'04 Silverado Radio Question

[brts96]

I have an '04 Silverado with a Yaesu FT-2800 (Ham) radio installed. It's wired switched with the ignition, through a relay. When I transmit, especially at full power (65 Watts), the Oil Pressure guage on my dash shows the pressure dropping, ultimately to zero; and my Driver Information Center will show an oil pressure warning. Once I release the transmit button, the pressure comes back to normal.


I had a Motorola shop review the install, and they couldn't locate an apparent cause. As a result, I've kept transmitting to a minimum. The installer that initally installed the radio told me to "live with it", so I had a different shop troubleshoot it and correct the faults they found. Motorola changed it to how it is now. The Motorola installer wasn't happy with the way the original installer did it.


Any ideas?

 

[TritonBoulder47]

Depends on where your antenna is mounted... Before I mounted my antenna on my '95 Tahoe, I had it just laying on my dash. Every time I transmitted my Tach would spike. It sound like its that kind of interference.

 

[brts96]

I forgot to mention, the antenna is a body mount on the roof (NMO 1/4 wave). If I remember right, the antenna cable is run on the passenger side .


You're probably right about being antenna interference, though. What do you recommend?

 

[TritonBoulder47]

Check you antenna cable... There may be a split in the shielding somewhere... Thats the only thing that comes to my mind...

 

[brts96]

Ok, will do. Thanks for the idea. I might need to wait until spring to check it.


If I put the antenna on a meter, would it show any change in SWR or gain, do you think?

 

[TritonBoulder47]

That I do not know... I'm not really a "radio guy"... lol

 

[brts96]

That makes two of us. I've been licensed for about 17 years, and most of my theory has passed into distant memory with lack of use.


Any rate, thanks for the help. I'll check into it in the spring, unless I can borrow a heated garage for a little while.

 

[FFParker]

If there is a bust in the shield of the coax you might show some reflected power. If your swr is good the try an rf choke of some type should help with the rfi you are getting. Also check all of your connections power and antenna make sure your gound hasnt come loose. Sounds wierd but I have had situations where a poor ground made for some strange things to happen on the dash. 73!

 

[twodogs603]

I have an 03 Sierra (basically the same truck) and my radio is wired hot with a heavy duty on off switch that powers all the equipment in the console. I'm not having those issues when I transmit. Try running power straight off the battery and see if it does it then. Make sure radio has a good solid ground connection. If it still does it I would suspect antenna or coax issues. Im curious if a bad factory ground on the truck could cause the guages to go whacky.

 

[Jarred J.]

why are you constantly running 65 watts? are you running a simplex net or trying to hit repeaters 3 states away?


FCC states "lowest amount of power needed to make contact"


running the radio at high power ALLL the time is not good for it....


The first thing I would do is check your swr.

 

[MtnMan]

why are you constantly running 65 watts?

Uh, let me read the OP for you: "When I transmit, especially at full power (65 Watts)"


Where did you get "constantly" and "ALLL the time"?


Anyway, I agree w/ checking SWR, although it's hard to imagine two installers would have overlooked that. Take a look the radio power and coax routing, relative to the truck's electronic control modules. Try running the radio off an isolated battery or power supply.

 

[Jarred J.]

Uh, let me read the OP for you: "When I transmit, especially at full power (65 Watts)"

Where did you get "constantly" and "ALLL the time"?


Anyway, I agree w/ checking SWR, although it's hard to imagine two installers would have overlooked that. Take a look the radio power and coax routing, relative to the truck's electronic control modules. Try running the radio off an isolated battery or power supply.

that's what skimming a paragraph does to ya... lol carry on

 

[brts96]

Thanks for the replies, guys! I'll check the SWR first, along with the grounds. Motorola checked the grounding, and couldn't find any issues with it. Running it through a dedicated power supply sounds like a good idea, I might have to try that, too. If the SWR is really whacked, I might try a choke or just changing cable.


The radio was originally wired hot all the time, but I asked Motorola to change it, since it was probably only a matter of time before I forgot to shut it off, and drained the battery. I wish I would have taken pictures of the original install, it would not have gotten a lot of praise from the Board.


