Cliff,
Are you sure the first 140' was RG6? I think that is 75 ohm cable so
that
may be a problem, if it was something else it still might have too much loss
at 5.8 GHz to get any signal to the SA. You may be on to something with the
adapters, if they were just using good quality N-Type for all the
connections it should not be a big deal, but if they were going from an N to
BNC or PL259 or any other type of connector not rated for 5.8 GHz that could
introduce big losses. I would have them inquire about the calibration (and
date) of the SA and it's rated sensitivity for 5.8 GHz. Operator skill might
come in to play, if they had too much attenuation switched in to the SA at
the time of the readings it could give the results you state. As far as
seeing your PTP signal, depending on how well you were doing the swing test
and/or the alignment of any nulls on the pattern it is possible that your
link signal would be low enough not to be detected with any of the above
situations. If your link has high gain antennas on both ends the beam width
of your signal could be narrow enough that it might not pass as close to
this tower as you would assume, the best way to check that is to draw a line
on the map between your sites and see if it really does cross this site in
the main beam.
Thank You,
Brian Webster
www.wirelessmapping.com <http://www.wirelessmapping.com>
-----Original Message-----
From: Cliff Leboeuf [mailto:[EMAIL PROTECTED]
Sent: Thursday, February 09, 2006 11:07 AM
To: WISPA General List
Subject: [WISPA] Flawed Spectrum Analysis (I think!)
We proposed a spectrum analysis for a client. This analysis was to be
performed with a hand-held spectrum analyzer at the height that the
equipment was to be mounted. Our offer was rejected.
However, we were asked to provide the climber for the other party's
analysis.
Their analysis was performed as follows:
1. Using a 'nice' spectrum analyzer
a. the analyzer remained in their truck
b. the antenna from a 5.8Ghz Redline system was hauled about
140'
c. the original RF cable used was RG6 for 140'(duh?)
d. the next 140' of RF cable used was LMR400
e. we know that we shoot directly through one of the sites
surveyed with 5.8Ghz P2P link, and have 5.8 P2Mp links at two other
locations surveyed
f. all analysis showed no RF interference (go figure!)
I'm not an RF engineer, so would someone help me to explain why there
was no 5.8Ghz interference shown at these locations even though I know
there to be other 5.8Ghz equipment hitting the towers tested.
What is the RF cable loss at 140' of using LMR400 as described above?
Also factor in about 4 connectors to adapt the RF cable from the
analyzer to the antenna.
Is this a valid analysis, or am I wrong to comment to this customer that
I feel this analysis if flawed?
"Ammunition" that anyone is willing to supply would be appreciated as
well as advice for me to keep my mouth shut. :)
- Cliff
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