If the spectrum analyzer is left in place for a period of time and setup
with "peak hold" you will quickly find that radio that is used at the end of
the day. It still speaks, handshakes and more. 

Just setting up big shots and blowing people out is bad business for
everyone. If the customer wants a quality shot then there should be no
problem doing a spectrum analysis, freq decision and installation shortly

I agree it's only good for a certain amount of time, but if the customer
wants a reliable shot then due diligence is better than chance luck.  


-----Original Message-----
Behalf Of Bob Moldashel
Sent: Friday, February 10, 2006 9:49 AM
To: WISPA General List
Subject: Re: [WISPA] Flawed Spectrum Analysis (I think!)


This whole thread......

Some have touched on pieces of it but how about this summary..........

The Redline is a two piece radio.  It does not send 5 Ghz up the cable. 
It sends an IF frequency which is lower and more forgiving as well as 
power to operate the outdoor unit. The Redline as pointed out does not 
have a spectrum analyzer (in the versions I have worked with).  As such 
they probably just checked for RSL on any or all channels.  This is not 
a spectrum analysis by any means. The Redline equipment is great 
equipment but it is not a spectrum analyzer.

A spectrum analysis is flawed in almost any case really because it is 
only good at the time of the testing and along the path of the test. You 
really will only see stronger signals with an omni. But you can still 
have your signal killed if someone is using directional antennas and 
looking down your path. There is a big difference from 8 dB to 29 dB.

The other case is a 5 Ghz. system in place that only is used at the end 
of the day or does "dumps' at certain times.  Unlike a full duplex radio 
like a Proxim Tsunami that is talking all the time regardless of the 
received signal, you may only see a signal when the associated equipment 
is passing data. 

In my book you can't do "reliable spectrum analysis" with any radio or 
assocaited radio card. Yes, there are systems out there that work really 
well but I would not be willing to bet my reputation on most.  Will they 
get you by in most cases???  Sure.  

To answer your question......Yes, the spectrum analysis was flawed.

Personally...we never do spectrum analysis.  It causes more headaches 
than what it is worth IMHO.  Is it great for finding interference??  Sure.

I have installed links in lower Manhattan (nearly 70 to date on 
unlicensed 5 Ghz), Washington DC and Boston without ever needing a 
spectrum analysis. All these locations are RF hotbeds.

A few things to consider. Use a radio with a very good C/I value. Use 2' 
or larger antennas to keep the beamwidth tight. Use radios that are 
capable of 5 or 10 Mhz. channels.  Use radios with high RF power output. 
If you need to run transmission line to the radio, use the right stuff 
for the job. LMR400 and 5 Ghz. are not my considered options unless the 
cable length is less than 24".  We use LMR600 up to 100' and 5/8" heliax 
after that. make sure the radio has a good receiver threshold. Wherever 
possible we use 5.3 Ghz.

Last and not least consider your neighbors. If there is only one tall 
building in town and everyone is on it use 5 Ghz. you are probably in 
for some challenges. But if you do a spectrum analysis, find a clear 
channel, build on it and then smile and walk away only to have one of 
the existing operators change channels and rain on your parade.

Its a game of chance but with the proper engineering you can move the 
odds more in your favor.

Good Luck!


Bob Moldashel
Lakeland Communications, Inc.
Broadband Deployment Group
1350 Lincoln Avenue
Holbrook, New York 11741 USA
800-479-9195 Toll Free US & Canada
631-585-5558 Fax
516-551-1131 Cell

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