Mobile Rigs - Static, interference, and thoughts on these issues...

[Cutlass327]

2NC995, no problem, taking it on tangents but also adding to it. Just more info to go on...



Ok, in this pic, you can see the ground strap tying the mount bracket to the frame. The crossmember that the bracket and bumper is bolted to is welded to frame at the time of manufacturing. The bracket and the tire carrier both are grounded thru a braided strap to the frame by a stainless bolt.

When I put a strap to the exhaust pipes, should I use the same bolt as those straps? I'll have to put another bolt thru the crossmember on the driver side for that pipe.

 

[Handy Andy]

Man, to see a true old "bucket truck" wow...

Ok, just so you know, your antenna and mount are closest to the noisiest part of that vehicle.

That rear bumper assembly is not a unitized part of the body. So in this situation. the main portion of the noise pickup is the ground plane of the bumper assembly that bolts to the frame. The coax shield is simply bringing back the counterpoise noise from that bumper assembly.

The Bolt On bumper bummer situation is part of this, so if you can even "reassemble" the rear bumper with clean work and fresh bolts recoated AFTER they are put together - this may work.

You know that SUV you have is pretty rare to see one in as good of condition as yours.

'Usually in winter - at least in the rust belt, these things fall apart in less than 10 years of service life - good to see you holding onto one.

Perhaps part of the reason you still have one as intact as it is, is due to the fact it's been take care of so well.

 

[Cutlass327]

Well, the reason it is in such good condition is also probably one of my biggest issues - it's fiberglass. Hood, grille, and dash are all that's left of the steel body. Fenders, tub, and windshield frame are all fiberglass.

 

[Cutlass327]

Why is that the noisiest point? Is it because of being on the "isolated" bracket?

The frame is galvanized, then coated with POR15, then the bumper was painted me installed, and the antenna mount there was an afterthought. I could weld it to the bumper... But the is also why I put a ground strap to the mount from frame.

I have a mount I welded into the carrier arm, it's about 6" lower than the spare tire "hub". That's why I put the ground strap to the swing arm, to ensure a ground in case the greasy bearings in the swing arm hub doesn't ground well.

Would I be better with it on the swing arm? Or better with the mount welded to the bumper?

I'll try to post pics of the grounds and mounts later.

 

[Marconi]

I seen similar mobile antenna setups work very good in spite of many claims otherwise by the naysayers.

I would not enter it into a CB shootout contest, but if it works and pleases you...go for it.

 

[Cutlass327]

I'm mainly wanting to get the noise levels down. I'm fighting varius noise levels, where I must have the squelch at least 3/4 high to not have the static break thru at times, but then it's about pointless to have the thing on as only the strongest signals break thru.

 

[ForestRunner98]

I am mobile as well and I have been chasing noise as well. I already did all the bonding goodies, SWR is great considering I am using a bracket mount on my 4Runner. I even tried a temp mag mount ant and same noise levels. About 3 to 5 s levels. Not wild levels but the same. Anyways long story short I think mine is due to a cheaper type radio.

So maybe try a different radio if possible. The one you are using could be more “sensitive” and pick up noise. Just my $.02

 

[Handy Andy]

Lots of traffic on this thread, but if you still see this...LOL...

Try relocating to the swing arm, can't hurt - it will raise the mount above much of the noise as long as the bonding issue takes care of the "floating arm" due to the bearing Grease.

If the Arm latch has got metal plate for bracing and it's mounted can you verify it's got a route for RF to make it to the Frame?

I also would think something like NAPAs' Copper Anti-Size might help with that swing arm. It's conductive.

 

[M0GVZ]

2NC995, no problem, taking it on tangents but also adding to it. Just more info to go on...

View attachment 38457

WINNER WINNER CHICKEN DINNER I think I know the answer. (Or I hope so otherwise I'm about to look a clown).

I'm so glad you've posted that picture, I think I've figured out what the biggest cause of your problems is.

As we know, RF flows over the surface of a conductor, not through it. Also as we know RUST ACTS LIKE A DIODE to RF. So seeing the full sized image you've posted what do you think is supposed to be conducting RF but is also rusty? The once nice shiny chrome spring at the base of your whip which has very little chrome left but a whole lot of rust.

I bet that if you took the spring out of the equation or replaced it with a nice shiny new rust free one that the majority of your problems will disappear. Personally I can't even understand why you're using a spring as there's sufficient flex in the whip already so you won't need one. Remove the spring, put the whip directly into the mount, see if things improve.

Even if the noise level doesn't go down the fact you've not effectively got a diode in line with your antenna cutting off half the signal you receive may make received signals a fair bit more stronger meaning you can use the RF gain on your CB and turn it down to reduce the noise but still be able to hear people better, although you'll need to possibly turn up the volume but winding down the RF gain will reduce the noise more than the wanted signals.

As an aside, having so much vertical metal so close to the antenna won't be helping your tuning at all.

 

[Cutlass327]

Lots of traffic on this thread, but if you still see this...LOL...

