Electrical and RF Interference

[brwkem]

Read other posts concerning this issue.
Is there anything that can be done to reduce this problem short of an attic antenna and/or removing the sources of interference?

 

[djeplett]

You can use a ferrite bead on the offending item. Hasn't always worked for me.

http://www.palomar-engineers.com/RFI_Kit/rfi_kit.html

 

[N_Jay]

Read other posts concerning this issue.
Is there anything that can be done to reduce this problem short of an attic antenna and/or removing the sources of interference?

All depends on the type and soutrce of the interference.

You have not provided enough information on YOUR issue to get any meaningfull answers.

(Of course that will not stop anyone from giving you THEIR answer!) :roll:

 

[LarrySC]

Usually if you have ATT and PL/DPL that takes care of 90% of the problem. Post more info on scanner, antenna, coax, and connectors.

 

[brwkem]

Thx for the responses.

The scanner is 246T with RS800 portable antenna.
Also have tried Diamond RH77CA.

Room Im using full of potential sources.
Two computers.
3 lcd's.
TV
lamp
phone.

Have been moving the scanner around the room this week and astonished
by the difference in reception.
There is a cell phone tower mile away which may also be a problem.

If I turn on ATT wont that decrease signal strenghts Im trying to receive?

Trying to figure out solutions for this before order the 396T

thx for any help.

 

[djeplett]

(Of course that will not stop anyone from giving you THEIR answer!) :roll:

Was that directed at me?

brwkem, if you have anything ethernet related that can be a large cause of it. I've gone so far as to switch to wireless and move the router and cable modem to the basement.

 

[brwkem]

UGh.
Have a router not wireless and a wireless mouse.

Whats so unusual is that an OLD Pro 39 doesnt seem to be effected that much as compared to the 246T.
Go figure.

thx for the help

 

[Al42]

(Of course that will not stop anyone from giving you THEIR answer!) :roll:

Was that directed at me?

brwkem, if you have anything ethernet related that can be a large cause of it. I've gone so far as to switch to wireless and move the router and cable modem to the basement.

I've read your comments on this before, but it just occurred to me:

The scanner in my signature is sitting - literally - about 5 inches from my Linksys WRT54G, and on my VoIP box, which is fed from that router. I think there's actually one CAT-5 cable routed around the scanner - which is a Pro-95. No metal box even.

And, as you can hear if you connect to the site, absolutely no ethernet interference.

Oh, BTW, this is the stock rubber ducky antenna, and this precinct still maintains its 156 MHz system, because the coverage on the 800 TRS (which is what I'm scanning) is so spotty. (You can hear when it rains by the picket-fencing of the signal.)

And it can't depend on luck - I'm the guy whose 396 was one of those lost by UPS on their way to Grove Enterprises.

 

[Al42]

Have been moving the scanner around the room this week and astonished by the difference in reception.

Now try this:
Turn on the attennuator
Set the scanner to a signal that's getting some interference
Move the scanner around, finding where you get the most interference

The device you're closest to is probably what's causing it. Move that device to another room and see if the interference moves with it.

There is a cell phone tower mile away which may also be a problem.

A mile? Probably not. Especially if the interference changes as you move around the room.

If I turn on ATT wont that decrease signal strenghts Im trying to receive?

Yes, but if there's a signal strong enough to cause intermod in the scanner, turning on the attenuator might reduce the signal enough to stop this, while leaving enough of the wanted signal that you can still hear it.

Trying to figure out solutions for this before order the 396T

There might not be a problem with the 396. Or you might fix it for the 246, but it'll reappear with the 396 (not likely, but possible). First see whether you can find out what's causing it.

Oh:
Lamp? Phone? Computer? TV? LCD? These have to be fixed at the source, not at the scanner, since any interference would probably be broadband noise. But, as N_Jay said, until we know what the source is anything is just guessing.

 

[djeplett]

Al42-

Two things might make your situation different from mine.
1) You're only using the rubber duck. Maybe it's not resonant on any of the frequencies your router would be interfering with.

I've been using one of the back of radio telescopic antennas that end with the right angle BNC. The farther my radio was away from my router/cable modem/PC the less interference I had. When I unplugged my router and powered it down the interference went away.

2) Your scanner is probably better than mine at dealing with the interference.

I have had a PRO-2030 and now a PRO-2035 and both had noise problems when anything ethernet was nearby. Soon as I moved the router and cable modem to the other side of the house into the basement my noise problems went away. And now with my new Yaesu I have less trouble with noise of any kind.

And it can't depend on luck - I'm the guy whose 396 was one of those lost by UPS on their way to Grove Enterprises.

THAT SUCKS! :evil:

 

[bsavery]

There is a cell phone tower mile away which may also be a problem.

Try living less than half a block from one. And another company wants to build another tower 2 blocks from here. I can look out my back door and see 2 more.

I wish someone made a filter that blocked cell freqs. I'd love to put up an antenna, but it'd probably blast everything unless I can kill cell before it hits the scanner.

If I turn on ATT wont that decrease signal strenghts Im trying to receive?

It will, but if you have bad interference, it might be the only way to hear it.

