2m/70cm Dual Bander Interference Issue

KF5DCI · #1 (**permalink**) 10-13-2009, 04:28 PM

Recently installed a dual band mobile in the vehicle. I have noticed if I use it on high power it creates interference with other electronics in my vehicle. I installed it with the power cable running to the + - poles on the battery and the antenna is mounted on a lip mount on the hood using uhf style antenna connectors with 10ft of rg58. i have noticed the interference is much more noticable on 2m rather than 70cm. on high power when transmitting i get high pitched noise in my radar detectors external speaker and oil light comes on in instrument cluster. i also noticed if i have the cb radio turned on while transmitting on 2m high it catches lots of interference as well. Any ideas?

ac7xc · #2 (**permalink**) 10-13-2009, 04:48 PM

How much high power are you running? You should not run more then 25-50 W in a car. One thing to check is to make sure all the antenna connectors are properly made with the coax, they are seated properly to the radio and the antenna is properly grounded to the car. The ARRL has a book on solving RFI problems. One thing I would try is to use a capacitor and/or choke on the power leads to the radio to elimante RF leading back into the car. One thing to do is to have the radio hooked up to an independent power source like a power supply and transmit using the cars antenna. If the interference goes away you know that RF is most likely being put into your car by the power cord.

http://www.arrl.org/catalog/9892/
http://www.amazon.com/ARRL-RFI-Book-...892/ref=sr_1_1

KF5DCI · #3 (**permalink**) 10-13-2009, 05:03 PM

The other thing is, unlike other radios/scanners I have, this ICOM dual band has a power button instead of a power/volume knob, so there is no way to make the radio cut on and off with the vehicle.

W0JJK · #4 (**permalink**) 10-13-2009, 05:24 PM

On the power of the radio, you can take a 30 amp relay from any parts store. I use them and they work great.

I use one's like this. Very easy to wire up. 12V SPDT 30 AMP AUTOMOTIVE RELAY | AllElectronics.com

KC8RFE · #5 (**permalink**) 10-13-2009, 05:27 PM

part of the problem might be antenna location. i would try to get the antenna to the rear of the car or to the roof. That way your getting the RF a little farther from the electronics having problems. That alone might solve your problem.

KF5DCI · #6 (**permalink**) 10-13-2009, 09:59 PM

Quote:

Originally Posted by W0JJK

On the power of the radio, you can take a 30 amp relay from any parts store. I use them and they work great.

I use one's like this. Very easy to wire up. 12V SPDT 30 AMP AUTOMOTIVE RELAY | AllElectronics.com

ya it would cut off with the car, but it would not come on with the car. you would still have to hold the power button to start it up.

KF5DCI · #7 (**permalink**) 10-13-2009, 10:00 PM

Quote:

Originally Posted by KC8RFE

part of the problem might be antenna location. i would try to get the antenna to the rear of the car or to the roof. That way your getting the RF a little farther from the electronics having problems. That alone might solve your problem.

i really dont have many options. i am in a ford ranger with tonneau cover, so its only roof or hood, and i have to meet a low clearance daily.

mrweather · #8 (**permalink**) 10-14-2009, 07:06 PM

Sounds like a simple case of overload. Only real solution is to move the antenna away from the problem area or use lower RF power.

Have you tried mounting it on the other fender?

JStemann · #9 (**permalink**) 10-16-2009, 05:47 AM

overload is definitely a possibility.

You might also ensure the truck's power connections are in good shape grounds to body, chassis and motor. As well as the positive connections going to the starter and alternator. You also might want to add(if it's not already there) a ground from the hood down to the body near the hinges.

Also, check this site for some very good information on mobile installs. Welcome to KØBG's Web Site

hope this helps,
jeff.

KF5DCI · #10 (**permalink**) 10-16-2009, 09:28 AM

I am going to replace the big three (batt - to chass, chass to block, alternator + to batt +) with some thicker gauge wire. Also found some stake hole nmo mounts that are supposed to work with a topper (they have a bar that sticks the actual mount out past the topper. Going to try that, and get the antenna away from the hood and truck electrical components. Hopefully that will solve the issue, we shall see. Also may take someone's suggestion above and put a capacitor between my radios and the battery, I have used caps for audio systems in the past and just never though of using one with my radios, although I doubt that will help much with the interference, it's likely a better alternative to the radio being directly connected to the battery and will also allow me a quick and easy place to connect radios inside the cab rather then running through the firewall all the time. I will report back in this thread once I get the above done and let everyone know how things are working.

Thanks again everyone for your suggestions and advice.

kb2vxa · #11 (**permalink**) 10-16-2009, 10:58 AM

The first thing that comes to mind is move the antenna as far from the engine compartment and instrument panel as possible. All else being wired correctly (power and control leads don't radiate BTW) there's nothing else you can do about the trucker's delight, keying the mic and the electronics go nuts.

For those who may think CB, no, you don't hear many truckers on the ham bands (VHF in particular) these days for this very reason, instruments and engine controls go berserk. Car alarms are very susceptible too, I'd often set them off in passing.

icom1020 · #12 (**permalink**) 10-16-2009, 11:36 PM

I had a FT90 mounted between the seat in a Subaru, it blanked out the am-fm broadcast radio for a min or two. The antenna was on the roof. The commercial icom with a fender mount 5/8 was ok with the remote mounted rf box just under the seat. You might relocate the dual band somewhere else.

rescuecomm · #13 (**permalink**) 10-17-2009, 12:35 AM

Borrow a magnet mount antenna, put on the cab about the center of the roof. See if you get the same problem? Also, if the SWR is high, it will cause the symptoms you are seeing.

Bob

KF5DCI · #14 (**permalink**) 10-17-2009, 02:09 AM

Quote:

Originally Posted by icom1020

I had a FT90 mounted between the seat in a Subaru, it blanked out the am-fm broadcast radio for a min or two. The antenna was on the roof. The commercial icom with a fender mount 5/8 was ok with the remote mounted rf box just under the seat. You might relocate the dual band somewhere else.

The radio is under the seat, but the antenna cable is routed through the firewall on driver side, from the suggestions in this thread I am guessing due to the proximity of the RF line to the instrument cluster and the antennas proximity to the main fuse box (hood mounted driver side) this is what is causing the issue. I plan on relocating the antenna to the rear of the truck.

rfradioconsult · #15 (**permalink**) 10-17-2009, 09:58 AM

If the radio is just stuffed under the seat, run a short lead from the radio chassis to a solid ground connection on the vehicle.

kc2rgw · #16 (**permalink**) 10-17-2009, 04:26 PM

Put an analyzer on the antenna...be sure your ground is solid.

As mentioned, ground your radio chassis as well.

I get this occasionally with VHF in my Jeep and it's always a bit of water in the base of the antenna or connections that have loosened when it happens. It likes to send my FM car stereo into scan mode.

jparks29 · #17 (**permalink**) 10-18-2009, 03:48 AM

Quote:

You should not run more then 25-50 W in a car.

Wanna clarify that?

I run 100W+ on 2m/440 in my car with no ill effects (to my car).

I'm actually gonna guess he has a mismatched antenna.