Try relocating to the swing arm, can't hurt - it will raise the mount above much of the noise as long as the bonding issue takes care of the "floating arm" due to the bearing Grease.

If the Arm latch has got metal plate for bracing and it's mounted can you verify it's got a route for RF to make it to the Frame?

I also would think something like NAPAs' Copper Anti-Size might help with that swing arm. It's conductive.

The arm is held closed by a bolt going thru the arm and into a nut welded to the bumper itself. The bolt is well coated with Permatex antisieze (the silver stuff).

 

[Cutlass327]

WINNER WINNER CHICKEN DINNER I think I know the answer. (Or I hope so otherwise I'm about to look a clown).

I'm so glad you've posted that picture, I think I've figured out what the biggest cause of your problems is.

As we know, RF flows over the surface of a conductor, not through it. Also as we know RUST ACTS LIKE A DIODE to RF. So seeing the full sized image you've posted what do you think is supposed to be conducting RF but is also rusty? The once nice shiny chrome spring at the base of your whip which has very little chrome left but a whole lot of rust.

I bet that if you took the spring out of the equation or replaced it with a nice shiny new rust free one that the majority of your problems will disappear. Personally I can't even understand why you're using a spring as there's sufficient flex in the whip already so you won't need one. Remove the spring, put the whip directly into the mount, see if things improve.

Even if the noise level doesn't go down the fact you've not effectively got a diode in line with your antenna cutting off half the signal you receive may make received signals a fair bit more stronger meaning you can use the RF gain on your CB and turn it down to reduce the noise but still be able to hear people better, although you'll need to possibly turn up the volume but winding down the RF gain will reduce the noise more than the wanted signals.

As an aside, having so much vertical metal so close to the antenna won't be helping your tuning at all.

I'll try it without.

I had heard on here where someone doesn't trust those springs as a conductor, as they rust, or the braid inside breaks off, so I have a braid going down the outside of the coil. Ihad thought of that when I was talking to someone half mile away and he said I was dropping out, and it was as I was stopped at a red light and started to move.

I'll take the spring off, try it tomorrow.

I think next chance I get, I'm going to get one of those NanoVNA analyzer things.

 

[Cutlass327]

Ok, took spring out, SWR with spring was 1.2, without was about the same.

My order from DXE came in, put a choke just under 12" from antenna connection, as thats the closest I can pit it and it still be safe from snags and debris. It has 5 passes thru the snap on bead.

Is there an advantage of a 2nd bead on the same winding? It would have 4 passes thru it.

 

[M0GVZ]

Did you see if your noise problem went when you removed the spring?

In regards to a second bead, you can never have too much choking and the more turns you get through it the more it chokes. I've got a RF choke on my Hustler 5BTV at the antenna and then one near where the coax comes into the house although on balanced antennas such as a dipole or a beam I'll typically just use one at the antenna.

 

[Slowmover]

WINNER WINNER CHICKEN DINNER I think I know the answer. (Or I hope so otherwise I'm about to look a clown).

I'm so glad you've posted that picture, I think I've figured out what the biggest cause of your problems is.

As we know, RF flows over the surface of a conductor, not through it. Also as we know RUST ACTS LIKE A DIODE to RF. So seeing the full sized image you've posted what do you think is supposed to be conducting RF but is also rusty? The once nice shiny chrome spring at the base of your whip which has very little chrome left but a whole lot of rust.

I bet that if you took the spring out of the equation or replaced it with a nice shiny new rust free one that the majority of your problems will disappear. Personally I can't even understand why you're using a spring as there's sufficient flex in the whip already so you won't need one. Remove the spring, put the whip directly into the mount, see if things improve.

Even if the noise level doesn't go down the fact you've not effectively got a diode in line with your antenna cutting off half the signal you receive may make received signals a fair bit more stronger meaning you can use the RF gain on your CB and turn it down to reduce the noise but still be able to hear people better, although you'll need to possibly turn up the volume but winding down the RF gain will reduce the noise more than the wanted signals.

As an aside, having so much vertical metal so close to the antenna won't be helping your tuning at all.

As mentioned, it’s now the heat of summer. And a nice ‘ol Jeep any of us would like to have.

Beer Rules are now In Effect

Enthusiastic responses are proportional and allowed according to the number of hands willing to apply themselves.

But, ends after midnight (and it’s someone else’s wife) wondering aloud at the Jeep turned on end and riders atop the shoulders of others, wrenches twirling, “come on, just one more turn!”

.

 

[Slowmover]

I'll try it without.

I had heard on here where someone doesn't trust those springs as a conductor, as they rust, or the braid inside breaks off, so I have a braid going down the outside of the coil. Ihad thought of that when I was talking to someone half mile away and he said I was dropping out, and it was as I was stopped at a red light and started to move.

I'll take the spring off, try it tomorrow.

I think next chance I get, I'm going to get one of those NanoVNA analyzer things.

CAL-AV recommends (aerosol) LPS
for their mil-spec Mark spring series braided weave bond. Just enough to wick through.

.