Interference

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stubbs

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With my 996XT with an outdoor antenna at 30 ft, I'm getting interference from weather radio from some of my channels.

At first, I thought my location and antenna were so good I was receiving from the next county, but after listening for a while, I have determined the signal is local.

I hear both the weather radio and the local police department, at the same time. It's frustrating.

Can any of you kind folks help me resolve this? I'm new to Uniden scanners, I bought my last scanner 20 years ago, a Radio Shack Pro-34. The new scanner is much better, but I have to work through this.

TIA

Stubbs.
 

stubbs

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No tone...

There is no tone on those channels. Locally, there are only tones on Fire.
 

ampulman

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There is no tone on those channels. Locally, there are only tones on Fire.
Are you talking about audible tones on the fire channels? If so, this is not what was referred to.

Look up your local frequencies in the database. In the column headed 'tones', look for a number.

If present, add this to the channel (Edit channel > Set CTCSS/DCS > add the number.

Amp
 

stubbs

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You know, I REALLY need to read the manual. I've been spending too much time getting my antenna up, I haven't had time. Now that the antenna is done, I will go RTFM and quit bugging you guys.

No, what is happening is Aztec Police has weather radio in the background. A couple of others, as well.

-stubbs
 

jackj

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You don't really give much info about your problem. What are the weather and police frequencies? Do you still get the interference when you use the antenna on the back of the scanner? How far away from you are the transmitters? Some of the weather transmitters are broadcasting at 1000 watts now. That power level will cause problems to close by scanners.
 

stubbs

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Weather is 162.4750. I don't know the location, but in Farmington, I assume close, and on the ridge that is above the city.

Aztec is 154.81500, at the edge of my listening range. 35 miles away.

I didn't know about the attenuation button until someone pointed it out.

I live in a city close to the transmitters that service the area. It is a really rural area outside of Farmington, I could believe that the weather transmitter is high power. The mesatop above us covers the whole area, there is an antenna farm up there. All of the local TV stations are there.
 

jim202

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One of my pet gripes is that people are asking for help on a problem with in a specific area. BUT,
they don't bother to put even their state in their information or in their post.

So, keep asking for help that you probably won't get much for specifics.

If we don't know the details, we can't supply suggestions. If we don't know the town and state, we
can't look up the weather service TX locations.

Being Farmington and Aztec have been mentioned, I might take a guess at New Mexico, but I
could be wrong.

Jim




Weather is 162.4750. I don't know the location, but in Farmington, I assume close, and on the ridge that is above the city.

Aztec is 154.81500, at the edge of my listening range. 35 miles away.

I didn't know about the attenuation button until someone pointed it out.

I live in a city close to the transmitters that service the area. It is a really rural area outside of Farmington, I could believe that the weather transmitter is high power. The mesatop above us covers the whole area, there is an antenna farm up there. All of the local TV stations are there.
 

stubbs

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Farmington/Aztec, New Mexico yes. Hey, I'm new to the forums, cut me some slack.

Geography plays a role here. We are in the bottom of a basin, in a river valley. The powerful radio antennas are a thousand feet above us, on the mesa going out of town.

I live on a lower mesa, with a 30 foot external antenna. I'm about 5 miles from the towers. I can hear Aztec, and even Bloomfield, 35 miles to my SouthEast. I can also hear Navajo PD in Shiprock, 45 miles to my west.

I sometimes have the problem of the NOAA Weather Radio stepping on some channels, particularly Aztec PD. Not tonight, but sometimes. Of course, it is Aztec PD which I'm most interested in.

-Stubbs.
 

Mike_G_D

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I would first try the IFX (IF Exchange) on the radio to see if that makes a difference. Unfortunately, I don't think this will help because the IFX function is primarily for image interference issues and not intermod; your problem sounds like intermod interference.

I would suggest getting a notch filter to notch out the offending transmitter's primary frequency. In this case it would be for 162.475MHz. There are fixed units from PAR Electronics which have gotten good reviews: PAR Electronics | Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave listening enthusiasts. You can get the pre-tuned unit for 162MHz (VHFSYM162HT) or, call them directly and ask for a unit specifically tuned for your weather frequency which will cost a little more. The 162MHz unit will probably work ok for you but having it tuned right onto the offending frequency is better.

Alternatively, you can try this tunable one that Scannermaster sells: Jim 96XI-1 Adjustable Notch Filter. In this case, you tune it yourself; just listen to the offending frequency transmission and tune the filter very carefully and slowly until the transmission either goes away completely or is reduced in strength as much as possible. I have one of these and they work but the tuning is tricky and it can detune easily over time making it necessary to retune it every so often.

In all cases, there will be some degradation in reception on frequencies around the center notched frequency so if you are interested in other frequencies in the 160MHz to 164MHz range (give or take - depending on the quality and narrowness of the notch filter) it may impact reception on them. This is why a fine tuned fixed unit may be better because they can sharpen it more and make the notch as narrow as possible (depending on the components used and the design). However, if you are mainly interested in that 154.815MHz frequency then you should be fine as that is sufficiently far enough removed in frequency from the 162.475MHz weather station frequency that it should not be severely affected.

-Mike
 
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jackj

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I think Mike is probably right on his take on your problem. I'd go with a tunable notch filter and one with a high 'Q' or Quality Factor. I have no experience with the ones sold by Scannermaster so I can't recommend one.

A couple of notes on this problem, the problem can only be fixed by a notch filter if the Intermod mix is occurring in the front-end of your receiver. If the mix is external then the filter will have no effect on the Intermod. All notch filters also attenuate frequencies around its center frequency. The farther away from the center and the higher the Q of the filter, the less the filter will attenuate.

Read specs on filters with a jaundiced eye. You can't always believe what a marketing department says about their product (I'm sure that's news to you). Just like car manufacturers say, "Your mileage may vary."
 
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