Cell Phone Tower Mystery

[TailGator911]

I noticed this off-chance as I was saving a few bucks on a house-call installation onboard my RV by driving over to their shop. A train happened to go thru at the time and I quickly keyed in the local rail frequency to hear his mile marker report while still sitting in my driveway. Loud and clear with full quieting, as usual. A little while later (and only about 3.5mi from the QTH, on the North side of a cell tower that has never caused interference before) another train came thru and he lit up on the same local freq but very noisy, choppy and static, and very faintly in the background I could hear a woman's voice. She was on a phone call. laughing and talking in a normal voice but too noisy for me to understand a single word. There was the usual up and down lilting inflection and tone that you would hear from a woman talking to a friend. Later that afternoon another train, and back to the usual good signal and tone of my SDS200 on the rail frequency, this time on the South side of the tower and parked back in my driveway. Not until today did I redo the test and I got the same exact results. I swear I am hearing a cell phone call! Unintelligible and faint, but very definitely a phone call. This is happening only on the Dayton District rail frequency 160.980. Any idears?

 

[RichardKramer]

I noticed this off-chance as I was saving a few bucks on a house-call installation onboard my RV by driving over to their shop. A train happened to go thru at the time and I quickly keyed in the local rail frequency to hear his mile marker report while still sitting in my driveway. Loud and clear with full quieting, as usual. A little while later (and only about 3.5mi from the QTH, on the North side of a cell tower that has never caused interference before) another train came thru and he lit up on the same local freq but very noisy, choppy and static, and very faintly in the background I could hear a woman's voice. She was on a phone call. laughing and talking in a normal voice but too noisy for me to understand a single word. There was the usual up and down lilting inflection and tone that you would hear from a woman talking to a friend. Later that afternoon another train, and back to the usual good signal and tone of my SDS200 on the rail frequency, this time on the South side of the tower and parked back in my driveway. Not until today did I redo the test and I got the same exact results. I swear I am hearing a cell phone call! Unintelligible and faint, but very definitely a phone call. This is happening only on the Dayton District rail frequency 160.980. Any idears?

Sounds like you may be hearing a 900MHz cordless phone, analog. The next time you hear it, scan the 902 - 930 Mhz range in 25Khz steps. The IF of the scanner may be mixing with harmonics letting the phone freq come thru. I don't think there are any analog signals in the cellular bands anymore; although I still pick up some control channels in the old 800 MHz cellular band at my qth on my AR8000's. One of the tricks to rx the old 800 MHz cellular freqs after the manufacturers removed being able to cut a diode to rx the band; was to tune in the 2nd harmonic of the freqs if your scanner would rx that much higher. The signals were a bit weaker, but very readable.

Rich - N3VMY - KAG 0096

 

[TailGator911]

What I figured but who in the heck has digital phones in the 900mhz spectrum these days? Never around here. So for S&Gs I took my SDS100 along this morning to compare with my SDS200 and lo and behold this does not happen on the SDS100, but happens on SDS200. Different voices today but still very readable. But, this morning I could make out a young guy's voice giving directions to someone. Today it sounded more like a GMRS radio, because the other person was asking where the local repeater was located and the other guy obliged and gave what sounded like a callsign. Maybe local FRS/GMRS/MURS repeater? There is a group around here that uses those bands on and off during rescue training. They are pretty good about identifying themselves when they are on the local repeater. I only hear it when I am on the North side of the cell phone tower, which I can see about .5mi from my rear deck, and it only happens on the SDS200. Very strange.