SatNOGS part III – the QFH antenna

And so begins the bitter sweet tale of Merv’s QFH antenna build … hang on in there until the end to find out why. By the way, I am in no way an expert in any of this. I am a complete noob so please feel free to leave a message if I’m talking rubbish anywhere in the post and I’ll get it corrected.

As you’d expect, there is a ton of useful info on the SatNOGS wiki pages. I’d recommend hitting the first menu option at the top of the page for their Build articles.

After a few observations of various satellite passes and delving into the SatNOGS forums to get a better understanding of what’s what I decided it would be interesting to capture the transmissions of the NOAA weather satellites. They are polar orbiting and pass North-South which fits in nicely with my urban location so I started searching for a suitable stationary antenna design (as opposed to a tracking antenna which is basically controlled by motors such that it can follow the satellite as it travels across the sky … this could be one for the wish list!). The design that kept appearing in my searches was the QFH or Quadrifilar Helix antenna … basically it promised excellent horizon to horizon gain (where you need it most as the distance from satellite to antenna is at its greatest) and minimal signal loss vertically (when the satellite is overhead and at its closest).

After much reading I plumped for the design from this site … disclaimer, without wanting to reveal the outcome of this endeavour, in no way am I laying blame at the doorstep of this website and the design contained therein!

And there it was, standing proudly atop my recently acquired aluminium mast waiting to receive it’s first signals from space. It even survived storm Ciara …

Despite all the effort I put in to produce what I thought at the time was a pretty awesome antenna it never received a thing, bupkis, nada, zero, zilch … empty waterfalls all the way! Early into my investigations of what might have gone wrong I discovered I’d wired the elements out of phase which meant rotating the wire connectors in the top of the antenna tube by 90° … fiddly but simple enough. Great excitement preceded great … disappointment as it still refused to work.

I spent a couple of weeks on and off trying to get to the bottom of the issue, trawling the Libre Space (and other) forums, checking continuity in the antenna, running various tests which had to be on a Linux machine (yet another challenge for someone who’s spent most of his working life supporting Windows!). It just wasn’t to be and the antenna is now sitting up in the roof space of my garage waiting for me to decide what to do with it. I invested a lot of time in the build and I’m loath to scrap it so I might come back to it when time allows.

In the meantime, the story isn’t quite over. Hang on in there for SatNOGS part IV – Return of the Satellite Signal … coming to a screen near you soon!

SatNOGS part I – An Introduction

A while back I wrote a post about my ADS-B setup for tracking aircraft. Around the same time I’d read that it was possible to track and receive signals from satellites but I’d thought it must be far too complicated & involved to do such a thing … until I received my copy of issue 18 of HackSpace magazine that is!

For anyone interested in further reading I’d recommend following the link above and downloading the free PDF file so you can read up a little more on the background to SatNOGS and more detailed information on what is required to setup your own ground station …

  • Information on the Libre Space Foundation which grew from the SatNOGS project can be found on pages 46 & 47
  • If you should feel the urge to create and launch your own small satellite, check out pages 36 – 41
  • How to build a SatNOGS ground station is outlined in pages 42 – 45
  • Making a slim jim antenna (my own experiences will follow in the next post) is described on pages 110 & 111
A little tease, my SatNOGS setup (top) and my PiAware ADS-B setup (bottom)