Fm radio interference.

[Roadgeekteen]

Why do two fm radio stations conflict somtimes and is there any way to stop this?

[bandit957]

Why do two fm radio stations conflict somtimes and is there any way to stop this?

Because the FCC puts powerful stations (sometimes even less powerful stations) too close together.

[dvferyance]

That was the case here for a couple of years. WNOV launched an FM transmitter on 102.5 which cut into WNWC out of Madison also on 102.5 WNWC fought this and won and the transmitter was shut down just 18 months later. I don't get it either I would think no overlapping stations would be allowed. I am sure there are other examples.

[Life in Paradise]

The FCC is allowing more and more stations on the air.  Now they are allowing translator stations that are broadcasting from the AM signal band.  We have quite a few here in SW Indiana.  Just about every stand alone AM station can now have a translator (don't know the wattage, but would guess its less than 3000 watts) and broadcast their signal on FM.  The old rules, and they may still apply for the lower wattage (3000 watts or less) was that you could not have transmitting towers any closer than 50 miles apart.  That still would cause a problem for people that lived farther than 20 or so miles from each transmitter which would then give them some interference based upon the terrain.  Higher power stations had other limitations, and when you had stronger stations, you also could not have other transmitters on some adjacent frequencies for miles due to the interference.

[bandit957]

There was a 92.9 in both Dayton and Lexington that clashed right where I lived, and you could always hear these stations battling it out.

I remember in the mid-1980s, if you went far south enough, 101.9 in Cincinnati would battle it out with another station. This one is a mystery, because I can't find any reference to any station on 101.9 in central Kentucky at the time.

[jp the roadgeek]

A few battles I know:

93.7: WZMX in Hartford and WEEI in Lawrence battle it out around Sturbridge

97.5: A low power translator for WKND in Hartford and WALK from Southold, NY battle it out just south of Hartford.

105.5: WWEI in Springfield and WQGN in Groton battle it out along CT 2 between Glastonbury and Colchester

105.9: WHCN in Hartford (transmitter in Meriden) and WQXR in NYC battle it out in the Greater Bridgeport area.  WHCN was required to operate on reduced power to the southwest so it only has a 30 mile range compared to the 60 mile range in other directions.

[CNGL-Leudimin]

There are no less than three 96.9 stations in my province alone. Fortunately the terrain doesn't allow them to battle (And if they were to, it would go unnoticed since two of them are low power amplifiers of the main transmitter, which broadcasts Los40). However, somewhere between the main transmitter and one of the amplifiers (located at a lower altitude) it gets to battle with a Catalan station which I haven't identified yet.

[hm insulators]

More and more low-power FM stations are showing up. Unfortunately, they tend to interfere with the stations I'm trying to listen to. How do you stop this?

[hotdogPi]

More and more low-power FM stations are showing up. Unfortunately, they tend to interfere with the stations I'm trying to listen to. How do you stop this?

I would imagine that changing the station by 0.02 (e.g. 100.1 → 100.12 or 100.08) would eliminate the weaker one much more than it would weaken the stronger one, but I have no way of knowing if you can change the station number like that.

[JJBers]

98.3 of Willimantic starts to battle out 98.3 of Springfield around the Ellington/East Windsor area.

[Jardine]

A characteristic of FM signals is for a reasonably well designed receiver to track the signal down to (IIRC) 3dB below the existing noise level.

Unfortunately, if some of that 'noise' is actually another FM station on the same frequency, well you see the problem . . .

[nexus73]

FM as a mode is about signal capture.  Let the signals be relatively even and there's a fight, otherwise the strong signal wins completely.  AM is not, thus the use of this mode in the VHF aircraft band.  If a strong signal overwhelmed the weak signal, then if the weak signal is declaring an emergency, it would not be heard.  AM allows a mix of audio to get through and thus makes this mode more emergency-friendly.

Rick

[mgk920]

I'm having problems with this on AM, too, mainly relating to what I believe is called 'IBOC hash'.  Here in Appleton, WI, I often like listening to an AM out of Milwaukee, WI that usually comes in very clearly at 1130AM.  The last several years, I've been getting a staticy interference that can best be described as a thunderstorm that is trying to sound out words, likely IBOC hash from an Appleton local at 1150AM, that at times renders the station at 1130AM unlistenable. It is very frustrating.



For the FM side, I agree, it is just too many stations being crammed into too little spectrum.

Mike

[nexus73]

I'm having problems with this on AM, too, mainly relating to what I believe is called 'IBOC hash'.  Here in Appleton, WI, I often like listening to an AM out of Milwaukee, WI that usually comes in very clearly at 1130AM.  The last several years, I've been getting a staticy interference that can best be described as a thunderstorm that is trying to sound out words, likely IBOC hash from an Appleton local at 1150AM, that at times renders the station at 1130AM unlistenable. It is very frustrating.



For the FM side, I agree, it is just too many stations being crammed into too little spectrum.

Mike

We could expand the FM band down to 76 Mhz.  Japan uses a longer broadcast FM band than we do.  Not much is going on between 76 and 88 Mhz in any case when compared to the amount of broadcast FM stations out there!

Rick

[CNGL-Leudimin]

This morning (overnight) I got to hear another radio battle on 90.3. Also I've discovered two of the 96.9 stations in my province get to fight atop a mountain pass, however this battle is subtle as both broadcast the same channel, and I managed to discover this as one has a slight delay with respect to the other.

[cl94]

A well-known case on Long Island is 102.3. The real station is the main Long Island rock station, but there's a pirate station broadcasting on 102.3 out of Brooklyn. The FCC has repeatedly gone after the pirates, but it keeps reappearing.

[SidS1045]

We could expand the FM band down to 76 Mhz.

No, we can't.  76-88 MHz comprise TV channels 5 and 6.  Although most US TV stations are now in the UHF band, there are still stations using channels 5 and 6.

[nexus73]

We could expand the FM band down to 76 Mhz.

No, we can’t.  76-88 MHz comprise TV channels 5 and 6.  Although most US TV stations are now in the UHF band, there are still stations using channels 5 and 6.

The few that remain in the old analog band can be moved.  There is a lot more demand for FM radio broadcast band than there is for obsolete TV channels.

Rick

[JMoses24]

We could expand the FM band down to 76 Mhz.

No, we can't.  76-88 MHz comprise TV channels 5 and 6.  Although most US TV stations are now in the UHF band, there are still stations using channels 5 and 6.

DTV is not compatible with analog radio (that is, you can't get DTV channel 6 audio at 87.75MHz). So, when all LPTV stations are forced to transition to digital, then at that point expansion of the FM band will be possible.