Dave,
You bring up an interesting problem and there have been a lot of very good
reply comments. I would like to add on one more to the pile.
I had the chance to evaluate Ethernet interfaces for RF emissions and
susceptibility a few years ago in conjunction with my present work. I can
tell you that aerospace susceptibility standards require robust interfaces
that are not "glitched" by the presence of relatively strong RF fields.
The RF fields that are generated for doing the tests may be straight
unmodulated CW, full carrier with 90% amplitude modulation by a 1 kHz
signal, or pulsed. The carrier with 90% AM is a brutal test, and many
interfaces fail that one unless properly designed.
I can also tell you that 10 Base-T is much more robust than 100 Base-T
Ethernet. The fact that you ran shielded CAT-5e helps, but as was noted
in another reply comment, that only works if the shield is taken directly
to the point of termination at the RJ-45 connector. I might add that
RJ-45 connectors do not pass aerospace RF emission or susceptibility
testing, although they do pass FCC emission test requirements. To pass
the RF susceptibility requirements, much testing work showed that very low
impedance terminations of the cable shield are required. Sadly, RJ-45s
don't provide a very good way to terminate shields with short, low
impedance connections. (Definition of short, low impedance =
shield-to-chassis distance of less than 0.25 inch and net Z less than 10
milli-ohms.)
My guess is that SSB has such an overall short duration to the voice
peaks, which occur at a variety of frequencies, that the interface works
well because I don't think you are really "stepping on" any data to the
point that errors occur. However, CW (or AM) provides milliseconds to
seconds of RF at a steady frequency and you may be running into problems
with internal clocking rates that are part of the Ethernet protocol. I
learned that to be one of the reasons that 100 Base-T interfaces are so
much more susceptible to RF than the 10 Base-T interfaces.
The fact that operation into a dummy load at only 5 watts causes problems
is a clue, I think, to some fundamental weak spot in your system. One has
to wonder if, in fact, the radio itself might not have some RF "sneak
paths" within it that are upsetting the Ethernet interface. Since you
operated for years with a slow dial-up interface, the problem only now
surfaces. I am assuming, of course, that the dummy load is fully shielded
(complete metal housing) and the cable from rig to load was not run near
the CAT-5e line.
Please keep the reflector posted on your work. Best wishes.
73, Dale
WA9ENA
"David Jordan" <wa3gin@comcast.net>
Sent by: rfi-bounces@contesting.com
06/25/2007 11:50 AM
To
"'Jim Brown'" <jim@audiosystemsgroup.com>, "'RFI List'"
<rfi@contesting.com>
cc
Subject
Re: [RFI] Ethernet Extenders
Tests were done with 5 watts into a dummy load. There is no problem in
SSB
even at 1500 watts to 1/2 wave antenna.
The problem appears to be something flaky in the actual command data
stream.
Since I'm using encrypted tunneling I can't really sniff the data
transmissions but I'm working on removing the encryption. I have installed
Telco Grade line filters (K-COM, 2 in series) on the CAT 5 lead to the
Ethernet boxes. The power supply line(s) is also configured as described
below, with toroidal filters (multiple) at both ends of the connection.
The CAT is buried and it is shielded like heliax. The shield is grounded
at
both ends. The barn has a ten point UFER ground (8ft ground rods), the
house
has two 8ft ground rods.
I think more and more that this is an RFI problem but wanted to here from
folks on this reflector.
Seems if I had any RFI the little Ethernet boxes would jump up and down
when
I run 1500 SSB. The connection lock-ups only occurs when a specific
command
string is send from the remote PC to the host PC. That Kenwood command
string, inside the encrypted pipe simple tells the TS-480 to go into
"send"
mode. The failure only occurs while the radio is in CW or AM mode.
This weekend I'll attempt to remove the encryption and try to sniff the
data
stream.
I really appreciate all the thoughtful suggestions.
Dave
Wa3gin
-----Original Message-----
From: rfi-bounces@contesting.com [mailto:rfi-bounces@contesting.com] On
Behalf Of Jim Brown
Sent: Monday, June 25, 2007 12:17 PM
To: RFI List
Subject: Re: [RFI] Ethernet Extenders
On Mon, 25 Jun 2007 11:03:48 -0400, Martin AA6E wrote:
>However, you might want to seriously look at
>your system grounding.
The problem is only on 40M and 30M.
This tells us that it is NOT a grounding problem, nor is it
related to noise or the grounding between buildings. The most
likely cause is that some wiring is acting as antenna and picking
up HIS transmitter. The obvious culprits are the 1,000 ft wire and
the power supply at either end. I also wouldnt rule out the
cables connecting the extender to his rig, other networking box,
etc.
The first thing I would try is 7-9 turns of that cable at the ham
shack end around a #43 or #31 2.4 inch toroid (FT-240). If that
doesnt fix it, add one around the power supply on the ham shack
end. If you still have problems, add chokes to those other cables
in the shack, and finally at the house.
These chokes will also suppress any common mode noise radiated by
these cables that you may be hearing on the HF bands. Ordinary
10BaseT Ethernet traffic, usually produces birdies on 30M, 20M,
15M, 10M, and 6M. 100MB Ethernet equipment is multi-mode -- that
is, it carries both 10MB and 100MB traffic, and most modems work
at 10MB on their Ethernet port.
For more detailed advice, see
http://audiosystemsgroup.com/RFI-Ham.pdf
73,
Jim Brown K9YC
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