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Author Topic: How do I know if my earth rod/connection is worki  (Read 2653 times)
2E0BSS
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« on: September 18, 2007, 07:04:19 AM »

How do I know if my earth connections are working? I have a 4foot copper plated earth rod pushed into the ground with a length of heavy cable connected to it then connected to my ATU, I've been told I should see a difference in the signal strength/noise level but Im not, infact I'd say the noise level has gone up, the noise is constantly at S7-9+ unless I switch on at 2am gmt then it's only S6 or use 10m which no one uses.

I'm planning on connecting the earth cable to the atu then a second cable to the radio not sure if this is going to do anything.

Can someone suggest a sensible way of checking the earth and not just sticking the earth into the plug socket and see if it powers the house (this does not seem a sensible option)

I know I'm going to have to live with a bit of QRN/QRM due to my location and the only way of being able to errect an antenna but im fairly sure with your help I can lower the noise to sensible levels

charlotte 2E0BSS
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2E0BSS
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« Reply #1 on: September 18, 2007, 10:18:24 AM »

In addition to my question the earth cable is making no difference at all, even if I plug a cable up to the multiple earth in the house there is no difference in noise or S points so I'm guessing something is wrong maybe you can suggest how to put it right.


Charlotte 2E0BSS
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WB2WIK
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« Reply #2 on: September 18, 2007, 11:00:27 AM »

A really terrific earth ground almost never has any effect on received noise level.  At least, no where I have ever lived has any sort of ground ever had any effect on anything.

The *reason* to have an "earth ground" -- other than for "safety," in the event of an AC line fault inside your equipment, which is a pretty rare event -- is to provide a low-impedance path from radio equipment chassis to earth to prevent RF voltage from building up on equipment chassis.  Normally, this should never happen anyway, so the ground typically does "nothing."

Lightning protection grounds are another issue altogether, and have nothing to do with "equipment chassis grounds."  I don't know what the "code" (regulation) is in the U.K. for electrical grounds, but here in the States a 4' rod would not be approved anywhere -- the code calls for an 8' rod hammered into undisturbed soil and connected with #6AWG (minimum gauge) wire, and it also calls for any "homeowner" grounds added to be also connected directly to the utility company service entrance ground at the service panel location, to create an "SPG" (single point ground).  Of course, all that has to do with safety and has nothing to do with reducing noise or interference.

If you have noise issues and cannot get to the *source* of the noise (of course, everyone has atmospheric static, lightning static and such -- we cannot resolve the sources of those), the ways to combat it are generally with improved noise reduction systems for the receiver.  

If adding an earth ground to radio equipment makes it receive less noise, there's a much bigger problem there.

WB2WIK/6
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2E0BSS
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« Reply #3 on: September 18, 2007, 11:27:27 AM »

That's cleared up some issues, as I was led to believe that adding an earth would cut my noise down, now I know different, wondered why nothing happened. I have some serious noise as I live in a small block of flats, two one up and the one below where I live, the noise could be coming from anywhere.

What kind of things are noise makers and how would I go about locating them? I've got ferrite filters on the fridge, radio psu and radio power cables, fish tank main line and heater, also filters. The antenna which is a half size G5RV is on the roof, this is the only place for it and it's non moveable or negociable due to local authority regulations.

I've daisy chained the ATU/PSU/Earth cable again no difference. You say an 8 foot earth rod my be better than a 4? I don't believe we have an earth rod code as you do if we do where would i find this out, 4 foots are the standard though.

If I start to think it's now not my earth but some external force creating noise I need to start thinking what's the noise cause.

Any further advice would be greatly appreciated.


Charlotte 2E0BSS
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WB2WIK
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« Reply #4 on: September 18, 2007, 02:11:37 PM »

A ferrite filter on a refrigerator isn't likely to do much good...the line current is enormous and it would take a similarly enormous ferrite.   But I really doubt that's the problem.

If your noise is really all "locally" generated (man made), ways to isolate the source include:

-Run your receiver by powering it from a battery (a car battery, lantern battery, whatever works) and turn OFF the power to everything in your home by pulling the mains fuses or circuit breakers.  I mean, shut off EVERYTHING including clocks, timers, doorbells, everything.  See if that impacts the noise.  If it does *not* impact the noise at all, then the noise source isn't in your house, it's somewhere else.

-Take a portable radio receiver (battery powered, obviously! - a cheap little one will do) tuned to the "AM" broadcast band, down below the bottom or up above the top of the band where there aren't any signals.  Turn up the volume to hear background static and walk around the house and the neighborhood while listening closely to see if the "noise" peaks anywhere.  If it does, try to figure out where -- the proximity of the radio will tell the story.  This can help find arching insulators, bad transformers, all sorts of wideband noise sources.  Do NOT use an "FM" receiver, that won't work.

If all else fails, you can try stuff with your own receiver to reduce the noise.  For one thing, some receivers have much better noise blankers than others.  I've had HF rigs where the noise blankers are very ineffective and did practically nothing, and other rigs where the blankers were so effective they eliminated 99% of all local noise to the point where I could hear very weak signals easily.  This is a huge "variable."  One of the best noise blankers I've ever used is in the old Drake TR-7 transceiver: It was an "option," called model NB-7 (for "noise blanker-7") and it's very, very effective.  But these only really work for man-made noise, they don't do much about real atmospheric noise (which comes from the sun, lightning, etc).

