Topband: It is not so much propagation

[N4IS]

"If I had room for 160m RX arrays"

Hi Steve

Congratulations for 1/7 acre you are a winner QRM fighter. May be you have
room, one issue with RX arrays is how to reduce the noise and increase the
signal noise ratio, the only answer is RDF or directivity. The second and
common unknown issue is the interaction between the RX antenna and the
resonant TX antenna, it means you don't have two antennas, you have an
antenna system with several elements. The only answer for that is identify
the elements and neutralize the coupling between them.

The TX antenna must be neutralized during RX, the house wiring isolated by
common mode chokes, the ground connection with no loops. Any wire coming
into the radio must have a choke, including rotor cables. 

When all elements are isolated them you can say you have a RX antenna and
the signal you hear comes from the RX antenna where you are using the RDF to
increase signal noise ratio. 

Every single detail adds up , like grounding, magnetic isolation of the
preamplifier, good quality connectors and more important, avoid common mode
noise.

The single flag RX antenna has 9 db RDF and can be small as 6 ft. wide by 12
ft. high, a dual flag or Waller Flag has 11.5 db and can be small as 4
elements bean for 15m, 24ft boom and 20ft elements. However if you don't
clean all interaction the RDF will deteriorate to 3 or 4 db and you won't
see any signal noise improvement comparing with the TX antenna. 

Larry W8VVG build a successful Waller Flag with 24 ft. boom. KD9SV is
developing a new low noise preamp that is very quiet and has high gain.
George  AA7JV  is working on a new small Flag with dual feed point. 

There is several solutions for small RX antennas but they requires big
effort to be implemented. It means lots of good projects to work during
spring and summer  time.

Dr. Dallas developed a QDFA, it is a quad flag array that can be optimized
to 150ft and can delivery up to 14.5 db RDB with 25 db F/B , it is narrow as
54 degree, narrow lobe like a good 5 elements beam.

The Hi-z 8 cycle array can delivery 13.2 db RDF w/ 150ft diameter, and 13.5
with 200ft diameter array, and 8 switchable directions.

My point is that we are just at the beginning of a new generation of high
efficient RX antennas with small foot print. I am not saying that is easy,
it's very demanding and complex but doable. 

Regards
Carlos
N4IS