SWR issues

[HELacey]

I want to start this thread by prefacing a few items first.
1: I do not have an external SWR meter
2: im using the built in meter on my President McKinley
3: I’ve been through several troubleshooting steps as far as checking for continuity on the coax, the antenna bracket, between both ends of the coax, and a few others I found from an internet list. I had none of said issues.
4: My current antenna is a donated Firestick ii given to me by a neighbor who should turn his house into a museum dedicated to radios, mostly HAM.
I cannot get my SWR below 3.2 with my antenna cap on, and roughly 2.0 with the cap off. I’ve tried moving the antenna so the coax is stretched out underneath the carpet of my pickup, through a grommet in the floorboard where the parking brake cable is routed, and up through the bed via another grommet. The cable is straight with one turn from the radio to the redirection towards the back of the truck. On top of this, I’ve tuned the antenna all the way out and in with maybe a difference of 1.0 in total at best. I haven’t check SWR on 1 or 40 because I can’t get ch20 low enough. My power source comes from the battery via a common power block that only feeds my trucks gauges (EGT, boost, fuel pressure) and nothing else.
The only time I get SWR to read 1.0 is when my hand makes contact with the nut where antenna threads into, and the base of the antenna itself, and with a firm grip running about 2” past the white coating on the antenna. If I loosen my grip, it slowly climbs back to 2.0~2.2 with no cap.

Do I just need a longer antenna like a 102” whip, or is there something else I’m missing. I’m assuming when I’m grabbing the antenna, my body is becoming an extension of the coils similar to that of EPZ ground, making me and the antenna one single unit, or is my though process wrong here?

 

[mmckenna]

I want to start this thread by prefacing a few items first.
1: I do not have an external SWR meter
2: im using the built in meter on my President McKinley

Internal meters are known to be less than ideal, but it should be enough to give you a good idea on how things are working.

3: I’ve been through several troubleshooting steps as far as checking for continuity on the coax, the antenna bracket, between both ends of the coax, and a few others I found from an internet list. I had none of said issues.

Good deal, that helps.

4: My current antenna is a donated Firestick ii given to me by a neighbor who should turn his house into a museum dedicated to radios, mostly HAM.

Old/used says questionable condition. No telling what happened to it before. If it was owned by a ham, it could have been used for CB, or could have been shortened for 10 meters. Any signs the antenna has been changed from original design?

I cannot get my SWR below 3.2 with my antenna cap on, and roughly 2.0 with the cap off.

The little rubber cap that goes over the adjustment screw? That should have zero impact on SWR. That's a red flag and suggests there's something weird going on….
Make sure there is no corrosion on the adjustment screw. Same on the inside of the antenna where it threads in.

I’ve tried moving the antenna so the coax is stretched out underneath the carpet of my pickup, through a grommet in the floorboard where the parking brake cable is routed, and up through the bed via another grommet. The cable is straight with one turn from the radio to the redirection towards the back of the truck.

Shouldn't really matter unless it's bent so tight the center conductor migrates over inside the dielectric and contacts the outer shield.
Ideally you want to keep that coaxial cable as short as reasonably possible. If a CB'er tells you it needs to be a certain length, walk away because they have no idea what they are talking about. Specific lengths of coaxial cable can hide issues from the radio, but if everything is working as designed, length should not matter.
If you have the skills and tools to put new connectors on, cut the cable to length, leave a foot extra in case you have to replace a connector.

On top of this, I’ve tuned the antenna all the way out and in with maybe a difference of 1.0 in total at best. I haven’t check SWR on 1 or 40 because I can’t get ch20 low enough.

Get channel 19 as low as you can (that's the center of the band, not 20). Then check SWR on Channel 1 and 40. Let us know what it shows and we can assist you in figuring out if the antenna is too long or too short.

My power source comes from the battery via a common power block that only feeds my trucks gauges (EGT, boost, fuel pressure) and nothing else.

OK, might be good, might be bad. As long as there isn't any noise from the gauges or LED lights, you should be OK.
Make sure you ground the radio negative lead to the vehicle body and keep the lead short. Don't run it all the way back to the battery.
While you are at it, run a ground wire from the radio chassis screw to the body also. This provides a good RF ground for the radio. It may not make a difference, but it won't hurt. I've had it fix intermittent issues.

The only time I get SWR to read 1.0 is when my hand makes contact with the nut where antenna threads into, and the base of the antenna itself, and with a firm grip running about 2” past the white coating on the antenna. If I loosen my grip, it slowly climbs back to 2.0~2.2 with no cap.

OK, that's normal. Your body is coupling with the antenna.

Do I just need a longer antenna like a 102” whip, or is there something else I’m missing. I’m assuming when I’m grabbing the antenna, my body is becoming an extension of the coils similar to that of EPZ ground, making me and the antenna one single unit, or is my though process wrong here?

