Transmitting on CDM1250 makes engine RPM's decrease.

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Engineer209
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Posts: 17
Joined: Sun Nov 21, 2010 1:12 pm
What radios do you own?: HT1250, XTS2500, 2-CDM1250's

Transmitting on CDM1250 makes engine RPM's decrease.

Post by Engineer209 »

Another issue I'm having, When I transmit on my radio it decreases the RPM"s on my truck. I have a 2003 F-350 Super Duty Diesel. The amount of RPM decrease depends on transmission length. It can be from 100 RPM's all the way to 1,000 RPM's. I have checked all of the connections and cleaned the connections on both batteries. I have also tried running the Positive wire on the DS battery then the PS battery. No noticeable change when connected to either battery. Have any of you guys seen or heard of this before? I don't know if its a Positive connection issue or a Ground connection issue or something with the alternator. It doesn't matter what RPM's I'm at it still happens. No noise or alternator whine is heard at all, on TX or RX, it's crystal clear.
Radios I currently own:

HT1250 VHF, XTS2500 800 MHZ, CDM1250 Low Band, CDM1250 VHF
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Bill_G
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Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Bill_G »

Yep. Chased problems like this many times. VHF loves to get into engine controls. But first, determine if it's RF getting into the ECM by either putting the radio into a dummy load and keying, or into a mag mount antenna stuck in the bed of the truck (or as far away as you can get it from the truck) and keying. Be glad it's not your anti-lock brake system being affected, or the fuel injection system causing engine stall. Likely culprit is the dash wiring is carrying it back into the ECM, or RF is clobbering a sensor and it takes a while for the ECM to react to the lack of input from the sensor.

Years ago I had a mid-engine pumper that would over-rev when you keyed the radio from the pump panel. 100W VHF with Firecom headset system. Worked fine when the crew was in the cab. But, when the engineer jacked into the pump panel and keyed the radio, the engine would lose it's governor and try immediately wind up to dangerousville. Ultimately, it was the ECM from the chassis manufacturer at fault. It just required the extra body standing by the panel to make it happen. It wasn't the Firecom and wiring at fault though it certainly seemed that way at first.
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Tom in D.C.
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What radios do you own?: Progreso soup can with CRT

Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Tom in D.C. »

I think we're lucky we don't encounter more of these types of problems with RF interfering with automobile electronics in one form or another. Years ago I had a Pontiac 6000STE whose cruise control would drop dead when I transmitted on VHF at speed. Let go of the PTT and the control would come back on, but all the while the PTT was on the engine dropped to idle. Scared the hell out of me the first few times it happened, but then I just avoided using the CC when using the radio to transmit. That car was an electronic nightmare; GM had to replace the ECM two times in the eighteen months I owned it. Now twenty-five years later I'm sure that cars are somewhat more bulletproof when it comes to RF but way back then they certainly were not.
Tom in D.C.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
Engineer209
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Posts: 17
Joined: Sun Nov 21, 2010 1:12 pm
What radios do you own?: HT1250, XTS2500, 2-CDM1250's

Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Engineer209 »

Thanks guys... I didn't even think of it being anything like that! As a matter of fact, I have an "Edge Juice w/ Attitude" aftermarket programmer for my truck, the main control or what I would call "Brain" for the Programming system is about 5" from the fender mount antenna. This type of programmer connects to 5 different places on the engine to sensors and one of them happens to be some type of idle control sensor I believe. I will try to relocate the programmer brain and the antenna and see what I can come up with. I will keep you guys updated. Do ya'll think this could or in any way hurt any of the electronics on my engine? Thanks for all the help!
Radios I currently own:

HT1250 VHF, XTS2500 800 MHZ, CDM1250 Low Band, CDM1250 VHF
Jim202
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Joined: Sun Sep 09, 2001 4:00 pm

Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Jim202 »

Had a problem some years back with a low band radio causing all sorts of issues in a
pickup struck.

Had to add some bypass caps to the dash instrument panel to keep the speedometer
from going wild. Fuel gauge would jump around and other issues. Solved the problem by
adding 2 aluminum bars vertically on the back window. Seems the opening was causing
a tuned cavity of some sort. By adding the straps over the rear window, I was able to
change the frequency of the window opening enough to remove the problem. Just had
to make sure that I got a good electrical bond between the straps and the metal frame
of the window.

