Andy, I'd definitely put the hardware in a grounded box. I'll bet your
problems disappear...
Norm
----- Original Message -----
From: "Andy Thomas" <andy@goldrushwireless.com>
To: <karlnet@WISPNotes.com>
Sent: Tuesday, December 02, 2003 10:47 AM
Subject: [Karlnet] Radio Interference from SR-4200?
Grettings All,
I wonder if anybody has come across a similar problem:
I have an SR-4200 that I am using for a backhaul link in bridging mode. It
appears to be creating or contributing to interference with a ham radio VHF
repeater at the same facility. Fortunately, I am a member of the club that
supports the repeater, so I have some access to it. We have determined that
a very small signal at 100 Hz is being generated when the SR-4200 is powered
on. We came to this conclusion because when the repeater is keyed on
(144.570 MHz input) it is held open as long as a 100 Hz PL (CTCSS) tone is
present. When the SR-4200 is powered up, the repeater will stay keyed after
the keying radio stops transmitting. With the SR-4200 powered off, the
repeater will drop normally.
I first came across the problem in late August and tried the following
remedies:
Swapped radio cards
Swapped entire CPE
Tried turning off Watchdog Timer and MAC authentication
Unplugged external antenna
Physically moved CPE and antenna about 15' lower on tower (this appeared to
solve the problem)
The problem came back last weekend. I did flash the SR-4200 up to the
4.44 firmware about 3 days before the problem re-appeared. I plan on
flashing it back down to 4.43 when I go up to the site later today (I
haven't had any luck in the past trying to flash it remotely).
The CPE is in a NEMA-4 plastic (ABS, I think) box. I wonder if anybody
has tried shielding a box like this...foil tape or a metal enclosure?
The problem has been pretty consistent this time around, but there have
been periods of time (usually at night) where it goes away. The only ground
I can see would be through the RF connector to the antenna, which is bolted
to the tower on a stand-off. The tower is painted, and I didn't scrape off
the paint to ensure a proper ground...I'll take a meter up and see how good
the ground is.
There is another backhaul on the same structure with an old POGO board
that has never given any signs of the same issue.
Any ideas?
Thanks!
Andy Thomas
Goldrush Wireless Internet
andy@goldrushwireless.com
(209) 736-0111 Ext. 1#
P.O. Box 934
Angels Camp, CA 95222-0934
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