My most *confusing* mission to date

[SJFedor]

Alright, so, I get the standard 5am phone call from my Wing DOS, saying there's a 121.5 hit on the SARSATs in my AOR. So, we go through the normal motions. Wake up an IC, plot the hits, which were showing up in BFE, so we spun up a GT along with an aircrew (I served as MP for the first out flight).

So, we roll out from where the closest aircraft to me is, in Nashville. It's about a 15 min flight to where the main cluster of SARSAT hits are (we got the call w/ 3, the 1st being just over the TN/KY border, 2nd and 3rd falling inside TN, #4 came as we were starting engines and was a mile or so from #3). Me and my MO head up, listening to 121.5 on both the Becker and the aircraft comm radio. Nothing heard so far. We get to the cluster of hits, don't hear a thing. I elect to turn north and essentially make a line between the cluster of hits and the 1st hit up in KY, since the hits were kinda forming a north/south line. We got about 10 miles north of the cluster, about 3000AGL, and I start hearing *voices* on 121.5. At first I couldn't really make out what it was saying, but as we chugged along it got a little stronger. Becker isn't providing any usable info on the direction of the broadcast, the marble is going everywhere, but I still hear these voices. Then, rather clearly, I hear "...for the low low price of only 19.95".

So, at this point, I realize two things. A) we're not chasing an ELT anymore, more like maybe someone's TV or baby monitor or something, and B) I'm gonna need a GT up here to handle this. So I land at a nearby airport, about 5 miles from where we were hearing this. Voices and all go away as we're inbound to the field. I call my IC and try my best to explain what we've heard and ask him to roll the GT up to the airport we were at, so we could meet up and play together. Ground team's ETA at this point is about 60 minutes.

So, since we had some time to kill, we got back in the air to see if we could figure this out. I went back to the area I first heard these audio transmissions, but when I got there, I heard nothing. Kept flying around a little more, and was able to reacquire it about 15 miles from where I was first hearing it strongly. This time, it's music. Like, Beyonce "Single Ladies" and Lady Antebellum "Love Don't Live Here No More". I, of course, sang along. My MO (and Group Commander) laughed at me.  So we heard it and tried to track it. I could only hear it through the Becker though, not on the CAP radio, including by trying wing nulls, etc. No usable DF info from the becker, as the marble is all over the place.

So, this went on for about 45 min, until the GT got into the area. We'd hear it for a little, start to loose it as we flew around, and when we'd go back to the point we first heard it, it wouldn't be there, or it would be a lot weaker then before. We ended up making a "search box" by essentially doing build/fade searching, going south to north and marking first heard and lost positions, then going back down the line, turning 90 degrees at the middle point, marking where we lost the signal again, doing a 180 and marking the other side. So now, we have a bit of a search area, which was about 50 square miles. We did this at 1000AGL to try and minimize our line of sight of the signal, so we could get the smallest search area possible.

So, we meet with the GT and show them what we've found. There was one area we had a decently strong signal once or twice, so we had them head there on ground. We got back into the air and tried to get a better direction for it, with no tangible results.

Anywho, the GT moved around to where we were hearing the stronger blurbs, and I kept writing the songs down as I heard them. Luckily, in Nashville, there are a boatload of country stations, but only 2 or 3 stations that play artists like Beyonce, Pink, and Lil Wayne. So, I had a pretty firm suspicion of what station I was listening to. But, even where we were hearing it decently, the GT couldn't acquire the signal.

So, they drove around a little, including stopping and talking to a car with an inordinate amount of comm gear on it in a parking lot, asking if it was them. It wasn't. We were flying across our search block when I started to get the signal again. For giggles, I kept on my present heading, which was almost due south. It held the signal, and we ended up flying about 15-20 miles out of the box. At this point, I wanted to get back on the ground and discuss with my IC the possibility that this is either something mobile, or something being emitted from the radio station itself. So, at 1000AGL, 20 miles south of our prior made search box, we turn back towards nashville. Without loosing the signal. We continued to have the signal at the same strength until we were about 1/4 mile from the end of the runway on short final.

The plot thickens....

So, I tell my IC what I've heard and found, and that I was able to hear the signal all the way back to our original airport maybe 25-30 miles from the SARSAT hits. I also compared my song list to those of the radio station's playlists, and sure enough, we isolated it to one radio station. So, we brought the GT back in, and the IC got on the phone with the chief engineer at the radio station, asking to check the equipment, because maybe there was some bleed through.

