I have acquired for cheap antenna of the YAGI design, that was designed for 806 to 906Mhz.
It has 7 elements, five directors, one reflected, and one folded dipole.
Some basic info.
There is a UAT uplink 17miles fro me. (or maybe 7 miles, for the beacon gives a location away from the airport, but DUMP978 says (possibility invalid) I can get a signal, if I do some fancy pointing, but I was thinking of trimming down a cheep YAGI.
From first director to reflector, the distance is 43CM long (430mm) . The reflector is 165mm. Spacing of the five deflectors are 73mm apart.
The first deflector is 110mm. The rest of the deflectors I can not tell if they grow in length, or not. If they do, not more than a mm or two.
Doe anyone have suggestions about making it more suited on 978Mhz. Changing the spacing is not easy, but shorting the directors is doable.
Well, even without turning, I am aimed the antenna around until I could get a signal from the closest UAT:
I am not sure if the ‘rs’ number are an indication of the number of errors in the signal. That is, the lower the number, the better the signal.
The ULAT’s beacon reports a location that dump987 says is (possibly invalid), which would place it off the airport this station is supposed to be at by around 8 miles. Using Google’s satellite view on that location, show a very tall antenna right off the interstate.
Has anyone else seen their UATs off airport property?
But, dump978 is working for me. This was my old R820T (black—first release) dongle plugged into my Chromebook that was converted to Ubuntu Linux.
The “rs” number is the number of errors corrected by the Reed-Solomon forward error correction used in UAT - so yes, higher numbers mean a worse signal. There is a limit to the number of errors that can be corrected.
The “possibly invalid” thing on the site location is because according to the specs I implemented from, there’s a validity flag that should be set when location information is included. But that flag never seems to be set even when a valid lat/lon are there. Maybe I used an out of date spec. The site location is generally the transmitter location not necessarily the airport/radar location, so if there’s a big antenna there that sounds right.
My limited understanding of yagis is that both the spacing and the element length are frequency dependent, so I’m not sure how much tuning is possible without changing the spacing.
As it stands, I am not going to tune it, or if I do I will just try removing some length from the directors. (based on the suggestion on using a ratio from the center freq.) This antenna is indoors, and pointed at the general location of the UAT uplink. So, given the lower "Redd-Solomon’ numbers, I think I am doing just fine. http://s27.postimg.org/vcdvi63yr/yagi.jpg
I have not figured out Nexrad decoding yet. They come out shifted:
http://s28.postimg.org/hmy6g9hvx/nexrad_Regional_22_35.png I have not looked at ‘C’ in years, but I do see that there is a lot of information online for UAT links. If I had the ability, I would just try to emulate a device like SkyRadar, and use their app for decoding. For without a valid subscription, SkyRadar APP will operate as normal, but will only display airports with runways longer than 8000 feet. I could pick up the weather, and other stuff.
