RE: LF: Noise R75 - rs232 from smpsu -

[Laurence KL7UK <hellozerohellozero@hotmail.com>]

Chaps - thanks for the all the advice - more to chew on -
 
Dave common mode chokes do a bit but I need more - the S meter on the main T array sits at S3 or so mostly non man made which is the best Ive had so far s/n wise but the dang noise adds a few dB (Im being really pe-nickity) - opto, Eddy boxes and more playing is needed - seems noise from the PSU getting onto the data lines mostly common I think  - opto is my best bet.
 
Cheers for the advice again on direct and indirect emails -
 
running the main "T" (actually an offset X and Y bottom loaded 50 ft vertical on 137 khz and really pleased -
 
grabber running on http://kl1x.com/alaska.html  
 
the slightest sniff of dcf39...not bad for July...
 
Laurence
 

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Date: Fri, 23 Jul 2010 22:26:06 +0000
From: davepick@btinternet.com
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Noise R75 - rs232 from smpsu -

Laurence

In my remote station I put the Dell brick in an Eddy box (die-cast box) with a proper mains filter on the input and chokes and feed-through capacitors in the DC output lead. Drilled some holes for ventilation. Quiet as a mouse.
A linear PSU should also be fine but quite large.
The RS232 is unbalanced of course, but if you run it in screened cable and use a ferrite common-mode choke dies it not help?

Dave G3YXM

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From: Laurence KL7UK <hellozerohellozero@hotmail.com>
To: lowfer@mailman.qth.net; rsgb_lf_group@blacksheep.org
Sent: Friday, 23 July, 2010 21:47:56
Subject: LF: Noise R75 - rs232 from smpsu -

 
Anyone done any common mode noise mitigation from the RS232 port of the R75 Rx> - the noise coming up from the SMPSU/processor from the old Dell puter - cable is double screened - choking off using J (75) type has seen little improvement - this is my last hurdle to unimpeded remote rx on 137 - any pointers appreciated - everythings bonded and Ive tried the on/off earth tricks at various locations -
 
Anyone had any success of powering a Dell D series from a non standard non switched PSU? (the noise goes away when the DC from the Black Dell brick is removed but it may also be partially screen/processor noise...)
 
with thanks
 
Laurence Kl7UK

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