Also, external DSP noise reducing systems can be effective.  The external ones work in "audio" only, not at radio frequencies, but they can make life a lot easier.

Also, noise blanking which works as an accessory in the receiving antenna line using a "sense" antenna to find a noise source and then literally pulsing off the receiver in phase with the noise pulses (MFJ sells a popular unit like this) can be helpful.  You kind of "miss" a little bit of what's on the band when using one of these, because your receiver will be literally disconnected from your antenna at some pulse rate, but it's surprising: You get enough "signal" to make weak signals very workable when without the appliance, they can't be heard.

WB2WIK/6

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2E0BSS
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« Reply #5 on: September 18, 2007, 02:34:34 PM »

I've started to check the house for noise on 135.9 AM with my handi unit so far the following noise levels

TV 4Bars
Radio itself 4 bars.(need more advice on this)

Computers 1 bar
Broadband modem USB Cable 4 bars
Lights just make a click with no apparent noise levels

Will do a complete check tomorrow as I live in a modern semi detached block I'm thinking that there are going to be underground power lines as apposed to over heads which are causing some of the noise.

Charlotte 2E0BSS
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G3RZP
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« Reply #6 on: September 19, 2007, 04:09:09 AM »

Do you have Protective Multiple Earthing on your mains supply? Have a look at the electricity meter: if earth and neutral are connected together, you do, and for safety's sake I'd recommend physically unplugging the radio from the wall when you're not using it. Otherwise, a fault in the street where somebody breaks the mains neutral with a digger (backhoe in American) could  cause a fire in your place if you have an external earh connected. You say the place is modern, so it probably has PME. A good  test is to check the voltage between the earth p[in of the 13amp socket on the wall and your earth rod. If it isn't zero at a time when everybody is drawing power, like around 6pm, you've got PME. There's a big difference here between US and UK practice.

Does the noise go away if you unhook the antenna? Then unhook the ground and see if there's any difference. But if the noise is coming in on the antenna, and isn't coming from anything in your place, you'll need to try things like noise cancellers - I think MFJ do them, and Waters & Stanton stock them, I believe.

Sometimes, a shielded earth lead works. You use coax to connect the  ground rod to the rig, but the braid is connected only to the inner at the rod - the rig end has the braid insulated off.
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2E0BSS
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« Reply #7 on: September 19, 2007, 04:49:18 AM »

Yes I've got PME and yes the noise goes away when I unplug the antenna.


Charlotte 2E0BSS
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G3RZP
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« Reply #8 on: September 19, 2007, 05:28:09 AM »

OK, is there a voltage between your earth rod and the the earth pin of the mains socket? I gather you have got the mains lead to the PSU wrapped around some ferrite: that's needed. Without an antenna, does the noise level vary when you connect the external earth?
What feeder have you got on the G5RV? If it's coax, then wrapping the coax round some ferrite might help: even if it's twin lead, that may help. What sort of tuner are you using - does it have a built in balun? Also, does it provide a DC connection to ground from both sides of the G5RV?

But at the end of the day, you might find a noise canceller is the only option. I have an old people's home about 150 metres away, bearing north east: I just have to put up with the noise from all their IT rubbish!
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2E0BSS
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« Reply #9 on: September 19, 2007, 03:03:58 PM »

The antenna is connected to coax then to ladder. The tuner is an LDG Z11Pro with no balun it has some kind of center connector on it obviously but there is no earth from the antenna. No the noise doesn't vary with or without earth, the ferrite on the antenna is one thing I have not done will get a large ferrite tomorrow as I've got RG213/westflex coax so the ferrite would need to be pretty big.

I went round the house locating noise making objects, i found the TV and the DVD machine were the biggest noise makers of all.

If I wander around the bands especially 10 and 11 I get some horrid amounts of noise from whatever source up to 9++ on the radios meter

I'm starting to think an external DSP system is going to be the answer even though it's not going to lower the meter reading


Charlotte 2E0BSS

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G3RZP
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« Reply #10 on: September 20, 2007, 01:20:15 AM »

I'd be inclined to go down the route of noise cancellation before DSP. The DSP can only do so much, and if the noise to signal ratio is too great, it isn't going to work. I don't know how good the MFJ products are - maybe someone else does. There's the MFJ 1025 and MFJ 1026. One has a built in active antenna, the other doesn't. One test is to short the feeder at the antenna terminals: that will tell you if there's pick up on the feeder - if all is well, there shouldn't be any noise with the feeder shorted at the antenna. If there is, there's some unbalance on the feeder.

As you've got PME, do remember to unplug your radio from the wall when not in use if you have an external earth connection to the radio.
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2E0BSS
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« Reply #11 on: September 20, 2007, 07:37:14 PM »

I'm starting to agree that noise cancellation is the road to go down. All the noise goes if I unplug the antenna.

Charlotte 2E0BSS
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WA9UAA
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« Reply #12 on: September 27, 2007, 09:17:16 AM »

Good Day,
I would get the MFJ 1025. Be prepared to use a tuner and wire as a receive antenna. I have found with careful tuning and balancing of the noise on each antenna the noise can be well curtailed. Good Luck!
Rob WA9UAA
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