My first encounter with long distance FM reception

[Rabepobemababe]

Starting at 10:30 p.m. or so yesterday (28.04.12), upto early hours of today, I received very strong FM signal with Malayalam programming content at my residence in Hyderabad, India, at 88.8 MHz. I did a bit of googling to find out if there were any nearby FM stations broadcasting in Malayalam on that frequency. There seemed to be none. The only Malayalam FM station I could find broadcasting at that frequency was Radio Mirchi overseas station at Dubai. Since the laws of Physics do not permit line-of-sight FM reception that distant, I am guessing that this may be a different (rarer) kind of FM reception (Tropospheric / Sporadic-E / Equatorial / Moon-bouncing etc.). I am going to try again tonight to see whether I can receive this signal. Can any other forum member with a good FM tuner cross-check and confirm the DX signal?

 

[sound1]

It is very much possible that someone was experimenting with electronics -- may be playing with FM transmitters. Here is a nice story from my uncle - he repairs and builds electronic stuff. One time (may be 15 years back) he was building a graphic equalizer for someone and he used to test it at 8.30 in the evening. Looks like people in the neighborhood started hearing the same song everyday on every station Of course it was on AM stations. After a week or so he found that it was his circuit doing all this.

Either that or they have recently opened Malayalam radio station on top of Burj Khalifa hyeah:

 

[Rabepobemababe]

It is very much possible that someone was experimenting with electronics -- may be playing with FM transmitters. Here is a nice story from my uncle - he repairs and builds electronic stuff. One time (may be 15 years back) he was building a graphic equalizer for someone and he used to test it at 8.30 in the evening. Looks like people in the neighborhood started hearing the same song everyday on every station Of course it was on AM stations. After a week or so he found that it was his circuit doing all this.

Either that or they have recently opened Malayalam radio station on top of Burj Khalifa

hyeah:

Actually, the reception continued in the morning, but with lot of static. As the day's temperatures increased, the reception faded away. I think there is a good possibility that it would return in the night. Since the transmission was continuous, and a female RJ was anchoring the programme (which contained film songs, one radio-drama, and intermittent advertisements), I suspect it is a regular FM station than some Keralite electronics enthusiast experimenting with his Pirate FM Transmitter.

Just for the record, it is not at all uncommon to sporadically receive, particularly during the nights of the drier months, VHF / FM transmissions of far away stations. The station need not be at the top of the Burj Khalifa. In fact, the hobby of FM DXing is all about receiving far away stations.

By the way, with all my efforts, and with a dedicated FM antenna on my roof, I was unable to receive University of Hyderabad's campus radio (Bol Hyderabad) transmission at 90.4 MHz in the area where I stay in the city. But I guess such are the quirks of FM reception.

 

[jls001]

What you are observing/hearing is perfectly normal at this time of year.

I have personally heard, driving around in a car in a Bhubaneswar, Mirchi, BIG FM and Red FM of Kolkata. By road, I believe this distance is more than 400 kms.

I also know of someone in Vizag hearing Chennai stations last year around this time.

Also I know of someone who heard in Shimla an FM radio station broadcast from Siliguri (WB). I don't know the exact distance between these two places but I think it must be a couple of thousand kms?

Explanation: I don't know. May be some funny atmospheric phenomena during spring time.

 

[baijuxavior]

Were you able to identify the FM channel from the announcements? Is it private channel or AIR? If you know Malayalam then you may be able to identify which FM channel is it and where it is located like Kochi or Thiruvananthapuram. I don't know which FM uses 88.8 MHz in Kerala as I rarely listen FM.

List of Malayalam-language radio stations - Wikipedia, the free encyclopedia

The phenomena may be due to the heavy rains we have these days accompanied with thunderstorms in the evening and night. Just like the last year this time also my modem conked off by lightning. Need to buy a new one.

 

[quad]

MaBabuE,
One of your neighbours is probably using one of those
mini FM transmitters to re-broadcast from a (PC or other) internet radio device.
I think these kind of transmitters default to 88.8 MHz. They are typically very
low power (10 - 50 mW).

