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

Cutlass327

Cutlass327

Well-Known Member
May 1, 2016
309
214
53
NE Ohio
Ok, I have been reading the "good book of K0BG", and bonding, common modes, etc. This has given rise to a few questions, thoughts, ponderings.

My 78 CJ5, with fiberglass tub, fenders, windshield frame, steel hood, and steel grille, is the vehicle. If has a Mustang 5.0HO with Ford factory EEC-IV A9P Ecu, in-tank fuel pump.

Antenna is a 102 with HD spring, mounted on right rear bumper mounting bolt, ground strap from angle iron bracket to frame. RG8X coax of unknown brand, will be DX Engineering RG8X here shortly.

TRC465 radio, previously Cobra 25 NWSTWX.

Stereo system - Blaupunkt Amp1504, Panasonic head unit, 2 6x9 speakers.

OK, I am trying to eliminate the static from the ECU, Fuel pump, and stereo. I have a snap on bead on the coax, a couple inches from the PL259 behind the CB, it was a "what do I do with this extra one" moment. I have one on the dual RCA patch cable, the cable loops once or twice. I did the same with the remote power wire, power feed and ground. No difference. I have no idea what "mix" these beads are. I believe in the Q/A section on Amazon someone said they were 43.

I am thinking I will try the 7 loops of the RG8X thru the Mix 31 like K0BG mentioned when I rework my coax. I plan to add some help to the radio, and re-route the coax down the driver side instead of down the passenger side bundled with the fuel pump power wires. I bought a few toroids of Mix 43 to make a choke for the fuel pump feed wires, but never did. I don't feel like dropping the fuel tank unless I need to do more than the choke. Would this 7-loop-thru-Mix 31-filter work for my noise issues?

I also plan to bond the dual exhaust pipes to the frame at the rear. In the article, he says in multiple places, I am guessing due to clamp-type connections. My pipes are welded. Is a strap on each pipe in the rear enough, or should I do one in front, too? It is a ball-flange type junction to the engine.

Bonding the hood - the braid would be a couple feet long to bond to the frame, and no way to bond to the grille, so should I worry about it? Bond to battery neg?
 

Hmm...

Best to start where the noise begins...

Lot's of times, the "fuel pump noise" - unfortunately, is due to the OEM assembly "seal" that things' supposed to have for it's lifetime. It is an emissions control device - regulates, et al. So there is a high pressure line, low pressure/vapor return and then there is that darn EVAP system to boot.

So I would hold off on that "bonding" of the fuel pump and stuff until you can get your hands on one from a junkyard and you'll see (disheartened really) how these things get put together and to try and remove the noise requires a tear down, reassembly and install of noise filters at the pump assembly. (If possible - you may have to make/create your own to solve this if there is any potential solution.)

You might have some success by simply cleaning up and re-establishing ground contact by making the harness do it's job of keeping itself self-contained and not vibrating loose.​
  • You can try to redo some ground points along the harness to the rear taillight assembly
  • Start by loosening bolts, and reinserting them to clean out their threads to re-establish better ground contact which in itself may cure much of the noise by providing the shielding return and also can improve the Reliability of parts that get tossed, coated in mud and banged on rocks and rinsed over streams.

It sounds simple but it's not as easy at it looks or sounds. You can try ferrite chokes and even rewire/redo the ground points - but remember it's dealing with fuel, a corrosive and a solvent of many things - including plastics and insulation. So to fix a noisy fuel pump can be as simple as loosening and retightening several bolts that hold the insert (float pump and screen) onto rewiring the harness and relocating a grounding point to handle the pump assembly and EVAP system at the same time.

Being a owner of several SUV's myself - dropping a fuel tank isn't the best way to start someone's day.
 
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I don’t think 1 bead on the coax (single pass) is adequate, at least with my minimal understanding. I went with 5 beads, should be close to 650ohms at 27mhz according to the data I got from Palomar. 4 turns is like having 16 single pass beads.
 
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i have seen instead of toroids that large nail with 7 to 10 wraps for power, ground, and speaker wires works,,, the coax needs to be 98% shielded or better the less shielding the easier for noise to come into antenna system then radio,,, on my blazer when installed a sony stereo it was picking up fan noise bad,, i pulled the antenna off and rigged up a rg58 cable instead of the oem and noise disappeared,,,
 
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I go up maybe 2S? When the stereo is up, it goes up at least 5S as the bass 'hits'. If I turn the radio up to a good song, it goes higher.

I have a poly tank, so the metal sender unit/fuel pump is insulated from everything other than thru the wiring.
 
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There is one important item to keep in mind about bonding specifically, and noise abatement in general; you can't always tell there has been an improvement by just listening! The reason centers around the AGC circuitry.

If this statement above is close to being true, how does anyone that goes to the trouble and the work of bonding...determine any differences as a result?
 
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Mudfoot said:
I think the levels of bonding he preaches is bullshit.
Click to expand...


Not a challenge, but asked rhetorically:

Where is the measure (would be the question)?

More, is easy.

Not enough, just frustration.

If SWR changes are that measure . . . . ?

It’s more to doing horizontal surfaces first, and vertical second, isn’t it? (Past genuine noise-sources).

Who is there thats’ removed bonds installed as found not necessary by such a method (more locations than my driveway tested), or found “ground loops” (equivalent) lessened by taking some off?

Which ones are unnecessary?

What statement suffices as advice?

My guess is that it comes first to vehicle description. Then brand & model.

Generalities. If it’s attached, bond it.

Useful: would be specialized military radio vehicle bond schematic.

.
 
Marconi said:
There is one important item to keep in mind about bonding specifically, and noise abatement in general; you can't always tell there has been an improvement by just listening! The reason centers around the AGC circuitry.

If this statement above is close to being true, how does anyone that goes to the trouble and the work of bonding...determine any differences as a result?
Click to expand...


In several posts in several threads (most recently: HIGH SWR) contributor M0GVZ uses SWR measurements as a gauge to bonding effectiveness.

By implication, there’s a point one has done enough.

.
 

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