With 140 ft of LMR-400 at 5.8GHz, the loss is about 15db.  With a good antenna topside, you might get some usable results, but not good ones....

For the RG6, I can't find any loss specs for freq. above 900MHz.  At 900MHz, the loss is about 10db for 140 ft.  Extrapolating that to 5.8GHz, I estimate the loss would exceed 30db at 5.8GHz!  Not gonna see much of anything!!!

If you connect RG-6 cable directly to LMR-400 or to N-connector antennas or equipment, you have an impedance mis-match.  I'd expect to loose 6db or more with that mis-match (at each connection!).  This is on top of the cable loss with the RG6.  If they did not use a balun to match the RG6 cable to the N based equipment, then the total loss on the RG6 'test' would exceed 42db!!!  Not gonna work.

This 'test' was a waste of time.

  JohnnyO wrote:
There was no noise detected b/c there was no signal going into the SPEC-AN ! - This sounds like something you would do Cliff - sure this guy wasn't related to you ? :)


On Thu, 2006-02-09 at 10:07 -0600, Cliff Leboeuf wrote:
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

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
	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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Blair Davis

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