 

[sound1]

Explanation: I don't know. May be some funny atmospheric phenomena during spring time.

You are right on spot. Loos like the phenomenon is called ''Tropospheric Ducting''. Quote from wikipedia:

Tropospheric ducting is a type of radio propagation that tends to happen during periods of stable, anticyclonic weather. In this propagation method, when the signal encounters a rise in temperature in the atmosphere instead of the normal decrease (known as a temperature inversion), the higher refractive index of the atmosphere there will cause the signal to be bent. Tropospheric ducting affects all frequencies, and signals enhanced this way tend to travel up to 800 miles (1,300 km) (though some people have received "tropo" beyond 1,000 miles / 1,600 km), while with tropospheric-bending, stable signals with good signal strength from 500+ miles (800+ km) away are not common when the HA JA JA index of the atmosphere is fairly high.

I used to think FM frequencies travel in straight line and only AM signals that bend

 

[Moviela]

There is another way FM Dxing is occuring. Around the world authorties limit the amount of pop culture that can be broadcast on FM. While it varies from country to country, 88 to 92 Mhz is restricted to public broadcasting. What some rascals have been doing is taking a license for a low power TV translator on 82 to 88 Mhz. They then purposely mistune the aural transmitter to 88.1 to 88.8 with FM stereo modulation. The audio signal is then heard on conventional FM receivers.

In some countries the station is licensed by a religious entity (mainly the Catholic Church) who uses the visual carrier to broadcast religious text and video. (I call it death by power point) and receives income from the commercial broadcaster who cannot get a license in the normal manner.

That said commercail radio is pulling into the station soon and will cease to be profitable. The new normal in broadcast distribution is via the internet. Internet audiences are easy to measure, and government censorship is eliminated. It is also much cheaper to distribute content on the internet. A broadcast transmitter requires a significant amount of electricty every month, and expensive engineers to operate. An internet station needs a single mains connection of 400 watts, and setup assistance from your cousins 10 year old son.

 

[Rabepobemababe]

jls001 @ #4,

We used to receive Srilankan TV channel, Rupavahini, on regular basis during the evenings of summer months (which used to be the time for school / college vacation) in a coastal town of Andhra Pradesh, and I had personally received Chennai AIR FM on an all-in-one Videocon boombox at a place several hundred kilometers away from Chennai.

Here is a video on Youtube of a Vietnamese FM station being received at Siliguri:

FM 105.1MHz Vietnam FM DX in Siliguri, WB, India, Sporadic E propagation - YouTube

DXing enthusiasts keep posting several such videos on Youtube.

Baijuxavier @ #5,

I can only sketchily understand Malayalam, and was unable to identify the station. The carrier signal of the station was not carrying its name-tag, which would normally be the case with most FM stations. But the programming content was sounding professional, i.e., advertisements, songs, etc.

Quad @ #6,

Very interesting observation! Quite possible, as I notice that even the Nokia 701 that I use contains an inbuilt FM transmitter. But who would continuously broadcast over a period of nearly 24 hours from his low-power / home-made FM transmitter? There were gale force winds and drizzle in the city yesterday evening, and the Malayalam station at 88.8 MHz disappeared. It reappeared again, albeit with lot of static, this morning when the sky cleared up. Therefore, the station is very much there all the time, and it is not an on-and-off kind of a transmission.

Sound1 @ #7,

That's what I think it was (and is).

Moviela @ #8,

I get what you are saying. Since FM is between channel 6 & 7 of the regular terrestrial (VHF) TV transmission, taking permission for VHF TV transmission, say in channel 5, and then purposefully mistuning the transmitter / antenna to get into the zone between channel 6 & 7 to work as an FM radio, is very much possible. Very interesting insight indeed!

But who would do it in India (=Hyderabad) ? Terrestrial TV transmission here is entirely the domain of Doordarshan, and even if somebody wants to venture into terrestrial TV transmission, it would be a more expensive proposition than running a private FM station.