Somewhat related, I just discovered more low-level switch-mode noise coming
from my Netgear 16-port Ethernet router. I cracked open the case and
discovered what I've recently been seeing elsewhere in consumer equipment:
Seemingly, manufacturers have a love affair with SMT mounted switch-mode
DC/DC converters. In the case of this router, 12VDC is divided and
regulated by two MP1410ES SMT devices. One chip regulates to 3.3VDC; the
other regulates to 1.8VDC. I have already suppressed the incoming line cord
with 10T on a #31 core and it helps, but the spurs can still be seen and
heard about 10 dB above the noise floor on 20m.
I would tackle the problem right on the PCB, but given some physical
constraints, it's just too cumbersome to experiment with more chokes on the
input and output side of those two tiny regulators. I have a pair of LM317
kits on their way. The new linear regulator boards will mount on the mother
board with 3M double-sided tape. This way, I can forever get rid of the
switch-mode noise from the router and if necessary, pull the LM317 boards
and place into a new router if it fails in the future. This will now be the
fourth device where I've replaced internal DC/DC switching converters with
linear regulators. And that's in addition to replacing a multitude of
switching wall warts with linear types. Linear wall warts are becoming more
difficult to find as the entire world strives for better efficiency and
economy with switching devices.
What's interesting is that some switching wall warts are extremely quiet. I
recently autopsied a Netgear switching wall wart and found zero RFI
abatement. Next, I need to compare that unit with a switching wall wart
that produces no RFI and investigate the circuit differences.
Paul, W9AC
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <rfi@contesting.com>
Sent: Thursday, October 07, 2010 1:39 PM
Subject: Re: [RFI] HomePlug Experience?
> On 10/7/2010 3:42 AM, Hare, Ed W1RFI wrote:
>>> I do know the CAT5e and CAT6 do radiate making the use of 2-meter HTs
>>> > problematic within about 75 feet of the cable runs.
>>
>> That almost sounds like something could be wrong. At ARRL HQ, we have an
>> extensive Ethernet and radio operation continues pretty much noise free.
>
> I don't use wired Ethernet here in CA, but I did in Chicago. 2M HTs
> heard a LOT of noise in close proxmity to the CAT5 wiring in the room
> that was my combined shack/office, and I did NOT notice an improvement
> when replacing low quality stuff with Belden Mediatwist (a very high
> quality CAT6/7 cable). My noise level there was far too high to hear it
> in a roof-mounted vertical 50 ft or so from that wiring. This is
> broadband noise I'm talking about, not the modulated carriers that
> clustrer around 14030, 21052, etc., which can be effectively reduced by
> multi-turn ferrite chokes.
>
> 73, Jim K9YC
> _______________________________________________
> RFI mailing list
> RFI@contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|