SatNOGS Wiki - User contributions [en]

Omnidirectional Station How To

2019-04-13T13:44:08Z

Iz7boj: added link to SPF5189LNA wiki page

[[File:Omnidirectional VHF Turnstile Antenna.jpg|alt=VHF Turnstile Antenna|thumb|VHF Turnstile antenna, [https://network.satnogs.org/stations/23/ SatNOGS Station 23]]]
This How-To is written to get you quickly receiving satellite data with an Omnidirectional antenna (an antenna that does not move).

== Prerequisites/Background ==
I'm assuming that you are a bit familiar with amateur radio, or linux in general, or you already have a Raspberry Pi.

=== Expectation Management ===
First off, I'd like to set some expectations around a SatNOGs station with an omnidirectional antenna. Yes, you will be able to hear satellites, Morse code beacons, maybe even some voice contacts on a FM transponder. But for CubeSats with 1 watt transmitters at 9600 baud, it's going to be really difficult to actually decode any data with an omni antenna. You'll definitely see squiggly lines on the waterfall plot, but demodulating the signal and extracting satellite telemetry is going to be pretty difficult.

The only way to get more signal is a better antenna. And a better antenna with more gain is going to be more directional, which means you will need a way to point that antenna at the satellite, and this How-To just got a lot more complicated. So we're not going there.

A better preamp helps a bit, see the LNA section below.

=== Hardware Required ===
This is a list of the hardware for indoor/testing purposes:
* Raspberry Pi
** Power supply + cable (see note below)
** Up to 16 GB Micro SD card
** Ethernet cable
* RTL SDR Blog v3 dongle
* Various short lengths of coax
* Preamp/LNA - Or not if your coax is short, see LNA section below
* Omnidirectional antenna - just a dual mag-mount on a cookie sheet will work OK for stronger satellites

== Setting up the Raspberry Pi ==
I chose the [https://www.raspberrypi.org/products/raspberry-pi-3-model-b/ Raspberry Pi 3 Model B] for my station.

=== Downloading/Writing the SD image ===
The SatNOGs team has done a great job creating a Raspbian image with all the required software. Simply navigate over to the [https://gitlab.com/librespacefoundation/satnogs/satnogs-pi-gen/tags latest tag on Gitlab], and click on the "Zipped image" link under the latest tag. It's about 650 MBytes.

For linux:
# Unzip the downloaded file: '''unzip image_2018-08-03-Raspbian-SatNOGS-lite.zip'''
# Figure out which device is the SD card. SD cards are usually start with mmcblk. '''sudo lsblk'''
# Write the image. This will take a while. Make sure you don't overwrite your host OS: '''sudo dd if=2018-08-03-Raspbian-SatNOGS-lite.img of=/dev/mmcblk0'''

=== Power notes ===
Thinking I could save a few bucks, I used a no-name generic 2.4 amp "tablet" USB power supply I got as a freebie, and a micro-USB cable I use for charging my phone. What a mistake! The Micro-USB cable wire gauge was too small, so there was too much voltage drop on the cable, so the Raspberry Pi reported power problems every time it was doing anything.

Power problems are indicated by either a lightning bolt in the upper right of the monitor, or the red power LED flashes on the board itself. If The Raspberry Pi processor itself is pretty forgiving of power droops because it runs at 3.3 volts. But the 5v USB ports are directly tied to input power, so undervoltage conditions will cause problems for USB devices, such as the RTL SDR dongle.

== Software Configuration ==

=== Creating a SatNOGs Network account ===
There are several different websites to be aware of and sign in to. As of 12/2018, most of our websites use a unified login provided by Auth0, so when you create an account on one of these sites it will work across the others as well:
* Required: [https://network.satnogs.org/ Network]: for registering your station and adding data to the network.
* Recommended: [https://community.libre.space Forums]: for asking questions.
* Optional: [https://db.satnogs.org/ Database]: Only if you want to add satellites/modes. Not necessary for receiving satellite data.

=== Registering the station ===
Log in to your Network account, and click the "+ Add Ground Station" button, or click [https://network.satnogs.org/stations/edit/ here] Fill out the short form, and your station will be added to the database. For "Antenna", pick something that encompasses the frequency range of your antenna. For wideband reception, use VHF Discone 26-1200 MHz.

