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Re: [RFI] RFI Susceptibility of DTV?

To: "RFI List" <rfi@contesting.com>
Subject: Re: [RFI] RFI Susceptibility of DTV?
From: "Jim Brown" <jim@audiosystemsgroup.com>
Date: Fri, 23 Jan 2009 19:12:19 -0800
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Fri, 23 Jan 2009 19:54:58 -0600, Gary \"Joe\" Mayfield wrote:

> www.antennaweb.org is very useful indeed. 

Depends on what you call useful. antennaweb got my address right 
on a map, and told me there were NO signals at my QTH. My local 
TV comes from two sites, one 42 miles away and the other 45 
miles, only 20 degrees apart.  

>Your mileage may vary. 

It certainly will. Yesterday, I stuck a 4x2 bowtie (with a 
reflector) on a 20 ft mast with its base on the ground and fed 
it into both an old analog TV and my new Sony XBR6. The analog 
TV made fairly good pictures on three channels. Some noise, but 
very watchable.There were several other channels that synced but 
didn't produce a watchable pix.  The XBR6, fed with 100 ft of 
low loss RG6 (about 5 dB loss), found only two of the analog 
stations but made perfect pictures on three DTV stations (a 
total of 8 digital programs). 

My 4x2 bowtie is a pretty simple antenna that probably has about 
10 dBd and about 60 degrees at the -3dB points. Now that I see I 
have some signal, I'll work on getting that antenna permanently 
installed and a bit higher and add a preamp ordered., I suspect 
that will pull out a few more signals and add some fade margin. 

I think it is safe to say the DTV signals WILL get better as the 
transition proceeds. Most stations with DTV transmitters on 
channels adjacent to their analog channels are purposely running 
less than their licensed power so that they don't QRM their own 
analog signal (we don't want ratings to suffer -- that's bread 
and butter). The stations that will switch to a new channel are 
using temporary antennas and transmitters now, and they may also 
be at temporary sites. 

Once the transition is complete (and that may take some time), 
we're going to see everyone getting up to whatever their full 
licensed power is and running from their best TX sites. So 
before you do too much weeping and knashing of teeth, give the 
broadcasters some time to work through it.  

73,

Jim K9YC


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