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# How to build an L-Band ground station.

Navigation: [home](README.md)

Quick Links on this page:
[Frequency List][l1]
[SDR Selection][s1]

Tip: Right click images and open in new tab for full resolution.

The easiest way to get started with satcom ACARS is to build an L-Band setup.
The clasic AERO ACARS L-Band data can be found around 1.5GHz and the signal footprint from each Inmarsat is broad enough that you do not require any antenna tracking. Simply point it at the middle of the satellite orbit and you can start receiving the signal and decoding ACARS messages.
To see what Inmarsat satellite(s) are over your location, review the [Inmarsat](Inmarsat.md) page.
Expand Down Expand Up @@ -132,22 +130,23 @@ And I know the real world uses mm, so here it is (since I also know people don't
<img src="https://raw.githubusercontent.com/thebaldgeek/thebaldgeek.github.io/main/img/helixinmm.png" height="320">

Even my wife understood that I needed something the size of the 3D print and the exact tube brand to form the coper on did not matter at all, so yeah, just find a tube the size of the holes on the 3D print and pre-form the coper to that size.
When you do that, its very low friction to just wind the coper onto the formwork, there is very littls stress or effort and your print wont break.
When you do that, its very low friction to just wind the coper onto the formwork, there is very little stress or effort and your print wont break.

Once you preform the copper to the right size, you can then wind it on the framework very smoothly.
Just work it up the 3D framework slowly, inching it from the top, middle and bottom to keep the tension even all the way up the formwork.

<img src="https://raw.githubusercontent.com/thebaldgeek/thebaldgeek.github.io/main/img/lbandpreformcopper.png" height="460">

For the feed, you don't have to, but I used a small round file to get the coper end nice and snug to the SMA post.
For the feed, you don't have to, but I used a small round file to get the coper end nice and snug to the SMA post before I heat the copper first, then solder the SMA center pin.

<img src="https://raw.githubusercontent.com/thebaldgeek/thebaldgeek.github.io/main/img/helixfeeddetail.png" height="460">

A touch of heat and solder and its very solid.

Trim the turns to roughly 7 and a bit turns (close to 8) and then drill the two large holes for the 3D frame in the reflector, then mark and drill the bulkhead connector mount near the left hand side support - you go near the left side of the frame so you can run the first 2/3rds of the copper parallel to the base, this improves the match and lowers the SWR. Solder the copper pipe to the connector and you are done building the antenna.

Once built, trim the total length to get the VNA dip on frequency and move the first 2/3rds of a turn close to the reflector to get the SWR nice and low and you are done.
Once built, trim the total length to get the VNA dip on frequency and move the first 2/3rds of a turn close to the reflector to get the SWR nice and low and you are done. \
If you don't have a VNA, just trim the top turn to exactly 7 turns, ie, on the left side of the support that the SMA is on and the helix will be really close and still work better than the RTLSDR Patch antenna.


<img src="https://raw.githubusercontent.com/thebaldgeek/thebaldgeek.github.io/main/img/7turnhelixantennas.jpg" height="460">
Expand Down Expand Up @@ -222,14 +221,15 @@ In no order, my thoughts / wish-list:
15. SMA female connector only.
16. Passive antenna option considered. (We can run our own LNA and thus Bias-T power no longer an issue. More affordable).
17. Different part number of a stubby LHCP antenna to fully illuminate a ~80cm or bigger dish. (Same LNA/pwer/connector etc).
[s1]


