QFH Antenna for 137MHz NOAA Satellite Reception

Fancy 3D Printed Quadrifilar Helix Antenna.. it's GREEN!


I decided that I needed a QFH antenna because my reception of NOAA satellites is less-than-stellar (I have yet to obtain a clear weather picture... just bits and pieces).  I currently have a dipole mounted horizontally (which should work), but I think that I just have too many obstructions around that interfere with the satellite transmissions.  This will be an exercise in 3D printing and learning some basics about how to build a QFH antenna tuned to around 137Mhz.  
QFH Antenna for 137MHz NOAA Satellite Reception
Status: In Progress
Updated: March 12th 2020

Tagged: NOAA, RTL-SDR, Satellite


Here is the current hardware that I have set up.  The only part needed from this list is the second one, the dongle:

  • HackRF (20Mhz Bandwidth)
  • Standard RTL-SDR dongle (2Mhz Bandwidth)
  • Cheap LNA #1 (seems to do something) 
  • Cheap LNA #2 (seems to do nothing)
  • FM Bandstop Filter (NooElec Distill FM)
  • Horizontal Dipole 
  • Long Wire Antenna

I would have thought that I would get at least *something* usable with the dipole… but nope.  I can see the satellite transmit signal, heck I can even hear it – but it seems the S/N ratio is too low to get a good image.  What to do? 

Build a QFH antenna, of course!  And finally get some decent NOAA weather images.  That’s the goal, anyway.


Project Log

March 12th, 2020
Overdue Update
Here are some more details on the design of the antenna. The smaller, second element: And... here are the choke calculations (Word format):   Choke_Calcs   Wiring diagram at the top of the antenna:   Wiring I didn't have a PCB, so I just used copper wire snippets to solder it together.
January 30th, 2020
The Beginning
Ok, so I cheated and I've already completed some of the antenna (notice that I posted a pretty finished looking antenna as the featured image!)... But I think I will rewind and start from the beginning for any other people out there that want to do the same thing. The items you'll need along the way:
  1. A 3D printer or a service that prints 3D stuff (you do not need a 3D printer at all to make a similar antenna, just in this specific project you do).  
  2. Some 2mm diameter copper wire.  You will need less than 5m total; I'd go for 5m to be safe (in my case, it came in a 10m roll for 10€).  I used something that is usually used as a "ground" type wire here in Germany - single strand solid copper, not multiple strands - and I had to strip the outer casing off.  If you want to use a different diameter wire, then you'll have to re-calculate some things and modify the 3D printer files accordingly.  More on that later.  Also:  I have read that coax cable is often used, but this is my first one so I am going with what I found.
  3. Some type of wire that will connect your SDR device to the antenna.  I used RG-58 with a female SMA connector on the end that will come out of the antenna.  You'll need somewhere around 1.5m at least if my eyeball calculations are correct (I might update this later if I am wrong).  I used RG-58 because that is what I had, and it is 50Ω  (<--wat, I can just cut and paste Greek willy-nilly?) which matches my receivers and I've heard that is important.  Some of the wire will be used for an open-air Balun tuned for a resonance at 137Mhz (more on that later).  The type of wire you use for this is up to you.  The diameter will change the Balun calculations later on, but don't worry about that.
  4. A SDR of some type, plus the software that makes it go.  I'll write more about this - but if you have a $15 RTL-SDR dongle, you should be in good shape and probably already know how to use it. 
  5. A soldering iron and some solder.  Optional: a piece of copper-clad PCB around 1.25" in diameter or a square or whatever shape.  The exact shape is not important, as you will see later, so don't worry about that quite yet (you don't even need this part).  Notice how I am mixing imperial (inches) and metric here?  It will only get worse.  I guess the $ and € mixture doesn't help, either.
  6. Epoxy (glue) to put the 3D printed parts together.  I used a 2-part epoxy (meaning you mix two different components to activate the epoxy, and then apply it).  In addition I added some support rings to make the whole thing stiffer than the original 3D project, which I'll provide a .stl file for later.  An open window for ventilation might be a good idea when mixing the epoxy components, too.
If you really want to skimp or possibly make your life easier, you can use PVC pipes and print much less than this project requires - that is a great approach as well.  There are other 3D QFH projects that take this approach.  However, this project might take away some of the uncertainty of the measurements and give you more time to wrestle with the more mundane parts of the project - like putting it all together and stuff.