Continuity at Radio SO 239 Connection

[WSFX665]

Will the radio circuitry produce a continuity reading at the SO 239 connection? Having issues with a transmission whine according to those receiving the signal. Checked all the fittings and cables. (There are 2 as I have a bulkhead fitting on the roof.) All test fine, but I get a definite short or continuity reading at the back of the radio itself.

[WSAM454]

Since you mention a bulkhead fitting on the roof, it sounds like a mobile installation.  

Some thoughts:

1- Do they still hear the whine if the engine is NOT running, and is the radio is connected directly to the battery?

2- Is the negative lead of the radio connected to a near-by chassis/ground, and not a cable also running back to the battery?

3- Is the radio possibly being powered from an accessory plug, rather than directly to the battery?

4- You may be getting noise into the system from the running engine, and/or its associated electronics.   Can you try the radio on a separate battery, not connected to the vehicle.  

5- It may also be a poor ground/chassis connection to the radio's power or antenna system.  Make sure all connections to the chassis (ground) are less than 1 ohm or so.

[WSFX665]

Engine was off. This is a brand new issue. Never had a problem before. Radio connected direct to battery.

[WSAM454]

One thought; I also  have my rig connected to the battery, but through a relay, so it won't accidentally be left on all night. (Does not have a 'turn off'  timer setting!)  Of course, the car has to be in at least the 'accessory' position to activate the relay, but even with the engine not running, there is circuitry activated.

Anyway, I don't have any other suggestions, especially since this is one of those "it had been working fine" situations.    Hopefully someone will offer a more viable solution.  Good luck!

[SteveShannon]

1 hour ago, WSFX665 said:

Will the radio circuitry produce a continuity reading at the SO 239 connection? Having issues with a transmission whine according to those receiving the signal. Checked all the fittings and cables. (There are 2 as I have a bulkhead fitting on the roof.) All test fine, but I get a definite short or continuity reading at the back of the radio itself.

I think you’re asking about testing the resistance between the center pin and the shield on the SO-239 jack on the rear of the radio. Testing it with a multimeter imposes DC which might give some continuity reading which might change over time.  There are inductors, which appear as shorts at DC and there are capacitors which will appear to be continuous while they charge, but then block DC.  A continuity test there isn’t necessarily indicative of anything.

Are you parked near an electrical transmission line or underneath lit streetlights or other electrical equipment when transmitting?

[WSFX665]

11 minutes ago, SteveShannon said:

Are you parked near an electrical transmission line or underneath lit streetlights or other electrical equipment when transmitting?

In my driveway where I always do my checks. Odd thing I just remembered is that, at the same time, I was only hitting the repeater about half of the time. When I did, is when the other guys would tell me it was a strong signal but a lot of whine or interference.

I installed the roof rack yesterday and relocated the antenna to the back corner of the rack. I added a bulkhead connector, so I checked all of the cables/components between radio and antenna. No shorts anywhere and continuity was good. None of the power components were altered at all. 

[WSFX665]

22 minutes ago, WSAM454 said:

One thought; I also  have my rig connected to the battery, but through a relay, so it won't accidentally be left on all night. (Does not have a 'turn off'  timer setting!)  Of course, the car has to be in at least the 'accessory' position to activate the relay, but even with the engine not running, there is circuitry activated.

Anyway, I don't have any other suggestions, especially since this is one of those "it had been working fine" situations.    Hopefully someone will offer a more viable solution.  Good luck!

Thanks! I appreciate the input.

[SteveShannon]

2 minutes ago, WSFX665 said:

In my driveway where I always do my checks. Odd thing I just remembered is that, at the same time, I was only hitting the repeater about half of the time. When I did, is when the other guys would tell me it was a strong signal but a lot of whine or interference.

I installed the roof rack yesterday and relocated the antenna to the back corner of the rack. I added a bulkhead connector, so I checked all of the cables/components between radio and antenna. No shorts anywhere and continuity was good. None of the power components were altered at all. 

