Cell tower proximity?

bobruzzo

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I was driving today down to town garage to dump off old TV set in the electronic recycle bin....it's about a mile away. I noticed across the street at the skate rink is a big cell tower. Never noticed it before, but I usually don't drive in that area. I looked on map and traced a path from my house to the tower....see pictures.
I am wondering if being this close to a cell tower could cause reception problems on 800 mhz freqs. Since there are so many variables that affect 800 mhz reception, it is hard to pin point but what would symptoms of cell tower proximity be? I measured the distance and it's about 1 miles. Terrain and elevation roughly the same at tower and my house. How can you tell if desense or simulcast distortion is the problem? I would like to figure out how to use the feature on my scanners (bcd996p2 & sds200) to "see" whats happening on adjacent frequencies. Not sure if there are other antennas/services that use that tower. I can go over and get pretty close to it and get a more detailed look at the antennas. I know this topic has been beaten to death and the usual response is "get a G5".....but I have plenty of time to trouble shoot. And I'd be interested in narrowing down the issue(s) for a little improvement in reception. There are a few things to consider that create bad reception....could be distance from system you are listening to, either P25 or trunked motorola, your antenna, your location, radio....its a lot of variables. So how can you tell if it's simulcast distortion or desense from a cell tower? Or could be both! Well just a thought because I didnt know I was this close to a cell tower and even tho I have an sds radio I still have a little distortion problem. Nowhere near what my 996 has. So I am just wondering if cell tower may factor in.
 

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bobruzzo

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UPDATE: Using the scope function on my bcd996p2 I set a center freq to 853.8750 which is the CC for RISCON SOUTH site, the P25 system in my area. There appears to be a nearly constant signal way over on left a few bars after 803.870. It will appear, stay there for a bit then go away before returning. There is also a signal right up along the left side of center freq. I am not sure how to decipher this graph.....I set the SPAN at 120, so range is 803.87 to 903.87. That should include any closeby transmissions to show up. After monitoring this a while this is pretty much all I get....with slight variations....sometimes 2 side by side transmissions on far left.amplitude of signals look full scale mostly. But there is no way to determine the EXACT freq of those signals other than the center freq.
 

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nd5y

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I Not sure if there are other antennas/services that use that tower.
Find the latitude/longitude coordinates and look it up on the main database page or the FCC web site.
It looks like there are no active PLMR licenses there so any transmitters will have market area licenses. There could be federal users that you can't look up. The picture resolution isn't good enough to see all the antennas. It's probably all cellular type stuff
 

TailGator911

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I live by the main gate of a military base (Wright-Patt AFB) and I can look out of my kitchen window and see a cell tower maybe 1/4 mi away, very close. I am in a sweet spot here and the tower does not interfere with my monitoring whatsoever. I do get a birdie at 159mhz but only when sweeping on CloseCall. No interference at all in the 800mhz realm.
 

ilgrant

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Chicago, IL
I am wondering if being this close to a cell tower could cause reception problems on 800 mhz freqs.
There is a cell tower that is a couple of blocks from my location and have had no problems with 700 and 800 Mhz frequencies. The tower provides for multiple carriers including T-Mobile which has the new 600 Mhz allocation. So far the 996P2 hasn't cared one bit.
 

bobruzzo

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Find the latitude/longitude coordinates and look it up on the main database page or the FCC web site.
It looks like there are no active PLMR licenses there so any transmitters will have market area licenses. There could be federal users that you can't look up. The picture resolution isn't good enough to see all the antennas. It's probably all cellular type stuff
Here is what came up on FCC search......not sure if this is helpful or if any useful info can be gotten from it.....
 

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vagrant

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A cell tower was installed 650' away and I did not notice an issue. It is between my location and a 200' TX tower seven miles away at about my same elevation that transmits at 100 W. Recently, another cell tower was installed 100' away in the opposite direction. I do notice degradation after that installation.

Most 800 MHz systems TX into the central valley here from 3500' or 5500' elevation via locations 25 miles away. There is now a slight degradation of signal from those systems as well after that new tower just 100' away was installed, but their respective HAAT (Height Above Average Terrain) busts right through.

What does this mean, mostly nothing unless you're in my house using my equipment. Everyone's topography and equipment are different, as well as the TX locations and frequency of whatever. Filters can be your friend.
 

bobruzzo

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A cell tower was installed 650' away and I did not notice an issue. It is between my location and a 200' TX tower seven miles away at about my same elevation that transmits at 100 W. Recently, another cell tower was installed 100' away in the opposite direction. I do notice degradation after that installation.