Before you buy a new antenna, I'd make sure you go through every single step again. Check everything, even if you've checked it before.

Do these steps:
-Disconnect the coaxial cable at BOTH ends. Using a multimeter or continuity tester:
Check for continuity from the center pin of one connector to the center pin on the other end. Should show continuity. If it doesn't, stop and fix.
-With it still disconnected, do the same test as above with the outer shield. Should be continuity. If not, stop and fix.
-With it still disconnected, check for continuity between the center pin and the outer shield. There should NOT be continuity. If there is, stop and fix.
—For all the above tests, try wiggling each connector and see if it changes. It's common for the failure point to be right at the connector. Bad solder/crimp joint can cause it to fail. Sharp bend can damage the cable, etc.

Now, reconnect the coaxial cable to the antenna ONLY. Do these steps:
-At the radio end of the coax (it should still be disconnected), check for continuity between the center pin and the outer shield. There should NOT be continuity. If there is, the fault is with the antenna mount. Often they get assembled incorrectly and the insulating washers get install wrong. That will create a short to ground for the center of the coax pin. That will show as high SWR.
-If that tests out OK, remove the rubber cap off the top of the antenna. Check for continuity from the center pin of the radio end of the coax to the tip of the antenna where the adjustment screw is. There should be continuity. If there isn't, there's an issue with the antenna. Might need to replace it, but check the mount and make sure everything is making contact. Check the continuity from the center of the connector pin to the base where the antenna screws in, there should be continuity. If not, stop and fix.
- Now check for continuity from the outer shield of the connector on the radio end to the vehicle body/truck bed. Should be a good ground connection. If there isn't, could be the mount is assembled wrong or it's not mounted to body metal.

When you are checking SWR, make sure you are well away from all metal objects. Don't do this up in the driveway near the metal garage door, or even out on the street next to a lamp post. Ideal place to test SWR is out in the middle of a field or parking lot.

If you can find someone local that has an SWR meter, borrow that (and the owner if possible) and compare to what you are seeing on your CB. Those built in meters should be relatively accurate, but they are not very precise.

There's other things we can try, but give those a go first, they are the most common failure points. Don't start swapping parts around unless you find an obvious failure. Troubleshoot until you find the issue, then swap parts.

 

[HELacey]

Internal meters are known to be less than ideal, but it should be enough to give you a good idea on how things are working.



Good deal, that helps.



Old/used says questionable condition. No telling what happened to it before. If it was owned by a ham, it could have been used for CB, or could have been shortened for 10 meters. Any signs the antenna has been changed from original design?



The little rubber cap that goes over the adjustment screw? That should have zero impact on SWR. That's a red flag and suggests there's something weird going on….
Make sure there is no corrosion on the adjustment screw. Same on the inside of the antenna where it threads in.




Shouldn't really matter unless it's bent so tight the center conductor migrates over inside the dielectric and contacts the outer shield.
Ideally you want to keep that coaxial cable as short as reasonably possible. If a CB'er tells you it needs to be a certain length, walk away because they have no idea what they are talking about. Specific lengths of coaxial cable can hide issues from the radio, but if everything is working as designed, length should not matter.
If you have the skills and tools to put new connectors on, cut the cable to length, leave a foot extra in case you have to replace a connector.



Get channel 19 as low as you can (that's the center of the band, not 20). Then check SWR on Channel 1 and 40. Let us know what it shows and we can assist you in figuring out if the antenna is too long or too short.



OK, might be good, might be bad. As long as there isn't any noise from the gauges or LED lights, you should be OK.
Make sure you ground the radio negative lead to the vehicle body and keep the lead short. Don't run it all the way back to the battery.
While you are at it, run a ground wire from the radio chassis screw to the body also. This provides a good RF ground for the radio. It may not make a difference, but it won't hurt. I've had it fix intermittent issues.



OK, that's normal. Your body is coupling with the antenna.



Before you buy a new antenna, I'd make sure you go through every single step again. Check everything, even if you've checked it before.

Do these steps:
-Disconnect the coaxial cable at BOTH ends. Using a multimeter or continuity tester:
Check for continuity from the center pin of one connector to the center pin on the other end. Should show continuity. If it doesn't, stop and fix.
-With it still disconnected, do the same test as above with the outer shield. Should be continuity. If not, stop and fix.
-With it still disconnected, check for continuity between the center pin and the outer shield. There should NOT be continuity. If there is, stop and fix.
—For all the above tests, try wiggling each connector and see if it changes. It's common for the failure point to be right at the connector. Bad solder/crimp joint can cause it to fail. Sharp bend can damage the cable, etc.

