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Old 8-Aug-2012, 4:41 PM   #11
ADTech
Antennas Direct Tech Supp
 
Join Date: Jan 2010
Posts: 2,942
Quote:
What makes the signal better at night/morning?
A good question but one without a really simple answer.

There are several mechanisms that may be at work when this happens. One is that, after the sun goes down, background atmospheric noise levels drop allowing weaker signals to have enough signal-to-noise ratio to become receivable. Another mechanism is that the temperature of the air changes at various altitudes, enough so that minor inversions may be created. These inversions, especially at their boundaries, will allow RF signals to propagate either more or less effectively than those same signals would otherwise have traveled through an atmosphere that is a quiescent condition. Summertime often brings large variations in the atmosphere that often brings both opportunity and frustration with fringe reception.

Getting the antenna higher in the air when in fringe areas often puts it into a stronger signal zone. An old rule of thumb for installation height back in the day was 10' of height for every 10 miles of distance. Not always practical, but it gives you a feel for what worked for the old-timers and analog. Digital signals behave in the same fashion and will usually benefit from the same measures.

Adding a low-noise pre-amplifier will help to boost weak signals (along with the background noise) and will often put the signal-to-noise ratio above the threshold of failure and will permit reception of signals that are otherwise too weak.

Last year I had a dairy farmer from Amarillo call me about reception he was getting with his C4. He said that when he got up at 4:00, he could usually get stations from Houston (hundreds of miles away), but they were always gone when he got done milking the cows after sunrise. He wanted to know what he could do to get them all the time...
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Last edited by ADTech; 8-Aug-2012 at 4:48 PM.
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