New mobile install very high SWR

[Big_Lebowski]

Hello I am new to CB radios and pretty bad with electrical wiring so forgive me.

I bought myself a mobile setup for Christmas installed and getting SWR above 3 on every channel. I started with a Uniden pro401hh handheld CB and wired in a Tram center load mag mount antenna. It is two feet tall and came with 16 feet of coax. I cannot mount on my roof as there are two sheets of glass for the moon roof and the rest of the roof is not magnetic. Only can mount on the trunk or hood. I placed the mount on the middle of my trunk and ran the wire inside my car to the front. I didn't tuck any wires as I was just testing everything. I made sure there are no kinked or coiled wires. I went to a parking lot with no trees or power lines above me. No building closer than 100 feet. I used an small cheap SWR meter from amazon and it showed in the 3+ red on all channels. I made sure to close the door and sit inside my car to test. I tried moving the mount around the trunk. I put in on the hood. I used the small Allen wrench to adjust the set screw and lowered and raised the antenna 1/4 of an inch at a time and it didn't change. I even raised and lowered the antenna as much as possible seeing if that extreme change would help but it didn't.

So I figured the antenna is broken. I bought a Firestik 2 feet 5/8inch antenna and the Firestik brand trunk lip mount. It came with 16 feet of coax. Followed all the instructions and it was pretty simple. I couldn't put the mount in the middle of my trunk by the window because of my rubber weather stripping wouldn't allow me to close my trunk so it is on the far right side of the trunk. It closes just fine. Measured SWR again and same exact issue 3+ on every channel. So at this point maybe it is the radio. I bought a president bill fcc and tried with the firestik and the mag mount antenna. Still in the red for SWR. I think it could be a ground issue. I found some scrap copper wire in my workshop wrap amount around the grounding screw on the mount. I wrap the other end around a screw inside my trunk by my tail light and put a nut on tight. This still doesn't change my SWR.

For fun I borrow my friend's old truck and put the mag mount on the middle of the roof. I tested with the president radio and with a little adjustment of the antenna length SWR shows 1 on channel 1 and 1.5 on channel 40. So it must not be an issue with my hardware? Do I need a no ground plane setup for my car? I just bought a heavy duty spring for the firestik and will be installing soon and test SWRs. I don't know if that will help. If you made it this far thank you for reading. I do not know anyone personally who can help with this or any local CB radio shops.

 

[K4EET]

Big_Lebowski, welcome to Radio Reference!

You stated "I used an small cheap SWR meter from amazon..." which will generally raise red flags since quality is not very good and small meters are not very accurate. Even if it did show a 1:1 SWR on your friend's truck, there are sooooooo many factors at play here. For the antenna that you were adjusting in 1/4 inch increments, is that what the instructions said to do? Is this the antenna that you initially purchased?

TRAM 703-HC Center Load CB Antenna Kit

What type of vehicle is this being mounted on? A Chevy Corvette perhaps (due to the double moon roof and the rest is not metal)?

Have you done any further testing on your vehicle since you got the 1:1 SWR reading on your friend's truck?

Let us know here at RR and we'll see if we can give you some more ideas...

Dave

 

[Big_Lebowski]

Vehicle is 2014 Kia Cadenza. Hopefully linking to imgur isn't against rules but I've included pictures to help. And to answer your question yes I've tested after removing from truck and the SWR is still high 3. That amazon link is what I have and the first antenna I tested.

Install pictures

https://imgur.com/a/E0RpC1A

 

[Big_Lebowski]

Update

Installed a firestik heavy spring. SWR still over 3.

https://imgur.com/a/MA0VfGy

 

[WA0CBW]

If the antenna didn't come with the spring then adding the spring will make the antenna too long.
bb

 

[jhooten]

If the antenna didn't come with the spring then adding the spring will make the antenna too long.
bb

That spring will have absolutely zero effect on a 2 foot helically wound Firestick CB antenna.

OP, the SWR meter will give you very limited information. You need to beg, borrow, or steal an antenna analyzer to see what is really going on.

 

[mmckenna]

What model SWR meter are you using and how are you connecting it?

Sounds like maybe the meter is not set up correctly.

 

[Ravenkeeper]

Update

Installed a firestik heavy spring. SWR still over 3.

https://imgur.com/a/MA0VfGy

Verify that your antenna is correctly built up on the mount. Speaking from experience, mine was around 3:1 with the insolator/isolator washer in the wrong location, dropped it to mid 1's after correcting. Also, make sure that your firestik mount is grounded.

 

[Big_Lebowski]

What model SWR meter are you using and how are you connecting it?

Sounds like maybe the meter is not set up correctly.

It is a workman meter. This exact one.

SWR METER for CB Radio Antennas with 3' Jumper cable - Workman SWR2T & CX-3-PL-PL https://www.amazon.com/dp/B002KRME3C/ref=cm_sw_r_cp_apa_i_i3mdEb9NMYPC5

I have the antenna hooked into the "ant" port. And the jumper wire hooked into "rtx" and into my radio.

I will take apart the mount and make sure the washers are installed correctly. I thought I followed the directions when I installed but I will triple check.

 

[mmckenna]

OK.

I like Ravenkeeper's statement about the insulating washers. That's often the cause. Key is that the threaded part where the antenna screws in needs to be isolated from the mounting bracket.

