YAGI pruning/trimming for 978Mz

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.

It looks a lot like this one:
http://s24.postimg.org/9b8rh2c8l/image.jpg

What about 1090Mhz? Would that be asking too much?

Thanks

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.

Parrot:~$ cat /proc/6052/fd/0
+2f46e3804828a4d0020f08a367561180002144e6f082102d5 501000615a60a012d5501000000000000000f0900bfc0c3154 4001580002144e83882102cd14900082f171e012cd14900000 0000000000fd9000813140709121600c0e342dfc0001580002 143c25882102d455000082eee1e012d4550000000000000000 fd900080f010b081e000bc0e0030bcc001580002143eb30821 02cd14900082ef91e012cd149000000000000000fd900080f1 526081e1526c0e342dfc0001580002144a4c882102cdd30000 830791e012cdd30000000000000000fd900081212190902121 7c1130302d000200006745d405011a02c6054832cf2cf2c1a8 32d30c2fcb4cb4833cb0c382d4810d933604c3532d7079c146 372d31d30c205920b0d0b5204364cd8130d4cb5c3d79d33800 67403503455014a040838c832d30c35cda831d70c712d4831c 133601855f0cf28130d4c34ce04c3530db58022cec73c2008b 3b2c7081e70408b3b2cb0833c6fcb6801cb9e3581234b8013f 2813310c70e205834c880e5ed3ad385b45814c33c36c32d76f 5e740000000000000000000000000000000000000000000000 000000000000000;rs=16;
+2f46e3804828b4d03b00067438505c93844e04063a0cb3c78 c306a0806520cf0c30836c30c1c1b9c30c1c0f1cb0c30707c7 8c30c1c0f2d30c30703cf0c30c1c133d30c30820cf9c30c1c6 5e703cf3c36833cf1c6bc77833cf1cabc71833c31cebc36832 e32cedc36832d71cedc76832cf1c73c60cb0c72d32832c72c3 5c9e7403b00067438505c93844e0243520cb3c78c306a08065 20cf0c30836c30c1c1b9c30c1c0f1cb0c30707c78c30c1c0f2 d30c30703cf0c30c1c133d30c30820cf9c30c1c65e703cf6c7 6833cf0e2bc76833c70d6bc73832e32d6bc39832e33c6dc388 33c33cadc79832e33d33d20cb7cf7d35832e33d75d1e7403b0 0067438505c93844e0235ca0cb3c78c306a0806520cf0c3083 6c30c1c1b9c30c1c0f1cb0c30707c78c30c1c0f2d30c30703c f0c30c1c133d30c30820cf9c30c1c65e703c34c38839e70c2b c77839e70c2bc72839e70c2bc37830e71c2dc36830df0e6dc7 7831cb0db3ce0c77c70d33831df1cb5d1e7400000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 000000000000000;rs=20;
+2f46e3804828b5d03b00067438505c93844e00cc160cb3c78 c306a0806520cf0c30836c30c1c1b9c30c1c0f1cb0c30707c7 8c30c1c0f2d30c30703cf0c30c1c133d30c30820cf9c30c1c6 5e703cb1c39832cf1cebc73832d71e6bc39832d32c2bc33832 d72c6dc39832df2dedc79832db4cf3d20cb7d38d34832e77d3 5d5e7403b00067438505c93844e0351520cb3c78c306a08065 20cf0c30836c30c1c1b9c30c1c0f1cb0c30707c78c30c1c0f2 d30c30703cf0c30c1c133d30c30820cf9c30c1c65e703cb0cb 2832cb3cabc38832c34c6bc34832c33e6bc30832c73dedc718 32c72dadcb5831e74d74ca0cb0d35d35832cb3df4dde7403b0 0067438505c93844e01d20a0cb3c78c306a0806520cf0c3083 6c30c1c1b9c30c1c0f1cb0c30707c78c30c1c0f2d30c30703c f0c30c1c133d30c30820cf9c30c1c65e703cb5cb3832d33ceb c38832cf3debc35832cf3e2bc32832cf4c6dc72832cb3dedcb 5832db6cf3e20cb6db2d35832d75d74e5e7400000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 000000000000000;rs=17;
+2f46e3804828aed0000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 000000000000000;rs=12;
+2f46e3804828bed0000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 000000000000000;rs=6;
+2f46e3804828b7d0000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000 000000000000000;rs=15

Some simple decoded signals.
INFORMATION FRAME:
Length: 78 bytes
Type: 0 (FIS-B APDU)
FIS-B:
Flags:
Product ID: 413 (Generic Textual Data Product APDU Payload Format Type 2) - Text (DLAC)
Product time: 00:53
Report type: METAR
Report location: KMCN
Report time: 240053Z
Text:
AUTO 13004KT 10SM SCT065 BKN080 24/23 A2994 RMK
AO2 SLP133 T02440233 TSNO=

INFORMATION FRAME:
Length: 118 bytes
Type: 0 (FIS-B APDU)
FIS-B:
Flags:
Product ID: 413 (Generic Textual Data Product APDU Payload Format Type 2) - Text (DLAC)
Product time: 14:05
Report type: WINDS
Report location: OMA
Report time: 231800Z
Text:
FT 3000 6000 9000 12000 18000 24000 30000 34000 39000
2918 3022+09 3132+07 3042+05 2945-08 2955-20 297136 297746 297256

INFORMATION FRAME:
Length: 118 bytes
Type: 0 (FIS-B APDU)
FIS-B:
Flags:
Product ID: 413 (Generic Textual Data Product APDU Payload Format Type 2) - Text (DLAC)
Product time: 14:05
Report type: WINDS
Report location: AGC
Report time: 231800Z
Text:
FT 3000 6000 9000 12000 18000 24000 30000 34000 39000
9900 2312+13 2613+11 2618+04 2422-09 2628-19 303734 314543 326554

INFORMATION FRAME:
Length: 118 bytes
Type: 0 (FIS-B APDU)
FIS-B:
Flags:
Product ID: 413 (Generic Textual Data Product APDU Payload Format Type 2) - Text (DLAC)
Product time: 14:05
Report type: WINDS
Report location: BDL
Report time: 231800Z
Text:
FT 3000 6000 9000 12000 18000 24000 30000 34000 39000
1006 1306+12 1713+07 1908+05 2514-09 2619-21 272637 283746 282452

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.

Thank you for taking time to reply.

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.

I have received some interesting traffic from over 400 miles away, relayed via the local uplink:
http://s8.postimg.org/3jqk9h4l1/Screenshot_25.png

Sorry to break in here. I am a Linux novice but did get Dump1090 up and running well on a RPi with a outside collinear antenna. Now I am trying to get UAT via Dump978 on another RPi. I am not having too much luck… Did I say I am a novice?

Does anyone know of any pre build RPi-2 disc images with Dump978 installed and running? I would like output via IP Port similar to Dump1090.

Any advise or help would be greatly appreciated!

TIA,

Steve
West Tennessee