FM: SO IF IT'S NOT GROUNDWAVE OR L-O-S, HOW DO CLASSIFY THESE

[fangio28]

Have now positively identified 6 FM stations between 132 & 172 miles
SW of my Coeur d'Alene, ID location: KRKL (93.3) K-Love, Walla Walla,
WA (132 miles); KIOK (94.9) Richland, WA (150); KNLT (95.7) Walla
Walla; KORD (102.7) Richland; KWHT (103.5) K-Wheat, Pendleton, OR
(172) and KONA-FM (105.3) The Mix, Kennewick, WA (148).
Incidentally their altitudes are all well below mine (2,130 here)...these 6
stations vary from 366' to 1068' above sea level, if that matters.
Too far for "ground wave" or "line of sight"?
Your thoughts!

 

[KR4BD]

Tropospheric Ducting... VERY common in many parts of the country.

 

[gar hi]

Elevation!

Fangio, your town of Coeur d'Alene is listed at 2188 ft. You are significantly higher up than the stations you mention.

That's one thing we sure lack here in Florida, elevation. I envy you guys at or near high altitudes.

 

[Darth_vader]

Yup. Definitely gotta be elevation.

That, and things are pretty flat on that side of the Cascades, so VHF signals, such as FM stations, can generally propagate pretty well out there. I pull in KPBX from Spokane and KFAE from Yakima (and their associated Evergreen Radio Reading Service SCAs) quite regularly on a portable radio when I'm in Pendleton, as well as along I-84 once I get out of the Gorge and up onto the plateau.

 

[KR4BD]

Elevation can definitely help, but in this case, I think Ducting is the culprit. Where Fangio lives may be elevationally HIGH, but there are MANY and I mean MANY mountain ranges between him and some of the distant stations he is reporting. Line-of-Site is probalby out of the question as a result of these higher mountains leaving Tropospheric Ducting as the probable means of propagation here.

 

[Darth_vader]

Tropo's really good over there, too... ;o)

 

[gar hi]

I don't know how recently these catches were but I ruled out tropo in that area just based on the recent maps.

Even though these are forecast maps, it doesn't appear there's been any ducting conditions at all in the recent past.

http://www.dxinfocentre.com/tropo_wam.html

That's why I went with elevation.

The only other thing I could think of is a combination of elevation and tropospheric enhancement which is when normally receivable signals are enhanced by weather conditions closer to the ground.

 

[asugeorge1]

I would say elevation is the culprit. You can find the same exact thing driving to and from Los Angeles, California. Everytime I drive back home to Phoenix from L.A. via Interstate 10, you lose the L.A. stations near Palm Springs. But, once you pass Indio and climb the hill and hit around 2,000 feet, you start picking up those Mount Wilson FM's again. I can continue to receive the Mount Wilson FM's for up to 180 miles out of L.A.

The one L.A. FM I listen to most of the time is KRTH 101.1, which comes in clearly all the way to Chiriaco Summit. Chiriaco Summit is approximately 157 miles east of L.A. I've heard similar distance reports of picking up KRTH heading south on I-5 past San Diego.

At an elevation of 5,712 ft, those FM sticks on Mount Wilson have got to be in some of the best locations for FM antennas in the entire country. KRTH's great monster FM signal is not the result of any sort of e-skip or ducting, it's because of elevation and the great location of their antenna on Mount Wilson. 5,712 feet above sea level will do that for you! ;D

 

[KR4BD]

My theory is still Ducting. Here's why I think that. If it was line-of-site these stations would always "be there". If it is elevation, again, these stations would always "be there". Ducting can and does enhance signals which are "just over the horizon".

 

[rtc]

IME tropospheric ducting occurs during temperature inversions.
While it is observable at 50 mhz and on b/c FM it's better at
2m (144 mhz) and can be spectacular at 70 cm (440 mhz):

http://en.wikipedia.org/wiki/Tropospheric_ducting#Tropospheric_ducting

That said,during the summer FM stations in the Bahamas have easily
been heard here.
Note the weather conditions necessary for best results in the article;
you don't need much power or a complex antenna.One night a guy in our chat group worked another station 90 miles away-direct-on a one watt handi with only the rubber duck antenna.
All you have to be is in the duct.And that can be on a hill or down
in a valley.

 

[Goat Rodeo Cowboy]

I think we still have a lot to learn about the FM broadcast band and coverage. Years ago I was working for a station that was "live and local" in the morning and at the noon hour. (Farm country.) Mid day we "rode the network" for several hours so as a young eager-beaver I grabbed all the manuals and handbooks in the engineers shop I could find and I read and I read and I read.

FM had not really happened. It was out there but I didn't own an FM receiver and didn't know anyone who did. I read all of the theory proposed by Mr. Armstrong and it was obvious that this was the PERFECT system, cast-iron solid. No static. No mixing of signals by overlapping stations like AM. Your reciever would grab one signal and TOTALLY reject the other.

Well. Now we know that book was full of horse-feathers or someting. Part of the problem is that the makers of receivers figured out how to make non-pure tuning devices that are pitiful when compared to early theory.

I live 40 miles from my favorite Atlanta FM station. 96Kw. 800 feet above ground. No mountains between me and the station. And when I strap on my vehicle in the morning and venture forth, I have no idea whether the station will come in today. The signal is there, but some days Greenville, SC 150 miles the other way with comparable power and slightly better HAAT blows my Atlanta station out of the saddle.

Someone show me a reputable engineering text book that calculates that behavior.

 

[K6JHU]

At least as far as having a mountain range between you and the station, I might suggest "knife-edge" propagation.