Now, reconnect the coaxial cable to the antenna ONLY. Do these steps:
-At the radio end of the coax (it should still be disconnected), check for continuity between the center pin and the outer shield. There should NOT be continuity. If there is, the fault is with the antenna mount. Often they get assembled incorrectly and the insulating washers get install wrong. That will create a short to ground for the center of the coax pin. That will show as high SWR.
-If that tests out OK, remove the rubber cap off the top of the antenna. Check for continuity from the center pin of the radio end of the coax to the tip of the antenna where the adjustment screw is. There should be continuity. If there isn't, there's an issue with the antenna. Might need to replace it, but check the mount and make sure everything is making contact. Check the continuity from the center of the connector pin to the base where the antenna screws in, there should be continuity. If not, stop and fix.
- Now check for continuity from the outer shield of the connector on the radio end to the vehicle body/truck bed. Should be a good ground connection. If there isn't, could be the mount is assembled wrong or it's not mounted to body metal.

When you are checking SWR, make sure you are well away from all metal objects. Don't do this up in the driveway near the metal garage door, or even out on the street next to a lamp post. Ideal place to test SWR is out in the middle of a field or parking lot.

If you can find someone local that has an SWR meter, borrow that (and the owner if possible) and compare to what you are seeing on your CB. Those built in meters should be relatively accurate, but they are not very precise.

There's other things we can try, but give those a go first, they are the most common failure points. Don't start swapping parts around unless you find an obvious failure. Troubleshoot until you find the issue, then swap parts.

Ok, so the firestick was a brand new antenna still in the package he just had in his museum which he gave me. I know 4 years ago or so, he gave me a 102” whip that was spot on 1.0SWR with a uniden bearcat 880 and worked like a charm. I will check tomorrow though to make sure it’s not damaged in any way.

I went as far as to check that the mounting bracket had continuity to ground, which it did, and the antenna did not, which I’m assuming it’s supposed to be that way. On top of that, I took scotch brite and cleaned all threaded connections


I’m going to change the 12v source tomorrow to the second battery on the truck, and shorten the ground per your recommendation. The mounting bracket is already grounded to the can of the truck via 2 #14 self tapping screws. I will verify that ground tomorrow as well.

I’m also going to follow all the steps you listed to rule out anymore doubts. I’m assuming if everything checks out, I should probably just change out antennas. What would be a good antenna. I had good luck with the whip on my old vehicle, is that still a good option, or more of a gimmick?

 

[mmckenna]

I went as far as to check that the mounting bracket had continuity to ground, which it did, and the antenna did not, which I’m assuming it’s supposed to be that way. On top of that, I took scotch brite and cleaned all threaded connections

Correct, there should be no continuity between the antenna mount stud and the mounting bracket. That is a common issue with new CB'ers, they'll install the antenna mount incorrectly and short it to ground, then pull their hair out trying to figure out why SWR is so high. Hurts when you see people buy new antennas without checking the obvious.

I’m going to change the 12v source tomorrow to the second battery on the truck, and shorten the ground per your recommendation. The mounting bracket is already grounded to the can of the truck via 2 #14 self tapping screws. I will verify that ground tomorrow as well.

The power source should not impact SWR, but it can be a problem with RF interference. Industry standard is to always pull power direct off the battery and be very careful what kind of loads you share that circuit with.
If the mounting bracket is anchored into body steel, then you probably don't need to add ground straps. Ideally, it shouldn't make a difference, but it can if there's any insufficiencies in the install. I got in the habit of doing it with all my installs since it's takes a few seconds and is a fool proof way to know everything is well bonded to ground.

I’m also going to follow all the steps you listed to rule out anymore doubts. I’m assuming if everything checks out, I should probably just change out antennas. What would be a good antenna. I had good luck with the whip on my old vehicle, is that still a good option, or more of a gimmick?

Yeah, if you have a 102" whip that you know is good, give that a try. If you can tolerate all the tree branches, drive throughs and other low clearance situations, it's a better antenna. Hard to beat a good 1/4 wave….

 

[slowmover]

Where’s the antenna currently mounted? (Not directly related to current questions).

My ROT is two-part: Antenna 5’ or longer AND as close to 13’ as possible (14’ on big trucks). Am waiting for son to show up to install a radio rig featuring a 6’1” Sirio 5000 on a PL-145 mag-mount that should come close to 13’. Leave no performance on the table antenna-wise. (This one can be folded-over, so to speak, to be garaged, etc.)

Grasping mount to see an improved SWR brings up RF Ground questions, to me.

MMcKennas epic post is what to go thru first in any event. Not seen previously anyone kind enough to lay that all out. !!!!

 

[k7ng]

Two suggestions regarding radio installations:
(1) Pay attention to mmckenna's inputs.
(2) See (1) above.