AREG’s New 160m/80m Contesting Portable Antenna – Progress

Update – July 12th: Mounting of the tuning capacitor and motor drive is complete. Just a few more things and we will be ready for final assembly and tune up!

A group of members inside AREG, inspired by Steve VK5SFA’s success with his transmitting magnetic loop antennas have banded together to construct for the club it’s own 160/80m TMLA, specifically designed to be portable. It is able to be knocked down into components that can be packed into the back of a station wagon.

Significant progress was made today in assembling the antenna as we had hoped to have it ready to try at the IARU HF contest next weekend. We didn’t quite make it unfortunately, running out of daylight before we completed construction. However, we are now planning another session next weekend with the goal being to have the antenna finished and ready to run for the Trans Tasman Low Band Challenge contest the following weekend.

The club’s version of Steve’s antenna is using LCF78 coax instead of the wave-guide, with the vacuum capacitor mounted inside a water proof ex-camera case (great for transport and moisture proofing). The frame is made out of laminated bamboo broomsticks and a timber hub arrangement with the frame held together through compression provided by 8 ratchet straps. The aim is for the antenna to be suspended from a tree (or trees) at least 1 loop diameter above the ground (to increase it’s efficiency). It has been designed to accept 400W input power as well to overcome the efficiency issues these antennas can have.

Today’s construction efforts were led by Steve VK5SFA, Grant VK5GR and Scott VK5TST. The project wouldnt have been possible without generous donations from Steve VK5SFA, Peter VK5KX and Trevor VK5YFR.

The next steps are to complete mounting the motor tuning drive, do some structural adjustments to the frame, assemble the coupling loop and then test the antenna. This work will be completed next weekend, so keep an ear out for us during the TTLBC Contest on July 15th on 160 and 80m using our Transmitting Magnetic Loop Antennas!

Next Meeting: Transmitting Magnetic Loop Antennas for 160-40m

The AREG is pleased to announce that our guest speakers for our next regular monthly meeting will be Steve Adler VK5SFA, Leigh Turner VK5KLT and Paul Lawson VK5SL. They will be talking about their work on Transmitting Magnetic Loop Antennas for the lower HF bands including both the theory and practical aspects of their operation and construction.


VK5SFA 160-75m Transmitting Magnetic Loop Antenna

Steve has been using one very successfully on 160m and was kind enough to loan the AREG SPDX RTTY contest team his 40m one for use up at Morialta this past weekend.


VK5SFA 40m TMLA (used by AREG in the SPDX RTTY Contest)

These are fascinating antennas in the way they work and in the way they perform. Their noise immunity is something in particular to consider in urban environments where amateurs are space and electrically environmentally challenged.

Full details of how to build these antennas and the theory behind them are available via Steve VK5SFA’s website.

When and Where?

You can meet Steve and the team who designed and built them in person at our next meeting on Friday May 20th, starting at 7.45pm (for an 8.00pm start). You can find details of where the AREG meet on the contacts page.

Visitors are most welcome to come along! A short business meeting will be held after the presentation.