According to Motorola, it was wired to the battery using wire that was too small, not fused within six inches of the battery connection, and should have been run through a relay to minimize power draw.


Jarred, thanks for the reminder about using the lowest power necessary to make contact. No worries. Although, some of the repeaters I use are a decent distance away (40-ish miles), and there are quite a few hills and valleys here. Sometimes, Medium is the right power, and sometimes High Power is right for the contact.

 

[twodogs603]

[


According to Motorola, it was wired to the battery using wire that was too small, not fused within six inches of the battery connection, and should have been run through a relay to minimize power draw.








HUH????

 

[brts96]

I'm trying to remember exactly how the Motorola tech phrased it, but they recommended running it through a relay. I guess my memory is a little fuzzy as to why, but I thought that's what he said. Sorry.


I do remember that you could use a relay if you were going to run something that pulled too much current through a switch and the properly rated switch wasn't available. I don't believe it was the case with this radio, though.

 

[txff914]

Shouldn't the radio have a key power since wire to use that turns it off when the vehicle is off and back on when its on? Then also have the leads that go to the battery that should be supplying the main battery power.

 

[brts96]

I don't recall seeing an option for key power, but it doesn't mean the radio doesn't have one.


I can do some checking, but the installers never made any mention of that option when I brought out to them.


Time to go to the manual for the definite answer.

 

[twodogs603]

Shouldn't the radio have a key power since wire to use that turns it off when the vehicle is off and back on when its on? Then also have the leads that go to the battery that should be supplying the main battery power.

I don't think it does, as most amateur radio units don't.

 

[brts96]

That makes sense. I can still double check the manual, though, just to be sure.


Any thoughts on why they wanted to run the radio through a relay, as opposed to not using one?

 

[txff914]

Most of the time its not used because you have to go and activate it in the programming. Another thing to check would be where they got the key power activation from, they might have gotten it from the power of the oil pressure sensor. They might have not put a big enough relay to use with it.

 

[txff914]

The relay steps up the amps. Example the key power is probably rated around ten amps, so then you put a relay in there to step that up to what is needed. The key wire just activates the relay with low draw, all the power is taken through the battery power in the relay.

 

[brts96]

Thanks for the great responses and ideas, everyone! I'll start troubleshooting these either in the spring, or once I can get into a garage with some room. I might start with the antenna, since the pressure dropped before changing to the current setup, so it could be the one common denominator. Although, the question about if it's getting its power from the oil pressure sensor is a good one, I wouldn't have thought of that. I'll keep the thread updated with my findings.


By the way, thanks for the refresher on the relays. It's been a while since I messed with electronics past the user level, so sometimes I get my facts mixed up. It makes sense now. I appreciate the help that this site has to offer. Thanks, everyone!


By the way, stay safe, and Merry Christmas!

 

[twodogs603]

The relay acts as a high current switch, activated by a low current signal-usually ignition sense. The radio on high power could eventually burn up a regular toggle switch, hence the use of a relay.

 

[brts96]

That makes sense, thanks. Some of this stuff is coming back to me, a little at a time.


I might need to get back into the practical/ technical side of electronics again, and dust off some stuff (knowledge and skill) that I've had sitting in the back of my head for a long time.

 

[P1808]

I'm trying to remember exactly how the Motorola tech phrased it, but they recommended running it through a relay. I guess my memory is a little fuzzy as to why, but I thought that's what he said. Sorry.

I do remember that you could use a relay if you were going to run something that pulled too much current through a switch and the properly rated switch wasn't available. I don't believe it was the case with this radio, though.

they where probably suggesting that you run a wire from the battery to a relay and have a on/off switch attached to the relay to control the power to the radio. this is how we run power to the patrol cars we wire up. battery-relay/switch-fuse block-device. that way all you have to do is push one button and all the devices you have turn off. Instead of a switch you can connect it to an ignition lead so it is automatic when you start and turn off the car.


hope this helps.

