[Elecraft] RFI resistant Monitor

[David Ahrendts]

May I encourage everyone to study the excellent work from Jim Brown, K9YC — he weighed in here and you’ll see his link below. I’m also taking his suggestion after careful study to replace the parallel zip line red-black cable with shielded twisted pair cable (18 AWG ) with the Anderson Power Poles connectors. The theory being that anything twisted will resist RFI while parallel cable invites it and generates it. A fist full of ferrites helps also. Getting surgical, but it really helps. 

David A., KK6DA  


> On Apr 11, 2016, at 6:29 AM, Myron Schaffer <thelastdb at gmail.com> wrote:
> 
> One thing I have noticed over the years is that the near-field noise is present with most any modern electronics. The switching frequency is between 200-300kHz and can be easily sniffed with a pocket AM radio (harmonics of that fundamental switching frequency are easily spotted with an AM radio). When I bring my CCrane Pocket Radio in the near field at the operating position, I can’t tune in the semi-local 600 KCOL out of Greely, CO. If I back up a few feet the noise level drops considerably and the station is audible again. The CC Pocket Radio has a fairly good front end with somewhat good selectivity but is still overloaded with IBOC noise.
> 
> I have battery chargers, an old Dell 1501 laptop, an external HD with switcher, the list goes on. Common mode noise and strong near-field noise is the bane of my ham radio existence in this RFI rich environment. 
> 
> Myron WV0H
> Printed on Recycled Data
> 
> From: Jim Brown
> Sent: Monday, April 11, 2016 12:14 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] RFI resistant Monitor
> 
> On Sun,4/10/2016 10:44 PM, KC6CNN wrote:
>> I just found that when the monitor is on it adds 2 bars of noise to my
>> meter. It is also turning off when I operate on certain bands.
> 
> I had exactly that experience with a Samsung that W4UAT gave me because 
> it did that in his shack too. It also makes RF noise. The good news is 
> that not all Samsung monitors are RFI dogs. I have two recent model 
> Samsungs in my house and four in the shack. They are designed to run on 
> power supplies labeled 14VDC, and the supply they sell you is a 
> switching power supply that makes RF noise. I throw those power supplies 
> away, cut the attached power cable and attach red/black PowePoles, and 
> run them from either the 12V battery system in my shack  or a small 12V 
> lead-acid cell that I float-charge from a linear 12V wall wart.
> 
> I also use ferrite common mode chokes on both the video cable that runs 
> to the computer and the power supply cable "just in case" some RF trash 
> is conducted to those cables, which the cables could radiate.
> 
> All that, and a lot more, is discussed in this "in progress" article for 
> the National Contest Journal.  k9yc.com/KillingReceiveNoise.pdf
> 
> 73, Jim K9YC
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David Ahrendts   davidahrendts at me.com