So after a week of rain, then realizing I had the wrong sized mounting brackets. My ADSB co-linear is back in the air. I’ve moved it about two meters along the side of the roof to the other side of the HF antenna to facilitate hooking up to the new lightning arrestor.
I’ve updated to Dump1090-Mutability over the normal Dump1090 supplied with the standard PiAware image as well.
In the theme of things in short supply, I’ve now run out of F-type compression connectors to plug my AIS antenna into the lightning arrestor 🙁
So the PiAware I operate has a problem: It isn’t uploading data! But in a weird way, it is. The receiver can still be accessed via port 30003 (Basestation format), this is the data stream that I scrape to operate the “Airplanes Nearby” widget to the right of this article. Normally this problem would require me to log into SSH and reboot it or go and unplug it. But this time its different, because while it is uploading data, SSH is inoperable and physically power cycling the device does not alter its behaviour. As you can see from the image, my housing isn’t very maintenance-friendly. So its time to upgrade.
I’m starting to build a Lindenbald antenna. Starting out I’ve cut up some 1″ wide 25ft SAE tape measures from a Canadian Tire sale into four 78″ sections, and folding them like my AIS antenna into four folded dipoles centered approximately on 151MHz, why the odd frequency? NOAA sats are on 137MHz and AMSATs are in the 145MHz range? Well we are relying on the wide bandwidth afforded to us by large conductive surfaces and the folded dipole design.
The other benefit of using folded dipoles in this fashion is their high impedance of ~300ohms, we will be feeding all four elements in parallel with 1/4 wave (at 137MHz) twin lead (again 300ohms) to a single point giving us an impedance of 75ohms which is trivial to deal with from a receiver or transceiver point of view. I’m going to be hooking the twinlead up to some 1/8″ heliax because I got loads of it (and 1/2″ heliax) at the BARC 2016 Hamfest. You can also just as easily put a chassis connector at the deadline at this point for more modularity but that’s up to you.
Here is a quick and dirty guide to making a pretty decent receiving antenna.
It looks pretty decent tbh.