Homemade QFH Helix Antenna For NOAA Weather Satellites
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- เผยแพร่เมื่อ 11 ก.ย. 2024
- In this video I'm attempting to make a fancier antenna for listening to NOAA weather satellites. This is called a "Quadrifilar Helix" or QFH Antenna. These are supposed to be better than the simple V-Dipole that you can make out of metal rods or TV rabbit ears. However, I didn't notice a huge difference in image quality with this vs the dipole.
Some info on how to make these can be found at the links below:
www.instructab...
www.rish.kyoto-...
f4bpp.com/arti...
I made one of these antennas years ago and was able to decode a picture of the western United States, it was pretty cool.
3:02 "Wrap it around a few times" This isn't to do with matching, but it does form a crude BALUN. The antenna is balanced, the coax is unbalanced, connecting one to the other will generate unbalanced currents in the antenna as the elements will be influenced by the grounded coax jacket, but NOT the equal & opposite current flowing in the coax core. The 4 wraps of coax forms an inductor that helps reject unbalanced current flow.
I built a 137Mhz QFH antenna a few years ago. I can honestly say it worked really well until we had a big storm and it got trashed in the wind. They are a great antenna but you have to be pretty precise with your measurements.
This was the first one I built and it didn't do super well. I made a 2nd one that ended up better!
@@saveitforpartsdo you have a video of you making the second one?
I haven't built an QHF yet (though I've considered it), but I've heard from some people that construction quality, and getting the bends EXACTLY right is important for a QHF. I've heard that cross dipole antennas seem to be easier to construct and get the same SNR as an ideal QHF. I'll probably stick to a V-dipole for now as portability is more important for my setup.
Muito importante suas informações. Qual a melhor dipolo disponível para compra ?
I'd invest in a NanoVNA... even the cheapest original version for starters and learn how to use that and what the measurements relate to. Really neat to be able to tune antennas and things. Then you can verify a lot of details related to how well your antenna, feedline and connections are performing since each part can be like an antenna and have characteristics that effect performance.
I actually have one, still learning how to use it.
You know there is a reason it looks like a DNA "helix" chain! 👀👍
Literally in the process of working on my own right now. Waiting on cutters for copper tubing (doing that instead of wire) and my RG-59 coax. Thank you for sharing your experience with it, Dude. 😁
I ended up with a slightly different one that what's in this video, my current version is copper tubing and slightly shorter. The guide on usradioguy.com helped me a lot!
I might be wrong but I believe the RG59 has 75 ohm impedance. You might need to get an RG58 or even better RG8.
It would be cool if next time you made a police scanner out of junk.
Very fine job. Thank you from Belgium. Pat
FYI .. To get good results from Antennas you need to be Crazy Perfect The coax used in this project was H-100 Coax with a velocity factor of .84 this is equal to LMR-400 (Try Again)
using a LNA will help big time.. (Also a Broadcast FM Filter inline if you are near a Broadcast Tower) 73s
I ended up redoing this with copper tubing and an LNA, it works better now.
@@saveitforparts Good for you with the Re-build and glad to hear it's better.. Radio Hobby is fun (DX'ing) we feel like Spy's :)
It’s been 2 hours since you posted there’s 15 likes and........ wat!!! Why how when did someone dislike. Boo to them 😒
Could you have used a large pipe with the wires hot glued to the outside in a perfect spiral and thus way more accuracy?
Just asking but.
That could be something interesting to try!
Please try both antenna again with a SPF1589Z LNA it will improve pass signal Good Luck!
Maybe a silly question, but what difference would a linear amplifier make? Those are for transmitting, not receiving.
Technically it's a Low Noise Amplifier, although I may have called it a linear amplifier (sorry!). The SAWbird series are combined with a filter so it cuts out interference and boosts the gain of the desired frequency.
@@saveitforparts Ok, thanks for clarifying.
How do you find so many useful items? All I ever find is broken glass and road signs.
I have no idea... just an instinct for useful trash I guess!
@@saveitforparts mc giver effect hahah
Yes you need a crossed dipole array ie two dipoles on
On the one mount gives very strong signal reception cannot remember how you wire the harness for the aerial but i do remember using a potting compound to protect the connections and also stability of the aerial elements worked a treat for adjacent and over head passes i cannot remember the gain but provide great real time daylight and also infrared image passes
I ended up rebuilding this antenna with plumbing parts, and it works a little better now!
Something totally different: For a video where the speaker does not use a clip-on microphone, yours has excellent audio. What are you using?
I had been using a Google Pixel 3 phone, but apparently if you use them daily for video it wears out the camera module :-P Now I use a Sony digital Handycam. I think this video might have been a mixture of those two, I switched to the Sony recently after the Pixel kept flaking out.
@@saveitforparts thanks!
Perhaps you should use thicker wire or some aluminum flatbar
I'm considering re-doing with copper pipe if I can scrounge up some connectors.
I thought the QFH image shown was the better of the two?
It might be slightly better, after staring at a few examples I think the QFH does a little better job (or it did, I've been messing with it more after this video and it got way worse!)
I completely agree. You can use the calibration bands on the side to tell, the high quality section of the image extended quite a bit higher and lower on the QFH.
Do you need a ground with this type of antenna?
I'm not really sure. Supposedly for the V-dipole they work better either right on the ground or with ground plane wires underneath. For the QFH design I haven't found much info on that. Some people seem to use them on tall poles with no ground plane and some people have them right on the roof or in an attic.
Cool
It is upside down. Don't know if it matters
I ended up trashing this one and building one out of copper plumbing. The new one seems to work better.
@@saveitforparts i'm working on my 3rd one. First was ok but couldn't get it tuned above 135mhz. 2nd was at 405 mhz. Wth!
Finish 3rd tomorrow. All from
tubing
Enjoyed your video by the way.
Looking from teh bottom end of the antenna to the top, the twists should be clockwise, not counterclockwise.
@saveitforparts >>> Great video...👍
I've been wondering what the point of wrapping the whole coax around the pole is. If YOU can't figure it out, I'm now fully convinced it's just a cargo cult.
It RF isolates the coax screen from the antenna arm. on a V dipole it makes the antenna work as circular rather than horizontal.
@@joefish6091 Yes, I've since learned that it really is using non-ideal cable physics. Very cool hack
that is dont look close to a egg beater antenna for sat reciving
BTW, I just discovered NOAA-APT. It seems to work better than wxtoimg for decoding the recorded sigs. Downloadable as a .deb so it's easy to install under linux.
I've tried it on Windows and Linux but can't get it to do anything other than resample and change file dates. Can't get it to process at all.
@@saveitforparts I think there's a bug. I had the same, it sent through the motions but no image appeared. Then I went to the process tab and change the rotation once or twice and suddenly the image appeared.
Repeated this on several decodes. It's gotta be a bug.
I'll talk about it in the video I'm doing on it this week.
Você tem twitter bora pra lá ?
I'm Saveitforparts on Twitter, but I don't get on there much.