Will a wire going from the mounting bracket on my mobile unit to a good ground improve my SWR or is that useless? I connected a wire from the thumb screw that goes into the case of my radio right to a ground. Is that useless, can I remove it, or should it provide me with some kind of improvement?
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Ground wire to my mobile mounting bracket?
- Thread starter MeatMan
- Start date
If your mounting bracket is attached to metal then that's a good enough D.C. ground as long that metal is part of the chassis.
If not, auto parts stores sell flat braided ground straps with eyelets that you can attach accordingly. Don't use common wire!
That radio chassis ground isn't necessary but it's fine to leave it.
Typically on mobiles, if your antenna doesn't have a good D.C. ground, your SWR usually shows 3.1 across the whole band.
A marginal ground may show better which may be your case.
If not, auto parts stores sell flat braided ground straps with eyelets that you can attach accordingly. Don't use common wire!
That radio chassis ground isn't necessary but it's fine to leave it.
Typically on mobiles, if your antenna doesn't have a good D.C. ground, your SWR usually shows 3.1 across the whole band.
A marginal ground may show better which may be your case.
In my truck I ran a ground strap to the mounting bracket, the reason is that I'm mounted to ABS plastic, it lowered some of the antenna noise I was receiving. If you're already mounted to the metal frame of the vehicle, it will do nothing for you.
The radio is mounted inside the armrest due to space constraints, and the bracket is screwed into the plastic. The lip mount has a great ground where it is, and the white cable goes from the mount to a grounding strap under the hood that is close by. I added some wire with a ring connector to my thumbscrews that go directly to a ground as well. The only thing I had on hand was 16 gauge speaker wire, so I put one side of it to each side of the radio and have them going to a single ground bolt under my seat, which is also a great ground. I say great grounds since my meter shows great continuity.
It looks as though your antenna mount is on a bolt under the hood, that should be sufficient.
Your radio case does make a ground connection through the coax braid. You can leave the wire you have on now but you should use flat braided straps though like this which auto part stores should have.
What are you checking your SWR with and what is the reading? Don't always trust your radio's meter. An analyzer is best if you have or know someone who has one. If not, an external SWR/Power meter like CB shops and some truckstops still sell work too.
Anything below 1.9 is acceptable. A decent mobile antenna should be able to tune down at least a 1.4 or better.
I tune my mobile antennas to the lowest SWR on the frequency I used most and let the antennas bandwidth cover the rest.
Typical CB antenna instructions say tune channels 1 and 40 to an even balance but this gives a compromised tuning across the band.
Your radio case does make a ground connection through the coax braid. You can leave the wire you have on now but you should use flat braided straps though like this which auto part stores should have.
What are you checking your SWR with and what is the reading? Don't always trust your radio's meter. An analyzer is best if you have or know someone who has one. If not, an external SWR/Power meter like CB shops and some truckstops still sell work too.
Anything below 1.9 is acceptable. A decent mobile antenna should be able to tune down at least a 1.4 or better.
I tune my mobile antennas to the lowest SWR on the frequency I used most and let the antennas bandwidth cover the rest.
Typical CB antenna instructions say tune channels 1 and 40 to an even balance but this gives a compromised tuning across the band.
I used the radio SWR, and as long as I'm not around wires and in an open area it reads almost dead flat on 1, 40, and 19. When using my fathers old radio shack SWR it kept reading around 3. Strange thing is mine read high too from the radio, but only when connected to the external meter. As soon as I removed it, the SWR dropped. The meter seems to work fine on my base unit, but every time my hands get close to it while trying to calibrate it the needle jumps all kinds of crazy. I felt like I got a slight burn from a screw on the case when touching it while keying the mic. I imagine I was creating a ground loop with my body perhaps?
My hands seem to have no effect on the external meter when testing my Washington base unit, only when testing the mobile unit. It only seems to react to my hands when they're near it while using my mobile.
The external SWR also causes a ground fault while checking continuity at the antenna mount. With the meter connected to my antenna cable I have continuity from the bottom of the mount to the other side of the nylon washer at the antenna stud. Once I disconnect the SWR meter from the antenna cable I have zero continuity between the mount and antenna stud. But if there is an internal issue, why does it not show on my base antenna?
That's what I'm trying to figure out, but the only item that seems to cause a high SWR is the external SWR meter itself, and only when connected to the mobile. All ground faults go away after disconnecting the meter, and the SWR from my radios internal meter shows a normal value again rather than into the 3's which it does when connected to the external one. It also reacts to my hands proximity which causes the needle to jump around a bit, as well as creating continuity in my antenna to mount. No external meter = no continuity... but then again, the external meter seems to work fine on my base unit...
Maybe I'll try to connect the meter to my mobile in my home again to see what differences are present when connecting the meter between my base antenna and mobile unit. I didn't record them last time.
Just curious. If you take the radio out of your vehicle and hook it up with a power supply in your house to your base antenna then does it do the same thing?
Ahh, but I just discovered this tonight... Why would my radio have continuity between the lead and the ground? Everything else checked out fine, I only have continuity between the antenna mount and stud when connected to my radio. Lo and behold, it's coming from the radio. The internal SWR meter shows almost dead flat, but why in the world would there be continuity here? I'm told I have a great sounding unit, even spoke to King Phillips Island Nova Scotia for about 15 minutes last week from Massachusetts.
The radio is an HR2510 if that helps. Same radio inside the house shows just fine SWR 1.4:1 not a 3:1 from grounding out. Weird...
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