The important info you'll need later on is the Station ID number, lat/lon/altitiude. I would also use a Minimum Horizon of 30 degrees or so, this will keep your station from allowing low-elevation passes to be scheduled. Make sure to keep the "Testing" flag checked, as this lets people know that your station isn't quite ready for real use.

=== Booting and Configuring Raspbian ===
After you have the image burned onto a Micro-SD card, boot it! I would recommend hooking up a keyboard and HDMI monitor, you can watch the boot process. If it doesn't boot at all, double check that you wrote the SatNOGs Raspbian image correctly.

After a successful boot, log in with username '''pi''' and password '''raspbian''':
# Change your password! '''passwd'''
# Update and upgrade raspbian strech: '''sudo apt update''' then '''sudo apt upgrade'''
# You'll probably update a lot of packages and get a new kernel, so reboot after this: '''sudo reboot'''
# Run '''sudo raspi-config''' to set up the base OS. ''Tab'' switches between the options and ''select''.
## 4 Localisation Options: I1 Change Locale: en_US.UTF-8 UTF-8
## 4 Localisation Options: I2 Change Timezone: None of the above: UTC
## 4 Localisation Options: I3 Change Keyboard Layout:
## 7 Advanced Options: A1 Expand Filesystem <br />This will expand the ~2GB Micro-SD card partition to fill the entire SD card.
The Raspberry Pi needs to reboot to expand the filesystem, so do this now. It might take a while. '''sudo reboot''

==== Disabling WiFi and Bluetooth ====
To disable WiFi and Bluetooth, edit the /boot/config.txt file, and add the following lines at the bottom:
# Disable WiFi and bluetooth
dtoverlay=pi3-disable-wifi
dtoverlay=pi3-disable-bt

Then reboot again. To make sure that it worked, run '''ifconfig''' and make sure that ''wlan0'' isn't listed. I'm not sure how to tell if bluetooth is turned off.

==== Additional software ====
I like to install this additional software with '''sudo apt install bmon''' ...
* bmon - a graphical network usage analyzer.
* vnstat - keeps track of your bandwidth usage
* vim - the world's best text editor ;)
* irssi - a terminal IRC client, for chatting on the #satnogs IRC channel

If you can't tell by now, I'm always a big fan of rebooting. It certainly doesn't take that long... '''sudo reboot'''

=== Configuring the satnogs-client ===
Once you have the base Raspbian Strech OS installed, updated, and looking good, you can configure SatNOGs. Plug in your RTL SDR if you haven't already.

First thing to do is update the satnogs-setup program. Run '''sudo satnogs-setup'''. This will probably take a while, then '''Update''', which will also take a while. Per usual, after the update I like to reboot the raspberry pi just to make sure everything was updated and is actually running the new code.

==== Basic Configuration ====
Then the actual configuration of the station:
# Run '''sudo satnogs-setup''' again
# Basic Configuration:
## SATNOGS_API_TOKEN: After logging in to network.satnogs.org, this is in the upper right under "API Key"
## SATNOGS_RX_DEVICE: rtlsdr
## SATNOGS_STATION_ELEV: station elevation in meters
## SATNOGS_STATION_ID: The number of your station. Newer stations are high 200s.
## SATNOGS_STATION_LAT and LON: Latitude and Longitude in decimal degrees
## HAMLIB_UTILS_ROT_ENABLE: no
Then back to the main menu and ''Apply'' to save the configuration. Ansible will run, change some stuff, and probably take a while. If you want to quit, just keep pressing ''back'' to exit.

==== Setting the gain ====
The next step is to set the gain on the RTL SDR. You're looking for a total gain of about 25 dB. If you have a 25dB LNA, perfect, set the RTL SDR gain at zero. Otherwise, do the math. There are only a few gain options that the RTL SDR supports. The easiest way to see what the options are is to run the rtl_test command. Ctrl-C immediatly to stop:
pi@raspberrypi:~ $ rtl_test
Found 1 device(s):
0: Realtek, RTL2838UHIDIR, SN: 00000001

Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Supported gain values (29): 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6
[R82XX] PLL not locked!
Sampling at 2048000 S/s.

Info: This tool will continuously read from the device, and report if
samples get lost. If you observe no further output, everything is fine.