 

[gar hi]

I think we still have a lot to learn about the FM broadcast band and coverage. Years ago I was working for a station that was "live and local" in the morning and at the noon hour. (Farm country.) Mid day we "rode the network" for several hours so as a young eager-beaver I grabbed all the manuals and handbooks in the engineers shop I could find and I read and I read and I read.

FM had not really happened. It was out there but I didn't own an FM receiver and didn't know anyone who did. I read all of the theory proposed by Mr. Armstrong and it was obvious that this was the PERFECT system, cast-iron solid. No static. No mixing of signals by overlapping stations like AM. Your reciever would grab one signal and TOTALLY reject the other.

Well. Now we know that book was full of horse-feathers or someting. Part of the problem is that the makers of receivers figured out how to make non-pure tuning devices that are pitiful when compared to early theory.

I live 40 miles from my favorite Atlanta FM station. 96Kw. 800 feet above ground. No mountains between me and the station. And when I strap on my vehicle in the morning and venture forth, I have no idea whether the station will come in today. The signal is there, but some days Greenville, SC 150 miles the other way with comparable power and slightly better HAAT blows my Atlanta station out of the saddle.

Someone show me a reputable engineering text book that calculates that behavior.

That's why I mentioned tropospheric enhancement.

It's different than ducting in that it only enhances 'line of sight' signals.

What you just described sounds like both can be at play at certain times and at other times, it's one or the other or neither.

I still think the OP's reception is mostly elevation related with possible tropospheric enhancement too.

The weather models, assuming it was only a day or two ago, were not favorable for ducting in that area.

 

[fangio28]

Thanks for all the great replies to my question.
The receptions were made TODAY (12/17) and yesterday (12/16) on the
car radio(2010 KIA Soul) at various places in town...some in my driveway,
some by Lake Coeur d'Alene, & I ventured up several hundred feet in
adjacent town, Hayden. (Best reception by far was by the lake, as Hayden
was somewhat obstructed). All within 5 miles of where I live in the middle
of this beautiful (pop 34K) town. There were no temperature inversions,
no snow, no rain, so I think it may well be a fairly common occurrence.
(Also, I don't think it's very mountainous between here
and the so-called Tri-City Area). The 6 stations listed are all 100K, except
one at 94K.
One unrelated logging of possible interest: CBTA-FM 94.9 in Trail, BC
(both days) only 13,500 watts @ 110 miles NNW of here running CBC
programming.

 

[fybush]

I'll join in the skepticism about ducting being the explanation for some of Fangio's catches. There are some parts of the country where ducting is almost a daily phenomenon - across the Great Lakes, for instance, or the almost daily path that develops down the coast from Cape Cod to Virginia. The inland Northwest is not one of those areas, in my experience. (Though, to be fair, the evidence is scarce; the most prominent FM-TV DX club, the Worldwide TV-FM DX Association, has few if any members from that area who actively report their DX.)

There are some really neat tools out there that didn't exist when I was getting started in the hobby. I've been playing with a site called GPSVisualizer.com. At its "calculators" page (http://www.gpsvisualizer.com/calculators), you can enter your coordinates and the coordinates of the station you're listening to (get 'em from radio-locator or FCCinfo.com) in the "Calculate a Great Circle Distance" box and tell it to "Draw profile" - and, bingo, there's a chart showing all the terrain between you and the station.

I have a hunch that for some of the paths from Coeur d'Alene to the Tri-Cities stations, there's not much terrain high enough to block a long line-of-sight path...but it's also possible that there's some funky knife-edge propagation going on there, too.

Another thing to remember for those of us trying to analyze Fangio's situation from the northeast or midwest is that the FM dial is very, very different out there in eastern Washington and the Idaho panhandle. A lot of potential DX for us is blocked by a crowded landscape of nearer co-channel stations. Out where Fangio lives, the stations are fewer and the cities much more widely spaced, and that opens the way for a lot of signals to be receivable that would be totally blocked out in more crowded parts of the country.

 

[pianoplayer88key]

So would Tropo, Es or extended LOS explain why I regularly can hear 103.3 KVYB Santa Barbara, about 212 miles distant at a heading of ~306°? BTW I can pretty much always hear the signal, usually strong enough for stereo, if I go about 1/2 mile NNW of me to the top of a hill at a few hundred feet higher elevation than where I'm at now.

 

[MarioMania]

I thought AM is for Groundwaves...not FM

 

[radioman148]

So would Tropo, Es or extended LOS explain why I regularly can hear 103.3 KVYB Santa Barbara, about 212 miles distant at a heading of ~306°? BTW I can pretty much always hear the signal, usually strong enough for stereo, if I go about 1/2 mile NNW of me to the top of a hill at a few hundred feet higher elevation than where I'm at now.

KVYB runs 100,000 watts an has their antenna at 3,000 ft. They have one of the best coverage areas of any FM in the country. I would think that the ocean path helps too.

 

[vibe]

I have a Bose wave radio. The FM tuner only provides stereo when the signal is at a certain strength. In SW Fla there are days where one can get only 5-8 true stereo stations. But there are days/mostly nights where stations usually received in mono can be heard in stereo.
But there are no tropo conditions present whatsoever.
Same thing back in MA but to a lesser extent.
It's my theory that there is such a thing as "tropo lite" (very light to be exact) where the range/signal strength of FM is extended slightly.
One example is the WHOM, Mt Washington NH which used to be received at approx 130 mi here S of Worcester. (a translator filled this in), On certain days the signal was just a LITTLE bit better with no tropo being received elsewhere on the band. The car radio managed to keep the signal locked in a fairly clean stereo signal more often than usual.
That could explain why, in some instances, a digital tv signal is received at slightly varying strengths when there has been no change in outside weather/other conditions.