Brian,
How about one vertical antenna on one RX and one horizontal antenna on a 2nd
RX, with the two signals combined in diversity mode? My K3 can do that.
73,
Steve
N6SJ
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of Brian
Beezley
Sent: Wednesday, August 13, 2025 4:47 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Circularly Polarized Receive Antenna
Fading can be a problem on 160. When it is due to polarization rotation of
the incoming signal, a circularly polarized receive antenna can eliminate
it. An elliptically polarized antenna can reduce it. I'll call both CP.
I describe a CP antenna for 20 meters here:
https://www.eham.net/community/smf/index.php?topic=143601.0
A compact CP antenna for 160 can use the same principle but with a tuned
loop replacing the dipole. I modeled an untuned square loop 3 feet on a
side. Optimizing for minimum axial ratio at 20 degrees elevation angle
yielded an antenna center height of about 71 feet and a loop tilt of about
23 degrees.
Geometry image (height above the X-Y ground plane not to scale):
https://i.postimg.cc/QN4dtMZd/geom.png
Axial ratio plot:
https://i.postimg.cc/6pQSQ9wt/cp.png
For this model I used Hagn generic ground constants for pastoral ground at
1.8 MHz (permittivity = 20, conductivity = 3.6 mS/m). Constants for other
ground types are here:
https://k6sti.neocities.org/hfgc.htm
I don't know whether this idea has merit. Fading on 160 may be mostly due to
factors other than polarization rotation. A tower supporting the loop may
interfere, as may other nearby antennas. It may be difficult to adequately
decouple the loop feedline. Your local ground constants might be quite
different than those you model.
I haven't operated on 160 for many years. But I recall the frustration of
waiting for a callsign during a slow fade only to have it disappear into the
noise. Maybe this antenna can help.
Brian
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|
