[mythtv-users] Antenna amplifier

Allen Edwards allen.edwards at oldpaloalto.com
Tue Aug 5 19:23:23 UTC 2008

David Brodbeck wrote:
> Allen Edwards wrote:
>> It may also help to have the two antennas close together, I don't know. 
>>   This point is, if the signals are in phase, they will add and not 
>> notch up the passband.  You can actually take two identical antennas 
>> pointed in the same direction, space them apart on the pole, and combine 
>> them for added gain but that is a well controlled situation.
> The trick, of course, is that if they're in phase on one channel they 
> won't be on another.  This is where you get the weird notch effects -- 
> if they happen to be close to 180 degrees out of phase on one particular 
> channel, they'll neatly cancel out each others' signals.

Exactly.  And if they are close together, the different channels are 
more likely to be of the same phase.  But think if they are far apart 
and the stations are off at different directions.  In that case, there 
is no way to match the phase.  However, if they are close together, the 
signals will at least get to the antennas at the same time regardless of 
the direction they are coming from.


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