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Antenna mounting and interference

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cpd18tpd501

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I mounted a R.S. 20-176 antenna (which gets rave reviews) just above the roofline and attached the mounting bracket to the back of my “butterfly” uhf TV antenna with the scanner antenna radials only a couple of inches above the T.V antenna.. The scanner antenna now receives worse outside than it did just sitting on a dresser indoors (I used a good quality RG8 cable). Could the TV antenna be interfering with the scanner antenna? Do I need to separate them with an insulated (plastic conduit perhaps) mast? THANKS!
 

wmbio

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Apr 22, 2005
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Cumberland, Md
Welcome, you did not tell us what scanner you were using?...Sometimes placing an antenna outside will simply overload the front end of the scanner...GRE and RS scanners are prone to this overlaod especially if your close to any Paging/TV/FM transmitting towers. You might try turning on the attunuator function if it is available. Many discussion on adding filters to your coax line are here at RR.

Enjoy
Wmbio
 

cpd18tpd501

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Ooooooooh! I’m only 1½ mile from a broadcast antenna farm (TV/FM/&AM) which includes a 1,300 foot tower. Indeed my R.S. scanner had the attenuation “off”. I think you are on to something. I’ll give that a try. THANKS!
 

benbenrf

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Domestic TV sets radiate all sorts of noise through the antennas they are connected to. Placing a scanner receive antenna alongside/next to your TV antenna is a great way of loading up it's front-end with rf noise.

Scanner/receiver front-ends are broad-band - designing and incorporating a 1Gig plus front-end into something that costs what a Radio Shack scanner/receiver costs is going to lead to comprimises (big time comprimises) - even companies like IZT Labs, Roke Manor, Rhode & Schwarz, Watkins Johnson, Agilent ect ect ..... all "struggle" to design & build broadband receiver front-ends to budget (and the cost of their gear is many times more than the typical consumer scanner receiver).

First thing to do, before anything else is to establish if indeed the TV set is the problem: compare demodulated scanner/receiver reception with the TV set plugged in & switched on versus switched off and unplugged. If there is little to no difference then obviously your TV set is not to blame ........ that antenna farm with its 1300ft tower combo down the road becomes a good suspect.

In any event - it all comes back to much the same problem i.e. the ability of your Radio Shack scanner/receiver front-end to handle "noise". It's limited - very limited.

Do some reading up on preselectors/preselection and band filters (in band, band pass ect ect ..). You'll be shocked just what an impact (for the better) carefully chosen aftermarket preselectors and/or filtering has on the ability on any scanner/receiver to receive, process & demodulate rf.
 

majoco

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Dec 25, 2008
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New Zealand
TV's and digital decoders have switch-mode power supplies that are usually 'on' all the time - even though you have turned them off with the remote. Switch mode power supplies are notorious for generating RF noise waaaay up in the frequency bands. Try pulling the plug out the wall socket for the TV (and other bits'n'pieces) and see if the noise stops. If it does, you'll have to move your scanner antenna away from the TV antenna.
 

cpd18tpd501

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Iowa Quad Cities
The Solution:
I applied all of the advice I received and the problem is solved. First I turned on the attenuator function and the reception was improved. Then I separated the scanner antenna from the TV antenna using a hefty piece of plastic conduit raising the scanner antenna a couple of feet above the TV antenna, and this really improved things, but still not pristine. When I retired from law enforcement, I received a RELM 100 channel VHF radio as a gift, so I hooked that radio up to the relocated antenna and am receiving clear crisp signals from everywhere. Obviously the RS scanner is still overloading to some degree from the antenna farm, a problem the more sophisticated radio is not experiencing. My listening rage is approximately 75-80 miles including the ability to hear mobiles. That was beyond my expectations using only an 18 inch RS antenna. I will get the appropriate filter(s) before I return the RS scanner online. THANKS to you all, each suggestion helped a great deal.
 
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