Reliable (24/7) FM at 211 miles - LOS, tropo or what?

[pianoplayer88key]

Hi all... I thought about posting this in the "Impressive Midwest Tropo" topic, but am putting it here instead, as I'm not sure if it's tropo, given its reliability. (From what I understand, tropo is an occasional / seasonal event.)

At a place less than a mile from my house, I can get fair to good reception on the Tecsun PL-606 from 103.3 KVYB Santa Barbara, CA, at a distance of about 211.225 miles. (I was at 32°46'17.45"N 116°57'0.12"W, give or take a few meters or so - here's a photo.) There was a station in Temecula that would interfere if I oriented the radio's plugged-in wire antenna wrong (the whip is broken), but I didn't record that (also I cut a couple commercials out of the recording I did upload).

This reception usually happens pretty much any time, any day. At that distance, considering reception is usually fairly reliable (except for the aforementioned co-channel interference), would that be normal line-of-sight, or is it possible there could be some 24/7 Tropo action? I'm assuming it's too close for E-skip or F2-layer skip, but is there any such thing as D-skip, and if so would that be possible?

At my house about 3/4 mile south, I have somewhat frequently heard KVYB like this on the roof, but it's not always like that every day.

Any ideas what mode of propagation that is?

 

[K6JHU]

103.3 is on a mountain outside of Santa Barbara (for some reason called "Broadcast Peak") . They have a wicked high power signal. I used to listen to them almost like a local in the suburbs of SF when the band was a little less crowded.

 

[jd]

It's not 24/7 tropo action, although it might seem that way, but instead a phenomenon associated with signals traveling over a low-attenuation path mainly over ocean waters. Of course, it has nothing to do with "salt-water enhancement," and it could be better described as "coastal ducting" (not to be confused with tropo-ducting). In this case the unique positioning of stations has to be considered and it works both ways, in that listeners in the Santa Barbara area often report reliable reception of stations from the San Diego area.

Even if the separation between stations is well over the required distance real world interference does occur. This was discussed when San Diego's KPBS-FM 89.5 filed an application to increase power a few years ago; it prompted two co-channel stations to file applications for modifications. KSBX Santa Barbara wanted a frequency change and KLFH Ojai applied for a power increase to deal with the expected increase in interference. The required separation between the stations (class to class) is nominally about 110 miles; the actual distance from KPBS-FM to KLFH is well over 150 and to KSBX it's about 175 miles.

The long-distance coastal interference issue is addressed in the narrative from the KLFH application: https://licensing.fcc.gov/cdbs/CDBS...?appn=101186676&qnum=5000&copynum=1&exhcnum=1

It's worth noting that KPSD-FM application was approved and a construction permit was issued last year, but there was no action on the applications for the other stations. It may be that the FCC is waiting to see what really happens with interference levels.

 

[w9wi]

Hi all... I thought about posting this in the "Impressive Midwest Tropo" topic, but am putting it here instead, as I'm not sure if it's tropo, given its reliability. (From what I understand, tropo is an occasional / seasonal event.)

Basically, if you can receive the station but are too far away to see the transmitting antenna, tropospheric propagation is involved.

Signals leave the transmitting antenna in a straight line. If not for the troposphere, those leaving the antenna above the horizon would shoot out into space. (no PPMs on the International Space Station, so it wouldn't do the stations much good ;D )

The troposphere bends some of this signal back towards earth, allowing it to be received by radios too far from the tower to receive the signal directly.

The effectiveness of this bending process is dependent upon weather. There's always *some* bending -- a 100,000-watt station in Nashville can pretty much always be heard on a car radio 60 miles away, etc.. -- but under some weather conditions the process becomes MUCH more effective. Signals are bent to a greater degree, and can be heard at far greater distances. (on rare occasions, as far as 3,000 miles away! - though it's unlikely any of us will ever hear anything like that)

Anyway...

There is some loss of signal in this process, and as you might guess the amount of loss increases with distance. And of course, a more powerful station can tolerate more loss.

If you consider both power and antenna height, KVYB is the most powerful FM station in the United States. There are stations back East using more effective radiated power, but their antennas are MUCH lower. KVYB's combination of high power and a high antenna is unmatched. So it's going to cover more ground. On the other hand, obviously there are plenty of mountains in California to block the signal -- but if your path to the transmitter is in a gap, (or sees the transmitter over the ocean) I can certainly see it propagating for 211 miles.

 

[vibe]

I have another take/theory on this. When I lived in Rutland MA, I received UHF stations from about 100 mi away (every day) with clarity on a HH TV. But on a hilltop with a clear view in all 4 directions.

Before a translator occupied the 94.9 frequency in Worc, Ma, one could receive a clear 24/7 WHOM, Mt. Washington NH from about 120 mi away. Station has MUCH less power than 103.3 SB. There were places where the station would lock on seek/scan S of Worcester MA I got this station, albeit more weakly (but in stereo) in Yarmouth NS the 3 days I was there on a car radio in stereo-at least 200 mi from Mt. Wash;
Not enough times in NS to determine if coastal tropo but I am not 100 % convinced that 211 mi reception IS coastal tropo. Could be one helluva powerhouse station.