Most 800 MHz systems TX into the central valley here from 3500' or 5500' elevation via locations 25 miles away. There is now a slight degradation of signal from those systems as well after that new tower just 100' away was installed, but their respective HAAT (Height Above Average Terrain) busts right through.

What does this mean, mostly nothing unless you're in my house using my equipment. Everyone's topography and equipment are different, as well as the TX locations and frequency of whatever. Filters can be your friend.
I am just trying to rule out possibilities. Wow you have some really high spots out there! Our highest area in RI is Jerimoth Hill at 812'....a mere bump in California terms! I have used filters and have got them set where reception is OK but the receive conditions and variables are so many that experimenting with filters is VERY time consuming and difficult. Especially when you dont know what each setting actually does! I have spent hours messing with them....then you find what seems to be a good setting....then next thing you know you have the same problem again! So you move on to set another filter only to go through this on and on. The only big difference I have noticed is switching to a yagi for the simulcast system here. Out of the 4 sites in the system, 2 come in near perfect, 1 is a bit better and the 4th one is not good....prob my location and the antennas for that site may be directional away from me.
 

vagrant

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I was referring to a physical filter one would put inline on the coaxial cable, typically near the antenna feedpoint, but not mandatory. One would need to know what freq or frequencies are interfering though, or what range to monitor. For example, I listen to Military Aircraft and a chunk of that traffic is between 225 - 400 MHz. I use a dedicated scanner, a tuned antenna and a bandpass filter for that 225-400 MHz range. That system works very well to mostly let that frequency range in. Military aircraft signals still come through (not all) when I transmit using an amateur radio antenna with just 10' of vertical and horizontal distance between it and the Mil Air antenna. I am happy with that system.

My two biggest issues are: (and probably for others)
- FM Broadcast stations
- 152 MHz and near there paging transmitters

Using an SDR and computer, I would see my noise floor jump hundreds of MHz away when that paging signal transmits. I use separate notch filters on each antenna to handle those problems. The elevation of the Sierra Nevada range is nice, but not so nice when offending TX signals are at those elevations as well. I even have filters for those two in my vehicle.
 

bobruzzo

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I was referring to a physical filter one would put inline on the coaxial cable, typically near the antenna feedpoint, but not mandatory. One would need to know what freq or frequencies are interfering though, or what range to monitor. For example, I listen to Military Aircraft and a chunk of that traffic is between 225 - 400 MHz. I use a dedicated scanner, a tuned antenna and a bandpass filter for that 225-400 MHz range. That system works very well to mostly let that frequency range in. Military aircraft signals still come through (not all) when I transmit using an amateur radio antenna with just 10' of vertical and horizontal distance between it and the Mil Air antenna. I am happy with that system.

My two biggest issues are: (and probably for others)
- FM Broadcast stations
- 152 MHz and near there paging transmitters

Using an SDR and computer, I would see my noise floor jump hundreds of MHz away when that paging signal transmits. I use separate notch filters on each antenna to handle those problems. The elevation of the Sierra Nevada range is nice, but not so nice when offending TX signals are at those elevations as well. I even have filters for those two in my vehicle.
I monitor a 383mhz P25 trunk system the US Navy uses and I get stuff from all the way down to middle east coast.....they have "Midlant" patched in to Newport Navy base here in RI. It's pretty interesting. No prob monitoring them, full scale on discone. I also listen to the Coast Guard P25 uhf channels. Not as much traffic but you do hear things. And I have frequencies that the military uses in the 225-400 band like you....hear a decent amount on there. This is all received on my bcd996p2 with discone up about 20 feet. My main issue is simulcast distortion on my sds200. It has been cut down quite a bit since I switched to a yagi pointing east. There are 2 strong sites for P25, North and South that come in very well and filter on radio is set to "off". The other 2 sites in this system are flakey and I have been trying to figure out why. It could be simulcast distortion, desense from nearby transmitters, who knows cause it is impossible to track down. And I dont have enough information on that system as far as exactly where and how their antennas are oriented, if they have lower power on the 2 other (Prov and East) sites I have trouble with. If its a pager signal, nxdn, who can tell? I suppose an sdr setup might help. And on my conventional monitoring scanner (bct15x) everything is perfect. So I am spinning my wheels with this sometimes. I think this fall when its cooler out I might pick up another yagi and mount near my other verticals on back of garage. Then I will have an easier time rotating it to check signals. Right now the yagi is in a difficult to access spot only cause its the only place I can mount it right now.
 

vagrant

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That's a nice location for plenty of marine and air traffic. Here in the middle of California I do have plenty of mil air traffic with most of it south of me, due to the bases and flight training/practice area in the desert in the SE. Still, I lose things when they're low as the Sierra's get in the way. Constant air tankers flying as well. I once heard an airman working the nozzle and talking to a jet refueling suddenly yell "break off..." and then scream, which was discomforting. About 30 seconds later she came back on and was quite calm. She told the pilot that was attempting to refuel to pull up along side so they could get pictures, I presume of damage to that aircraft. I probably would have yelled too with a jet flying up into my face. Turbulence is unhealthy.
 
