[BC] RF absorption by foliage

[gRAdy Moates]

> This happens with dead carrier.  When you're in the area 
> where this happens it makes no difference what station you 
> tune in.  You can dial up any Detroit, Toledo, Monroe station 
> and watch the meter bounce up and hold then bounce down 
> and hold.  WJR is Non-directional and I've seen it happen on 
> their signal.  It will do it for hours and then it just quits and 
> may not come back for hour or days.

Here's an idea. . . 

Certain cellular telephones, when held within ten feet of 
the meter, will cause an FIM-21 or FIM-41 to 'desense'.  

I've seen the meter drop by as much as 1/3 scale when the 
cell phone would 'phone home' for whatever reason. . . 
checking in and reporting it's presence, taking or initiating a 
call, whatever.  It drove me crazy on a few 'talk-downs' until I 
figured it out.  

Apparently, the cell phone gets into the meter movement, 
gets detected, and feeds back into the meter-drive electronics 
in some way that causes the meter to deflect *downscale*.  

I wrap the front, lower portion of the meter of all my FIM's with 
aluminum foil because the foil covering the lower half of the 
meter face eliminates the behavior.  The foil doesn't have to 
be grounded to the case.  It just has to be there.  

Since the power output of the cell phone is internally regulated 
so that transmit power is low when the phone is near the 
cell site with which it's 'conversing', this might only happen 
out in the boonies, where there isn't a cell site nearby and 
the phone cranks itself up to max output power.  

This was happening with Cellular One digital phones by Nokia 
(among others) before the big switch to GSM.  

Grady 

Grady Moates 
 
Owner, LOUD & Clean Broadcast Science 
  Voice        800 946-7007 
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