moire pattern of nodes and nulls that are more apparent in the fringes. The reason why I think this happens is based on two extremes:

(1) The owner of WAPN, Holly Hill was a diabetic, subject to frequent mood swings. Having acquired a 6 kW transmitter, he promptly had it installed, and ran it through a single bay. With losses, he hit his licensed ERP of 2.2 kW. This was a temporary configuration, due to tremendous power bills compared to his very reliable 900W unit and multiple bays, giving him a ERP of 1800W. But during the short time he operated with the single bay - there was NO picket fencing in the fringes, about 20 to 25 miles out. When driving down the road, the signal was suddenly gone, or coming back to town, suddenly there.

(2) Extreme 2, the Roswell towers. Short towers west of Roswell, with 10 or 12 bays installed over half the vertical height of the towers. Worst picket fencing I've ever heard in the fringes!

I've found lucky nodes when traveling - a Texico station just east of Lake City, FL with perfect reception of 97.1 from North Georgia. An auto parts store on Hempstead Road in Houston with perfect reception of KLTY Dallas. And a Hartz chicken nearby on Hollister road with another node. And so forth - if you go the same places enough, and they happen to sit on a node, you will get reliable reception of a distant station inaudible sometimes a hundred feet away either side. And the reception may vary with the wind at the transmitting tower!

 

[OKCRadioGuy]

I went from a 3-bay in-town at 300ft to a 1-bay at 1.6kw (like 4.7kw transmitter power). There is a marked improvement in coverage in-city because there are less places the signal can see, first and formost. But, the other very noticable thing is within the first five miles there aren't the nulls like there used to be in places because it's just one glowing level of bay. *It's a ERI 4-round baby panel actually on a big TV tower). We are VERY, VERY happy with it's preformace. We have more solid coverage and as a bonus, more range. We happily pay more for electricity. At our power level I'm convenced that one-bays kick ass with something within a city.

 

[charlestondxman]

Here in Charleston it is like that too. Savannah stations like 97.3 and 102.1 (plus 98.3) are often inaudible in the metro Charleston area, especially on the Mount Pleasant side, but once you get north of town (Awendaw, north of that), those stations come in as clear as they do in the Beaufort area most of the time.

Another: back when 101.7 was a weaker signal, I used to hear WIKS New Bern coming in three or four years in a row on the 4th of July coming out of Isle of Palms.

There's a hill on I-26 at about MM 155 near Bowman (only headed toward Columbia), where you lose the Charleston stations. They come back though a few miles farther N.

Back before a translator moved in on 97.1 in Columbia, there were several places in metro Columbia where WFOX came in, and well at that. WSSL 100.5 and WSPA also have that same effect. There are places on I-26 below I-77 where those signals are strong, even though WSPA is well over 100 miles away.