The antenna has a 50-ohm designed driver. The Yagi has a unique element called a ‘Open Sleeve’ which is a director very close to the driven element. The driven element is sized for 2M. When operating on 70cm the ‘Open Sleeve’ acts as part of the driven element on 70cm (Third harmonic of 2M).
The original concept was developed in 1946 by Dr J T Bolljahn of the Stanford Research institute but was not introduced into amateur radio until the 1950s. The AMSAT SA version is based on a design by DK7ZB with modifications by WB5CXC.
The first South African version was a collaboration between Guy Eales ZS6GUY and Dr Gary Immelman ZS6YI. It was developed for YOTA 2018 where young people successfully used the antenna operating satellites using hand-held transceivers.
The mechanical structure was redesigned by Dr Gary Immelmann ZS6YI. A choke around the boom was added to isolate the antenna from the coax and reduce the effect human contact has on the antenna. A handle was added on the boom end which makes it more comfortable to hold and further isolates the antenna from the handler. The AMSAT SA yagi is manufactured in one of his factories in Vereeniging. It has two elements on 145 MHz and 3 elements on 435 MHz.
For its size the antenna has excellent gain:
145 MHZ: 4.12 dBd or 6.3 dBi
435 MHz: 6.23 dBd or 8.4 dBi
The Yagi is broadband with measured SWR as follows and almost flat over the entire bands
145.800 SWR 1.1
435.000 SWR 1.12
The antenna is plug and play. No tools are needed except for soldering on a connector to suit the application. It comes complete in a carry bag with full instructions. This antenna can be assembled and dissembled in minutes.
The cost
AMSAT SA and SARL members:
R250.00 plus packing and courier charges.
Non-members:
R350 plus packing and courier charges
Packaging and courier charges:
Postnet – Postnet R120.00
Postnet to home delivery R230.00 (main regional town) Smaller towns courier charge on request.
To order click here for the order form. All orders must be prepaid by EFT. No cash transactions are available.
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