I'm receiving 2 FM stations simultaneously - WUT?

dowtchaboy

(Mods - if you feel this belongs in some other forum, please move it. I can't see any purely radio tech discussions. Thanks)

I was messing around yesterday with the car radio looking for Freedom FM which it seems used to be on 104.4 around here (Carlow/Wexford border). I believe Freedom may have gone purely online now. But there is a station on 104.4 here but what is it? I get Lyric FM, and RnaG (slightly lower in volume) simultaneously! They don't interfere as such - both are perfectly audible when the other one is quiet. AFAIK there is no RnaG or Lyric anywhere near this frequency here.

The car radio is one of those Chinese ones off AliExpress or similar. Guy installed it, gave me no installation or operating instructions, and it works OK but there's a lot of pressing random buttons until I get the function I need.

Any of you radioheads/techies got any ideas? Software Defined Radio?

Pelvis Parsley

Maybe this is a SDR phenomenon (or maybe there's a software fault), but it's not possible to receive two FM stations simultaneously, due to a phenomenon knows as capture effect.

Not sure what's happening in this case tbh.

https://en.wikipedia.org/wiki/Capture_effect

TheBMG

https://www.boards.ie/discussion/2058323159/im-receiving-2-fm-stations-simultaneously-wut

Are you by chance near a large transmitter site like Mount Leinster? It can happen in close proximity to a transmitter (or if a transmitter is having a conniption).

94.0 is R na G from Mt Leinster

99.2 is Lyric

5.2Mhz between them.

However if you take the next step and add 5.2 to 99.2 you get .. 104.4

could be a simple case of overload on the radio

dowtchaboy

https://www.boards.ie/discussion/comment/121384891#Comment_121384891

How very interesting!

Yes, I am at the base of Mount Leinster, about 6km from the transmitters. That seems like a very plausible explanation.

I must make an effort to see if the effect goes away as I drive west. And if I go up to the Nine Stones, which is about 1km down the mountain from the transmitters, I might have a look at the other possibilities for this effect with RTE Radio 1 +/- Lyric, or +/- RnaG

Thank you (both).

dowtchaboy

Just an update on this radio overload:

Yesterday I had a look at the other end, on the assumption that the overload should produce a sideband below the group as well as above - ie 94.0 MHz minus 5.2 = 88.8Mhz. (I say "sideband" - it's been a long long time since I did RF theory so maybe that's not the correct term?)

When I tuned to 88.8MHz - surprise, surprise - I got RnaG and Lyric together again, but this time distorted as there were 1 or 2 other stations breaking in. One was playing Country or Country n Irish, and the other was probably RTE Radio 1. At 6 pm I could hear The Angelus like it was played on tubular bells! But strangely it was slightly after 6.00 - the tolls ended after 6.02 (per my phone) - the only station that plays the angelus is RTE Radio 1 afaik.

I drove West to see how long the phantom stations would last. At Graiguenamanagh, about 10 km from home, 15km from Mt. Leinster, the sound stopped over about 10 seconds as I went downhill slightly to the level of the Barrow - pure silence on 104.4. On 88.8 RnaG and Lyric had disappeared, but the 2 other, mistuned, stations were noisily coming and going - basically what you'd expect when you haven't tuned in properly.

So I think that is a fairly strong vindication of your overload suggestion.

Paul.kavanagh

https://www.boards.ie/discussion/2058323159/im-receiving-2-fm-stations-simultaneously-wut

Hi Freedom's temp licence finished up at the end of October , you will find them online @ freedomfm.ie , you're smart speakers and the app.

we were on 103.8 in that area.

Antenna

https://www.boards.ie/discussion/comment/121391148#Comment_121391148

Tuned to 88.8 where you were - probably also hearing the edge ("mistuned") of Community Radio Kilkenny City (CRKC) on 88.7 ? They were probably playing the country and Irish you heard?

This is their on-air schedule: CRKC 88.7fm Schedule – Commun:ity Radio Kilkenny City

Macy0161

I've been having this with Newstalk and Heart (I think) coming off the mountains with line of site to the sea in the last couple of weeks. Happened in both cars - just for the few hundred metres over the top of Altidore and Killiskey. I put it down to atmospheric conditions?