## Which SDR?
In regard to SDRs, I like the silver v3 RTL-SDR for L-Band, but in this case, because of the requirement to use Bias-T to power the LNA, I might also use the Nooelect SmarTee SDR as it has Bias-T always on without needing to run the v3 software bat file to turn it on. The performance of the two SDRs seems to be identical. With that said, I have had some issue using the SmarTee with [SDRReceiver](SDRReceiver.md) that I am still working through. Also note that I have tested the RSP1a on L-Band and the more expensive SDR showed no benefit at all over the cheaper RTLSDR v3. This is mostly due to the fact of using the LNA, a more sensitive SDR does not perform any better since the system noise is not limited by the SDR, its set by the LNA noise figure. In short, use the cheaper SDR on L-Band and the other on HF where the difference in performance between the two is dramatic.
In regard to SDRs, I like the silver v3 RTL-SDR for L-Band, but in this case, because of the requirement to use Bias-T to power the LNA, I might also use the Nooelect SmarTee SDR as it has Bias-T always on without needing to run the v3 software bat file to turn it on. The performance of the two SDRs seems to be identical. With that said, I have had some issue using the SmarTee with [SDRReceiver](SDRReceiver.md) that I am still working through. Also note that I have tested the RSP1a on L-Band and the more expensive SDR showed no benefit at all over the cheaper RTLSDR v3. This is mostly due to the fact of using the LNA, a more sensitive SDR does not perform any better since the system noise is not limited by the SDR, its set by the LNA noise figure. In short, use the cheaper SDR on L-Band and the other on HF where the difference in performance between the two is dramatic.
## Mounting
How you mount the antenna is up to you. A few people have put them under a flowerpot and mounted them outside and used a bracket that is pointing at their satellite.
Some have attached them to camera tripods and used them inside their apartment's. In this case, you do not need to weatherproof the antenna, but it comes at a signal strength drop. Also experiment with positioning, a **window may not offer the best signal**. The reason for this is that a lot of windows have a Low-E coating. The metal coating really knocks back the L-Band signal. Often putting the antenna pointing out a wall or roof next to the window gives a better signal. No really. Trust me on this.
Bottom line, the antenna and LNA are *NOT* water proof and you must put it under cover.
## Coax
## Coax
Be sure and run some quality coax. The longer the length required to get from the antenna to the SDR, the more you should spend on the coax. 1.5GHz is rather lossy, more so than the 1090MHz from an ADSB antenna that you might be used to. (And even more so than the VHF ACARS frequency of around 130MHz). If in doubt, LMR-400 is the coax to use.

Ok, so you have the antenna mounted and pointed roughly in the [right direction](Inmarsat.md).
Expand All @@ -249,14 +249,13 @@ Please NOTE!!! As of Jan 15th 2024, the following screenshots are out of date/ol
Please use the frequency list!! They are very accurate.
Use the screenshots get an idea of what things should _look_ like, but USE the frequency LIST, not the frequencies on the screenshots.
The tables of frequencies/modes are accurate and should be primary, but the screenshots are helpful to show what you should be looking for when you first get running.


# ACARS Frequency Lists for all Inmarsats
Provisional Inmarsat frequency list prepared in February 2024 by David L. Wilson and Sergi.vdl2
Huge thanks to these two guys for collecting and checking every single one of these frequencies!

[l1] ACARS Frequency Lists for all Inmarsats


### 4A4F4 25-East
Frequency Region Use Use Hex Oct Provider GEO Location Beam
Frequency...Region......Use..................Use......Hex Oct..Provider......GEO Location......Beam
1545,1200 EMEA 25E Aero-L(600) P-Chan 90 220 ARINC & SITA
1545,1250 EMEA 25E Aero-L(1200) P-Chan 90 220 ARINC & SITA
1545,1300 EMEA 25E Aero-L(600) P-Chan 90 220 ARINC & SITA
Expand All @@ -272,7 +271,7 @@ Frequency Region Use Use Hex Oct Provider GEO L
<img src="https://raw.githubusercontent.com/thebaldgeek/thebaldgeek.github.io/main/img/alphasatLband.PNG" height="400">

### 3F5 54W
Frequency Region Use Use Hex Oct Provider GEO Location Beam
Frequency...Region......Use..................Use......Hex Oct..Provider......GEO Location......Beam
1545,0250 AORE 54W Aero-L(600) P-Chan 44 104 ARINC
1545,0300 AORE 54W Aero-L(600) P-Chan 43 103 SITA
1545,0350 AORE 54W Aero-L(600) P-Chan 44 104 ARINC
Expand Down Expand Up @@ -331,7 +330,7 @@ Frequency Region Use Use Hex Oct Provider GE
<img src="https://raw.githubusercontent.com/thebaldgeek/thebaldgeek.github.io/main/img/54wL-Band.png" height="380">

