Subject: [NEXTEL-1] RE: Pericle Communications to FCC's OET on 800 MHz Interference in Denver CO

From: [email-masked]
Date: Tue, 23 Sep 2003 02:00:31 -0400

-------- Original Message --------
From: <[email-masked]>
Subject: RE:  Pericle Communications to FCC's OET on 800 MHz Interference in
Denver CO

I'm still 3/4 fried.. The thermometer in the shade at the Piestewa Peak (aka Squaw
Peak) trailhead said 110F as I started up the hill.  The clouds came in after I
finished...figures.....  

I was reading the newest Denver report and it is interesting how many to think
that the IM and other strong signal problems will go away if 800MHz is rebanded. 
Also, it is interesting to read that Consensus Plan, if it is adopted, will
RESOLVE the interference problem.

The Consensus Plan will fix transmitter noise problems. The amount of improvement
depends on whether anyone really goes out and buys better transmitter filters or
just waits until a problem is noted and then does something about it.  This isn't
a problem with the Consensus Plan, so I'm not worrying about this.

Look at page 9 of 45 of the latest Denver report before reading the next
paragraph.

>From the receiver's point of view, the Consensus Plan retune really doesn't change anything in a meaningful way.
1) Cellular's frequency allocations remain unchanged.
2) ESMR is still within the receiver's preselector.
3) The same receivers are in place.

Since all the signals seen by the receiver's LNA and mixer are unchanged in
strength, I think it is reasonable to believe that the receiver would still have
the same problems that it was having before any retune.

For my "mind IM studies" I'll use the 875MHz number mentioned on pages 9 and 16
(of 45) in the latest Denver report.  This frequency was mentioned as the point
where a 800MHz land mobile radios' front ends begin to provide useful attenuation
of cellular signals.  So, if your wondering why I chose 875MHz, this is it.... 
Yes, I did these studies in my head.  I needed something to take my mind off of
the heat! :-)

If an A band cellular carrier is generating RF in the 875MHz range of their band,
then there will be potential IM hits in the 851-861 band anytime Nextel uses any
channel in the 861-868MHz range.  

If the cell carrier is using CDMA (1.25MHz bandwidth carriers), then the ability
to carefully pick channels to avoid potential IM problems is greatly eliminated. 
Many A band cell carriers are at 4 and 5 CDMA carriers...this puts the A band
cellular CDMA RF from nearly 880MHz down to about 873MHz...so it is very likely to
encounter a situation where there is CDMA RF at 875MHz and below.

So, in the places where both A band cellular carriers and Nextel are strong (which
is where the 3rd order IM problems are already occurring), after a Consensus Plan
retune, either the A band cell carriers would have to not use about 1/2 of their
spectrum, or Nextel could use only about 1MHz of the post Consensus Plan
spectrum.  

I don't see how the Consensus Plan can be called a fix.  

Now, if the Consensus Plan would replace the 800MHz users' receivers, I could
support the plan.

Eric

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