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Re: [RFI] 14028 to 14034 hashbirdietrash

To: Jim Brown <jim@audiosystemsgroup.com>
Subject: Re: [RFI] 14028 to 14034 hashbirdietrash
From: Ron Rossi <kk1l@intergate.com>
Reply-to: kk1l@arrl.net
Date: Thu, 28 Jul 2005 09:46:32 -0400
List-post: <mailto:rfi@contesting.com>
Folks,

How might incorrectly wired RJ connectors effect this condition. If the
correct pairing is not maintained I would expect that there
would be a higher level of radiation.

-- 
73 es God Bless de KK1L...ron (kk1l@arrl.net) <><
QTH: Jericho, Vermont
My page: http://www.qsl.net/kk1l


Jim Brown wrote:
> On Wed, 27 Jul 2005 15:17:48 -0500, Frank Brady wrote:
> 
> 
>>Greetings,
>>I've avoided this s5 to s7 noisy area at several QTHs, but now I've 
>>rediscovered the joy of DX hunting recently and I hate to give up this part 
>>of the 20m band.
> 
> 
>>I've asked other hams about this and many, but not all have experienced 
> 
> this.
> 
>>I'm not looking for anything peculiar to my current (2nd floor apartment) 
>>QTH because I heard it in our home and other apartments.  The same sounding 
>>interference is on the low end of 30m as well - around 10.106 to 10.108.
> 
> 
> 1. I am SURE that this IS Ethernet trash.
> 
> 2. I believe it is 10BaseT traffic, which can occur on a 100BaseT connection 
> if there are 10BaseT cards. Many cable modem and DSL modem outputs are 
> 10BaseT. 
> 
> 3. The trash on 30m is also Ethernet, and you will also hear it at 21.052 
> and at several places on 10 m. 
> 
> 4. You will hear multiple carriers with modulation on them when there is 
> data transfer, and each of your neighbors will be on a slightly different 
> frequency. I have wire antennas at the front and back of my city lot, and 
> some carriers are stronger or weaker on each antenna, and on each band. 
> 
> 5. An effective FIX for this trash is to wrap the offending Ethernet cable a 
> 6-8 turns around an FT-240-43 toroid AT EACH END of the Ethernet cable that 
> is longer than about 5 ft, and at one end of shorter ones. That's because 
> the two ends of the cable take turns talking, so the Ethernet cable radiates 
> the trash as common mode. BTW -- shielding the cable will not be effective. 
> (Common mode means that the cable is working as a long wire antenna. 
> 
> 6. The fix above will knock the trash down by at least 3 S-units for each 
> offending source (that is, each Ethernet cable that you are hearing), but 
> each birdie may be the sum of trash from several cables. And the fix will 
> not touch the trash that is radiated directly from an unshielded box. 
> 
> 7. There may also be some common mode radiation from the power supply. 
> 
> 8. Start with your own house, fix it, then move to your neighbors after 
> you've had the experience with your own system. 
> 
> If you would like to read more about this, see the publications section of 
> my website for a presentation on this that I gave to my local ham club. 
> 
> BTW -- some other ways to minimize it are use the shortest Ethernet cables  
> possible and run as much as practical of your system (and your neighbor's 
> systems) on a WiFi link. The WiFi causes no QRN or QRM, but you will need to 
> cool off the Ethernet cable that connects it to a cable modem, DSL modem, 
> and other wired Ethernet connections. 
> 
> 73,
> 
> Jim Brown K9YC
> http://audiosystemsgroup.com
> 
> 
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> 
> 
> 

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