Canadian TV, Computing and Home Theatre Forums banner

Rudiments of FM dx. I ain't got 'em.

3K views 11 replies 4 participants last post by  Phycks 
#1 ·
Although I've listened to SW dx off and on for four decades, I've never thought much about FM dx. But yesterday (Fri 21/6/13), in my car in Mount Pearl, Newfoundland (which is adjacent to St John's, to the south and with somewhat higher elevation), I listened to a strong signal on 88.1 MHz of an unknown station from the Toronto area. Toronto is about 2000 km west (and a little south) of here.

It was between 3:00 and 4:00 my time (thus 1:30 - 2:30 pm Toronto time). I didn't hear it the whole time (I was in and out of the car) and I heard no ID. I heard eight or ten ads that clearly indicated the Toronto area and, near the end, as it started to break up, I heard what sounded like a station motto: "Four-one-six is on the Edge!" That is the area code of Toronto, 416. "The Edge" seems to be the informal name of a large number of stations around North America, including one in Toronto (though not on 88.1).

The peculiar thing is that there is apparently no one broadcasting on 88.1 right now in Toronto. A station is preparing to take the frequency over and I emailed with the manager of the station late yesterday afternoon; she confirmed they are not yet on air. She also suggested the ads I listed could not have been aired on the closest 88.1 station, in Erin, ON.

So this is my question to FM dx-veterans: is it possible that I heard a spurious flake off a different frequency? I know that with sw stations spurs can be produced; is this likely with VHF stations?

If that's so, is there a likely distance (like, say, an IF fq of 10.5 MHz) that might indicate the home frequency of the dx station? The "Edge" in Toronto is on 102.1 which is 13 MHz away from 88.1: is there a significance to that distance (13 MHz) that would make it likely that that's what I was listening to? I emailed the station last night but have only received an auto-reply from them yet.
 
See less See more
#2 ·
It's very unlikely the station you heard is from Toronto. It's more likely that you heard CKDU 88.1 FM in Halifax or another station within 200 miles. FM DX is usually limited to about 200 miles but it can travel further in unusual conditions. Toronto did have a station on 88.1 (Ryerson University's CKLN-FM) but it's been off air since 2011. Spurious signals on FM may be caused by transmitter malfunction or receiver overload. Again, that's highly unlikely at that distance. Spurious transmitter emissions are highly regulated (almost non-existent) for commercial FM stations and receiver overload is almost always limited to strong local stations.
 
#3 ·
Phycks, Since it's just too far away to reach any 88.1 FM dial from your area (Yeah, CKDU Halifax should be the most possible case, but base on what you've heard and the assigned format of CKDU - a campus radio, it's just doesn't make sense), maybe it's just the case that one of your neighbour is using a FM transmitter which is plugged to a device streaming the audio from the Edge.
 
#4 ·
Thanks guys for some common sense -- common among those who know FM dx better than I do! I didn't know enough yesterday to figure out what's likely dx-wise.

The signal certainly is 102.1 Edge from Toronto -- I've now heard several IDs today (Saturday). Today I happened to take a similar path in my car through Mount Pearl as yesterday and discovered the signal was strong in the same places and faded out in similar places to those of yesterday. So I think Swan_ch's idea that someone is transmitting the web feed is the most likely explanation. Certainly it does not sound like dx. It covers a fairly big area -- something like a circle of three or four km circumference, so it's not a simple txr to cover someone's livingroom and kitchen area.

The plot thickens . . .
 
#6 ·
Yeah, legally it's a rather dangerous thing to be doing.

I'm interested in trying to narrow down the area it's coming from. If this were a medium wave/ AM txr, I'd use a simple radio with a ferrite bar antenna to triangulate. Is there a simple equivalent for DF with an FM transmission?

By the way, I see I mistyped the size of the area of coverage of this station -- I meant 3 or 4 km *diameter*. And, in fact, I discovered yesterday it's covering a valley that is nearly ten km long. If this were an actual local commercial station, it would reach about 20,000 people: not bad for a local pirate. :)
 
#7 ·
An FM yagi or similar directional design would be the tool for triangulating an FM signal. It's not exactly small. A simple FM dipole might do the job. One can be made from 300 ohm twinlead or speaker wire. It would need to be optimized for 88.1 to be very useful.
 
#10 ·
With comparatively weak signals, is there any way to adjust the whip antenna of a portable radio for directionality? That is, for example, when the whip is (partly?) extended, will pointing it toward the transmitter make for a null?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top