Help vhf-lo major interference

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SCPD

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What would cause vhf-lo interference... everything unplugged and main in breaker box turned off and still get interference... outdoor RS antenna mounted to side of the aluminum siding i live in a valley and seems only have interference where i have antenna mounted... also a new Cell tower was put up about 1/8 of a mile from my house... i doubt cell tower will cause vhf-lo interference but everything has interference in lo... please help ... also running lmr-400 direct from antenna to scanner....
 

SCPD

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What would cause vhf-lo interference... everything unplugged and main in breaker box turned off and still get interference... outdoor RS antenna mounted to side of the aluminum siding i live in a valley and seems only have interference where i have antenna mounted... also a new Cell tower was put up about 1/8 of a mile from my house... i doubt cell tower will cause vhf-lo interference but everything has interference in lo... please help ... also running lmr-400 direct from antenna to scanner....
oh yea and i have tried with att on off global on and global off... still no help
 

JoeyC

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...and seems only have interference where i have antenna mounted...
Based on that statement wouldn't it be easier just to move your antenna installation since it appears you have ruled out your house as the source (aside for that aluminum siding nearby) ?
 

brandon

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Do you have Cat-5 UTP (unshielded twisted pair) network cables by chance? They cause tons of interference/noise in VHF low. Try unplugging your Internet router and see if the noise goes away.

Upgrading to Cat-6 STP (shielded twisted pair) network cabling solved all my VHF-low noise problems.
 

SCPD

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Do you have Cat-5 UTP (unshielded twisted pair) network cables by chance? They cause tons of interference/noise in VHF low. Try unplugging your Internet router and see if the noise goes away.

Upgrading to Cat-6 STP (shielded twisted pair) network cabling solved all my VHF-low noise problems.
will try but its wierd cause with the main circuit breaker off and no power to anything in mobile home i get total interference... could it be do to the antenna only being about 12 inches off the metal roof
 

737mech

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VHF-LO noise

Was this something that just started or has it always been this way? Double check all connectors for corosion and water or shorts to shield. Are you using high quality connectors or too many of them? If always this bad try adding the FM Trap to your antenna coax.
 
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SCPD

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same with or without fm trap... kinda sucks abr industries abrind.com is where i bought the lmr 400 and came with 2 pl259 connectors and then a bnc adapter to the scanner... and things are so far away up here the att will block out all transmissions...
 

zz0468

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should fm trap be close to antenna or scanner
Put it close to the scanner, but before any preamps or active splitters you might have.

You haven't really given us a whole lot of information to work with. Interference? What sort of interference? Can you record and post a wav file? What antenna are you using? What receiver are you using? Have you tried an indoor antenna, or walked around with a portable antenna to see if there's anywhere it actually works better?

Have you tried any other filters besides the FM trap? Just because low band is so far removed from the cellular frequencies doesn't mean a nearby cell site isn't causing problems. A scanner receiver has ZERO front end selectivity, and anything reaching the antenna connector can and will overload the receiver front end, if it's so inclined.
 

737mech

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VHF-LO Noise

Did you check for shorts? Take a volt meter set to (continuity or ohm meter) to the center conductor and chrome outside of the bnc. Should be a full open.
 

SCPD

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Did you check for shorts? Take a volt meter set to (continuity or ohm meter) to the center conductor and chrome outside of the bnc. Should be a full open.
No BNC center to Outside continuity...

center pin on BNC to antenna element is 0 on multimeter meening no breaks in center conductor
checked continuity from outside of bnc to antenna ground plane and still turns out good

no shorts in coax....
ground from antenna to Ground Pole is good


I Just dont know 3 scanners and all the same... even when running off batteries

think my pro-106 needs alignment and adjustments but the 396xt works on another antenna and my pro-107 also works on another antenna...

Is it possible the groundplane or uhf elements couldt pick up this interference? and would it be worth trying to take the 3 lower groundplane poles off the antenna?
just a thought...
other antenna i use is a CB steel whip about 40 inches long with no ground plane but mounted on addition to trailer which is not aluminum sided and shingled roof.. and works great... kinda sucks cause i dont wanna rerun the antenna and coax unless i absolutely have too... aluminum siding on trailer has been grounded as well
 

SCPD

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Put it close to the scanner, but before any preamps or active splitters you might have.

You haven't really given us a whole lot of information to work with. Interference? What sort of interference? Can you record and post a wav file? What antenna are you using? What receiver are you using? Have you tried an indoor antenna, or walked around with a portable antenna to see if there's anywhere it actually works better?

Have you tried any other filters besides the FM trap? Just because low band is so far removed from the cellular frequencies doesn't mean a nearby cell site isn't causing problems. A scanner receiver has ZERO front end selectivity, and anything reaching the antenna connector can and will overload the receiver front end, if it's so inclined.
its the cheap 20.00 VHF/UHF radioshack antenna
cell tower is about 1/8 of a mile from here at most and was recently put up and activated about august and theres been alot of complaints about static shock in the area ever since...
several people have complained or talked about static electricity since the darned think was put up...
is it possible to buy a filter to filter the cell frequencies seeing we dont use 800 mhz here just vhf hi and lo
 

737mech

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VHF LO Noise

Lot's of possibilities, just remember if this was easy everybody would be doing it.:) Might be time for a better than $20.00 antenna? Or if you are willing to try building your own, search for OCFD in this Radioreference forum. I've done it, it works, I've tried tuning stubs as well. Maybe the j-pole, I never tried it so I can't speak up for it.
 

SCPD

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well out of nowhere it is working perfectly... no interference and barely any rssi level on vhf lo band.... possibly a freq of nature? warmed up to 40 today when its been about 10 degrees out and the snows melting...lol i just dont get it....
 

737mech

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VHF LO Noise

Best guess you had a bad connection and with all your checking you fixed it. Time to replace all the connectors with upgrades, amphenol is a good company for coax connectors. Also need a new antenna.
 

SCPD

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Best guess you had a bad connection and with all your checking you fixed it. Time to replace all the connectors with upgrades, amphenol is a good company for coax connectors. Also need a new antenna.
yes. Will start with antenna... cant really have too big of an antenna or too high but any suggestions on a vhf-lo/hi antenna?

needs to be outdoor antenna because of the aluminum siding blocking rf signals...
 

737mech

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Antenna upgrade

DPD Productions - Antennas & Accessories for the RF Professional & Radio Hobbyist Dave is a Radioreference member and he makes great antennas. He is one of the few American Companies (BUY USA) left in our hobby. His products have been reviewed by many satisfied customers. In my opinion you have good guys and bad guys in this world, some still believe in customer service and satisfaction and high quality products. Dave at DPD is one of those good guys. :) Maybe the Omni X would suit you best?
 
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