 

[Schroedingers Cat]

I PMed Chris Tarr, a radio engineer from Milwaukee, a few weeks ago about how I used to be able to get Milwaukee FMs WFMR 96.5 and WLPX 97.3 on a regular basis on a Panasonic RF-2200 and Technics ST-G5, in Southeastern Michigan (about 220 miles away) on an Archer/Antennacraft FM-10 antenna. (He's at WSSP (WEMP) and a couple of competing FMs there. Seems like the type that will QSL. I can never remember all the new call letters but one he is at is/was WMYX 99.1) It was before all the new FMs came on the former Class B-C frequencies. The signals are still there I'm sure, if you can null the new ones and IBOC hash out with an interferometer antenna arrangement where the lobe is narrow enough. The path is partly over water (Lake Michigan). Also Chicago area stations WMBI 90.1 WYCA 92.3 and WYEN 106.7 used to come in regularly also. The higher ERP stations are favored (>=~50 kW), which is why those came in more reguarly than the Sears and Hancock antenna farms. Same was true for (NTSC) WLS-TV and WTTW when they were 316 kW. 112 kW WGN-TV would come in quite regularly in the middle of the night, but only after CKLW-TV/CBET and WWTV signed off.

 

[boiseengineer]

When there were only 2 FM stations on in Boise, way back in the 60s, I could listen to KONA Tri-Cities, WA @ 300 miles almost any time. Then there was Salt Lake City @ 350 miles. Not the ones on the mountain (now called Farnsworth Peak) but when KRSP was running 100 kw from a tower in S. SLC.. Could reliably listen to them most days. Twin Falls @ 120 miles was solid. All with a 10-element antenna and a classic Hallicrafters AM/FM tube radio. Later a Pioneer TX7500.

While the Boise signals coming from the common site are way cleaner than even 12 years ago, there are 18 signal. Scan stops on 30+ signals in this valley now making DX really rare. Even when the power goes out 90% of AM-FM-TV stations have generators. Besides, I’m too busy to DX when the power goes out!

 

[gar hi]

103.3 is on a mountain outside of Santa Barbara (for some reason called "Broadcast Peak") . They have a wicked high power signal. I used to listen to them almost like a local in the suburbs of SF when the band was a little less crowded.

I found some info on Broadcast Peak which is 4,200 ft.

http://www.well.com/~dmsml/b-peak.html

From 4,200 ft, the visible horizon is 92 miles. Add to that any height of the tower itself and it's even more.

Now take into account how FM stations normally with no unusual tropo conditions exceed the visible horizon by quite a bit and it makes sense an FM station atop a 4,200 ft peak can be heard at 211 miles.

 

[gar hi]

Just for comparison, 93.3 WFLZ from Tampa has a tower height of 1358 ft.

That means the line of sight to the visible horizon is 52 miles.

All the times I've driven up I-4, 93.3 FLZ is still heard in Orlando (80 miles) and beyond to a point about half way between Orlando and the exit for I-95 where I- 4 ends.

It just goes to show how much FM normally goes well beyond line of sight.

I think the reception of KVYB at 211 miles is a height issue.

 

[jd]

It just goes to show how much FM normally goes well beyond line of sight.

I think the reception of KVYB at 211 miles is a height issue.

Yes, it's a factor and a big one in their case. But what accounts for the reverse situation when San Diego (and Tijuana stations, some of which have notoriously short towers) can be heard along the California coast all the way up toward Santa Barbara seemingly much too often? The KVYB situation isn't the only example I've heard that cited a "coastal ducting" effect or a similar description. And it not only came from engineers pleading their case but from the FCC itself.

For clarity I should have pointed out, of course, that this is related to tropospheric conditions. But it's certainly an unusual version, with not only frequent or extraordinarily long temperature inversions but also a uniquely long ocean path in the region, with high elevations on one side. Some theories seem to support the idea of signals being reflected, and then redirected into a more concentrated path because of that. Because of these factors I'm of the opinion that the term has merit.

 

[MarioMania]

Can you please put it on youtube..somedays I don't feel like downloading

 

[Schroedingers Cat]

There is a novel, the name of which escapes me, that describes a temperature inversion situation in Baja California which somtimes reflects wavelengths all the way to optical frequencies. They referred to a mountain 200 miles away which is visible part of the time, well beyond the optical line of sight. La Paz is mentioned in the novel. I remember this because I thought they meant Bolivia, not Baja California. So there is indeed a strange inversion phenomena in that region. Anyone remember the novel? It is a famous one as I recall, one read in schools in the 1960s and 1970s.

I just looked up La Paz on Wikipedia, and I'm thinking it was The Pearl by John Steinbeck. I was thinking Steinbeck. As a trivia aside, what radio station is mentioned in "The Grapes Of Wrath"? I'll give you a clue, it's not FM (LOL). It's an AM and it's 5000 watts fulltime. It still has the same call letters.

 

[jd]

As a trivia aside, what radio station is mentioned in "The Grapes Of Wrath"?

Good question, and I'm sorry I don't have the book nor remember the mention. But here are two guesses, one from the original home of the migrants and the other somewhat near their destination: WKY and KHJ (although the latter had a short-lived call letter change).

 

[Schroedingers Cat]

Oddly, I don't remember the context of the mention. But if they were listening in Oklahoma, it was DX.

I don't know the complete history of the station, but skywaves of stations on regional frequencies were regularly heard by listeners if they were 1000 watts or even 500 watts night. By the context of the book, this was the 1930s. Essentially all stations were nondirectional. It was kind of like the expanded band signals are now. The 100 watt locals were difficult. This is logical, but I have also pieced this together from what people told me who listened at the time.

The station was 1000 watts in 1933 and its frequency was 30 kHz lower pre NARBA.