[SBE] 950 STL curious problem

[Jack Davis]

Is there a wireless ISP (WISP) in a 20 mile radius?  A lot of them use
illegal high power amplifiers to increase coverage area.  I have a couple of
ham repeaters on 902/927 and they are a constant problem.  Depending on
channel loading the spread spectrum clusters in different places.  Overdrive
one of the amplifiers and you have exactly what you are describing.  The
crud is on channel for you so there is no amount of filtering that will take
it out.  You might try direction finding it, perhaps a chat with the
operator about part 15 power levels would be in order?

 

Jack

K6YC

 

  _____  

From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org] On Behalf Of
A9xw at cs.com
Sent: Monday, July 20, 2009 8:54 AM
To: sbe at sbe.org
Subject: [SBE] 950 STL curious problem

 

Follow with me, this is wierd.   

Day 1,  14 mile STL path for radio, Moseley Starlink 9003Q with LanLink. 
Signal level  - 77.   Less than expected. Turns out trees in middle of path.


Waise receive antenna 50 feet and signal level improves to -73. All nice and
stable. 

2 months later, suddenly signal level drops to -80.  Check coax, (1/2"
Heliax)  couple of bumps.  By pass LanLink box at TX end, gain 2 db.  Bypass
LanLink box at RX  end gain 5 dB.  Back to -73.   

Receive level unstable, jumps from -73 to - 93 and back every few seconds.


All connections checked, and rechecked.  RX does not work at -93 (below
threshold). Patch in Comprex line.   

Replace 1/2" line with 7/8" line. No improvement in signal level.  -80 with
Lan link in, -78 with TX lanlink out, -73 with TX anbd RX Lanlink out and
signal begins jumping again -73, -93. 

OK, Lanlink serves as bandpass filter but only other signals on site are 2
class A FM's. 

Can't find cause of  -73, -93 signal level jumps ( a couple seconds between
levels and fairly regular). No improvement in signal level with increase in
coax, that should have gained about 2 dB since 1/2" had 4 dB of loss)
(260'). 

Antennas check good. (Scala grid type) 

Only other signal is 950 STL at 90 degrees and distant channel.  Rotating
antenna shows typical and smooth lobes and is dead on.   

Called Moseley, tech says he would bet his house it is not receiver. 

Any guesses other than LGM?  Nothing within 2.5 miles of RX site,  path is
clear and not near intersecting anything else. 

Henry 

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