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[aprssig] 220 MHz transceivers

Stephen H. Smith wa8lmf2 at aol.com
Sun Nov 16 23:18:25 UTC 2008


Chris Rose wrote:
> 85MHZ is fm commercial broadcast range.  Anything local to you there?
>
>
>   

The bottom of the FM broadcast band is 88 MHz with a (very) few minor 
stations on 87.9.   

85 MHz is the center of NTSC (North America) TV channel 6 which extends 
from 82 to 88 MHz.   I through of this, but neither the visual or sound 
carriers of this channel land on the frequency originally mentioned. 



Speaking of TV channels, I am predicting a MAJOR renaissance of 
six-meter activity next year.   

Channel 2  (54-60 MHz)  has rendered 6M operation almost impossible in 
many major cities of North America.   Even when the lower visual 
sideband of channel 2 is suppressed 60-70 dB (from a quarter-megawatt or 
more), the net result is to blanket most of the 6-meter band with 
S9-plus sync hash and noise.   Not to mention the potential for 
interference to TVs from 6M transmitters (TV tuners with lousy adjacent 
channel rejection).   This will change radically 17 February 2009. 



The chaotic transition to all-digital TV broadcasting in the US has 
stations currently simulcasting on analog and digital channels. Nearly 
all digital transmission is currently in the UHF band.  After the analog 
shutdown next Feb 17, about half of the VHF HIGH-band TV stations (chans 
7 through 13) will move their digital operation to the classic VHF 
channel occupied currently by their analog operations.  The other half 
will just shut down the analog operation and continue the digital 
operation on UHF only, although there is going to be a lot of jumping 
around from one UHF channel to another.

To add to the confusion, the (UHF) digital channels identify with the 
VHF channel numbers of their legacy analog counterpart stations no 
matter what channel they are actually on.  [The digital transmission 
protocols allow you to send any arbitrary channel number as part of the 
transmission.]  For example, here in Los Angeles, the station that shows 
up on my digital TV as "Channel 7.1  KABC-DT" is actually on UHF channel 
57, but will move to the "real" channel 7 when the analog side shuts 
down.     


However, virtually ALL analog LOW-band TV stations (chans 2 through 6) 
will just shut down the analog operations, and continue their current 
digital operations on UHF only.    A new generation of "all-channel"  TV 
antennas from Channel Master and Winegard are now on the market. They 
are about half as large as their traditional versions, because they no 
longer cover the low-VHF band.  

The bottom line is that channel 2 is going away COMPLETELY!!!    Not 
just going digital but going silent which will make the 6 meter band 
instantly far more usable than it is now.  

Lots of info on the DTV channel changes and re-assignments at this website:

     <http://rabbitears.info>





--

Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      14400    [Think bottom of the 2M band]
Home Page:          http://wa8lmf.com  --OR--   http://wa8lmf.net

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