Grounding issue

[n5wta]

I'm hoping that one of you guys have ran into this problem.

I'm chasing the noise around my house and slowly either killing noisy devices, or putting line filters in front of everything. So far I've gotten down from S9-S5 noise floor. I have a CHA250B on the roof, but I've also had a few other antenna's with the same issue.

Getting to the actual weird issue I am having, I pounded in a ground rod just outside of the room where my radio is (less than 6' away from the radio) installed a polyphaser, hooked everything up, and no matter what I did in the house, outside of cut the power, I have massive amounts of S9 on every band. As soon as I bypass the ground rod, (which is on the opposite side of the house from the electrical box ground rod), noise drops to S5.

This ground rod is by itself, not near anything else, not even the water pipes. Has anyone ever come across this? If so, Did you have to burn your house down to fix it?

Thanks in advance! N5WTA

 

[prcguy]

What you are experiencing with the ground rod is not that unusual. Many people think that noise will automatically take a path to ground and that's simply not true. In fact I can't remember a single reduction in noise from connecting a ground rod in the many base station installs I've done or seen. There is also lots of noise on ground conductors since its common with most everything in your house that uses AC power, so connecting a radio to that can increase your noise level from RFI traveling on the shield of your coax up to the antenna.

Another problem you have created is any additional ground rods you install must be bonded to the main electrical entry point ground with no less than 6 ga copper wire and that must be upsized if the run is over a certain length. Its going to be difficult and expensive to run this big ground conductor to the other side of your house so its better to remove it or not use it as it will probably cause more damage to your home electronics if you get hit by lightning than not having it. With a lightning hit you want all the ground potentials in your house to rise and fall together, which can only happen when all ground are bonded together. That extra floating ground rod will cause a huge difference in ground potential between your radio room and the rest of the house, maybe thousands of volts and that can wipe out everything plugged into an outlet even if its turned off.

And even another problem is your new ground rod might be closer to your neighbors electrical entry point and ground rod and your new ground rod may be at a potential closer to your neighbors AC power ground, which could be fed off a different pole transformer or ?? and now your coax has a bunch of AC current on it trying to equalize the potential between your main AC entry point ground and your neighbors. Try putting an AC voltmeter or even an AC ammeter between your coax shield and the ground on a nearby AC outlet when that new ground rod is connected. You might be surprised or shocked. This is why NEC requires you bond the new rod to your house AC entry ground.

So what do you do about the noise? Continue shutting off power or unplugging items until you find the offenders. Get rid of them or wrap all wires entering or exiting the devices with the proper ferrite mix and number of turns through it. Put a really good common mode choke on your antenna! I'll try not to go into a rant about your specific Comet antenna and all the bad things about it, but one if its problems is the coax is not really decoupled from the antenna and the coax becomes a radiating part of that antenna. Your coax run from the radio to the antenna can pick up noise from computers, wall wart power supplies, routers, ground connections, whatever, and conduct it right up to the antenna where it gets received and fed to your radio. Placing a really good common mode 1:1 choke balun in the coax near the antenna will stop the RF currents or RFI traveling on the shield of the coax to the antenna. In some cases you can see a really noticable decrease in noise by installing a good RF choke. I install them both at the antenna end and at the radio end as my coax exits the wall.

The problem is most 1:1 choke baluns are not very good and are simply a few ferrite beads over coax inside a plastic tube and will barely reach 20dB of isolation at some frequencies and that is not enough. At the very least get one that uses a large ferrite ring with turns wrapped around it. Those properly done will reach maybe 30dB of isolation at some frequencies but the best chokes have multiple ferrite cores in series with various mix ferrite and different windings to target different parts of the band. The very best I have seen is from MyAntennas and they are not cheap, but there are some that cost more and do basically nothing, so in that case they are a bargain.

 

[buddrousa]

How old is the GROUND ROD at the Electrical Service?
I would Replace the OLD GROUND ROD.

 

[n5wta]

The old ground rod is less than 5 years old. I also, removed the lug, scrubbed down the rod, and the ground wire and reattached it. PRCGUY, thank you for the eloquent description. I let my wife read it, who is also a ham. She is allowing me to take over the spare bedroom which is closer to the mains ground. (about 15 feet away) I'll run to big box and grab a 20 foot run of their thickest gauge wire and see if I can get the noise down that way.. Thanks alot!

 

[buddrousa]

If your soil is sandy and your site has had any heat dissipation you know what heat and sand make. Got this from a tower guy they replaced several

 

[prcguy]

Again, I've never seen noise on a radio reduced by grounding, only by addressing the noise at the source or choking off your feedlines when the noise is conducted up the shield of the coax as it passes by an RFI generator. Its good that you improve the grounding in general for safety, etc, but look into some ferrite for noise reduction.

The old ground rod is less than 5 years old. I also, removed the lug, scrubbed down the rod, and the ground wire and reattached it. PRCGUY, thank you for the eloquent description. I let my wife read it, who is also a ham. She is allowing me to take over the spare bedroom which is closer to the mains ground. (about 15 feet away) I'll run to big box and grab a 20 foot run of their thickest gauge wire and see if I can get the noise down that way.. Thanks alot!