FRS Radio causing scanner interference

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xpawel15x

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Whenever I transmit on my old motorola walkie talkie and my scanner is receiving a PD frequency, that frequency will stop and not be received at all when I have the talk button pressed on my walkie talkie. When I'm farther away with the walkie talkie, the scanner will receive, but very staticky. Is this normal for FRS radios to cause interference on scanners? It's only when I press the talk button.
 

bravo14

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If your PD is on UHF than yes it will cut their transmission off because you are close to the scanner. If you have a vhf 2way and talk on it and PD is on UHF the VHF will not cut off the uhf PD channel since it is a different band. Be careful heard it can fry some scanner if too close my nextel did that to my base unit and my stero.
 

K4ZXT

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it's not just frs, any radio that is transmitting nearby would mess up your scanner and make it stop receiveing. the stronger the power of the radio, the farther away it will have to be to stop the interference.

and another thing is that it doesn't have to be the same band (uhf/vhf) i have had somebody trnsmitting on uhf and mess mine up on vhf (300 mhz away) so frequency doesn't matter
 

n2mdk

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Yes it's normal you are overloading the radios front end in effect jamming the scanner with strong near field RF.
 

xpawel15x

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Okay thanks for the replies, I turned my scanner off right after I noticed the UHF PD channel was getting cut off. Could this cause any permanent damage to my Pro-83?
 

K4ZXT

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i wouldn't think something like an frs radio would (since their only like .5 watts or something) if you took something higher powered (amateur/business/gov) it might if you do it for a long time

thats just my guess
 

mikeydcg2003

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bravo14 said:
If your PD is on UHF than yes it will cut their transmission off because you are close to the scanner. If you have a vhf 2way and talk on it and PD is on UHF the VHF will not cut off the uhf PD channel since it is a different band. Be careful heard it can fry some scanner if too close my nextel did that to my base unit and my stero.

Nextel's are the worst for interference. Stick them up near computer speakers and all you hear is interference. Don't know if it's something to do with the GSM Freqs they use
 
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ACU1000

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mikeydcg2003 said:
Nextel's are the worst for interference. Stick them up near computer speakers and all you hear is interference. Don't know if it's something to do with the GSM Freqs they use

Has nothing to do with "GSM" - maybe one could argue that it has something to do with "TDMA" - but it has more to do with the fact its a transmitter thats always transmitting. The rumble you hear is probaly more of the fact there is a digitally modulated signal radiating from that little antenna. And, I would rather classify it as the AMBE (i90 series) or VSLEP (i703 style) vocoders used in digitizing the audio signal that eventually is coming out of that device and into the airwaves, etc. Combine that with the TDMA format and thats what you get.

Stick any portable walkie talkie up to speakers while transmitting and you will likey hear something that will not sound good coming from your speakers. I dont think it has anything to do with Nextel, but more with the unshielded wiring leading to the speakers!

:)
 

scanfan03

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I believe it's due to the Nextel being iDEN. iDEN for some reason causes a lot of interference with most devices. I don't think GSM causes as much interference as iDEN.
 
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ACU1000

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Guys.... iDEN doesn't cause interference per se - see my previous post above.
 
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N_Jay

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The iDEN interference is due to the TDMA transmitter switching on and off quickly. It happens to a greater or lessor amount with almost all TDMA formats.
It has very little to do with the frequency band, and has nothing to do with the vocoder format.
 
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ACU1000

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Isnt that what I said above: "it has something to do with "TDMA" - but it has more to do with the fact its a transmitter thats always transmitting."
 
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N_Jay

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lemish said:
Isnt that what I said above: "it has something to do with "TDMA" - but it has more to do with the fact its a transmitter thats always transmitting."

Close, but it has NOTHING to do with a transmitter that is always transmitting, and MUCH to do with a TDMA transmitter that is transmitting in little packets (On-Off-On-Off-On-Off).
If it was "always transmitting, it would NOT be TDMA.

Just to clear up another falicy, it also has littel to do with that fact it is a digital transmission. If you cycled an analog transmitter on and off at the same rate you would get similar interference.
 
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ACU1000

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In theory you are 100% correct. In my opion a transmitter sending an rf carrier every other 15mS or 30mS is the same as continuous when it comes down to answering this guys initial question. I was trying to keep it simple for the guy who asked the question.

But if you insist on details... according to my iDEN System School manual the MS (Mobile Station) takes the output of the vocoder and uses M16QAM to modulate it onto the radio carrier. Vector Sum Exciter Linear Predictive (VSELP) coding is combined with TDMA and M16QAM to achieve up to six-to-one gain in RF channel usage allowing each 90mS of voice to be carried over one or two 15mS repeating timeslots (relative to the MS's ablilty to transmit on any pair of TDD [Time Division Duplexed] timeslots assigned by the PCCH [Primary Control Channel]) on the right frequency carrier (under synthesizer control.)

I will jump off here now - before I get flamed ;-)
 
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N_Jay

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lemish said:
In theory you are 100% correct. In my opion a transmitter sending an rf carrier every other 15mS or 30mS is the same as continuous when it comes down to answering this guys initial question. I was trying to keep it simple for the guy who asked the question.

The point is that you are hearing the 15/30 mS repetition rate of the TDMA switching NOT the 4800 Hz rate of the M16QAM modulation you are hearing.
You would hear almost the same thing is you pulsed a clean carrier at a 15/30 mS repetition rate with the same turn-on and turn-off times.

My point is I believe your clarification is likely to cause more confusion than help clear it up.
 
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ACU1000

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The only thing I was really trying to clear up was when someone said iDEN caused interference. I think your last statement sums up what I was saying in that any carrier (pulsed or otherwise) will do the same thing. Thanks.

Now - as long as someone doesnt dig up the 800MHz rebanding issue because I said Nextel doesnt casue interference - we should be able to end this thread. I really dont want to start quoting the TA manual for rebanding next!
 
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N_Jay

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lemish said:
The only thing I was really trying to clear up was when someone said iDEN caused interference. I think your last statement sums up what I was saying in that any carrier (pulsed or otherwise) will do the same thing. Thanks.

Now - as long as someone doesnt dig up the 800MHz rebanding issue because I said Nextel doesnt casue interference - we should be able to end this thread. I really dont want to start quoting the TA manual for rebanding next!

You are still missing the point. It is the PULSED carrier that causes much more interference than a constant carrier. The sharper the rise and fall rates of the carrier, the worse the interference. TDMA transceivers require faster raise and fall times than most other formats (hence making it worse).

Additionally the repetition rate tends to have some affect, with lower frequency repetition rates being worse. iDEN is 11/22 Hz, GSM is 50 Hz, USDC (TDMA Cellular) is 30/60 Hz.

We don't need to discuss rebanding because the interference caused by iDEN on 800 MHz land mobile systems is a completely different issue than the interfeirence iDEN and other TDMA formats cause to audio (and some RF) equipment.
 

Big_Ears

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Part 95 of the FCC code states that the apparatus may cause interference to other electrical devices, or that the other electrical devices may cause interference to your apparatus. It's the nature of the beast and it is your problem, either way.
 
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