Topband: 2Wire, Inc. 3800HGV-B Gateway. RFI --Problem fixed for now..

[ZR]

Im well aware of that but the only noise generator in that system was the 
router switching PS and I replaced that with a linear one.

Over the years Ive spent days or weeks eliminating noise sources going back 
to the early 80's at 2 homes. Ferrites come in handy but only after 
bypassing and LC filtering wre done. The ferrite cleaned up the remainder 
but both differential and common mode must be addressed as seperate items if 
you want silence.

Carl
KM1H




----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: <topband at contesting.com>
Sent: Saturday, February 04, 2012 1:38 PM
Subject: Re: Topband: 2Wire, Inc. 3800HGV-B Gateway. RFI --Problem fixed for 
now..


> On 2/4/2012 8:13 AM, ZR wrote:
>> Im running 250' of shielded CAT5 from house to equipment trailer where 
>> the
>> router resides and then another 120' up the tower to the 5.8GHz link.
>
> The issues, Carl, are not with CAT5, shielded or unshielded, but rather
> with the equipment on either end, which can generate RF trash or be
> susceptible to RF trash. Some commonly used Ethernet products produce
> birdies on the HF bands (a couple of frequencies on 30M, around 14,030,
> 21,052, the low end of 10M, the low end of 6M are places I hear them,
> and there are others). Some digital equipment produces loud broadband
> hash. I've seen some POE stuff used with data links at tower sites that
> were quite noisy on the MF and HF bands. This trash gets radiated
> several ways -- usually most strongly from common mode current on the
> Ethernet and power supply cables (or coax if it's used), and often
> directly from wiring internal to unshielded boxes.
>
> Ferrite chokes can greatly attenuate the common mode part of that.
> Using shielded CAT5/6/7 can help if, and only if, the shield is
> optimally terminated at both ends (both ends are likely generators of
> digital trash). That usually means bonding to the shielding enclosure at
> both ends.
>
> 73, Jim Brown K9YC
> _______________________________________________
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