Reading samples in async mode...
^CSignal caught, exiting!

User cancel, exiting...
Samples per million lost (minimum): 0
pi@raspberrypi:~ $

Since I have a LNA with a gain of slightly under 20dB, I picked 8.7dB of gain for the RTL SDR. This value goes into the SATNOGS_RF_GAIN setting under Advanced settings in satnogs-setup.

=== Checking the setup ===
SatNOGs come with a built-in web server on port 5000. So just surf over to IP address of your Raspberry Pi on port 5000, and you should see a screen similar to this:
[[File:Satnogs client screenshot.png|center|thumb|800x800px|Satnogs Client]]

== Hardware Configuration ==
Basic hardware configuration is Antenna > Short coax > LNA > Coax > RTL SDR.

=== LNA ===
The way to measure the performance of an antenna is using a figure of merit called the Antenna gain-to-noise-temperature (G/T). It's a positive unitless number, higher the better.

G/T is comprised of antenna gain (in dB) on the top, and the system noise temperature (in Kelvins) on the bottom. There's a lot of somewhat-hard math involved, but here's the bottom line: to make your system perform better, you either need to increase the antenna gain or decrease the system noise temp. [https://en.wikipedia.org/wiki/Antenna_gain-to-noise-temperature Wikipedia]

Increasing the antenna gain is difficult, only because we decided on an omnidirectional antenna as the basis for this How-To. Omnidirectional antennas top out at maybe 7 dB gain or so, and that's just from pushing the radiation pattern up to the sky away from the ground. Any more gain than that and it's not an omni antenna; it's got a direction that the antenna needs to be pointed in. And we want to stay away from pointing antennas for now.

Reducing the system temperature is the the way forward then. The RTL-SDR dongle has a noise figure of [https://network.satnogs.org/stations/edit/ 6dB or so], depending on frequency, which is pretty horrible. But it turns out that the system noise temperature is largely determined by the first device in the receive chain. Since we can't change the antenna, adding a low-noise amplifier helps quite a bit. See this [https://www.youtube.com/watch?v=snifc_x_2sE youtube video] from Adam 9A4QV on how a LNA helps. (Also check out his other videos about the RTL SDR dongle, and SDR in general)

More info on noise and preamps:
* [https://en.wikipedia.org/wiki/Noise_temperature System noise from wikipedia], pretty high-level
* [https://www.rtl-sdr.com/tutorial-on-properly-positioning-a-preamp-lna-in-a-radio-system/ Where to put an LNA], from rtl-sdr.com
* [[SPF1589 LNA measurements|SPF5189 LNA measurements]]

=== Antenna ===
For testing on the bench, pretty much any antenna will do. Or if you have a whip antenna already outside for repeater work, use that. As I mentioned before, I've successfully used a mag-mount antenna stuck to a cookie sheet, sitting inside my living room window.

Also, remember that some new low emissivity double-pane windows use metal films to keep heat inside. Unfortunately, this also attenuates pretty much all RF signals, see [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5501855/ this article] for more background.

== Testing the station ==
[[File:Pass predictions.png|300px|right]]
Now that you have the hardware and software up and running, go ahead and schedule some passes. Navigate to your station page, and click on the Schedule button on the right side of some promising passes. The green and red bars beneath the satellite name is a quick visual indication of the number of Good and Bad passes on the network. Unfortunately, this data is not time-stamped at all, so a satellite that had a lot of Good observations a long time ago, but recently died, would still show as Green.

=== Rating an Observation ===
[[File:Rating.png|right]]
After each observatios, you should rate it. More information [https://wiki.satnogs.org/Operation#Rating_observations here], but the bottom line is rate the observation:
* '''Good''' if the satellite is seen in the waterfall at all. The satellite will be a straight line in the middle of the waterfall plot.
* '''Bad''' if the satellite is not seen.
* '''Failed''' if there was a problem with the station, such as a mis-configuration, or if the waterfall is missing or a solid color.

=== Calibrating frequency offset (PPM) ===
This is not super important for a new station.

== Next Steps ==
Now that you've got this station working on the bench, what's next?