Bob

 

[Al42]

And it can't depend on luck - I'm the guy whose 396 was one of those lost by UPS on their way to Grove Enterprises.

THAT SUCKS! :evil:

Expecting it on Friday, then being told I won't get it until Tuesday sucks.

Being resigned to getting it on Tuesday (I really wanted it for my drive from Long Island to Virginia), then being told it won't arrive until next Friday, when I will have left where it's being shipped to - but it can't be shipped to my house, because I won't be there yet when it arrives - worse than sucks.

I'll see what they say when I call them in the morning. If they want to be really nice to me, they'll ship it overnight without charging me too much extra. (I'd drive down and pick it up, but Maps & Streets says it's a 9:45 drive each way, and I don't want it badly enough to spend almost 20 hours on the road.)

 

[brwkem]

Still trying to figure out the interference problem here.
Turning things off 1 by 1 then testing.
Have noticed this:
RS scanners hand held Pro 39 is nott affected by interference anywhere near as the Uniden 246T. 246T definately affected by router, and LCD's.
Grrrr.

 

[GTO_04]

I've read your comments on this before, but it just occurred to me:

The scanner in my signature is sitting - literally - about 5 inches from my Linksys WRT54G, and on my VoIP box, which is fed from that router. I think there's actually one CAT-5 cable routed around the scanner - which is a Pro-95. No metal box even.

And, as you can hear if you connect to the site, absolutely no ethernet interference.

Oh, BTW, this is the stock rubber ducky antenna, and this precinct still maintains its 156 MHz system, because the coverage on the 800 TRS (which is what I'm scanning) is so spotty. (You can hear when it rains by the picket-fencing of the signal.)

And it can't depend on luck - I'm the guy whose 396 was one of those lost by UPS on their way to Grove Enterprises.

I think that a lot of the noise problem is when monitoring 800 MHz signals. A lot of your noise may be atmospheric, and contrary to what most would think, there is a lot of noise in that band. Couple that with weak signals that are common in 800 MHz systems, and presto, you have a noise problem. I never had nearly the same noise problem monitoring VHF systems that I do monitoring 800 MHz systems. It seems that a lot better antennas are needed to monitor even close by 800 systems compared to VHF.

While at home or work, ideally you would use a yagi antenna to zero in on the stations you want to listen to. It will help reject noise coming from other directions.

GTO_04

 

[Al42]

It seems that a lot better antennas are needed to monitor even close by 800 systems compared to VHF.

The system in my sig is being monitored on a 1/4 wave whip about 10 feet above the ground, and the area is one in which the police regularly have problems hearing the transmitter.

If you're in the primary coverage area of a well-designed system you should have no problem receiving it with a 1/4 wave whip at 4-5 feet above average terrain - which is what the system should be designed to cover. Problems are poorly designed systems, receivers with poor sensitivity and bad antenna systems - as well as various noise sources. Atmospheric noise is accounted for in system design.

 

[cg]

when you are chasing down interference, you cannot just shut off items as many have some circuits or power supplies that are hot all the time.

Most of my interference came from my Linksys equipment ... not from the units but from the power supplies. I put them in the basement as far away as I can and that helps a lot.

If you are in a single family dwelling, you can kill all the breakers, listen to the handheld and see if you have any interference. If there is no interference, turn the breakers on one at a time and see when it appears. That should narrow the search.

chris

 

[brwkem]

Finally figured out my problem lies with a computer. Now wonder what inside that is the major problem? Wonder if blue led fans would be the culprit

 

[kb2vxa]

Hi BRW and all,

The long and short of it is "everything" and "no". The "no" part of it is because that's the only thing that's not digital and those square wave pulses produce harmonics throughout the spectrum and they radiate like crazy. There are so many variables like problem ground points on the motherboard, inadequate filtering and/or shielding on the cables, radiation from the monitor (on and on and on...) you simply have to use process of elimination and hope you don't end up eliminating so many you eliminate the whole computer.

There's only one sure cure, bury the computer in a copper lined concrete vault and connect to it with fiber optic cables. (;->) SURE I'm being sarcastic, this computer is the worst radiator of any I have ever used except perhaps an IBM System 3 mainframe that clobbered every device in the building that used RF and probably emitted X-Rays. Well, it kept the employees from doing anything but work on company time. The crazy part is the silly thing affects certain frequencies depending on what it's doing and not always the same ones or the same things, no correlation whatsoever and right about now it's behaving itself affecting none at all. (If it's reading this I'm done for.)

Thanks for the vent, it's better crying on your shoulder than throwing the computer, scanner or both out a third story window. (;->)

 

[brwkem]

Thanks for the vent. Glad its not only me. Tore apart my entire setup computers and all and it did nothing. Moved things around. Who wants to have there scanners in another room or on the opposite side of the room. Its funny how it only effects certain frequencies and not all, like you said. Decided to work around the frequencies that wont work by going with the scanner where those will work and using others on different scanners. A definite hassle!

 

[brwkem]

WOOHOOOOOOOOOOOOOO.
Solved my long standing interference problem.
On Friday ISP swapped out my Motorola Modem with an Ambit broadband modem.
Interference gone.
And I thought it was the router.
Have to admit could have more than one device causing trouble.
At least a major one is gone.