This was Friday morning/early afternoon when all this happened. It's now Sunday evening. The mission is still open, AFRCC continues to get SARSAT hits (mainly at night, they stop getting them between 10am-5pm, assumed due to atmospherics). The engineer at the radio station has checked the equipment, it's not his. Yet we can't get any definitive bearing on where it's coming from.

FCC has been notified and is getting involved with it in the AM. Not too sure what else we can really do at this point.

Anyone ever had any experiences like this? Any solutions or avenues to try that we haven't thought of?

[Stonewall]

Sorry bro, gonna have to wait until I'm on paid status at work to read that one.  Eyes are glazed over after playing Mr. Mom all weekend...

[KyCAP]

Sounds like the week of "Weird" missions.   I had an AFRCC mission last Wed where we sare certain that we silenced two ELTs (at two different airports) and an PLB on a vest in a Navy Helicopter at Fort Knox...

My guess is that a SAR trasciever or AM two-way radio with open mic near a radio tuned to your station?    Let us know how that one shapes up...

[Gunner C]

A long time ago I was on a similar mission.  We kept hearing conversations and music on 121.5.  We went through most of the stuff you did.  We finally tracked down the source - it was a military emergency radio (either URC-10 or PRC-90, can't remember which).  They purps were having fun transmitting music and laughing in the background, giving a running commentary.  This may be what you had here.

Gunner

[RiverAux]

My wing had something similar not all that long ago.  After we came to the conclusion that it was a radiotransmitter signal it was turned over to the FCC.  Don't recall ever hearing the end result. 

[major pain]

I can remember a mission YEARS ago (my cadet career).. an aircrew was lost and asked our GTL for help finding their way to our OA, when they replied back "roger, we are flyin next to a grain elevator now... standby...." "Wigwam 603.. we are in Coop Nebraska...." Laughing in the radio or GTL said "do you mean our near a CO-OP somewhere in the state of Nebraska!!!" Needless to say there were a lot of Coop Nebraska's in Nebraska!!!!

[♠SARKID♠]

Fedor, your story makes me wonder if somebody boosted the signal on their personal FM transmitter (the kind you can use to broadcast your iPod around the house) or maybe its plugged into the wall and malfunctioning.  Just a theory, YMMV

[IceNine]

That was my first thought sarkid.

This is a tough one I'd be interested to see how this works out.

[_]

The playlist matched a radio station so it's probably not a personal FM transmitter.

Fedor:  What was the frequency of the radio station? 

Isn't there a frequency 101 point something where you're supposed to be able to hear an ELT when close up.  It's possible that the radio station is close to that frequency and something happened to their equipment where it's transmitting a little bit out of their allotted frequency.  If you can possibly hear an ELT on a FM frequency then it should be theoretically possible to hear a radio station on the ELT frequency.

[♠SARKID♠]

That's a sympathetic frequency.  If its a radio station (107.5, I have inside info ), the SF would be around 85Mhz, not up around 121.5.  Pick up a radio that listens in the TV band and you'll hear all sorts of SFs.

[_]

Fedor is this roughly near the center of your box?  107.5 transmitter site

[SJFedor]

Negative. If you track northwest up I-24 about 10-15 miles, you'll see pleasant view right next to 24. That's where most of the hits were centered, and my little made box centered about 4 miles northeast of pleasant view.

What was interesting for me really is that the signal almost seemed to be moving. Like I said before, I could mark one area with a strong signal, and come back in 5 minutes on the same heading, altitude, everything duplicated, and the signal would either be a lot weaker or not even there anymore.

However, that transmitter for 107.5 is up on a pretty good hill, and the tower is massive (>1000ft) so I had line of sight on that tower both in the search area, as well as at my arrival airport where we were still hearing it. That's how I came up with the hypothesis that it was coming from something like the station. Because some decent sized terrain between my arrival airport and that search area, and any local transmitter would have been blocked when I was landing.

Waiting on the IC to call me back and give me another update.

[ol'fido]

Many years ago there was a joint IL/MO mission run out of Bethalto airport near Alton, IL across the river from St. Louis. During an air-ground coordination problem, the A/C from MOWG is telling us that the target is at the intersection of Highway and Highway 22 just west of Greenville, IL. We were on Highway but we couldn't figure out where Highway 22 was.  Finally, we looked at the map and found a road that intersected Highway from the north and up a little ways on the map was the number 22. It was the mileage indicator to the next town. We finally found the target after we figured out what road they were talking about.

