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Kevin Bailey wrote:
<blockquote cite="mid:20080702151959.GA842@malamute" type="cite">
<pre wrap="">On Tue, Jul 01, 2008 at 08:32:53PM -0400, Jay R. Ashworth wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Big ChannelMaster corner-reflector widebands aimed at Tampa, and one
little dinky tuned 14 element yagi pointed 90 degrees from it.
</pre>
</blockquote>
<pre wrap=""><!---->
And you join them with a common splitter ? Or separate tuners ?</pre>
</blockquote>
I just wanted to point out that if you combine two antennas with a
common splitter there are a few things you might want to consider. <br>
<br>
First is that if there are hills or buildings around, you might get
multipath problems. It has been pointed out on this list that most
multipath is taken care of by the tuners and not generally a problem,
but it can be. <br>
<br>
Second is that each antenna is a noise source as well as a signal
source. If you just add them together, you might increase your S/N for
the distant stations. If you have an amplifier on the distant stations
and a combiner after that with no amplifier on the local station, you
would be drastically increasing the noise on the local station, but
that may not matter. <br>
<br>
Finally, even with the antenna pointed off at 90 degrees, it is going
to be receiving some of the signal from the distant station. This will
either increase or decrease the signal from those stations depending on
the phasing. Again, if you have an amplifier in one path, this won't
matter. By the way, one way of increasing the power of an antenna is
to add a second identical one on the same pole phased just right so
they add. This increases the directionally up and down so it increases
the signal. I think the math is the signal goes up by 6db (double the
voltage) and the noise by 3db (double the power) so you are 3db ahead.
Of course, that is what you see in those UHF bow-tie arrays.<br>
<br>
Just some things to consider if you have problems or are thinking of
doing this. I have not thought to try combining with a passive
splitter because of the theoretical problems but it may very well work
fine in practice.<br>
<br>
Allen<br>
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