Radio Cuts Down Engine RPM's

[225/Greg]

My friend has a 99 F250, Diesel Pickup, a Ham Radio & a Wilson 5000 antenna on the roof. Every time he keys the mic he can watch & hear his RPM's drop. He has tried different power sources, antennas & ferrite cores attached. How can he eliminate this problem? [/size]

[Popcorn501]

Does he have a amped hooked up also?What size wire is he using and where is the radio hooked up to?

[Johnny Relay]

It depends on what the actual problem is. Would help to know more info. If it is an Rf problem then he will need to find a way to shield the IDM (Injector Driver Module) from the RF. Good luck on that one. Not so easy to do. If it is a problem where as the radio/amp/system combination is drawing so many amps that the alternator and or batteries cannot keep up will cause the IDM voltage to drop too low. On Board ECM's, PCM's, IDM's and such are not designed nor will work properly with supply voltages of less than 10 volts or inadequate amperage. Below 10 volts there is no telling what the modules will do. I've seen some really flaky stuff over the years.

[causmik]

I want one of those radios.....

[drdx]

Yep, that radio has serious problems. I better take it off his hands and do this guy a favor. I wouldn't want him harming that truck. -drdx

[225/Greg]

Does he have a amped hooked up also?What size wire is he using and where is the radio hooked up to?

No Amp, just an Icom 725 with 100 watts. #10 gauge wire is being used directly hooked to the battery, with extra grounds all over the truck. The radio is mounted on the center floor hump in the truck.

[Sheriff Bart]

he might want to increase the wire connecting the radio to the BATTERY to larger than 10 gauge.



73's

[225/Greg]

It depends on what the actual problem is. Would help to know more info. If it is an Rf problem then he will need to find a way to shield the IDM (Injector Driver Module) from the RF. Good luck on that one. Not so easy to do. If it is a problem where as the radio/amp/system combination is drawing so many amps that the alternator and or batteries cannot keep up will cause the IDM voltage to drop too low. On Board ECM's, PCM's, IDM's and such are not designed nor will work properly with supply voltages of less than 10 volts or inadequate amperage. Below 10 volts there is no telling what the modules will do. I've seen some really flaky stuff over the years.

Thanks for responding! The problem is that the engine RPM's drop while modulating on SSB or AM/FM. He can have the truck idling at 1500 rpm, key up and the rpm's will drop by 400-500 rpm's. He thinks that you could be right on with the IDM shielding and RF problem. I just spoke to him and he would like more information on how to shield this or the other modules. So, if anyone out there knows how or has more information, please respond. Also, see other quotes to replies.

Thanks.
225/Greg

[225/Greg]

My friend has a 99 F250, Diesel Pickup, a Ham Radio & a Wilson 5000 antenna on the roof. Every time he keys the mic he can watch & hear his RPM's drop. He has tried different power sources, antennas & ferrite cores attached. How can he eliminate this problem? [/size]

Oh yeah, I forgot to say that he even put a temporary separate battery in the back of his truck and even changed to different antennas with the same result, when he keys down, his engine rpm's are reduced.

[drdx]

Based on the info given and things tried, it sounds like RF, definitely not load. Many run that model of vehicle with power I'm sure. Rednecks all over drive those and they aren't all barefoot, but someone running an ICOM 725 in that model is a rare combination. I wonder if it is coming from a harmonic being radiated by the radio. Can you temporarily put another radio in there and try it?? As crazy as it sounds for a mobile, try a low pass filter??? Does it vary based on frequency being transmitted on??? -drdx

[225/Greg]

Based on the info given and things tried, it sounds like RF, definitely not load. Many run that model of vehicle with power I'm sure. Rednecks all over drive those and they aren't all barefoot, but someone running an ICOM 725 in that model is a rare combination. I wonder if it is coming from a harmonic being radiated by the radio. Can you temporarily put another radio in there and try it?? As crazy as it sounds for a mobile, try a low pass filter??? Does it vary based on frequency being transmitted on??? -drdx

Hey, Thanks for responding. He tried a low pass filter and same thing. He thinks it is RF as well. He also tried different frequencies and different radios.... When he switched to the 102" whip, it was ok for a brief while and then it started doing it again. Same problem with different radios as well.

225/Greg

[drdx]

You must have a wire going to the ecu or whatever they call the engine management system that is extremely resonant in the 27 mhz region. Maybe its getting too much rf induced from this "accidental" antenna. If you've changed every variable but the vehicle, what are you left with?? Does it drop in RPM when another mobile next to it keys up?? How about the 102" whip, as it is farthest away probably, with a tuned ground lead, or 1/4 wavelenght ground ran under the vehicle for an RF outlet?? That's a weird deal. I wonder if you can try a mag mount and keep moving it around on the vehicle keying it up and look for a change. It might lead you to a suitable antenna location, or better way to route coax or power wires. -drdx

[225/Greg]

You must have a wire going to the ecu or whatever they call the engine management system that is extremely resonant in the 27 mhz region. Maybe its getting too much rf induced from this "accidental" antenna. If you've changed every variable but the vehicle, what are you left with?? Does it drop in RPM when another mobile next to it keys up?? How about the 102" whip, as it is farthest away probably, with a tuned ground lead, or 1/4 wavelength ground ran under the vehicle for an RF outlet?? That's a weird deal. I wonder if you can try a mag mount and keep moving it around on the vehicle keying it up and look for a change. It might lead you to a suitable antenna location, or better way to route coax or power wires. -drdx

Hey Thanks DR.
These are some good suggestions. He said that he will try to park his van next to his truck and key down in his van to see if it still does it. Oh, he has tried to put the radio equipment in a different vehicle (non-diesel) and it doesn't do it. He will have to try the van next to the truck tomorrow. He did say that when he disconnected the 102" whip coax from the radio, he laid the whip down horizontally on the side rail of the pick-up box. The coax to the whip was still connected to the antenna but, not to the radio. He then hooked up the Wilson 5000 mag mount, keyed down and it did not do it. When the whip and coax was completely removed from the truck and he transmitted it started doing it again. He tried moving the 5000 around on the roof with no change. The suggestion that you give about running a ground under the vehicle is worth a try. We can figure out how to do this with the whip but, can this be accomplished with the Wilson 5000?