For permanent mast-mounted installation, I would recommend adding:
* [https://www.adafruit.com/product/3785 PoE splitter] - Make sure to get one that actually conforms to the 48-volt IEEE 802.3af standard
* POE injector for powering station remotely - Again, get a real 48-volt IEEE 802.3af standard
* Large mast-mounted waterproof box
* Waterproof cord grips, both to keep out the rain but also spiders and critters
* Desiccant to keep the humidity down
* Mastic tape for weatherproofing antenna connectors
* Better omnidirectional antenna

=== Building a Box ===
* [https://wiki.satnogs.org/No_rotator No-Rotator setup]
== External links ==
* IQ3KU Omnidirectional station [https://www.i3vfj.net/SATNOGS/Satnogs_348_notes.pdf build write-up].
[[ Category:How-tos ]]
[[ Category:Omnidirectional Antennas ]]

SPF5189 LNA measurements

2019-04-13T13:22:29Z

Iz7boj: Created page with "If you want to improve your receiving station performances, you could consider to add an LNA near your antenna. One of the cheapeset LNA available on the market is SPF5189. It..."

If you want to improve your receiving station performances, you could consider to add an LNA near your antenna.
One of the cheapeset LNA available on the market is SPF5189. It's available already mounted on a PCB, shielded and connectorized, as in the figure below.

[[File:Foto.jpg|center]]

I bought one board for few euros on ebay. It arrived in a pair of weeks, then I measured it on a Vector Network Analyzer, in order to compare the real gain with the datasheet.

Once the LNA has been powered at 5V, the current absorption is 90mA, perfectly aligned with the datasheet range.

Here below, the S21, S11 and S22 plots are reported between 50MHz and 3GHz (the LNA reaches 4GHz but the VNA not).

I placed these 4 markers: 144MHz, 435MHz, 1GHz, 2GHz .

[[File:S11.jpg|600px|center]]
[[File:S21.jpg|600px|center]]
[[File:S22.jpg|600px|center]]

When I downloaded the datahseet, I saw that the SPF5189Z has two possible configurations:

- Optimized matching at 900MHz
- Optimized matching at 1900MHz

From ebay description and board P/N, it’s not possible to understand the frequency optimization.

Here below, I reported a comparison the datasheet (green line) and the measurement (red line) data, for both configurations. The frequency range of the datasheet is smaller than my measurements, sto the comparison is only on the datasheet frequencies and not wide-band.

[[File:900MHz_measured_vs_datasheet.png|600px|center]]

[[File:1900MHz_measured_vs_datasheet.png|600px|center]]

The gain seems to be 1dB less than the datasheet on both configurations, while the input matching shows better results on 900MHz range.

At the end, the LNA is quite wide-band and is a compromise between the 900MHz and 1900MHz configurations.

File:1900MHz measured vs datasheet.png

2019-04-13T13:16:35Z

Iz7boj: SPF5189_1900MHz_meas_vs_datasheet

== Summary ==
SPF5189_1900MHz_meas_vs_datasheet

File:900MHz measured vs datasheet.png

2019-04-13T13:16:00Z

Iz7boj: SPF5189_900MHz_meas_vs_datasheet

== Summary ==
SPF5189_900MHz_meas_vs_datasheet

File:S22.jpg

2019-04-13T13:13:53Z

Iz7boj: SPF5189 LNA board S22

== Summary ==
SPF5189 LNA board S22

File:S21.jpg

2019-04-13T13:13:36Z

Iz7boj: SPF5189 LNA board S21

== Summary ==
SPF5189 LNA board S21

File:S11.jpg

2019-04-13T13:13:16Z

Iz7boj: SPF5189 LNA board S11

== Summary ==
SPF5189 LNA board S11

File:Foto.jpg

2019-04-13T13:09:48Z

Iz7boj: SPF5189 LNA board

== Summary ==
SPF5189 LNA board

Build

2019-04-12T07:57:23Z

Iz7boj: Added link to SPF5189 LNA review

__NOTOC__
== Introduction ==

Building a ground station need not be complicated. There are a few things to consider when working out what it is you are going to do. Choices such as the desire to have a fixed or steerable ground station will play a big part in the amount of equipment needed and the time taken as well as the complexity of any build. If you are new to this and a little unsure then a fixed (no rotator) option is a good choice. If you fancy a challenge and want to pick out the weakest signals then the steerable ground station might be what you are after. There is more detail in the [[Ground Stations]] page

The illustration below sets out the various major components to give an idea as to what is commonly used.

