[RFI] RF getting into 4-port wirelss router.

[Roger (K8RI)]

On 1/12/2015 11:49 PM, KD7JYK DM09 wrote:
> :I suppose if you're an expert at everything, there's no reason to try to
> : help.

I know of no one who is an expert on everything. Actually I know a 
number of knowledgeable people, but no experts.

I'll repeat what I said before (as did several others) and ask some 
questions.  The remedies of RFI suppression have been pretty well 
covered.  Jim's tutorial does an excellent job of showing how to 
suppress RF that gets in the line.

*If these remedies have not worked, it's time to stop and look for 
reasons!*

Is the problem really RF?  If RF, it almost has to be common mode. There 
has to be a reason why this particular setup is so prone to problems. 
It's not just RF getting in, it's RF (Or Something. It could be AC, or 
DC as well when the equipment is powered up)  at a magnitude that is 
frying the equipment. It again, (if nothing mentioned previously has 
been overlooked)  almost has to be something we'd not expect as the 
regular approaches have not worked.  Jim's air core resonant coil should 
be effective at removing a specific narrow band of frequencies. Get too 
many, or too few turns and they don't do much.  (Old terms and thinking 
die hard) while the chokes should suppress a wide range of 
frequencies.   They are wide band, but switching  power supply 
frequencies take more turns than the ham bands.  OTOH the Power supplies 
can have frequencies well up into the ham bands

Remember the RF getting into the house wiring and tripping GFIs. Might 
this be a key?
Knob and Tube wiring in some areas.

IF this is RF getting into the CAT5 why aren't the failures almost 
immediate? (as has been noted previously)
Loads connected and disconnected?

Are the failures temperature, or weather related.

Knob and tube.  I lived in a house like that many years ago. Normally, 
"Knob and Tube" is only two wires with no ground wire so the outlets 
would not have a proper ground even if they do have a ground.  Knob and 
Tube use only two pin sockets..  IE, they won't work with GFIs and 
should never be part of a circuit that has GFIs. IE an extension.  
Running a separate ground wire to outlets on knob and tube is begging 
for problems and can be dangerous.  A house with ham gear and computers 
should have the K&T replaced and removed as soon as possible.

What is different about this setup besides the Knob and Tube?  IIRC he 
has a vertical that's fairly close.  Do any of the radials come close to 
the CAT5? Is the equipment "earthed" at each end? Are the coax and 
radials "earthed" at the base of the vertical.  If so, are all 
connections secure? Is the CAT5 a resonant length?  Is there something 
common between the rig and network?
I keep thinking Knob and Tube.

If removing the CAT5 eliminates the problem, disconnect it and measure 
voltages to ground while transmitting.  Borrow an O-scope or spectrum 
analyzer, but expect abnormally high voltages.  If you are not familiar, 
borrow the owner of the equipment too.  That way you shouldn't be 
responsible.  A quick and check would be to disconnect the CAT5 and put 
an NE51 between it and ground to see if it really is RF of substantial 
voltage.

It would help to know the layout of the entire "wired" network.  I lieu 
of a drawing a good description might help
Are the other computers still connected when the router/switch are 
disconnected?
Does your local ham club have an RFI group, or individuals well versed 
in hunting down problems?  If available make generous use of local brain 
power.

A knowledgeable person, or persons present can do a lot more, quickly 
than we can here.

I will relate a problem I had a while back,  I had fried two relatively 
expensive duoband (VHF/UHF) verticals which in turn took out some 
expensive finals. The problem turned out to be a combination of a power 
supply and grounding problem which all agreed shouldn't happen.  I'm 
still not sure about it, but with all grounds in place, its been working 
for some time.

Knob and Tube...That is the main difference between this house and most 
with ham stations and computers.
BTW At the risk of dating myself, when I was a kid, Knob and Tube was 
not uncommon.

73

Roger (K8RI)

>
> Well, not on RFI since the OM asked for help...  I would start by making
> chokes out of all wires entering the device.  Wrap a half-dozen turns around
> your hand in a loop four to five inches across and secure with plastic ties.
> See what happens, try a few more or few less turns if the problem persists.
>
> I did this with a monitor that eliminated all radio usage 135' from the
> antenna.  When I was done, RFI was limited to roughly three inches.  I used
> spectrum analysis software as I wound my chokes and monitored the RFI with
> my primary radio and could see it disappear on the monitor and audibly as I
> made the loops.  Simple, effective, free, been in use about seven years now.
>
> Kurt
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
>


---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com