144 and 432 MHz mixed mode helix antennas

144 MHz prototype helix antenna

144 MHz prototype helix antenna

You can use the free SUWS Web Software Defined Radio (WebSDR) via your PC or Laptop to receive the International Space Station (ISS) and the many amateur radio satellites transmitting in the 145.800 – 146.000 MHz band.

Martin Ehrenfried G8JNJ has equipped the SUWS WebSDR with omni-direction helix antennas for both 144 and 432 MHz which have proved effective for high altitude balloon and satellite reception.

Listen to the SUWS WebSDR at http://websdr.suws.org.uk/

Martin says “I had been experimenting with single turn ‘twisted halo’ design, and decided to try stacking them to see if I could achieve more gain. Modelling suggested that a stretched 3 turn helix with a helix circumference of approx 1/2 wave length and an overall length of 1/2 wave at 70cm, and fed with a gamma match at the centre would offer reasonable gain, an omni-directional pattern and mixed polarisation.”

Full details of the antennas are available at
http://g8jnj.webs.com/currentprojects.htm

WebSDR for 144, 432, 1296 and 10368 MHz
https://amsat-uk.org/2013/12/28/websdr-for-434-and-1296-mhz/