Mobile use of police scanner and 2m ham rig

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wbswetnam

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In my car, I have a Whistler WS-1095 scanner and a Kenwood TM281A two meter transceiver. Each radio has its own antenna mounted on the roof of the car, about 18" apart. I've always taken the precaution of turning off the scanner and removing its antenna connection from the back of the set before I key up the transceiver, for fear of destroying the front end of the scanner. However, this is rather unhandy, to say the least. Does anyone have any suggestions as to a better way of managing the two radios without damage to the scanner?
 

AI7PM

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I ran a scanner in that configuration in two different vehicles. Never took any precautions other than having the scanner antenna about 20 inches away from the tranceiver antenna. 20 years later, the scanner still works fine.
 

teufler

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Agree with KC4RAF, when mobile , I use trunk mt antennas, probably 3 ft separation. Depends on where the scanner stops and what frequency the 2 meters is at, "feedback" is a real problem. Finally ran scanner antenna to a mfj 2 position antenna switch to run the scanner antenna to ground while I am talking. Only switched to ground if I needed to.
 

ladn

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Other than desense when transmitting (and occasional local oscillator intermod), my mobile scanners and transceivers have peacefully coexisted for 30 years with their antennas less than two feet apart.
 

jonwienke

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Get a power meter and a dummy load, and connect the meter to the scanner antenna lead. Key up your radio and see how much power is feeding into the meter/dummy load. My 436HP handles 500mW regularly with no issues, but if you're getting more than that, I would proceed with caution.
 

FKimble

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Just to provide a little more safety margin, you could just use "low" power on the 2m rig. Since low is 25 watts, you should be able to still reach most repeaters with little to no difference in signal quality.
 

jonwienke

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It's always best to measure. 25W could be dangerous, and 100W could be safe, depending on the exact configuration of the antennas and their tuning. With my particular setup, 25W of VHF feeds 500mW of RF into the scanner. But on UHF, TX with the same radio and power level doesn't even budge the meter needle. 80W in the 10-11 meter band doesn't budge the needle either, mainly because the scanner antenna isn't tuned for those bands.

YMMV, but the only way to know is to check.
 

wbswetnam

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Since I don't care one whit about the factory installed broadcast radio in the car, I tried keying up the Kenwood while the FM radio was playing... no damage and it didn't seem to affect the car radio's operation. But, the car radio's FM broadcast band is 40 MHz below the 2 meter ham band, and it is receiving wide-band FM. Anyway, it didn't fry the car radio if that counts for anything.
 

mmckenna

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Since I don't care one whit about the factory installed broadcast radio in the car, I tried keying up the Kenwood while the FM radio was playing... no damage and it didn't seem to affect the car radio's operation. But, the car radio's FM broadcast band is 40 MHz below the 2 meter ham band, and it is receiving wide-band FM. Anyway, it didn't fry the car radio if that counts for anything.
As Jon said, it depends on the car and specific setup.
My wife drives a 2009 Ford Escape. 45 watt VHF CDM mobile with a 1/4 wave whip centered on the roof. When keyed up, the FM side of the AM/FM radio will desense and lose the radio station. That's a couple of feet of separation and an elevation difference. And, no, the coaxial cable runs no where near each other.
 
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