[Gunner C]

That's a sympathetic frequency.  If its a radio station (107.5, I have inside info ), the SF would be around 85Mhz, not up around 121.5.  Pick up a radio that listens in the TV band and you'll hear all sorts of SFs.

Aren't you talking about a harmonic?  60.75 would be the next lower harmonic.  I don't think that's within the broadcast band.  BTW, 243 is the next higher - that's the military distress freq.  This relationship is why you will get satellite hits on both.

Gunner

[♠SARKID♠]

That's a sympathetic frequency.  If its a radio station (107.5, I have inside info ), the SF would be around 85Mhz, not up around 121.5.  Pick up a radio that listens in the TV band and you'll hear all sorts of SFs.

Aren't you talking about a harmonic?  60.75 would be the next lower harmonic.  I don't think that's within the broadcast band.  BTW, 243 is the next higher - that's the military distress freq.  This relationship is why you will get satellite hits on both.

Gunner

Negative, they're two different things.  I don't really know a whole heck of a lot about them, we only talked briefely about them in my Ham class.  I know its around 85 because I turned on my shortwave/MW/FM radio, tuned down to the TV band and heard my local country station (106.9) down there.

[SJFedor]

The chief engineer there had mentioned something about the possibility of his signal mixing w/ another station's signal and somehow part of it bleeding over onto 121.5 

I'm not all that comm literate, but he was thinking of possible ways for this to happen. Dunno.

[_]

The chief engineer there had mentioned something about the possibility of his signal mixing w/ another station's signal and somehow part of it bleeding over onto 121.5 

I'm not all that comm literate, but he was thinking of possible ways for this to happen. Dunno.

I'm not an expert in this area but I know multiple frequencies can be used to create something that acts like a third.  I know in the digital world several frequencies can be used to create a signal that more closely resembles a digital data stream (think 1's and 0's).  It could be possible that multiple signals were transmitted in a way that acted like another signal.  The antenna, that one website indicates is the radio stations transmitter site (see my link above), also appears to be set up for multiple transmissions.  It's possible that the equipment in the satellite and the becker were picking up the energy from multiple transmissions and interpreted that as being a transmission on 121.5. 

As I said I'm not an expert but from what I know of electro-magnetic radiation this makes sense.  Now whether what I wrote makes sense is another thing.

[SarDragon]

When you mix two signals of different frequencies, you get a result of four freqs - the two originals, the sum, and the difference.

intermediate frequency (IF)
local oscillator
heterodyne
IF amplifier
image frequency.

If you wanna know a lot more, search on any of the bold terms. The one we're specifically looking at here is image frequency - 121.5 minus 10.7 = 110.8 A station at that frequency can cause significant interference on the ELT channel.

[sardak]

Isn't there a frequency 101 point something where you're supposed to be able to hear an ELT when close up.

Tune to 100.1.  This technique is listed in material from L-Tronics and included in CAPP 2, since L-Tronics helped write it. The reason it works follows up on Dave's prior post.

Image frequency = Tuned frequency +/- (2 x the intermediate frequency, [IF]) of the receiver. 
The most common IF for receivers in the FM broadcast band (and most VHF receivers in general) is 10.7 MHz, so
100.1 + (2 x 10.7) = 121.5 MHz 

This technique works best with cheap FM radios that don't have good filtering. You might have to get close to the 121.5 transmitter, particularly if there is a broadcast station on 100.1, in which case the broadcast station still might wipe out the 121.5 signal.

This can be done on a vehicle FM radio, but the old vehicle radios with continuous tuning (and lousier filters) worked better than vehicles with digital tuners. A CAP VHF-FM radio held close to a 121.5 transmitter can also work.

This also should explain Sarkid's "sympathetic frequency" (a term not listed in any of my sources).  In his example, 85 + (2 x10.7) = 106.4. Harmonics are simply multiples of a frequency, like the previous example 121.5 x 2 = 243.0.

"Birdies" in scanners are often image frequencies because there are multiple IFs in scanners.

And since we're here, the carrier frequency for video on cable TV channel 14 is 121.2625 MHz (there are several CATV carrier freqs in the aviation band). A break in a CATV coax can cause a Sarsat alert. I've chased them down.

As for Fedor's original problem, it could be a number of things that the FCC will hopefully figure out.  By the way, SJ, did you try tuning off 121.5 to an adjacent freq to see if you could still hear it?

Mike

[♠SARKID♠]

This also should explain Sarkid's "sympathetic frequency" (a term not listed in any of my sources).

Oops, my bad.  Confusing my terms, SF comes from the music world.