### 4F3 98W
Frequency Region Use Use Hex Oct Provider GEO Loccation Beam
Frequency...Region......Use..................Use......Hex Oct..Provider......GEO Location......Beam
1545,0500 AORW 98W Aero-L(600) P-Chan 05 005 SITA
1545,0600 AMER 98W Aero-L(600) P-Chan D0 320 ARINC & SITA
1545,0650 AMER 98W Aero-L(600) P-Chan D0 320 ARINC & SITA
Expand Down Expand Up @@ -359,7 +358,7 @@ Frequency Region Use Use Hex Oct Provider GEO Locc
<img src="https://raw.githubusercontent.com/thebaldgeek/thebaldgeek.github.io/main/img/98w_L-Band_rtlsdr_activepatch.PNG" height="380">

### 4F1 143E
Frequency Region Use Use Hex Oct Provider GEO Location Beam
Frequency...Region......Use..................Use......Hex Oct..Provider......GEO Location......Beam
1545,0250 APAC 143,5E Aero-L(600) P-Chan 50 120 ARINC & SITA
1545,0300 APAC 143,5E Aero-L(600) P-Chan 82 202 ARINC
1545,0350 APAC 143,5E Aero-L(600) P-Chan 82 202 ARINC
Expand All @@ -380,23 +379,23 @@ Frequency Region Use Use Hex Oct Provider GE
1546,0550 APAC 143,5E Aero-H+ (10500) P-Chan 85 205 SITA
1546,0700 APAC 143,5E Aero-H+ (10500) P-Chan 82 202 ARINC
1546,0850 APAC 143,5E Aero-H+ (10500) P-Chan 50 120 ARINC & SITA
1542,9350 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9400 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9450 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9500 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9550 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9600 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9650 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9700 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9750 143,5E APAC Aero voice(8400)AMBE C-Chan 82/85 202/205 ARINC/SITA Perth, AU Global beam
1542,9800 143,5E APAC Aero voice(8400)AMBE C-Chan 82/85 202/205 ARINC/SITA Perth, AU Global beam
1542,9850 143,5E APAC Aero voice(8400)AMBE C-Chan 82/85 202/205 ARINC/SITA Perth, AU Global beam
1542,9950 143,5E APAC Aero voice(8400)AMBE C-Chan 82/85 202/205 ARINC/SITA Perth, AU Global beam
1542,9350 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9400 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9450 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9500 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9550 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9600 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9650 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9700 143,5E APAC Aero voice(8400)AMBE C-Chan 50 120 ARINC & SITA Paumalu, HI Global beam
1542,9750 143,5E APAC Aero voice(8400)AMBE C-Chan 82/85 202/205 ARINC/SITA Perth, AU Global beam
1542,9800 143,5E APAC Aero voice(8400)AMBE C-Chan 82/85 202/205 ARINC/SITA Perth, AU Global beam
1542,9850 143,5E APAC Aero voice(8400)AMBE C-Chan 82/85 202/205 ARINC/SITA Perth, AU Global beam
1542,9950 143,5E APAC Aero voice(8400)AMBE C-Chan 82/85 202/205 ARINC/SITA Perth, AU Global beam

<img src="https://raw.githubusercontent.com/thebaldgeek/thebaldgeek.github.io/main/img/143eL-Band.png" height="380">

### 6F1 83E (No screenshot for now)
Frequency Region Use Use Hex Oct Provider GEO Location Beam
Frequency...Region......Use..................Use......Hex Oct..Provider......GEO Location......Beam
1545,0050 83,5E Aero-L(600) Psmc2 C1 301 ARINC Perth, AU Global beam
1545,1600 83,5E Aero-L(600) P-Chan C5 305 SITA Perth, AU Global beam
1545,1650 83,5E Aero-L(600) P-Chan C5 305 SITA Perth, AU Global beam
Expand Down

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