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

[Handy Andy]

So my thought of running CB ground, stereo amp ground, fuel pump ground, etc all to the batt neg post is actually doing the opposite of my thought? I thought a common ground point to battery, same as common power point at batt pos post, would eliminate ground loops and other noises..

Should I be grounding to the frame??

What you need to do is what it takes to remove the noise...

IF it can't be done at the sources of them, you will have to attempt other means.

Simply put, we can't do much about the POSITIVE side of the power supply.

What we can work on and improve, are the ground returns from these noise sources to keep the sources that generate them, reduce the wires' lengths (as possible), reduce their ability to transmit and radiate - by taking steps - reducing wire run lengths - shorter the better - grounding returns closer to the parts to lower their wires' inductive paths - let the vehicle provide the return path and shielding effects to attain this.

Shorter wires that radiate less noise of the device - mounting and tying off as short as possible to ground return provides as a shielding potential-drop as well as shielding itself to - by using- the same NEGATIVE the battery uses. The individual circuits used in the vehicle HAS TO return it's power from all the accessories and even the engine block - to the very source of power providing it - that process is Grounding. To provide the lowest ohmic and reactive impedance effects - I call it "bonding" as in Bonding to Frame. Example: The vehicles' sensors - to simplify such wiring headaches, already attempt to do this thru single wire supply or single port routing with the main ground return built into it's own housing.

Long wire runs are the bane of the industry, anywhere - Home, Car - Radio - Wire is used to obtain a signal - you can also use it to radiate, so that means if there is noise in the area, that very wire will receive it and radiate it back into that area and into your radio - simultaneously.

 

[Shadetree Mechanic]

I have heard of people putting a capacitor at the connection of the offending noise source like a fuel pump or wiper motor.

 

[2NC995]

I have heard of people putting a capacitor at the connection of the offending noise source like a fuel pump or wiper motor.

Me too.

I’d imagine a capacitor could be very effective, but that some toying with values would likely have to take place.

Pretty much the same thing done to smooth output in a power supply, voltage regulators and etc.

 

[Road Squawker]

I have heard of people putting a capacitor at the connection of the offending noise source like a fuel pump or wiper motor.

... and "maybe" one of these on the antenna mount. (hint, hint)

 

[Cutlass327]

... and "maybe" one of these on the antenna mount. (hint, hint)

That wouldn't last long, unfortunately. Unless it could be sealed, salty winters would make fast work of it.

 

[M0GVZ]

Read the original post. That site is what got me to posting this....

So if you've read the website you'll know that .

Antenna is a 102 with HD spring, mounted on right rear bumper mounting bolt, ground strap from angle iron bracket to frame.

Means that you've basically no RF ground and that the ground strap does nothing. If you look through the HOS folder on the picture gallery on that site you'll see similar installs and they all have the same comments attached..."virtually no ground plane under this antenna"

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.

Yup. You find that out when you add another ground strap and the resonant frequency no longer shifts. Unless of course it's the exhaust or engine you've just put one on in which case it won't move but you're adding those to reduce electrical noise, not improve the RF ground.

 

[M0GVZ]

I think the levels of bonding he preaches is bullshit.

As someone who has taken the time to do it as per that website I don't. When I'm on my CB with 4W I talk to the next town 10 miles away with a S9 signal report, when I'm going to a nearby city and with my 4W mobile managing to talk to people on Ch19 over the top of local home bases and when I'm driving down the road with the preamp on and still able to make out what people with S0 signal strength are saying because I've zero engine noise it's proof to me it works. When I'm running 200W on the amateur bands with my TS480 with no noticeable common mode RFI issues then it's proof to me it's worth it.

When I changed cars recently I had proof installing as per his website works. I had to use a magmount and cig lighter socket for power and boy was that interesting. Increase in noise levels, big reduction in range despite using the same antenna and CB and a very interesting issue where in the white noise on a couple of channels I could hear a change in the hiss that coincided with the beat of the song playing on the car radio and when I increased the volume on the car radio I could kind of make out the tune in the background hiss too.

If you're bored with nothing to do for a couple of days reinstall your CB gear in the car following all the advice on that site in regards to mounting, grounding, bonding, power etc. I say a couple of days because if you take the time to do it well, doing things like removing seats to run cabling properly, it'll take you a couple of days or one long ass single day. The worst that'll happen is you'll notice no difference but I'd be surprised if you don't.

 

[M0GVZ]

SM, I promise to check out the thread HIGH SWR) by M0GVZ using his SWR meter to chart the effectiveness of bonding while he installs his bond connections.

Right off the bat, such a process sounds like it would be a very tedious effort to chart.

