Re: Digest Number 939

Dave Martindale <[email protected]>
Newsgroups gmane.recreation.radio.hardware.icomr2
Message-ID <[email protected]>
At 08:56 20/05/2003 +0000, you wrote:
>   From: "blueray777" <bluestarborn-/[email protected]>
>Subject: "Reception 2"
>
>  Most of the frequencies that were listed as active were in the 
>123.ooo mhz up to 330.000 mhz. The web page I downloaded the info 
>from said to monitor these freq's in the AM band. But the little bit 
>of reception I got was in Wideband. I tried all the bands, only WFM
>worked.

Aircraft communications are definitely AM.  I use my R2 frequently to listen 
to them, and it works fine except when I'm very close to the transmitter 
(e.g. within a couple hundred yards of a control tower).  Maybe your AM 
detector isn't working properly.

The easiest way to test this is to find a nearby airport that has an ATIS 
frequency.  This broadcasts voice information continuously, though at fairly 
low power (you'll probably need to be within line of sight of the airport).  
You should get clear audio in AM mode when tuned to the ATIS frequency.  If 
not, there's a problem.

WFM just isn't going to work well, since the transmission isn't FM.  You may 
detect a strong signal because there *is* a strong signal from a nearby AM 
transmitter, but the voice is carried by varying the amplitude of the RF 
signal, and a FM detector is designed to ignore this as much as possible.  
In contrast, a FM detector is designed to respond to changes in frequency, 
and an AM transmitter is designed to minimize these.

        Dave 


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