Re: A Group of Towers in Acton

[Brian Vita <brian_vita@cssinc.com>]

Today for radio navigation pilots use a system called VOR (VHF Omni 
Range).  Essentially this is a VHF transmitter in the 108.1 - 118.0 (?) 
range that transmits a phased signal.  By reading the phasing coming off of 
the transmitter, the aircraft's receiver can "see" a number of different 
radials on the signal.  The phasing of these is aligned so that the 0 
degree radial corresponds to magnetic North.   Thus if I'm over the 
Lawrence VOR transmitter and I set my radio to track the 153 degree radial 
I can "follow the needle" and end up in Beverly.  The "needle" is called a 
CDI (Course Deviation Indicator) and is generally nothing more that a 
needle that indicates if I'm to the left or right of the desired 
radial.  This is a simplified explanation.

Prior to these they had a system that I believe was called a radio range 
whereby they used four transmitters, each transmitting one of two 
letters.  I believe that "A" & "N" were used.  The antennas were somewhat 
directional and you listened to which letter was stronger to determine if 
you were to the left/right of the course.  This, again, is over simplified 
and the system was long since gone before I started flying.

Brian

At 01:56 AM 2/17/00 -0500, SteveOrdinetz wrote:
>I remember when I was a kid there being some sort of beacon in a neighbor's
>field (antenna looked kind of like an upside down spark plug) that was in
>the VHF band...indeed, it made reception of channel 5 difficult.  It
>constantly sent Morse code "A".  Someone told me it was some sort of beacon
>for the local airport.  The building and antenna were fenced in, and there
>was a sign sort of identifying it as being a government facility and that
>all sorts of bad things would happen to you if you messed ith it.  I didn't
>examine it too closely, as the people whose property it was on weren't very
>friendly.  If I'm not mistaken it was shut down by the early 70s.  Anybody
>know what this was?

--Brian T. Vita, President
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