On 2020-08-05 01:13:50 +0000, Hackaday via rec.radio.amateur.moderated
Admin said:

amateur radio - Hackaday

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A Hybrid Helical Antenna for the Eshail-2 Geosynchronous Repeater

Posted: 04 Aug 2020 07:00 PM PDT https://hackaday.com/2020/08/04/a-hybrid-helical-antenna-for-the-eshail-2-geosynchronous-repeater/

Amateur radio operators like to say that working a contact in space can
be done with a simple handheld transceiver and a homemade antenna. And
while thats true, its true only for low Earth orbit satellites such as
the ISS. If you want to reach a satellite in geosynchronous orbit itll
take a little more effort, and this dual-feed helical ice cream cone
antenna could really help.

Until recently, the dream of an amateur radio repeater in
geosynchronous orbit remained out of reach, but that changed with the
launch of the Qatari satellite Eshail-2 last year. Since then, hams
from Brazil to Thailand have been using the repeater, and UK-based
[Tech Minds] has been in the thick of the action. The antenna he
presents is a hybrid design, needed because of the 2.4-GHz band uplink
and 10-GHz downlink on the satellite, also known as QO-100. Both
require a largish dish antenna, with the downlink requiring a low-noise
block downconverter (LNB) and feed horn. The uplink side of [Tech
Minds] antenna is a helical design, with three-and-a-half turns of
heavy copper wire and a tuning section of copper strapping that
attaches directly to an N-type connector. The helix is just the right
size for the feed horn of an LNB for the downlink side, nestled in a
hole in the helical antennas aluminum reflector disc. There are
3D-printed parts to support everything, plus a cone-shaped radome to
keep it all safe from the elements.

It looks like a great design, but sadly, North American and East Asian
hams can only dream about building one, since QO-100 is below the
horizon for us. Were jealous, but were still glad the repeater is up
there. Check out this article for more on how Eshail-2 got the first geosynchronous ham repeater.

One of the coolest hacks on Hackaday in years! Thank you for posting this

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