Not saying this is your issue, but keep the strange issues in mind.

Also had a low band radio installed in a Jag. When the operator keyed the radio, it
would cause the engine to go to an idle. Antenna was mounted on the center of the
trunk. Adding several ground straps from the vehicle frame to the trunk lid got rid of
this problem.

Jim
Engineer209
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Posts: 17
Joined: Sun Nov 21, 2010 1:12 pm
What radios do you own?: HT1250, XTS2500, 2-CDM1250's

Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Engineer209 »

Okay....Tried another antenna with the same results, however, if I key up the radio without the antenna being attached to the fender the RPM decrease is very minimal to almost nothing. Any ideas?
Radios I currently own:

HT1250 VHF, XTS2500 800 MHZ, CDM1250 Low Band, CDM1250 VHF
pfd radio
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Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by pfd radio »

If the RF is getting in through the brain ("Edge Juice w/ Attitude"). I wonder if shielding that box in a metal housing would help the situation.

Just a thought
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Bill_G
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Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Bill_G »

Got a dummy load?
Engineer209
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Posts: 17
Joined: Sun Nov 21, 2010 1:12 pm
What radios do you own?: HT1250, XTS2500, 2-CDM1250's

Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Engineer209 »

I tried that, however it didn't help. This morning I finally pulled the "Edge Juice W/ Attitude programmer off of the truck. Keep in mind that this setup hooks to 4 different sensors on the engine and 1 at the gas pedal. Cranked the truck up and...... no RPM decrease during transmit. Everything works fine now. Don't know exactly what part of the programmer was causing the problem but I'm afraid I won't be able to use it no more. It kinda sucks though.. I just sunk around $700.00 into the programmer and accessories a year or so ago.. :o
Radios I currently own:

HT1250 VHF, XTS2500 800 MHZ, CDM1250 Low Band, CDM1250 VHF
Engineer209
New User
Posts: 17
Joined: Sun Nov 21, 2010 1:12 pm
What radios do you own?: HT1250, XTS2500, 2-CDM1250's

Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Engineer209 »

Thanks for everyone's help and suggestions!
Radios I currently own:

HT1250 VHF, XTS2500 800 MHZ, CDM1250 Low Band, CDM1250 VHF
motorola_otaku
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Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by motorola_otaku »

Fair warning - if you have any MSD aftermarket ignition parts on your engine expect to have RF problems.

I put a MSD Optispark distributor on the LT1 motor in my '95 Caprice 9C1 when I had the engine rebuilt. Not only does it radiate ignition noise where there was none before (all the way up to UHF and beyond, no less,) but keying a Syntor X9000 on 6-meters will damn near stall it and set a fail code in the PCM. Adding ground braid to the already well-grounded body and chassis made no difference whatsoever. I have heard similar horror stories from others with MSD ignition systems on non-fuel injected engines and Children's Band radios.
Engineer209
New User
Posts: 17
Joined: Sun Nov 21, 2010 1:12 pm
What radios do you own?: HT1250, XTS2500, 2-CDM1250's

Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Engineer209 »

My trucks a diesel, everything seems to be good now, Just wish I could keep my programmer lol!
Radios I currently own:

HT1250 VHF, XTS2500 800 MHZ, CDM1250 Low Band, CDM1250 VHF
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wx4cbh
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Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by wx4cbh »

Over the years in the two way business I've found that the huge majority of aftermarket electronic performance add-ons seem to be made without a single thought about the possibility of RF effects. Edge is one of the worst, especially if high power 30-50 MHz equipment is used. My '06 6.0 would absolutely shutdown when using the low band radio. That was exciting the first time it happened. I installed the low band and checked SWR with the engine off outside the shop away from the metal building components. Then I took the truck out to test and see if the ABS and other systems might be affected by the new radio. I for sure didn't expect it to completely shutdown the engine, especially at 35 MPH. I also didn't expect the 100 watt 150 MHz Spectra or the dual band ham radio to do the same thing 3 out of 5 times either. All the antennas were roof mounted NMO mounts, so no brackets and side mounts were involved, BTW. Needless to say, any wire connected to the Edge is an antenna, and there didn't seem to be any way to sufficiently shield the thing. I tried everything we could think of, and no luck. Yep, it went back with a note to the manufacturer about their apparent lack of RF knowledge. They responded with a short terse letter that they don't recommend installing that unit on a truck with two-way radio equipment, especially by "unskilled and non-dealer supported personnel." Did I get my money back? Nope, still waiting.
curmudgeon.....and I like it.
Engineer209
New User
Posts: 17
Joined: Sun Nov 21, 2010 1:12 pm
What radios do you own?: HT1250, XTS2500, 2-CDM1250's

Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Engineer209 »

It sucks, I was lucky enough to find someone to purchase the programmer from me. However, I would love to have been able to keep it on my truck. I just think the benefits of having the radio far outweigh having the programmer.
Radios I currently own:

HT1250 VHF, XTS2500 800 MHZ, CDM1250 Low Band, CDM1250 VHF
Jim202
Posts: 3609
Joined: Sun Sep 09, 2001 4:00 pm

Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by Jim202 »

wx4cbh wrote:Over the years in the two way business I've found that the huge majority of aftermarket electronic performance add-ons seem to be made without a single thought about the possibility of RF effects. Edge is one of the worst, especially if high power 30-50 MHz equipment is used. My '06 6.0 would absolutely shutdown when using the low band radio. That was exciting the first time it happened. I installed the low band and checked SWR with the engine off outside the shop away from the metal building components. Then I took the truck out to test and see if the ABS and other systems might be affected by the new radio. I for sure didn't expect it to completely shutdown the engine, especially at 35 MPH. I also didn't expect the 100 watt 150 MHz Spectra or the dual band ham radio to do the same thing 3 out of 5 times either. All the antennas were roof mounted NMO mounts, so no brackets and side mounts were involved, BTW. Needless to say, any wire connected to the Edge is an antenna, and there didn't seem to be any way to sufficiently shield the thing. I tried everything we could think of, and no luck. Yep, it went back with a note to the manufacturer about their apparent lack of RF knowledge. They responded with a short terse letter that they don't recommend installing that unit on a truck with two-way radio equipment, especially by "unskilled and non-dealer supported personnel." Did I get my money back? Nope, still waiting.



You could build an in line box just before your add on to include an inline RF choke and a by pass capacitor to
try and remove any RF from the wires.

Have run into the holier than thou attitude with some equipment companies. If that is the way they want to
be, then the word will spread and their sales will show the results. Pass the word and let market pressures
take their effect.

Jim
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wx4cbh
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Re: Transmitting on CDM1250 makes engine RPM's decrease.

Post by wx4cbh »

One of the frustrating things with the wiring layout involved coming and going in many directions is that shielding the critical individual wires is difficult, if not impossible, so we passed on the thought of shielding. Snap around ferrites had little effect because the wiring layout is mostly in manufactured harnesses which means the optimum ferrite locations are not available, and even if the desired wires could be pulled out of the harness, that doesn't allow for sufficient wire to wrap as a choke without building a weatherproof length of extension harness with the matching multiple weatherproof connectors. I thought about Jim202's suggestion of external RF chokes, but location and heat and weather protection are a real concern with where the wiring harness is already located, and there is just too much wire rework to do to cover the particular wires that lead here and there. Time already invested turned me to eliminating the "chip" and looking for another route.

The other thought is that mine had the idle speed control modification in the auxiliary wiring harness at the upper left cowl area. That would be easy pickings for an antenna mounted on a lip or fender bracket on the drivers side, even though that was not the case in my situation. Even though the hood was ground strapped on each side at the hinges, that doesn't necessarily mean it's effective.

Third idea: After that I ended up installing the large diameter exhaust downpipe to mate up with the already installed catback system and then had the dealer retune for max factory parameters. That did way more for the overall driveabililty, response, and towing than the Edge gizmo ever produced, lowered the EGT, and it was cheaper and kept things inside the warranty fold to boot. I realize we're talking 7.3 vs 6.0, but I'm now a firm believer on Diesels of going exhaust mods first.

Just some thoughts.
curmudgeon.....and I like it.
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