[TowerTalk] 435 MHz QFH antenna for ham radio satellites

[Jim Lux]

These QFHs are great for LEO satellites in general, because they can be designed to have more gain at the horizon and less and less as you get close to zenith, so you have about the same link properties during the contact period.

You see them on lots of fishing boats and the like (for 137 MHz), and, for instance, the recent Mars rovers (Curiosity and Perseverance) - there's a Quad Helix a bit larger than a 3lb coffee can for the 400 MHz link to the orbiters.  (That particular application has some tricky aspects, not the least of which is that the low air pressure on Mars means you need to be careful about corona discharge, even at 10 Watts - you have to worry with a monopole.  The MER rovers had a monopole at 12W

https://descanso.jpl.nasa.gov/DPSummary/Descanso14_MSL_Telecom.pdf. has some nice antenna patterns (including modeling all the stuff around it)



On Sun, 11 May 2025 14:31:20 -0700, David Gilbert <ab7echo at gmail.com> wrote:

If your looking for a mostly foolproof construction for a homebrew 435
MHz satellite antenna and have access to a 3D printer, you might check
this out.  It's a weak choice for general 70 cm terrestrial use, but
I've had good results on it for various satellite passes that require a
high elevation pattern.  It can't compete with crossed yagis and an
az/el rotator, but it is an easy and inexpensive way to get started.

https://youtu.be/AMrPPIv-bcs

My video and narrative skills are clumsy so please take that into
account if you watch it.

Dave   AB7E


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