RE: Re: Interference by cell towers

Regarding Nextel, I have found that adding about 12db of attenuation
with an inline attenuator on the feed line can help to keep the Nextel
signal from bleeding into the desired frequency. I was plagued with
Nextel sites on every other corner here in San Diego. For best results,
get a switchable attenuator so you can "turn of off" by going 0 db when
you are far away from the desired system or in a fringe area.

Basically, this method is weakening the Nextel (as well as the desired
signal) to the point where the Nextel, which is off frequency but
overloading the front end of the scanner and bleeding over. Once the
offending signal is weakened sufficiently, the bed signal is too weak to
bleed over the channel spacing.  This wouldn't work if you were trying
to pick up a desired system that was weak to you to begin with, but if
you're in the city and trying to monitor that cities system, it may
help.

A variable attenuator may be a good option so you can change the setting
until an acceptable balance is found. The amount of attenuation needed
is based largely on how strong the indented signal in your situation.

In my case, at several intersections the BC780 display would go
completely blank and lose lock with the TRS while monitoring the San
Diego city TRS and be scratchy for blocks around as I moved away. With
this method and some experimenting, I could now sit right at the
intersection and hear just fine, however a little more scratchy than
optimum conditions.

You may be able to locate your city here and determine if Nextel is a
problem.

http://www.911dispatch.com/information/nextel/nextel_plan.html

http://www.apcointl.org/frequency/combined.txt

It may be worth a try once, and if, you determine your culprit is
Nextel. I have spent a lot of time researching and experimenting with
resolving Nextel interference and this is the only method that provided
**any** relief for a scanner.
 
Sean
W6PIX
******************************************

If the interference is originating from a cellular or Nextel source, 
and the direction of that source is different from the direction of 
the system you are trying to monitor, a directional antenna (yagi) 
may help.  Attentuation might also help.

I'm not familiar with any consumer-grade filters which would filter 
cellular interference without impacting the 800 public safety band.  
You can't filter Nextel, since their frequencies are interwoven among 
the same 800 MHz frequencies public safety is using.






------------------------ Yahoo! Groups Sponsor --------------------~--> 
$9.95 domain names from Yahoo!. Register anything.
http://us.click.yahoo.com/J8kdrA/y20IAA/yQLSAA/DLTolB/TM
--------------------------------------------------------------------~-> 

If you have come here to find out about the 785D you have come to the right place! In fact the discussion of the BC-785D and how it works is the only acceptable topic on this list. Any discussion about anything other than the BC-785D is OFF TOPIC. I hope this is clear to all group members..