I know you said that it wasn't an image, but subtracting 10.7 Mhz from the signal yields 147.535 in the 2 meter ham band. What the heck, I'm 3000 miles away in South Carilina, but I thought I would weigh in because there have been some husband/wife traffic around here in the old days that never used any call signs and thought they were invisible because they were on a "splinter" frequency..
Strong unknown on 158.235MHz in north Carlsbad
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Images don't work that way - it would be twice the IF of the receiver, usually twice the first IF. The older dual superhet scanners had first IF's at 10.7MHz, 10.8MHz and various others in and around that range. Twice 10.7MHz would be 21.4MHz; it was common to be able to hear ham broadcasts in the 165-169MHz range due to that problem - it was also a way to hear "out of band" stuff in the early programmable scanners (like listening to 406MHz to 420MHz fed at 427MHz to 442MHz area. Most receivers nowadays use triple conversion with the first IF in the 200MHz to 300MHz range. In addition, I have verified this on multiple receivers which use different internal frequency conversion methodologies - it would not result in the same "image" on all of those. Also, if it were fundamentally on that frequency, my close range GRE "Signal Stalker" functions would have locked on that more than likely rather than the non-fundamental ("image"). Believe me, I do know what I am writing about here - I know my way around the inside of a superhet receiver - I did this professionally for many years. I am 100% sure it is not an image nor a half IF nor internally generated intermod (in my receivers).
-Mike
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Yeah, same here - maybe a few key clicks again but no voice traffic.
As a hunch, if this is an old LMR system meant for that frequency then looking at the old FCC frequency usage methodology it would be a water and power utility frequency. Much of the old and some current FCC licenses reflect that also. The old Gene Hughes "Police Call" books had a handy section that showed what those old frequency allocations were. Although those old allocations are no longer valid many such systems were licensed and in operation long before the changes (which I think occurred in the late nineties or so - can't remember). Anyway, if this old system was licensed on 158.235 which used to be an old water and power utility frequency based on the old allocation system then the mobile input is also likely to be one of those allocations. Most likely in the 153MHz area. Specifically those ranges were:
1) 153.410MHz to 153.725MHz in 15KHz steps.
2) 158.130MHz to 158.265MHz in 15KHz steps.
3) 173.250MHz, 173.300MHz, and 173.350MHz.
My guess is the most likely mobile input would be in the first list above (153MHz range) especially since we know that the repeater output is in the second list (158MHz range).
So, if and when they ever use the system again that would be where I would search for the mobile; of course, given the mobile and lower power nature of that signal one would have to be pretty close to it and/or have a good antenna system and good location to hear it.
Long shot maybe but I think that's a good place to start for looking for the mobile input.
-Mike
Mike, just for grins plug 147.135 into one of your monitors and see if it talks when the 158 channel does.
Back in the 1970s when San Diego PD was using a particular vintage GE mobile radio, one could always tell when a SDPD car, operating on one particular 159 MHz channel, was within a quarter mile (or so) because of the receiver IF spurs at +/- 11.1 MHz...
Back in the 1970s when San Diego PD was using a particular vintage GE mobile radio, one could always tell when a SDPD car, operating on one particular 159 MHz channel, was within a quarter mile (or so) because of the receiver IF spurs at +/- 11.1 MHz...
Huh...ok I think I get what you're saying...but, wouldn't that be the associated LO's spurs? I'm not sure I see how the math works on that one but complex spurious stuff can always throw up some weird unintentionals! Anyway, if I am getting what you're saying right, you're thinking someone's ham rig near me throws out a strong spurious when listening to the Palomar 147.130 repeater which contains the modulated audio of the fundamental 147.130MHz signal? Interesting but here's a few problems with that:
1) I never hear any other individuals talking on the system besides the two folks (man and woman) previously mentioned and they have never identified with any ham callsign (or ANY callsign, as far as I have heard). They also never seem to be talking with anyone else; I can detect no hint of the usual type of discourse I hear on the Palomar ham repeaters (and I do monitor those from time to time) nor any of the "regulars" on those repeaters on the system I am hearing on 158.235MHz.
2) The signals are VERY clean; well, I lack a spectrum analyzer so I can't say exactly how clean, of course, but the audio sounds like very clean 100% full quieting FM with no background "gunk" (including no hint of another carrier mixing with it so I don't think it's any kind of intermod). It's one of the cleanest sounding FM signals I have heard (if they're unlicensed, I guess they at least are using decent equipment, near as I can tell, except for the wider-than-now-legal deviation).
3) I know the 147.130MHz repeater and am reasonably familiar with the nature of the conversations on it as well as the operating practices of those involved. Definitely does not sound like them!
Also, the steady use of the 192.8Hz CTCSS tone doesn't match Palomar's 107.2Hz tone; of course, if a weird spur is involved then the tone could be severely distorted and show up as something else on the spurious signal but, what I am receiving is very steady and there are no drop outs or obvious distortion artifacts that I can detect.
Whoever these folks are, they are very sparing in the use of the system at least on some days; I can go days not hearing them at all and then suddenly hear them clearly at the usual strong unwavering signal level (it never changes) multiple times a day for many days thereafter. This has been a dead week - heard them on Monday very briefly and haven't heard them since so far.