 

[brts96]

That helps a bit. It sounds like their intention, since that's what happens when I start the truck. Thanks for the clarification.

 

[brts96]

If there is a bust in the shield of the coax you might show some reflected power. If your swr is good the try an rf choke of some type should help with the rfi you are getting. 73!

Talked to the folks at the amateur radio store about borrowing an SWR meter, since I don't have one. Never did get to check the coax, though.


When I explained the issue to them, they recommended a choke. Spent about $30 , and it worked. Thanks everyone, especially ffparker for the ideas.


I appreciate the help. Stay safe, everyone! 73

 

[rescue52]

Talked to the folks at the amateur radio store about borrowing an SWR meter, since I don't have one. Never did get to check the coax, though.

When I explained the issue to them, they recommended a choke. Spent about $30 , and it worked. Thanks everyone, especially ffparker for the ideas.


I appreciate the help. Stay safe, everyone! 73

What kind of choke? Homemade or store bought??


I having similar issues, I have horrible background noise when I transmit.


Thanks.

 

[brts96]

These were MFJ chokes, I don't have the part number, but it looks like this: Suppression Choke :: Aero Smith - Amateur Radio Products.


The guys at the radio shop suggested putting them on the cables going into the computer, rather than on the cable for the radio itself. It seemed to go against what I learned about chokes, but I guess that was a long time ago. Either way, they worked. I've tried using the radio, and once in a while when I'm transmitting, the oil pressure dips, but never bottoms out. I wound up getting two packs of chokes, and the other is an MFJ 701. It's also a four pack.

 

[rescue52]

These were MFJ chokes, I don't have the part number, but it looks like this: Suppression Choke :: Aero Smith - Amateur Radio Products.

The guys at the radio shop suggested putting them on the cables going into the computer, rather than on the cable for the radio itself. It seemed to go against what I learned about chokes, but I guess that was a long time ago. Either way, they worked. I've tried using the radio, and once in a while when I'm transmitting, the oil pressure dips, but never bottoms out. I wound up getting two packs of chokes, and the other is an MFJ 701. It's also a four pack.

Thank you

 

[brts96]

No problem. Hope your interference issue gets fixed. ARRL does also have a book about tracing RFI and correcting it. I think the most current Rev. is #3. The guys at the shop referenced it yesterday, but didn't find anything conclusive. Maybe it might help your case, though.


Review: ARRL RFI Book (3rd Edition) | EDN

 

[FFParker]

What kind of choke? Homemade or store bought??

I having similar issues, I have horrible background noise when I transmit.


Thanks.

What does it sound like? Discribe the noise. Is it a whine that is in rythm with your vehicles engine? is it a hum? Does it go away if you switch to a different power setting on the radio? Details would help us figure out your problem? Also does noise ever go away ?


I guess in short, discribe the noise and if and when it comes and goes.

 

[rescue52]

Not to hijack your thread.


I don't hear any noise on my end. When I transmit on my VHF CDM1250 radio it sounds like I have a train driving in the background. It only happens if the motor is running but RPM speed don't effect it.


I have 2 CDM's a UHF & VHF 2 separate power wires and same common ground.

 

[brts96]

No sweat, this thread was about RFI, so I figure it's related.


Hopefully, you can get your interference issues fixed.

 

[FFParker]

Not to hijack your thread.

I don't hear any noise on my end. When I transmit on my VHF CDM1250 radio it sounds like I have a train driving in the background. It only happens if the motor is running but RPM speed don't effect it.


I have 2 CDM's a UHF & VHF 2 separate power wires and same common ground.

With any radio noise I would start with the Power wires and the connections. If you are using ring terminals to connect make sure your wire hasn't pulled out or become corroded. You might try running straight to the battery. If everything is good on that front then try a choke. Chokes help with alot of issues believe it or not. Good luck and if I missed anything someone else will be along to give some more ideas.

 

[brts96]

I did some more testing today, and it seems like the chokes didn't completely solve the problem. I might try one on the coax as well as on the line into the computer.