== Options for Ground Stations ==

A satellite ground station is made up from different parts. The following diagram can help you select your setup based on your needs and/or your existing setup.

[[File:Satnogs_imagemap.png|center]]

Here are some links explaining the different options:

{| class="wikitable" style="margin: 0 auto;"
! Platform
! Controller
! Rotator
! Radio
! Antenna
|-
| [[Raspberry_Pi_3|Raspberry Pi 3]]
| [[SatNOGS Rotator Controller|SatNOGS Controller]]
| [[SatNOGS_Rotator_v3|SatNOGS Rotator]]
| [[Radio#SDR|SDR]]
| [[Antennas|Yagi]]
|-
| [[SatNOGS_Client_Ansible|Debian system]]
| [http://spid.net.pl/en/rot2prog-2/ Rot2Prog]
| [[SPID Big RAS]]
|
| [[Antennas|Helical]]
|-
| [[Linux Desktop]]
| [[G-5500|lsf-g5500]]
| [[G-5500|Yaesu G5500]]
|
| [[Antennas|Vertical]]
|-
|
| [https://wiki.satnogs.org/SatNOGS_Arduino_Uno/CNC_Shield_Based_Rotator_Controller Arduino UNO CNC Shield based controller]
| [[No rotator]]
|
| [[Antennas|Cross-Yagi]]
|}

{{Message|Use the above table to select your setup. E.g. RPi3 > Yaesu G550 > SDR > UHF helical & VHF Cross Yagi}}

== How do I pick? ==

'''Client''': The Raspberry Pi 3 is the reference platform for SatNOGS, and is currently the option that has the best support from the community. Certain SDRs may benefit from a more powerful CPU, like what you'd find in a desktop machine; however, currently you'll need to set that up on your own.

'''Rotator''': A rotator, like the [[SatNOGS_Rotator_v3|SatNOGS Rotator v3]], will allow your antenna to follow satellites as they move across the sky, and thus pick up fainter signals. But if you want to get started quickly, or don't have the hardware skills to build your own, you can still pick up stronger signals (the ISS, NOAA and Meteor weather satellites) with a [[No_rotator|no-rotator]] setup. If you already have [https://github.com/Hamlib/Hamlib/wiki/Supported-Rotators a rotator supported by rotctl], you can use that.

'''Signal Reception''': The reference radio for SatNOGS is the [https://www.rtl-sdr.com RTL-SDR v3], but other latest-generation SDRs like the [http://www.nooelec.com/store/nesdr-smart-sdr.html NooElec NESDR SMart] should work as well. Higher-end SDRs should work as well, but can get a bit expensive. Alternately, [https://sourceforge.net/p/hamlib/wiki/Supported%20Radios/ any radio supported by rigctl] should work.

Amplification is generally done by a low noise amplifier, or LNA. There are multiple options:

* A wide-band LNA next to your SDR (see [http://lna4all.blogspot.com/ LNA4ALL], [https://iz7boj.wordpress.com/2019/04/11/spf5189z-lna-measurements-on-vna/ SPF5189] and similar)
* A band specific (or two) pre-amplifiers next to your antennas ([http://www.wimo.com/mast-preamplifier_e.html example])
* No amplification at all...just pump the gain of your SDR. (This is not recommended for the rtl-sdr.)

'''Antenna''': Stationary antennas (eg: [https://en.wikipedia.org/wiki/Turnstile_antenna Turnstile], [https://community.libre.space/t/parasitic-lindenblad-on-uhf/1128/2 Lindenblad]) will be easy to build and mount, as they won't require rotator hardware. They will let you receive stronger broadcasts, like NOAA weather satellites and ISS broadcasts, but may not work for receiving fainter cubesat broadcasts. Directional antennas (eg: Yagis, Helicals) can be more complicated to build, but will also require a rotator to track satellites across the sky. The advantage is that they will let you pick up fainter broadcasts from cubesats or ham radio satellites.

== Next steps ==

Once you have a ground station ready, you should go ahead and operate it! More info can be found on the [[Operation]] wiki page.