As far as I am concerned I think I have come to the following tentative conclusions barring new and unforeseen major developments:
1) They are very close to me, say within five miles or less - no more than 10 miles or so at a guess.
2) They are really running some kind of system consisting of one base and one mobile with the base capable of repeating the mobile's signal on its output on 158.235MHz.
3) Pretty sure the audio is deviated at 5KHz based on how it sounds - without the proper equipment, of course, I can't be sure but that's how it sounds to my ear.
4) The "base" is located at "home" for the two users based on the content of the conversations I have heard.
5) Assuming #4 and #1 above are correct, that "home" may be near enough to me for me to hear very well but, if the repeater is really located at that "home" and that "home" is a normal residence then the antenna is likely not extremely high (as it might be if it were really located on a mountain, say, like Palomar). Therefor, I don't think it likely that anyone else outside of maybe 10 to 15 miles of my immediate area (the Calaveras Hills area of northeast Carlsbad) will likely hear them very well, if at all.
Or, of course, it's all just a very persistent, detailed, and consistent form of delusion on my part; I have a lot of problems but that would seriously freak me out if it were proved to be the case (and couldn't my delusional brain come up with something more exciting than a lone couple discussing mundane personal matters on a possibly illegal radio system? I mean SHEESH!...at last add covert foreign agents and sultry femme fatales or something!)!!
-Mike
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Exactly. The particular GE receiver's LO/IF generated a spur on frequencies + or - 11.1 MHz from the operating frequency. Clean audio on the spurs, as if it was an on-channel signal. [This is when SDPD was operating on a couple of 159.0 - 159.1 MHz channels, and the spurs showed in the 147.9-148.0 MHz section of the two meter band.]
You indicate that it sounds like +/-5kHz deviation, which suggests it is a totally illegal setup (all ops in the 150MHz band business and public safety services are now +/-2.5kHz deviation), or coming from another band where +/-5kHz ops are still permitted (like the 2 meter ham band).
In my nearly 45 years of VHF-FM ham ops, I have seen numerous small-coverage pirate stations (many made from old commercial mobile radios) operating in the two meter band. Since the Palomar 147.730 in, 147.130 out repeater is operating offset and reversed from the "standard" 15kHz channel plan (147.135 in, 147.735 out), a CTCSS of 192.8 would make sense as a method to protect an 'on the normal split' small area operation in the band.
Anyway, just one possible scenario ...
Don
If you think it's a telephone of any sort, you should block the frequency and not listen to it again. Even if the device is illegal, the speakers still have a reasonable expectation of privacy. To intercept a telephone communication in California you need the consent of all parties (most states only require 1 party consent) or a court order in furtherance of legitimate governmental interest based on reasonable suspicion of criminal activity. Knowingly intercepting a telephone conversation is a violation of Cal. Pen. code section 632, the Federal Wiretap Act, and a slew of FCC regulations.
Or, of course, it's all just a very persistent, detailed, and consistent form of delusion on my part; I have a lot of problems but that would seriously freak me out if it were proved to be the case (and couldn't my delusional brain come up with something more exciting than a lone couple discussing mundane personal matters on a possibly illegal radio system? I mean SHEESH!...at last add covert foreign agents and sultry femme fatales or something!)!!
Funny then why listen to them at all. If it is that boring let it be or is it the mystery of the signal itself thats killing you. Secret stuff??? Or maybe some goverment agents talking in code. WindTalkers.
Funny then why listen to them at all. If it is that boring let it be or is it the mystery of the signal itself thats killing you. Secret stuff??? Or maybe some goverment agents talking in code. WindTalkers.
I'll check again around there, Don, next time they transmit (and I'm around to hear it) with CSQ, but I'm pretty sure it's a fundamental (well, insofar as it being a desired "fundamental" mixed up [or down] inside a transmitter). I respect your knowledge and experience greatly!
-Mike
To add to what Don said, I'm familiar with some older phone patch systems that used a point-to-point radio link to carry the traffic. They've all long since converted to cellular, but apparently the National Park Service used to use a 400 MHz radio link between the Farallon Islands off the coast of San Francisco to allow their rangers at the remote outpost there to make phone calls.
There's also a very real possibility that it's some sort of pirate equipment. My friend's dad is a ham and has his own commercially licensed simplex lowband channel to talk to his wife back home in a very similar manner (although they are strict about identifying their station license when required), so it wouldn't surprise me if other people chose to do the same using pirate equipment. Could also be spurious emissions from hams talking on 2M simplex and simply not following license discipline (I really like the ex-SDPD radio equipment theory), or it could be pirate radio or extremely old cordless phone use.
If I were you I'd keep an eye out for VHF antennas on your neighbor's houses/cars as that may answer your question.
I'll program the frequency too, but I doubt I'll hear anything if you're all the way up in Carlsbad.
I don't understand anything you just said, but it was entertaining.
