L-Band antenna comparison. A thread.
A fun, 'typical use' setup for getting a feel for the SNR (signal to noise ratio) of a few different L-Band Inmarsat ACARS antennas.
98w. 4-F3 from Southern California.
Using the 10500 ACARS signal since its a contestant. QANTAS shirt approved.
L to R.
1/
Its a small GPS type puck with the filter removed to allow 1545MHz reception.
Inside is a small patch antenna with amplifier.
I always tells folks to put it on a paint tin lid or something like that to help with a ground plane. Tested here without as is the usual way.$15US
2/sdr-kits.net/L-Band-Receive…

tl;dr The dish has a little more gain than the helix.
Ok, so rushed home and unpacked the dish and feed.
The two key bits. The dish and (in my case) the L-Band #Inmarsat #ACARS feed.
Later home than I wanted, so failing light. If you want better photos just let me know.
1/
Both the dish and the feed are beautifully packed.
Really nice multi language instruction book with great photos and illustrations.
The feed had some nice swag in the form of some stickers to boot.
Really great unboxing experience. Top marks for the foam insets etc.
2/

I finally got the email that my #DiscoveryDish will be delivered on Wednesday, so I figured I'd better get ready to test it.
@ElbaSatGuy will also be (hopefully) doing the same test.
Turns out, I don't have one of my helix spare to test.
So, lets print one.
So far, so good.
1/
@ElbaSatGuy I decided to go with aluminum pizza pan this time around.
The copper tube needs to be 59 inches or 1.5m long.
Remember, thread the copper backwards out the main coil to keep the natural curve. Do NOT straighten it out.
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Warriding rig - a thread.
After my last rim-to-rim Grand Canyon run I told my son, no more long ass tough runs. Just short stuff (5miles). Also, I want to try electric longboarding to mix things up.
Random call with a mate, he offered to sell me his old one "the battery is a bit weak" cheap.
1/ Did about 15 rides, racked up about 30 miles pretty quick. Its waaay more fun than I thought it would be, but yeah, the battery was trash. About 2 to 5 miles depending on its mood.
The original is prismatic (pancake pillow), the remote sucked (bad trigger and connection issues)....
2/

A thread - "I'm out of my depth - Sorry the site is slow"
7ish years ago, I started with a single SDR and Raspberry Pi decoding PoA.
I'm pretty comfortable with RF, antennas, SDRs, coax, LNAs and some networking.
Where I get wobbly is putting the data on a website.
1/ I was already using Node-RED for 'stuff', so just added the first ACARS messages to the private website I already had running with it.
Then we added a few more CA/AZ feeders and the site went public.
During the Afghanistan Extraction, the site went viral and cratered.
2/

Building an L-Band computer:- A thread.
(Steps I took to replace the NUC with the dead SSD for 98w - No RF covered in this thread).
Raspberry Pi peaked with the 3, the 4 was okish, the 5 is junk so most #avgeeks have moved to MiniPC or NUC. Better value.
I like Beelink.

1/amazon.com/dp/B0CKMM2CT6 Plug in a screen, keyboard and mouse.
Press delete to get into the BIOS and change the boot order making the USB the first option.
Once you have things setup, you won't need the peripherals, its just to get the BIOS settings changed.
I don't dual boot. Not much ACARS software in Windows.
2/

Iridium update.
I'm going to try (and hopefully fail) and keep a lid on my excitement for this thread.

Because of the work on @thenewarea51 'AT1.' decode question it was very fresh in my mind as I was working on the site.
I noticed the same 'AT1.' ACARS messages on Iridium.
1/n @thenewarea51 It was a case of 'cant see the trees for the forest'.
The AT1. messages had been there since day zero, but it had not 'clicked' in anyone's minds eye what they were.
They are arinc622 encoded messages, just like in the VDL2 feeds.
libacars is the right tool to decode them.
2/n

Deep breath. Sorry up front if this is long and hard to follow. Consider it a work in progress. Input more than welcome.
@thenewarea51 asked (commented? complained? ) about the lack of .AT1. messages sent via VDL on the website 48 hour search.
I _love_ feedback like this. It was open ended enough that I felt compelled to dig in and understand what was being described.
1/n First up, TNA51 rightly makes the distinction between satcom and VDL AT1 ACARS. This is tightly coupled with the remark that "the most interesting traffic I find is from AT1 messages". 'Interesting' can be subjective, but regardless, lets stick to VHF vs satcom for a sec
2/n

For better or worse, I am going to 'live' X this.
Got the Middle East geofence ACARS limping.
So lets do this. Lets roll it out to the site in real time.
Here is the box. I had @GuardedDon help me position it, so if you don't like it, tag him! <grin> Right, so lets look at the @NodeRED flow that makes this work.
We get the aircraft every 10 minutes from an API call (via the yellow 'http request' node).
Then we have to split up the ADSB / ADSC aircraft into separate database calls. Then we look up each ICAO of what's inside the box.

Iridium Mega Thread.
Lets start by looking at a bit of history, what it is, how it works (very roughly) and then focus on ACARS via this 'new' mode. The original satellites had large antennas and reflected sunlight like crazy. Fun to watch for sure, but not something you want in the night sky.
The new satellites have reduced this 'flare' effect dramatically.