[TenTec] Low-pass filter?

[Jim Brown K9YC]

On Mon, 01 Mar 2010 15:42:24 -0600, Dr. Gerald N. Johnson wrote:

>many went back to their VHF channels, more high VHF than low
>but there are a few stations still on the low VHF channels and 
running
>digital. 

There are VERY FEW broadcasters still using the low VHF channels (2-
6) (most are in the great plains and Michigan). That is by choice -- 
those originally licensed to Ch 2-6 were given the choice of their 
newly assigned channel or a high-band VHF channel. In addition to the 
antenna bandwidth issues (which were just as much a factor with 
analog TV), the primary reason is IMPULSE NOISE, which is 
significantly higher on those low VHF channels, and DTV is quite 
susceptible to problems from impulse noise. 

W1RH, Chief Engineer for several major TV stations around Sacramento 
and formerly CE of WBZ-TV, told me a third reason why VHF is iess 
used is that the FCC allocates less power to VHF DTV as compared to 
UHF (even taking propagation into account). 

You can find the RF channels, antenna locations and heights for all 
US TV stations by plugging your lat/long coordinates into the search 
window at 

http://www.fcc.gov/fcc-bin/audio/tvq.html

I repeat my bottom line -- a low pass filter on a ham transmitter is 
NO LONGER IMPORTANT in preventing TVI. The far more common causes of 
problems are leaky cable systems, pin 1 problems in receiving 
equipment (including assoicated audio and A/V system), and poor 
shielding of receiving equipment. 

73,

Jim Brown K9YC