New Antenna , New problems

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scottish558

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Hey everyone, maybe someone has an idea as to why this is happening , I have a Uniden BCD536HP scanner mounted in my Van, I was using an old Radio Shack magnet mount mobile antenna for the longest time decided to replace it because of deteriorating performance (had it for 15 years). I replaced it with a Austin spectra mobile antenna, It has great range. My problem is that when I turn on the scanner in my Van the scanner stops on a frequency with noise ( like white noise,static) and I have to lock it out I have to do that about 8 times before it can cycle a full scan of the channels I have programmed in to it , the antenna is run in the same place as the other , It happens when the vehicle is running or not, the frequencies it stops on can be in the aircraft band or in VHF and sometimes around 30 Mhz. If I am driving down a country road it will stop on other frequencies and i will have to lock them out too. I can bring the scanner inside and connect it to a chimney mounted antenna that is probably 100 feet from where my vehicle is parked and it wont stop on any frequencies except when there is voice transmission. Is it just that the new antenna is just more sensitive ? Is there anything I can do? I read this forum a lot and hoping someone can help.....thanks.
 

popnokick

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Based on the symptoms you describe there is a strong possibility it is RFI coming from something that is USB-powered in, on, or near the van. Exactly the same thing was happening to my mobile scanner and I discovered that it was the 12V to USB cigarette socket adapter that I use to charge my cell phone. These 12V to USB power converters use cheap switching power circuits that usually generate huge amounts of RF noise. If you search the forums here on RR you'll see people writing about it happening with USB-powered dash cams, inverters, and all sorts of other vehicle accessories. And it can happen with the ignition off if the USB device is plugged into a 12VDC source that is hot when the key is off. So let the scanner sit "locked" up on one of the noisy channels, and start unplugging USB and 12V devices. One of the USB adapters I had would even drift in frequency, causing the locked up / interference channel to stop doing it after awhile... but then a new one would start. It was so severe that even turning the squelch all the way up didn't help.
 

scottish558

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Thanks popnokick for getting back to me, I will try your advice, but the thing I found strange was that I did not have that problem when the old Radio shack antenna was installed, all I did was change the antenna everything else in the van was the same. Could the new antenna be just that more sensitive? I will try to power down different accessories in my van and see what I can find.
 

mmckenna

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Thanks popnokick for getting back to me, I will try your advice, but the thing I found strange was that I did not have that problem when the old Radio shack antenna was installed, all I did was change the antenna everything else in the van was the same. Could the new antenna be just that more sensitive? I will try to power down different accessories in my van and see what I can find.
More than likely, it's picking up something that is internal to the car. That might be because of coax cable with less shielding.

I agree, look at your USB power devices, they are often noise generators. You can also try moving the antenna, scanner and the routing of the coax.
 

Ubbe

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What's changed are that you had a magnet antenna capacity coupled to the roof and replaced it with high performance hole mounted one that has a zero ohm direct connection to the chassi?

There could be some grounding problem, the scanners ground are not at the exact same potential as the antenna ground. Can be tested by running the scanner on a stand alone 12v batteri. And as already mentioned, the coax are preferable of a double shielded kind in a car or try it routed differently.

Have you tried changing the IF (func+7) instead of locking out a frequency?

/Ubbe
 
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