I don't use a SWR meter, I use an antenna analyser. You don't need to chart anything. The goal when using a 1/4 wave antenna is to end up with a feedpoint impedance of 36.8 Ohms where the resonant point (X=0) of the antenna is as that's the feedpoint impedance of a 1/4 wave antenna over a perfect ground. Second thing to note as explained in the ARRL antenna book RF grounding section is that as you improve your RF ground, without adjusting the length of the antenna the resonant frequency of your antenna lowers.

So it's simply a case of either monitoring the frequency where X=0 is if you have an analyser, or seeing where the SWR dip is if you only have a SWR meter and seeing if it falls in frequency/channel when you add bonding. If it does then your bonding is improving the situation, if it doesn't it isn't adding anything. The antenna analyser will give you the added advantage of gauging how efficient your RF ground overall is, seeing how close the feedpoint impedance is when you've finshed to the perfect 36.8 Ohms, which a simple SWR reading won't.

Given the cheapness of nanoVNAs now to the point you can buy one for much less than a decent mid-range Power/SWR meter, there's no reason not to have an analyser especially if you're serious about doing it properly.

 

[Marconi]

Sorry M0GVZ, I got a bad tip on something I was told you reported.

 

[Cutlass327]

Is it possible to do too many? If I have one before the amp, and one before the radio?

 

[Slowmover]

As half the answer is lousy audio quality in the first place.

An external speaker with DSP somewhere between radio and speaker-cone tunes up the ears.

Ferrites, bonding and the rest aren’t nearly as efficacious (Mobile).

(Somewhere, perhaps on this site, is the comment that with RG59 you have noise that Heliax better attenuates, but now you can make out the words not earlier heard).

What is signal, and what is noise? (where signal contains distant environmental influences, and noise is much to do with the vehicle constantly changing capacitance while in movement).

.

Gonna quote myself to add context.

I’ve found it easier to carry a conversation with another truck driver heading a separate duration.

That is, the speaker type already makes his end retain clarity longer.

Even a modicum if bonding seems to help both that and his ability to hear me.

Can’t swear to it. It seems to be a more regular occurrence.

I’d want to know more about how his audio is either processed or reproduced (before Id accept what did or didn’t work re bonding).

.

 

[Slowmover]

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.

.

Bad tip. Right.

My mistake.

Corrected info by M0GVZ above.

.

 

[M0GVZ]

Sorry M0GVZ, I got a bad tip on something I was told you reported.

I'll hold my hands up and given I work nights, do at least 10 hours and sometimes up to 15 and flip from nights to days and back again with the inevitable lack of sleep it wouldn't be beyond the realms of possibility for me to post some absolute complete unadulterated bollocks I'd never post when functioning normally and thinking clearly.

 

[2NC995]

So it's simply a case of either monitoring the frequency where X=0 is if you have an analyser, or seeing where the SWR dip is if you only have a SWR meter and seeing if it falls in frequency/channel when you add bonding. If it does then your bonding is improving the situation, if it doesn't it isn't adding anything. The antenna analyser will give you the added advantage of gauging how efficient your RF ground overall is, seeing how close the feedpoint impedance is when you've finshed to the perfect 36.8 Ohms, which a simple SWR reading won't.

This is something you've mentioned many times that I have yet to get a good understanding of. So, a 1/4 wave antenna has a 36.8 ohm impedance over perfect ground - ok, I've read that many times. Yet, with a 1/4 wave ground plane antenna the radials are nearly universally dropped to 42 or whatever degrees (from 90) to get closer to 50ohm impedance.

The question that leads to is why would we not be happy with a 50ohm match on a vehicle - and I'm referring to an R of 50ohms at a Z of zero. If that's the results then should we keep "improving" the ground seeking a perfect 36.8 ohms? It seems that at the end of the day a vehicle-shaped-object isn't ever going to behave exactly like a theoretical perfect ground.

I've seen your posts talking about antennas tuning short indicates a good RF ground. Mine have universally tuned short. In fact, I am puzzled every time the subject of 102" whips come up and folks assert that it needs a 6" spring, or a riser, to be 108" and work properly on the CB band. That's never been the case for me. The same with other antennas...7' skipshooter I toyed around with a couple months back looked best around 26mhz, with the tuning stub completely removed. It worked well, but was way too long. Same with Wilson antennas I always have to trim several inches to get them in the ball park.

If you feel like entertaining my thoughts, please feel free. Not intended to second guess, rather trying to wrap my head around what I could gain by lowering the feedpoint impedance below 50ohms....and if it would even be possible.

 

[ForestRunner98]

Is it possible to do too many? If I have one before the amp, and one before the radio?

I think I read that if you go more turns it will have an opposite effect. I would like to know for sure. Anybody??