Thanks again.
Greg

[drdx]

I'd start with the 1/4 wave insulated wire counterpoise (tuned ground lead) connected to the ground lug on the back of the radio. Just run it around the cab and bury it under trim panels later if it works. Tape the end so it can't touch anything. For the 5000, assuming it is roof mounted, make sure the metal is nice and bare underneath where it is mounted. I've never seen it done, but right at the ground side at the base is where it would go. Try the radio 1st, and you would only do one or the other, of course. Or, maybe a coax coil/choke at the base of the antenna? Is the exhaust system grounded too? I wonder if it is radiating into an exhaust sensor or something, but I know nothing about diesels. -drdx

[225/Greg]

I'd start with the 1/4 wave insulated wire counterpoise (tuned ground lead) connected to the ground lug on the back of the radio. Just run it around the cab and bury it under trim panels later if it works. Tape the end so it can't touch anything. For the 5000, assuming it is roof mounted, make sure the metal is nice and bare underneath where it is mounted. I've never seen it done, but right at the ground side at the base is where it would go. Try the radio 1st, and you would only do one or the other, of course. Or, maybe a coax coil/choke at the base of the antenna? Is the exhaust system grounded too? I wonder if it is radiating into an exhaust sensor or something, but I know nothing about diesels. -drdx

Thanks.
We will try these suggestions tomorrow. By the way the Wilson 5000 is a magnet mount on top of the roof of the truck. Perhaps we could just run the counterpoise for the 5000 the same way as the 1/4 wl stainless steel whip? Also, good suggestions/brain storming on your part. Keep up the good work. I'll keep you posted.

225/Greg

[dud muck]

This is where its useful to have a dummy load on hand.
Then you can transmit into it, and be sure its RFI causing your troubles.
Because unless the coax feeding a dummy load has a busted ground, a dummy load will not radiate with any significance.

You said you have "extra grounds all over the truck". So how is your VSWR?
Proper grounds for RF are c0pper braided straps. In the case of troubles with RF getting into the engine computer, the first place to strap is the hood hinges.
Since this is a truck, its also important to strap the bed to the frame, and the cabin to the frame. This has an effect of general RF improvement of your vehicle for both transmit & receive.

Other symptoms of faulty installation are engine noises on your receive, or alternator whine on your transmit.

[225/Greg]

This is where its useful to have a dummy load on hand.
Then you can transmit into it, and be sure its RFI causing your troubles.
Because unless the coax feeding a dummy load has a busted ground, a dummy load will not radiate with any significance.

You said you have "extra grounds all over the truck". So how is your VSWR?
Proper grounds for RF are c0pper braided straps. In the case of troubles with RF getting into the engine computer, the first place to strap is the hood hinges.
Since this is a truck, its also important to strap the bed to the frame, and the cabin to the frame. This has an effect of general RF improvement of your vehicle for both transmit & receive.

Other symptoms of faulty installation are engine noises on your receive, or alternator whine on your transmit.

Wow, really great ideas! Thanks. These are things that I will investigate with my Friend Mark/495, later tonight or Tomorrow. I'm trying to get him to join here. He said he will. The dummy load is a great idea. I will report on the VSWR and the grounding straps information in a soon to be forthcoming post/update. Everyone here has been really great! This Forum is great!

225

[225/Greg]

My friend has a 99 F250, Diesel Pickup, a Ham Radio & a Wilson 5000 antenna on the roof. Every time he keys the mic he can watch & hear his RPM's drop. He has tried different power sources, antennas & ferrite cores attached. How can he eliminate this problem? [/size]

Update: Mark said that when he parked his Van next to his truck and keyed down in the Van, his truck slightly decreased in RPM's. Additionally, his VSWR is 1.2:1. He is in the process of providing more grounds and said that the grounds that he has added to his hood/fender recently, has helped some but, has not eliminated the problem. He continues to complain about the excess static noise he gets in his radio and generally poor receive. He's actually considered replacing his truck even though it gets good gas mileage.

225/Greg

[distortion69]

I tried for a long time to trace this exact problem out in sonoma.. with a 2x4 it did it a little, and with a 2x8 it did it terribly.. barefooted it'd do it just a touch, never did figure it out... i'd plug into a base antenna and it'd stop completely, so it wasn't voltage drop.. just straight up interference into something.. who knows what.

An OBDII diagnostic reader in real time could give you sensor readings and maybe give you an idea what's fudging when you key it. Like if the idle air is giving erratic readings, or whatever the case may be.. if the fuel trims go crazy.. what not.

Unfortunately when my 2000 z28 was doing the same thing, i never thought about hooking up my hp tuners software to it at the time

You could also check the voltage on your injectors and other items to see if it changes when keyed and/or other sensor voltages.

In general, though, most late model vehicles will have at least some troubles Although most begin to happen well past the scope of an 8 pill.

Peace,
Josh