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bobruzzo

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That's a nice location for plenty of marine and air traffic. Here in the middle of California I do have plenty of mil air traffic with most of it south of me, due to the bases and flight training/practice area in the desert in the SE. Still, I lose things when they're low as the Sierra's get in the way. Constant air tankers flying as well. I once heard an airman working the nozzle and talking to a jet refueling suddenly yell "break off..." and then scream, which was discomforting. About 30 seconds later she came back on and was quite calm. She told the pilot that was attempting to refuel to pull up along side so they could get pictures, I presume of damage to that aircraft. I probably would have yelled too with a jet flying up into my face. Turbulence is unhealthy.
You never know what drama unfolds on the airwaves. The most exciting things I hear is the RIPTA (busses) drivers loudly whining and complaining to dispatcher about freaky passengers and idiots. I like the milcom traffic cause sometimes it is interesting. I never bothered to monitor it before, but I thought since my radio covers those freqs, I might try it. A lot of the traffic is from over at Cape Cod.....there are some air bases out there. I can hear the planes way out from there. Marine traffic here is good if you live close to the bay. I can hear some of it though. Conventional scanning here is not to bad, and there is plenty to listen to. I like my bct15x for all conventional scanning. I have that hooked up to an Omni X antenna up about 30' and I can hear very good distances.
 

WeldGuy

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I experienced first hand the ability of a nearby cell tower to overpower the desired scanner reception. I have been helping a friend with difficulties receiving MARCS digital transmissions from our local police department and sheriff's office. It's the perfect storm - in a negative way.

There is a cell tower just a few feet hundred feet from her house. The nearest MARCS tower is at least 15 miles away. I added an external antenna which made the problem WORSE. I explained to her that we are trying to receive a "thimble" full of signal while the cell tower is dumping a "bucket" of 800 MHzs signal on the scanner. I verified the problem with her Uniden 436 with my Uniden 436... virtually NO reception. I have borrowed a Yagi to try, but haven't had time to check it out. I plan on installing the directional antenna with a two-sided metal shield to help block the cell tower signal. Her only hope is the new MARCS tower being built closer to her house.
 

bobruzzo

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I experienced first hand the ability of a nearby cell tower to overpower the desired scanner reception. I have been helping a friend with difficulties receiving MARCS digital transmissions from our local police department and sheriff's office. It's the perfect storm - in a negative way.

There is a cell tower just a few feet hundred feet from her house. The nearest MARCS tower is at least 15 miles away. I added an external antenna which made the problem WORSE. I explained to her that we are trying to receive a "thimble" full of signal while the cell tower is dumping a "bucket" of 800 MHzs signal on the scanner. I verified the problem with her Uniden 436 with my Uniden 436... virtually NO reception. I have borrowed a Yagi to try, but haven't had time to check it out. I plan on installing the directional antenna with a two-sided metal shield to help block the cell tower signal. Her only hope is the new MARCS tower being built closer to her house.
Yeah I am not sure if I have cell tower issues. RF is invisible so you cant see it and that makes it nearly impossible to troubleshoot with all the other variables. What I ended up doing is getting a 6 element 800mhz yagi. It took a lot of turning this way and that way but I found the sweet spot finally. I have a cell tower less than a mile from here. And also simulcast distortion, even with my sds200. But yagi improved things a lot. I think the problem was some of the P25 simulcast towers for the north, south and Providence sites are nearby, so I am right in the middle. The east site is further away like 16 miles. So what I did the other day was point antenna to one of the east zones antennas, southeast direction. I thought that might cut down any overlap from the towers near me causeing simulcast issues. It sure did help because now I get all 4 state zones perfectly. Maybe picking signals up off side of beam lessens the strong signals and brings in the site further away better. I didnt have much luck with a vertical antenna. I tracked down all the locations of all the sites antennas and each zone has about 5 to 7 antennas. Some of those antennas are close to me. To the north, south and right up the hill for me to the east. So maybe being close to those antennas, with yagi pointing away from them and focused on a site much further away that solved my problem. My RSSI numbers were pretty high. Now the RSSI averages to about 50. Sometimes a little higher but D-errors have been cut way down on 3 of the zones. And it has been very consistent too. So I think a yagi was a good choice.
 
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