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Re: Question "nesting Helix antennas"



Here is one thing to watch out for when using a S-band helix:

If you look at a helix, it bears a curious resemblance to a helically
loaded ground-plane dipole antenna.  In fact, it will probably
resonate somewhere in the VHF range.  If you are unlucky, there may be
some strong signal source at this frequency that might cause an overload problem
with your S-band preamp.  Most, but not all, preamps will have an input
network that acts as a high-pass filter and reduces the problem.
But if you hear voices on your S-band setup, you might suspect
VHF overload...

One advantage of an antenna like a loop Yagi, or a dish with a horn or
"coffee can" style feed, is that it will have very little response to
frequencies below the design frequency.

Doug
NA1DB

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