FM DX in NORTH IDAHO- DON'T CALL IT GROUNDWAVE!

[fangio28]

Is this a good location or what? Loggings on 2010 KIA Soul car radio @
Hayden Lake, Idaho (3 miles from home QTH) today 1430-1600 PM PST:
94.9 CBTA Trail, BC (13.5kw) 110 miles in and out with
94.9 KIOK Richland WA (100kw) 150 miles
95.7 CJAT Trail, BC (13.5Kw) 110 miles in and out with
95.7 KKSR Walla Walla, WA (94kw) 132 miles
102.1 KPQ Wenatchee, WA (35kw) 166 miles
105.1 KWOL Whitefish, MT (62kw) 111 miles
106.3 KDBR Kalispell, MT (60 kw) 102 miles
All but the two Montana stations are at elevations well below my 2190'.
Driving from the Lake to my home within a mile, the MT stations are gone!
Lots of mountains in between here & MT, virtually no mountains between me and the other US stations listed.
stations.

 

[boiseengineer]

Back when there were only 2 or 3 FM's down in Boise CJAT was a regular. Seem to remember they dropped power & HAAT at some point & never heard them again.

 

[Dxer1105]

That is just darn good line of sight. The height helped it too. No tropo or e-skip. A good example of far line of sight reception from hundreds of miles is dxing from an aeroplane.

 

[fangio28]

DXer 1105....good point about the airplane! Not having a local on every other
channel helps too, of course. Tnx!

 

[radioman148]

DXer 1105....good point about the airplane! Not having a local on every other
channel helps too, of course. Tnx!

I've DXed a few times from a plane and the FM reception is tremendous.

 

[spunker88]

I notice a lot better FM reception during the winter compared to the summer on days with no tropo. I think part of it has to do with the absence of leaves on trees and vegetation. This probably enhances line of sight reception. The snow on the ground tends to fill in ravines and make the ground smoother. Combined with the leave-less trees, edge propagation is probably more efficient.

I notice many low power stations come in better during the winter, distance for reception increases slightly, but it mostly seems that winter brings better reception of local and low power stations for me. For example I get a 50 watt station from over 50 miles away during the winter only.

 

[Dxer1105]

I saw a youtube video on dxing on an aeroplane. This guy had a station on every frequency. He was flying over europe and those stations have 100 khz spacing. all of the signals were like semi locals that had stable reception, an example of how good the reception was ex: 88.1, 88.2, 88.3, 88.4, 88.5 etc.

 

[BRNout]

I saw a youtube video on dxing on an aeroplane. This guy had a station on every frequency. He was flying over europe and those stations have 100 khz spacing. all of the signals were like semi locals that had stable reception, an example of how good the reception was ex: 88.1, 88.2, 88.3, 88.4, 88.5 etc.

I've done it and - yes - in many parts of North America, there's a signal on every frequency! For the most part, the signals often change so fast that you often hear merely a mish-mash of competing stations with the result being audio that is unidentifiable. There are the exceptions, however, as some signals seem to hang in for a long time. Those are generally the ones that are near the horizon and which come from "your" side of the aircraft. So, when hunting, look for the higher powered stations that are located roughly 180 - 300 miles from you at cruising altitude. Preferably those that are in the same approximate cardinal direction as you're facing from the aircraft window. Also, the window seat is - by far - the best spot for onboard reception.

All that said, most airlines take a dim view of the use of FM radios and (as a disclaimer) I cannot endorse violating any rules which prohibit such use.

By the way, onboard aircraft reception is a wonderful teaching example of how - once again - the use of "groundwave" or "skywave" when discussing FM band signals is inaccurate. These signals don't follow the ground - they are all based on line of sight. When you have tropospheric ducting, that line of sight signal is reflected back to earth by meteorological conditions in the lower atmosphere - resulting in reception of signals from 60 to (in the most extreme cases) 450 miles distant. When the rarer phoenomena of e-skip occurs, that line of sight reflected off of the upper atmosphere.

But, unlike AM where there are divergent groundwave and skywave components - FM is all about line of sight.

 

[Schroedingers Cat]

The thing is, once you get to a certain altitude, AM is line of sight also. It has to be, or you wouldn't get skywave that is anywhere near inverse field. There is very little loss of signal in the incident or reflected waves below the ionosphere. The ionosphere just reflects the incident waves, but only a portion of the incident waves are reflected. The ground actually attenuates the medium waves and bends them over the horizon but at great loss except over sea water. In the one time I was up in a small aircraft with just an AM radio, it was clearly much better than groundwave at 3000 feet. "Radio's Best Friend's" father was a pilot and Jr. reports that he could get WJR in his plane very well over Pennsylvania in the daytime.

 

[BRNout]

The thing is, once you get to a certain altitude, AM is line of sight also. It has to be, or you wouldn't get skywave that is anywhere near inverse field. There is very little loss of signal in the incident or reflected waves below the ionosphere. The ionosphere just reflects the incident waves, but only a portion of the incident waves are reflected. The ground actually attenuates the medium waves and bends them over the horizon but at great loss except over sea water. In the one time I was up in a small aircraft with just an AM radio, it was clearly much better than groundwave at 3000 feet. "Radio's Best Friend's" father was a pilot and Jr. reports that he could get WJR in his plane very well over Pennsylvania in the daytime.

Yes, of course what you're saying is true. To summarize, there's no such thing as FM groundwave (in the definitive sense). That is a function of lower wavelengths in the LW and MW bands.