However, since the SWR was high on the other antennas, I think there might be an issue with the SWR meter.
Sounds like you have it hooked up correctly.
You may not be calibrating it correctly.
Try this:
1. Set the switch to FWD.
2. Key up the radio, turn the CAL knob until the needle sits on the high end of the scale where it says SET
3. Release the key, meter should go back down to the left side of the meter.
4. Set the switch to SWR.
5. Key up the radio and read the SWR value.

 

[Big_Lebowski]

OK.

I like Ravenkeeper's statement about the insulating washers. That's often the cause. Key is that the threaded part where the antenna screws in needs to be isolated from the mounting bracket.

However, since the SWR was high on the other antennas, I think there might be an issue with the SWR meter.
Sounds like you have it hooked up correctly.
You may not be calibrating it correctly.
Try this:
1. Set the switch to FWD.
2. Key up the radio, turn the CAL knob until the needle sits on the high end of the scale where it says SET
3. Release the key, meter should go back down to the left side of the meter.
4. Set the switch to SWR.
5. Key up the radio and read the SWR value.

Yes this is how I am doing it. After on set I switch down to ref and it goes to 3. I also set on fwd and stopped transmitting. Then switch to ref and transmit but it is still the same swr as in my picture.

I ran a ground wire I think? See my first post with the set of pictures. The red wire is attached to the ground screw on the mount and then to my frame.

 

[a417]

can we rule out end to end wiring issues? lets check for continuity on the conductor end to end with low/no resistance, same for the shield, and the open circuit between conductor and shield. Hate to have a bad piece of coax be the problem here, or contributing to the problem.

Just moving the antenna to your friend's car (with different bends and contours) might have temporarily alleviated the issue, and then going back to yours might have brought it back.

 

[prcguy]

Sounds like the antenna is probably ok and it has insufficient ground plane on your glass roof vehicle being mounted on a small ungrounded trunk lid floating in rubber and no nearby horizontal sheets of metal to supplement the ground plane. I've seen this before and specifically with 1970s Toyotas or Datsuns that had a small insulated trunk lid they used as the car AM/FM antenna. A mag mount or permanent mount would work fine anywhere else but not the trunk lid. The OP mentioned the antenna works ok on a friends truck roof and that backs up this theory.

How big is the hood on this car? If its several times larger than the trunk lid then stick the mag mount in the middle of that and test again. If it works better there then you have a couple of options. Move the trunk lip mount to the front of the vehicle and hope you don't get too much ignition noise or stick a 25 to 50pf ceramic disc capacitor across coax inside the firestick antenna mount. That will fool the antenna into thinking it has more ground plane under it and can lower the match to a good level. I will not make up for degraded on air performance from the missing ground plane.

 

[FiveFilter]

As cars are made with more fiberglass attached to isolated pieces of metal, they become more difficult to use with a radio antenna. Even big trucks with composite cabs have this problem, so drivers often place their antennas on the outside rear-view mirrors and use wide copper straps to electrically connect the mounts/doors to the frame in order to achieve ground continuity. Prcguy is on the right track.

I place a magnetic antenna on the hood of my Jeep Wrangler with good results. Some with Jeeps use the lid mounts there as well.

You may get improved results by using a copper strap from the trunk lid to the body if you want to place the antenna there.

 

[Big_Lebowski]

Just an update I installed the mag mount on the center of the hood. I tested channel 40 and it was 2 SWR without adjusting the height of the antenna. So the issue with the trunk mount is no ground plane? I can't deal with an antenna in the front of my car. Time to buy a no ground plane antenna and coax wire?

 

[Big_Lebowski]

As cars are made with more fiberglass attached to isolated pieces of metal, they become more difficult to use with a radio antenna. Even big trucks with composite cabs have this problem, so drivers often place their antennas on the outside rear-view mirrors and use wide copper straps to electrically connect the mounts/doors to the frame in order to achieve ground continuity. Prcguy is on the right track.

I place a magnetic antenna on the hood of my Jeep Wrangler with good results. Some with Jeeps use the lid mounts there as well.

You may get improved results by using a copper strap from the trunk lid to the body if you want to place the antenna there.

Do I need something like a braided ground strap for the trunk? I ran a small copper wire already from the mount to a bolt on the frame close to my rear brake light and that didn't make a difference.

 

[prcguy]

An antenna like you are using wants to see a flat sheet of metal under it and the size will depend mostly on the frequency of interest. A small trunk lid like 2ft X 4ft would not work very well for CB but if that flows into other parts of the vehicle that have more surface area and the trunk is well bonded to the other metal it can work ok. At best a trunk lid makes a little contact at the lock and the big curved hinges all but disconnect it from the rest of the vehicle RF wise. The perimeter of the trunk sits on rubber to keep water out of the trunk. A simple ground wire will not fix that and you would need a couple of wide braided straps to make a good RF connection to other adjacent body parts, assuming they offer enough surface area to be beneficial.

The convertible vehicles I've installed antenna on are older (70s and 80s) and much larger than yours and I don't remember any specific problems with trunk lid mounts or mag mounts on the trunk lid back then. We didn't have any glass roof vehicles back then so that's why I'm comparing to a convertible.

A no ground plane antenna is an option.

Do I need something like a braided ground strap for the trunk? I ran a small copper wire already from the mount to a bolt on the frame close to my rear brake light and that didn't make a difference.