[amsat-bb] Re: T adapters and Elk Antennas for HTs?

["Pieter Ibelings" <sietetrescincoprimo@xxxxxxxxxxx>]

Using T adapters to connect the two sides of an arrow antenna is not 
recommended. For certain impedances and cable lengths, you could have 
extremely bad SWRs. You could also end up having non optimal patterns and 
polarization. The proper way of connecting two antennas of different bands 
is using a diplex filter.
There is a way that a diplex filter used with an arrow and an HT can help 
your desense. Antennas can create distortions in their metal to metal 
junctions (even at 5 watts). If you use a diplex filter to combine both 
antennas in an arrow, the distortions created by the 145 MHz transmitter 
will not be able to get back to the radio through the low pass side of the 
diplexer. It is true that the 435 side antenna will capture some of that 
harmonic energy, but the fact that they are 90º spatially will minimize it.

On the ELK antenna, any distortions produced in the antenna with be "common 
path distortion" (CPD). There will be no way to filter these because they 
occur in a common path to both the 145 and 435 sides.

Pieter
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Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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