Gary, the RFI is almost surely coming in on the CAT5 cable. I doubt the WiFI
transceiver is picking it up through its antenna. (You didn't say so, but
I'm guessing the transceiver uses an integrated flat panel antenna) Also,
you didn't specify the band the transceiver works on, but I'm guessing it's
a 2.4GHz device, but it might be 5 GHz. Either band shouldn't be a problem,
but if it's a 900 MHz device, it might be more susceptible to RFI.
Your first line of defense would be to use shielded CAT5 for the run from
the transceiver to the router. Next, you could install a surge suppressor on
the CAT5 cable next to the transceiver, such as the Polphaser unit. These
have MOVs across the shielded pairs to ground, but the capacitance of each
MOV is typically about 1000 pF, so it should provide some RF bypassing
capability. Wrapping the CAT5 around a few ferrite cores, at the transceiver
end, might also help.
Lastly, you might try bypassing the DC power supply for the transceiver. I
imagine is uses a POE ("power over internet") adaptor, which inserts the
voltage over an unused twisted pair in the CAT5 cable. You could open it up
and solder a couple of .01uF bypass caps to the output.
Also, make sure the transceiver is well grounded to the tower. It is
probably clamped to a tower leg, so I don't imagine that is a problem. G5RV
antennas typically are a bit squirrely on 40m. I have trouble matchng mine
at all on the band. So changing the length of the coax a few feet might also
help.
73,
Jim W8ZR
**********************
Jim Garland W8ZR
Santa Fe, NM
www.w8zr.net
*********************
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Stone, Gary R.
Sent: Tuesday, July 17, 2007 7:26 AM
To: towertalk@contesting.com
Cc: fsiebenthall@sbcglobal.net
Subject: [TowerTalk] help with interference problems
I am experiencing some interference problems with my wireless broadband
connection. I am using a new 'radio' for the Internet and did not
recall this problem with the old one - but it is possible it was there
but I don't think so. Here is what I know - and I sure would appreciate
some feedback.
1- My set up is as follows: 80 foot tower and at the top of the tower
is a Cushcraft 8 element Log antenna. I have made lots of tests and
can't find any problems with interference from the log on any bands it
covers (10-20 meters).
2- About 22 feet below the log is my broadband wireless 'radio.' I do
not know the brand or model.
3- About 12 feet below the broadband is the top of my G5RV. The 2 legs
go out at about 60 degrees from the tower. The ladder line (32 feet)
runs about 3 feet away from the tower and parallel to the tower. The
ladder line and top of the G5RV is about 12 feet below the broadband
antenna. The CAT5 from the broadband goes from the tower to my home at
about a 45 degree angle and attached to my house about 8 feet from the
router connection. It has a six foot ground rod and a lightning
protector (installed by the broadband company) - at the house entrance.
The radio (I am told) is also grounded properly on the tower.
4- As normal, the G5RV is fed at the bottom and I use LMR400 to an Array
Solutions rat pak switch box mounted a few feet up the tower then a
single LMR400 into the shack (mostly underground - about 80 feet from
the rat pak to the shack).
5- About 5 feet below the top of the G5RV I have a 30 meter sloper
running toward the house and fed with coax down the tower to the Rat
Pak. The sloper is about 20 feet away from the CAT5 from the Internet
and roughly parallel to each other.
6- For my testing of the Internet this is what I have been doing: When
transmitting use an Internet speed check (like Internet Frog) and watch
the speed. I performed the tests many times and have consistent
results.
Now, my interference symptoms:
1- When using the Log antenna at 600 watts I can't detect any problems
with the Internet connection. The speed is good is consistent. And the
speed during these tests consistently hit about 3 megs down and about 1
meg up - which is great for me living in the sticks!
2- When using the G5RV on 80 meters (never or rarely use the amp there)
but at 100 watts I detect no problems.
3- Now the problems: When using the G5RV on 40 meters CW (rarely use it
on SSB 40 meters but would likely be the same results.) When using 100
watts the Internet connection definitely is affected and slows to a
crawl. When using 600 watts on 40 meters and the G5RV the Internet
connection is lost completely and I have to wait awhile for it to come
back. When using 50 watts I can detect no problem. So, to recap the 40
meter problem: 50 watts or less - no problem. 100 watts the Internet
connection is greatly slowed and with the amp (about 600 watts) the
Internet connection is lost.
4- Second (and last) problem: When transmitting on 30 meters I
experience the same thing as on 40 meters with 50 watts no problem and
100 watts the Internet connection is greatly slowed. (Of course no amp
has been using on 30 meters).
So, the bottom line is that my 40 meter and 30 meter transmissions (when
using more than 50 watts) seems to slow or stop my Internet connection
quite a bit. I do have two small ferrite snap on emi protectors on the
cat5 after it enters the house and right before the router - but they
don't fit too good - too loose. If a series of several of them would
work I could order the right size to snap over Cat5 and I have about 5
feet of Cat5 from the house entrance to the power injector on the
Internet - so lots of room to put some snap on ferrites there?
Open to suggestions. Moving the Internet antenna is possible but would
be a problem. Are there different degrees of 'RF proof' Internet radios
on the market?
Gary Stone, BA, LCDC J
Case Manager, DSAP
O 903 - 583 - 6411
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