Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar)

Tim Shoppa tshoppa at
Fri Mar 4 09:59:34 EST 2016

The RDF seems to be the best we have at the moment, for taking a
3-dimensional pattern and turning it into a single number. Of course the
details of the 3-dimensional pattern are lost.

In addition to the quantitative RDF or S/N numbers, the qualitative change
in pattern as you move up the RDF is remarkable. We go from

* no directivity
* a null in back with not much differentiation between forward and side
* increasing side rejection
* near-complete side rejection
* increasing rejection of directions near forward but not quite forward

The 8-circle is mind-blowing.

Tim N3QE

On Fri, Mar 4, 2016 at 12:37 AM, Richard (Rick) Karlquist <
richard at> wrote:

> In this webinar, it was asserted (without explanation) that
> for every 1 dB increase in RDF, you get 1.5 to 2.0 dB
> improvement in S/N ratio.  I've never heard that before
> and don't even see how it makes sense.  Actually, I don't
> even know how you can make generalizations like that
> unless you are describing a theoretical QTH with uniform
> isotropic noise.  I'd like to believe this is true.
> Can someone educate me as to why I should believe this?
> Rick N6RK
> _________________
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