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RE: LF: Noise R75 - rs232 from smpsu -

from [Laurence KL7UK] [Permanent Link][Original]
To: <[email protected]>
Subject: RE: LF: Noise R75 - rs232 from smpsu -
From: Laurence KL7UK <[email protected]>
Date: Mon, 2 Aug 2010 18:38:12 -0800
Importance: Normal
In-reply-to: <[email protected]>
References: <[email protected]>,<[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Dave - can you enlighten me on the filter values both on the X and Y caps and inductance AC side and filtering on the DC?  I have about 5 bricks here; some I picked up in a market in Beijing (Beijing Lu akin to the old Lyle st in london (dont think you spell it like that - that dates me)) - Ive taken a couple apart and I have some that are 2 wire AC and some 3 wire - all appear to have pretty good filtering and various screening materials even the Chinese cheapies. Any values to knock off 137 especially welcome - of course each psu has a slightly different osc/pulse freq - some at 60 some at 300Khz! The opto isolator really helped the AK rx with good/reasonable signals from Japan every nite so far...
 
Im running out of good Oklahoman LF projects!
 
Laurence
 
Date: Fri, 23 Jul 2010 22:26:06 +0000
From: [email protected]
To: [email protected]
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

From: Laurence KL7UK <[email protected]>
To: [email protected]; [email protected]
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

The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with Hotmail. Get busy.
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