Did your neighbors have any fancy Christmas lights on at the time?  I’m more inclined to believe it’s something external since your engine is off at the time.  
Does your antenna require a ground plane?  I’m not certain the corner of your roof rack would substitute for one.

[WSFX665]

15 minutes ago, SteveShannon said:

Did your neighbors have any fancy Christmas lights on at the time?  I’m more inclined to believe it’s something external since your engine is off at the time.  
Does your antenna require a ground plane?  I’m not certain the corner of your roof rack would substitute for one.

I have a ground plane kit as it was previously mounted on the fiberglass roof. No Christmas lights.

[SteveShannon]

6 minutes ago, WSFX665 said:

I have a ground plane kit as it was previously mounted on the fiberglass roof. No Christmas lights.

I would drive somewhere else and see if people still report the whine.  Do you have a different radio you can swap in?

[WSFX665]

12 minutes ago, SteveShannon said:

I would drive somewhere else and see if people still report the whine.  Do you have a different radio you can swap in?

No, just the one mobile and 2 HTs

[SteveShannon]

1 hour ago, WSFX665 said:

Engine was off. This is a brand new issue. Never had a problem before. Radio connected direct to battery.

What has changed?

[WRYZ926]

Something has had to change when you added the roof rack and moved your antenna.

Now you didn't mention what radio you have, though that should not make much difference.

I just checked my Wouxun KG-XS20G with my multimeter. I had zero resistance between the center conductor and the outer part of the SO239 on the back of the radio. I don't have that radio hooked up to any power leads right now. Again that shouldn't make a difference.

[WSFX665]

Well, apparently I am a liar, or senile (most likely) I put everything back together and set one of my HTs out where I could here it. Terrible noise! Tried it again after a short break and no noise. Clear as a bell. I then realized this time engine was off. So I was incorrect answering earlier about that. My apologies! So... I need to fix the engine noise. Researching that now. Thank you all!!

[SteveShannon]

1 minute ago, WSFX665 said:

Well, apparently I am a liar, or senile (most likely) I put everything back together and set one of my HTs out where I could hear it. Terrible noise! Tried it again after a short break and no noise. Clear as a bell. I then realized this time engine was off. So I was incorrect answering earlier about that. My apologies! So... I need to fix the engine noise. Researching that now. Thank you all!!

No apologies necessary. At least you figured it out.  Ferrites on the power leads might help.  Keep your ground wire short; go to a chassis ground nearest the transceiver.  The positive line should run all the way back to the battery or fuse box near the battery.

[WRYZ926]

Another place to put clamp on ferrite beads is the main cable going from your alternator to your battery. I would get occasional whine while transmitting until I put clamp on ferrite beads on that cable. I put one bead on each end. I also have clamp on beads on the hot and ground wires going to each radio. If that doesn't help, then make sure that your alternator has a good chassis ground. Newer vehicles can be temperamental about grounds with all of the computers.

Make sure to use a good quality electrical tape and tape up the ferrite beads to help keep them from falling off.

As @SteveShannon mentioned, always run the ground wire to a good chassis ground, especially on newer vehicles that have the Battery Management System. Doing so can help prevent problems.

[WSFX665]

You guys are great. Thank you!

[WSFX665]

As an update, the ferrite beads were attached to alternator main as well as the radio power at each end on both. Ground is attached about 2 feet from radio at the seat mount. Still have that irritating whine on transmitting only.

[WSFX665]

Grounded the antenna and still have the noise. Next step, new alternator

[SteveShannon]

14 minutes ago, WSFX665 said:

Grounded the antenna and still have the noise. Next step, new alternator

Before doing that, what about the spark plug wires?

Also, see this:

https://forums.radioreference.com/threads/rfi-interference-how-to-eliminate.247596/

[WRYZ926]

Also check that the alternator body has a good ground to the chassis. Normally it just uses the engine block but sometimes you need to add a ground strap from the alternator directly to the chassis. I would try that before replacing the alternator.

And I agree to check your spark plug wires and coils. If your vehicle has coil packs that mount directly to the spark plugs then check them too. I've seen coil packs go bad without throwing a code. It's worth checking.