A Different Kind of Day

[jon]

What a difference a day (or two) makes in FM DX.

This morning, I was out a little earlier than usual in the car. It was just after 9 a.m. and I was hearing stuff on 95.7 MHz, but it sounded a bit different than Arizona and Fresno a couple of days earlier.

After listening for a while, I checked some other frequencies, and noted Whitecourt and Red Deer coming in quite well, side by side, on 105.3 and 105.5 MHz. That is not unheard of, but unusual. Usually I get neither, and sometimes I get one or the other, but not both.

Going back to where I started, I switched to 95.5 MHz and noted CKGY-FM Red Deer coming in a like a local. So strong, in fact, that when I switched over to 95.7 MHz, I could still hear them which, of course, was my 95.7 reception just minutes earlier.

So, today seems like a day for occasional more distant than normal regional reception, but none of the exotic stuff.

[skyvalleyradio]

jon - this is an entirely different mechanism of VHF propagation called "Tropospheric Scatter" or 'tropo' for short. This has nothing to do with the E-layer of the ionosphere or signals bouncing at long distances. As the name suggests, the tropospheric region above us (approx 6 miles +/-) will "bend" VHF signals that would normally radiate off into space as the earth curves away from the straight line of transmission. When troposhperic enhancement occurs, VHF & even more so - UHF signals travel parallel to the earth instead of heading out into space. What this means, is enhancement of FM & TV signals beyond locations considered normal reception distance. It's possible under the right conditions and location, for 'ducting' to occur which will propagate VHF & UHF signals over exceptionally long distances. These ducts are created by the clash of moist, cooler air near the ground and dry, warmer air aloft. Out here on the coast, fog and temperature inversions create these clashing layers of air, producing 'tropo' Usually fade-ins/fade outs are quite slow, with a steady build in signal then a slow gradual decline. Tropo is a function of elevation. The strongest of tropo signals for any given path or distance is usually specific to a particular elevation. Pay close attention to the weather when these conditions occur. Was there low-level ground fog when this occurred. Was it a cloudy day with a very low cloud ceiling??? Was it early in the morning or after sunset when the air aloft is probably warmer than the air at ground level?? These are factors that likely created enhancement for you to Alberta FM signals in places usually beyond normal "Ground-wave"