Horizontal long wire MW aerial.

[Murphyv310]

Also try measuring between mains earth and your rods. Check on AC volts initially, I get 45mv and 0.5 ohms. If I connect a long wire directly to a set and a mains earth noise is awful, use the earth rod and it reduces considerably, connect both and its nearly as bad as the mains earth on its own.

[Crackle]

The more I look into this and the possibility of my earth being used, under fault conditions, as a return to the supply by all the houses in my block, the more attractive your idea of a transformer looks Trevor.
Can you give me specific details of the number of turns on each winding and the size of the ferrite ring. I suppose for conformity reasons it ought to be in a waterproof box outside the house.
Would you use coax to feed into the ATU and or the radio, I believe most old radios need high impedance aerial circuits.

thanks
Mike

[pwdrive]

Trev, I assume that measurement you did was with the earth rod connected to the mains earth?

Lawrence.

[Murphyv310]

No Lawrence. I do though have a series of earth rods and the ground is wet. We also have the block where we stay earthed at the location with its own official earth rod.
I have to say in dry weather the voltage rises and the old meter will buzz on the continuity test.

[Murphyv310]

I found triAl and error the best way. The ferrite rings that you get in power supplies that the mains cable wraps round are good.
Try ten turns for each winding initially then just experiment for best results.

[Crackle]

Tomorrow I am off to buy a 5/8th earth rod and cable clamp, I will do a bit of experimenting to see how it goes with some thinner wire (7mm) before I spend a whole lot of money on 16mm cable.

Mike

[Murphyv310]

Hi Mike. TBH I only use 2.5mm cable from my earth rods. Again there is a lot of discussion in amateur circles regarding the cross sectional area of the cable, overtime and after erecting many different long wire aerials I've found no practical difference by spending a fortune on thick cable. There is no safety aspect when you consider it in all honesty. If you use the RF earth for your radios and them only then in reality there is no connection between mains and RF earth. Where it can fall down is AC DC sets, if following good practice then all your chassis's will be wired correctly to mains neutral, if the set has an aerial and earth connection then I'd also say the relevant caps should have been replaced as a matter of course with modern mains rated types. The only snag now though the RF earth will "see" noise from the mains neutral as the two are now coupled together at RF via the earth cap and chassis of the Radio. Where I stay I have dreadful noise from overhead cables, smps, powerline adaptors and other sources. To get reasonably noise free reception is a major challenge and I've even resorted to fully isolating the shed from the mains when I'm doing some serious listening. I use a transistor comms set at times fed from my 12 volt system. It's quite surprising the mains is such a good transmitter of noise, even a large inline RFI filter rated at 30amps doesn't make a big difference. The only thing that did help was a 10kW isolating transformer at the house end of the shed mains feed, with another earth rod driven into the ground and the effective new neutral grounded. It worked but was totally impractical and drew a couple of amps residual current, so as constant supply some what costly.
I'd like to hear how you get on and what works best in your location, sometimes the oddest things help noise and trial and error often is the best way.
Good luck.

[Crackle]

In the end I bought a 3/8th inch rod as the 5/8th ones were a next day order item. Rod and clamp less than £5 from Screwfix.
Yes I will report on any improvements, at the moment reception on Gold on 1458kHz is diabolical, "right back in the box" as they would say in the days of CB, with 4 out of 5 bars on the signal strength meter, but then I thin 2 of the bars are interference.

Is the thickness of the conductor used for the aerial important from a reception point of view.
I have 1mm² tinned multistrand PVC wire and I have 5mm² solid copper PVC insulated cable.
I notice commercial antenna wire looks as if it is bare copper, does the PVC insulation make much difference?


thanks
Mike

[Crackle]

It worked but was totally impractical and drew a couple of amps residual current, so as constant supply some what costly.
I'd like to hear how you get on and what works best in your location, sometimes the oddest things help noise and trial and error often is the best way.
Good luck.

Would that 2 amps be actual watts though, or would it be inductive, could it have been corrected with a PF correction capacitor?
Was the transformer getting hot with no load?


Mike

[Murphyv310]

Again the thickness of the aerial wire makes only marginal difference. It might be a bad location you are in and a magnetic loop may be the best. A one metre alloy circular loop into a balanced amp works really well.
Try some more experiments first though.