In message , Roy Lewallen
writes
J. B. Wood wrote:
In article , Roy Lewallen
wrote:
One of the properties of the splitter, as opposed to just a tee
connector, is that the two receivers are isolated from each other. So
turning one on or off or disconnecting it should have no effect on
the other.
Roy Lewallen, W7EL
Hello, Roy, and all. I would also add that the degree of isolation
achieved in an n-way splitter is predicated on how well the port being
split n-ways is terminated in the splitter's design characteristic
impedance (e.g. 50 or 75 ohms). Sincerely,
John Wood (Code 5550) e-mail: Naval
Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337
A good point, and one I hadn't considered. The chances of the antenna
impedance being 50 ohms over the band of frequencies likely to be used
by a scanner is about the same as its being 75 ohms, which is to say
about zero. (This is almost certainly true for most TV antennas over
the whole TV frequency range also.) Whether the isolation is good
enough will have to be determined by experiment. If it isn't, the only
solution would be to put a pad at the splitter input to stabilize the
impedance. It probably wouldn't take much attenuation to make an
appreciable improvement in the isolation. But this application might
not require a great deal of isolation anyway.
Roy Lewallen, W7EL
Just buy it and try it (a TV splitter will only cost a couple of
dollars). It will probably work more than well enough, even if the
isolation is well short of the (say) 25 to 30dB you might get under
'ideal' conditions. I wouldn't add any extra attenuation just to ensure
that the input port is matched better. You're already going to lose 3dB
+ just because you are splitting.
Ian.
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