the more i am doing research on this the more confusing i am getting. now i am wondering if i am getting intermod from strong RF from surounding cell and towers that are within 2 miles from me. and not wanting to spend money on antenna that could possibly make it worse. i am asking all miamisburg area scanner hobby listeners to lend a fellow listener out , before i completly go bald from pulling out my hair. Maybe someone that lives close that could come listen to the MCSO trunk system on my street. PM me for my location info. And tonight i will do another audio record.
odd interferance
- Thread starter andy1974
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ok i did record alot more audio , sorry that the video is on its side i recorded it from my phone. heres the link
More audio - YouTube
More audio - YouTube
Have you tried another scanner on the same system or freq that your getting the interferance on?
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Where are you located? Does your house have a "Smart Meter" on it? If so, try putting your HH scanner up against it to see if the noise gets dramatically worse.
How about the power lines in your neighbor,or the street lights.I heard that a street light that is failing will cause interferance.
Are you talking about filters for a outside antenna or a handheld scanner antenna?
either. one i can use on both ?
I listened to the audio clip, but nothing jumps out as an immediate cause. It's hard to trouble shoot stuff like that by remote control, especially when so many details are lacking. It sounds like it could be on-channel. There could be some co-channel stuff you're hearing, as well as being in a poor overlap area of a simulcast system.
You mentioned that the system is your county's trunked system... But what system do the cops that patrol YOUR STREET listen to? Many systems sound really bad outside their designed coverage area, and there's not always a whole lot that can be done about it.
Try approaching some of the suspected cell towers and see if it gets noticeably worse. Get a yagi and see if there's any direction you can point it to change the interference, better or worse.
If it comes to spending money, I'd suggest a directional antenna first.
yea, i have cocidered all of what you have said. the County system i listen to dispatches for about 10 + jurisditions. i am VERY close to one of 6 towers that the systems use to transmit.They dispatch for the city i live. I in inbetween 2 cell towers and 2 or 3 ham operators on my street at first it seemed to be just major RF overload (intermod) even with a mix of IDEN intermod (chopper sound). so i honestly think i have multi problem so i been trying to nip away lil bit at a time. so i am at the next phase of my solution which is to try a filter to block out the celluar band.
W2PMX
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It could be primary overload. Have you tried listening with no antenna? Very few receivers work well when they're VERY close to a transmitter - even the one they're listening to. (Picture someone using a bullhorn placed right up to your ear - you won't understand anything.)
That's not the problem if it's 24/7 interference. The last ham who operated 24/7 died of exhaustion centuries ago. (That's supposed to be a joke - even a ham repeater doesn't transmit 24/7.)
Cell towers, maybe. Good luck in figuring out which channel on which tower is causing intermod with which channel on which other tower to end up at the frequency you're listening to. (And you're not limited to 2 - you could be hearing the product of 67 different signals all mixing and producing a signal on the frequency you listen to - because there's a rusty joint on the fence surrounding one of the towers.)
If it's intermod, unless the intermod is occurring in the scanner (very rare), a filter on the primary frequencies won't do a thing. You're receiving on-channel garbage caused by X and Y (some unknown signals). If you filter that out, you're also filtering out the signal you want to hear, since they're on the same frequency.
Intermod is the most difficult type of interference to determine, let alone eliminate. (From a commercial viewpoint - with access to a lot of expensive equipment. A hobbyist is at a great disadvantage.) If the intermod is being created in one of the transmitters (common), or a fence or rain gutter or some other bad metal-to-metal contact on property you don't own, it would be almost impossible for you to get it eliminated. (the owners of the transmitters causing it, and the owner of the transmitter or other object in which it's occurring, have to get together to eliminate it.) Just hope that it starts getting bad enough to interfere with the county's use of their system - then they'll find out what's causing it and try to eliminate it. (It took about 15 years - and a move to a different band - to eliminate the problem locally. We have a hill - which naturally has lots of towers on it - from which everyone knew it was impossible to use a cellphone or two way radio. The paging system of a hospital 6 miles from the hill was part of the problem. So was some VHF-hi equipment the county was using. When they went to an 800MHz trunk system, the problem went away. And they spent years trying to eliminate it.)
Your best bet is to just do a "hot and cold trace". Walk around with a portable that gets the interference and try to localize it. When it gets bad enough that - with no antenna - it totally overwhelms the portable, you're probably looking at the source. Then it depends on what the source is. If it's owned by the county, or a large phone carrier, you're a gnat trying to toss an elephant over your shoulder. If it's some small company's dispatch system you might stand a chance.
yes, i hear everything your saying. Also if i turn on the ATT on the scanner the electric sound goes away if the halps any.....its so frustrating. it is on my whole street.... once i go into town anout a 1/4 mile down the road boom the problem is gone. ( so before you say it, Yes i have concidered moving , lmao) . i think i will dive in and by a yagi and see what happens, anyone in the miamisburg area who has one and wants lend a hand and bring theirs over i will give 25.00 for the test.
W2PMX
Member
Not really. If the intermod is low level the attenuator would kill it, and if the scanner is overloading the attenuator would stop that. It's still probably one or the other.
Still doesn't say anything. If it's intermod, and it's coming from something on your block (a rain gutter making bad contact, a rusty fence joint, etc.), that would fix it, but if driving 1/4 mile into town drops the tower's signal strength, that would fix it also.
See if you have a ham radio club in the area. Some hams love trying to solve problems like this.
update......i have a friend at work that works for a cable company and i decided to talk to him about my issue.....he gave a FAM-12 12dB Attenuator/Pad .....i installed it between the rubber duck Ant and the scanner, and it completely remove the electric sound but left the signal choppy.. am i on to somthing ? or and i wasting my time? there is a variable Attenuator/Pad out there but again is 75.00 am i barking up the wrong tree?
here is the pad
http://www.cyberestore.com/installa...tenuators-pads/12db-attenuatorpad-fam-12.html
here is the pad
http://www.cyberestore.com/installa...tenuators-pads/12db-attenuatorpad-fam-12.html
W2PMX
Member
Definitely sounds like primary overload. You could try a few things - a 6db pad, a stubby antenna, etc. What you're fighting is enough antenna to receive the signal you want versus not enough antenna to overload the scanner. There may be some amount of attenuation that will do both, or you may have to settle for some interference or some choppiness.
Absolutely, you're on to something. One well known trick in the two-way industry is measure the strength of the interference with, and without, some attenuation in front of the receiver. If a 6db pad gives you a 10 db improvement, then the interference is overload of the receiver. Just what's causing the overload can be tricky to find without help, though.
Example: Where I live, there are cell sites nearby that will drive a scanner into overload. The cell sites are outside the frequency range of the scanner (880 and 1900 MHz) but that doesn't stop it from overloading the receiver's front end. Lucky for me, I have several spectrum analyzers on the bench, so tracking the source of the problem took minutes. I put a notch filter on those frequencies, and the intermod I get on the 440 ham bands goes away.
Your previous comment about getting a filter to block cellular might be a worthwhile investment.
I strongly disagree with this. Scanner front ends have little to no out of band filtering, and the active devices are chosen for cost effectiveness, not IP3 performance. When a scanner is getting whacked with interference, the first thing I'd do is blame the scanner.
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