There's also a very real possibility that it's some sort of pirate equipment. My friend's dad is a ham and has his own commercially licensed simplex lowband channel to talk to his wife back home in a very similar manner (although they are strict about identifying their station license when required), so it wouldn't surprise me if other people chose to do the same using pirate equipment. Could also be spurious emissions from hams talking on 2M simplex and simply not following license discipline (I really like the ex-SDPD radio equipment theory), or it could be pirate radio or extremely old cordless phone use.
If I were you I'd keep an eye out for VHF antennas on your neighbor's houses/cars as that may answer your question.
I'll program the frequency too, but I doubt I'll hear anything if you're all the way up in Carlsbad.
I don't understand anything you just said, but it was entertaining.
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???...Huh??!? Umm, I'm confused...maybe I'm misinterpreting you but are you actually recriminating me for indulging in self deprecating humor? I thought you were interested too...or was I mistaken?
As I said before, it's a puzzle to me and I like puzzles - I posted here for those others in my area who do as well. I am house bound and can only do so much with the limited equipment that I have and my situation is getting pretty tenuous in terms of me being able to follow this for too much longer; I wanted to pass on my observations so that others who might be interested and have better equipment and are in more stable situations might be able to follow up and figure it out even if I am no longer able to.
For those who are not interested they need not read or check this thread.
-Mike
It's not a phone - or at least, if it is an illegal high powered import cordless phone system then they are certainly not using it as a phone; there has never been any tie-in to the phone service in any of their conversations. They have strictly been using it as a base-mobile two-way radio system, PTT-RTL, half duplex, no different than any other repeater system you may hear out there (in terms of its technical operational details, if not its traffic content and nature).
-Mike
MIKE please do not take it the wrong way just, just kidding around.
Ok! Not a problem; I am not very good at social stuff period and am a little paranoid that I say or do the wrong thing and cause problems I seriously didn't intend; and one can't always be sure of intended emotions in written communications (at least without emoticons;-)).
Thanks for the reply and clarification and I apologize for my misunderstanding!
-Mike
Don,
A couple of observations I wish to outline for you...
I have been using the Signal Stalker feature on my GRE equipment (in case these folks can change their radio frequency and/or CTCSS tone). Anyway, I routinely pick up a lot of local ham traffic, particularly those folks close to operating on the input of the Palomar repeaters, both PARC and ECRA. When I have listened to the system in question (the 158.235MHz mystery system) I have not ever had an equivalent snag on the 2 meter band - this during multiple previous occasions while using the SigStalker feature and have caught the users talking. Granted, in severe cases, a spur can be stronger than its fundamental but that is usually pretty extreme and usually accompanied by notable forms of distortion, based on my previous experience. Anyway, normally, I would think that it would lock on the fundamental first and, if it were in the 2 meter band, after so many previous occasions with different antennas, locations in the house, and receivers (three different GRE units), they have ALWAYS locked on the 158.235MHz signal. Doesn't disprove your theory, granted, but I would think I would have caught them on the 2 meter frequency on at least one occasion.
Also, I find it odd that they would be using a strong output frequency of a local (well, Palomar mountain) repeater even with a 5KHz offset, to use - there are a lot of cleaner simplex frequencies and repeater pairs available. Granted, if they are unlicensed and don't know any better, but still...
Anyway, as I said, I'll force a search there (2 meter band) next time - if and/or when there is a "next time" (that is, if they haven't caught wind of this thread and/or otherwise changed operation/frequencies/whatever).
-Mike
A couple of observations I wish to outline for you...
I have been using the Signal Stalker feature on my GRE equipment (in case these folks can change their radio frequency and/or CTCSS tone). Anyway, I routinely pick up a lot of local ham traffic, particularly those folks close to operating on the input of the Palomar repeaters, both PARC and ECRA. When I have listened to the system in question (the 158.235MHz mystery system) I have not ever had an equivalent snag on the 2 meter band - this during multiple previous occasions while using the SigStalker feature and have caught the users talking. Granted, in severe cases, a spur can be stronger than its fundamental but that is usually pretty extreme and usually accompanied by notable forms of distortion, based on my previous experience. Anyway, normally, I would think that it would lock on the fundamental first and, if it were in the 2 meter band, after so many previous occasions with different antennas, locations in the house, and receivers (three different GRE units), they have ALWAYS locked on the 158.235MHz signal. Doesn't disprove your theory, granted, but I would think I would have caught them on the 2 meter frequency on at least one occasion.
Also, I find it odd that they would be using a strong output frequency of a local (well, Palomar mountain) repeater even with a 5KHz offset, to use - there are a lot of cleaner simplex frequencies and repeater pairs available. Granted, if they are unlicensed and don't know any better, but still...
Anyway, as I said, I'll force a search there (2 meter band) next time - if and/or when there is a "next time" (that is, if they haven't caught wind of this thread and/or otherwise changed operation/frequencies/whatever).
-Mike
Mike what is a signal stalker? Is that like doing a high and low freq search?
Signal Stalker is the GRE equivalent of Uniden's "Close Call." It acts like a frequency counter and rapidly searches multiple bands for nearby strong signals.
Thanks.
teamballsout
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Palomar repeater? Seems like a good place to start?
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