Re: [IRCA] [NRC-AM] Re: [DXFlorida] Computer noise in connected receivers.

["Rick Shaftan" <shaftan@xxxxxxxxxxxxx>]

So putting those on my charger cord in the car will get rid of the noise
they create? 

> -----Original Message-----
> From: rscotka@xxxxxxxxxxxxx [mailto:rscotka@xxxxxxxxxxxxx] 
> Sent: Wednesday, July 06, 2005 8:37 AM
> To: DXFlorida@xxxxxxxxxxxxxxx
> Cc: WWWR@xxxxxxxxxxxxx; irca@xxxxxxxxxxxxxxxx; am@xxxxxxxxxxx
> Subject: [NRC-AM] Re: [DXFlorida] Computer noise in connected 
> receivers.
> 
> It might be possible to try snap over ferrite chokes on the 
> connecting cable or wrap it through a core. When I found that 
> my cell phone charger pumped noise into my Grundig portable 
> sitting nearby I was able to wrap the charger cord through an 
> Amidon 75 material core and got rid of the offending hash 
> produced. I would imagine anything with an initial 
> permeability of 850 (Material 43) or higher might do, that's 
> what the Radio Shack clip over chokes are made of...you'll 
> notice that most modern era monitor cables have built in 
> chokes to keep noise down but many higher performing video 
> cards in conjunction with the occasional oddball modeline 
> will swamp them. My current monitor/card combo wipes my 
> entire house out though you are on the right track with the 
> older laptop, I don't get as bad interference from my old 
> Thinkpad 380D when pressed into service as a thin client 
> around the house....
> 
> 
> Russ Scotka
> 
> 
> 
> 
> 
> 
> On Wed, 6 Jul 2005 03:39:12 -0400 (Eastern Daylight Time) 
> "WWWR" <WWWR@xxxxxxxxxxxxx> wrote:
> 
> > A while ago I asked here about noise generated by LCD versus CRT 
> > displays and got several responses which related 
> experiences and offered suggestions.
> >  With that valuable insight, I began to think what I wanted 
> to do to 
> > implement computer control on my receiver.
> > 
> > Years ago I had tried it with a desktop computer and CRT which 
> > introduced so much noise I gave up.  At the time I had a 
> poor, indoor 
> > antenna arrangement which didn't help any either.
> > 
> > Considering my options, I remembered a decade old laptop, put aside 
> > when no longer needed for work.  I decided to try that as a 
> > bottom-line benchmark for what I might expect.  I had some 
> equally old 
> > control software -- DOS based Scancat Gold (Anyone remember 
> that?) -- 
> > which would be more than adequate to evaluate the concept, 
> if not actually provide a solution.
> > 
> > I moved the laptop around the receiver and found that a couple feet 
> > away there was little problem with noise pickup from the 
> computer and 
> > monochrome LCD display.  Pleased with that result, I 
> connected to the 
> > receiver RS-232 port.  A raucous cacophony broke out.  Clearly this 
> > laptop was not going to be usable.
> > 
> > After some thought, though, I had an idea.  The noise was obviously 
> > passing through the interconnecting cable.  Breaking the electrical 
> > connection while still maintaining the communications connection 
> > seemed a viable solution.  I grabbed my Google and began 
> looking for 
> > RS-232 optical isolators.  I found a few that seemed to address my 
> > situation, and settled on one that was reasonably priced.  
> In went my on-line order.
> > 
> > An optical isolator inserts a light path into the electrical path.  
> > The two sides of the connection are electrically separate, while 
> > through the light beam, signal transfer is achieved.  This 
> eliminates 
> > ground loops and other sources of transferred noise.  Just 
> what I needed, it seemed.
> > 
> > A few days later the isolator arrived thanks to UPS and I rushed to 
> > test my theory.  It seemed sound, but since it  involved a 
> null modem 
> > style connection between computer and receiver, I had a 
> slight concern 
> > that might somehow be incompatible with the isolator.  The notion 
> > noise might still seep through was also still a possibility, not to 
> > mention that my whole idea was bogus and nothing would pass 
> through at all, not even noise.
> > 
> > I am very glad to report that the idea was not bogus and I may just 
> > have a fairly cheap -- under $85 for the isolator -- solution to my 
> > computer control objective.  Now I know -- should I decide a more 
> > elegant solution is desired involving added expenditures 
> for a newer 
> > computer or more sophisticated software -- I can rest assured any 
> > expenditures will not be lost to a noisy connection.
> > 
> > If when connecting computer and receiver, a noise level increase is 
> > noticed, this solution might be worth looking into.  The 
> noise may be 
> > squeals and squawks created as computer functions are performed, or 
> > just an increase in the usual background hiss. Which and where the 
> > noise manifests itself may be possibly isolated at places 
> on one band, 
> > or changing on different bands. A little experimentation 
> will quickly 
> > show if the connection is the source of any induced noise.
> > 
> > I hope my experience may prove of value to others.
> > 
> > W. Curt Deegan
> > Boca Raton, (Southeast) Florida
> > [JRC NRD-535D; IBM ThinkPad]
> 
> ===============================================
> 25th Edition of the AM Radio Log
> ON SALE NOW - ON LINE
> http://www.nrcdxas.org/Deals.html
> 

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