Thanks for the input - Im going to build out a G3YXM version with additional input filtering and use a 3 wire version and decouple the output, perhaps with a switch on the "earth" side for plug and play.
What I did find out in Alaska were that not all Earths are equal - here I mean noise wise. Their are a protective couple of 8ft Earth rods back to the "mains" switch box where the incomer (2 phase and Neutral) terminated on the other side of the property -
I guess within 15ft of one of those I have a segregated " RF " 8ft rod and thick copper cable coming back to the shack (long run about 80ft) - this is primarily for the LF/MF vertical and part of some other 25 radials and rods that litter the garden - however if I attach this closest radial to the other radials its induces a fair bit of conducted noise from the power lines - removing the rf rod and leaving the radial removes the noise - so Im guessing some noise currents running around the 'AC' nearest rods.
I still use it for tx purposes as it along reduces the resistance to 85 ohm (just this radial) compared with a similar radial on the other side of the property which gives 110 ohms. At present I keep the RF and power earths segregated as more noise in induced if connected -
It does vary from each qth and building earthing and how the supplies are grounded and Ill play more when I get back to Alaska. As ever I add or take radials off and on and some add and some subject given their location and electrical RF Z. Using the AIM 4170 some of them just dont make sense, but hey RF is a strange bed partner.
Laurence KL7 UK
> From: [email protected]
> To: [email protected]
> Date: Wed, 4 Aug 2010 10:21:40 +0100
> Subject: Re: LF: Noise R75 - rs232 from smpsu -
>
> Dear Laurence, LF Group,
>
> ----- Original Message -----
> From: "Alan Melia" <[email protected]>
> To: <[email protected]>
> Sent: Tuesday, August 03, 2010 11:35 AM
> Subject: Re: LF: Noise R75 - rs232 from smpsu -
>
>
> > Hi Laurence I have found some problems with the "two wire" versions where
> > the powered instrument has no proper ground connection....VLF receivers
> > etc.
> > But often this can be cured by grounding one side of the low-voltage
> > output.
>
> My experience would agree with Alan - several times with laptops, and also a
> "compact" desktop with external PSU, making a direct connection between the
> mains ground and the chassis of the computer has made a substantial noise
> reduction. It seems to be fairly common that there is no ground continuity
> between input and output of PSU. With no ground connection to the output
> side of the PSU, any common-mode noise due to the PSU has to find its way to
> earth via the RF connections usually, and can get into the signal path in
> the process. Winding as many turns as possible of the DC output lead round a
> large split ferrite core can also be helpful in reducing the noise current.
> I find >10 turns are needed to make a useful difference.
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>
=
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