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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