SatNOGS Wiki - User contributions [en]

Antenna switching

2021-03-15T14:17:22Z

Vittorio:

Sometimes it is necessary / useful to be able to switch between different antennas. In this way the observations can take place on different bands, or it is useful to have only one feeder, with excellent performance in terms of attenuation, from the antennas to the receiver.

Read carefully the full thread in [ https://community.libre.space/t/antenna-switching-project/2311 ], where it's possible to find different solutions, ranging from "parallel" control exploited via GPIO pins, to "serial" solution via USB connection or via RS485 (under tests) for longer physical connections.

Several parts (software & hardware) are necessary to activate this kind of control. Once the type of control has been established there are some software setting to be done, mainly to write scripts which will be performed before and after the observations.

Firstly, run 'sudo satnogs-setup' , then into "Advanced" section edit the parameter SATNOGS_''PRE_''OBSERVATION_''SCRIPT to <path_''to_script>preob.sh -f <nowiki>{{ FREQ }}</nowiki>.

In the same manner in satnogs-setup set the parameter SATNOGS_''POST_''OBSERVATION_''SCRIPT to <path''_to_script>postob.sh

This, for example, is the content of preob.sh and postob.sh, invoked by the client to switch the correct antenna using an USB serial connection. Pay attention to the exact syntax and to the following described permissions on scripts and users:

 

*'''preob.sh''' : called just before observation starts, set the right antenna and write to the local satnogs log.

 <pre class="">#!/bin/bash
#set the ports up to known state and disable close between calls
stty -F /dev/ttyUSB0 9600 -hupcl

date=`date +"%d/%m/%y %H:%M:%S %Z"`
freq=0

while getopts f: option
do
case "${option}"
in
f) freq=${OPTARG};;
esac

if ([ $freq -ge 399900000 ] && [ $freq -lt 470000000 ]) ;
then
echo "$date --> 399.9 to 470 frequency, ANT0 selected" >> /home/pi/tests/satnogs_log.txt
echo -e "ANT0\n" > /dev/ttyUSB0
fi

if ([ $freq -ge 136000000 ] && [ $freq -lt 150100000 ]) ;
then
echo "$date --> 136 to 150.1 frequency, ANT1 selected" >> /home/pi/tests/satnogs_log.txt
echo -e "ANT1\n" > /dev/ttyUSB0
fi

if ([ $freq -ge 24000000 ] && [ $freq -lt 30000000 ]) ;
then
echo "$date --> 24 to 30 frequency, ANT2 selected" >> /home/pi/tests/satnogs_log.txt
echo -e "ANT2\n" > /dev/ttyUSB0
fi

done</pre>

*'''postob.sh''' : called at observation end, puts RF relays in ‘deactivated’ position and to setup a know switch position.

 <pre class="">#!/bin/bash
# disable all relays... no power waste!

date=`date +"%d/%m/%y %H:%M:%S %Z"`
echo -e "ANT0\n" > /dev/ttyUSB0
echo "$date antenna switch reset " >> /home/pi/tests/satnogs_log.txt</pre>

Please take note about the following mandatory permissions, because the scripts are executed as “satnogs” user:

*<code>sudo usermod -a -G dialout satnogs</code>, to access serial device by satnogs user
*<code>sudo usermod -a -G pi satnogs</code>, to permit execution to satnogs as member of pi group
*<code>touch satnogs_log.txt</code>, to create the log file
*<code>chmod 666 satnogs_log.txt</code>, to permit everybody writing on this file
*<code>chmod +x preob.sh</code>, set script to be executable
*<code>chmod +x postob.sh</code>, set script to be executable

To test the whole stuff try to execute:<pre class="">./preob.sh -f 435000000

./postob.sh

tail ./satnogs_log.txt</pre>and satnogs_log.txt should contain something like:<pre class="">18/02/21 12:15:25 GMT --> 399.9 to 470 frequency, ANT0 selected
18/02/21 12:30:23 GMT antenna switch reset </pre>

Build

2021-03-15T14:05:47Z

Vittorio:

__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|Raspberry Pi]]
|[[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]]
|-
|[[Fedora Installation|Linux Fedora (old)]]
|[https://wiki.satnogs.org/SatNOGS_Arduino_Uno/CNC_Shield_Based_Rotator_Controller Arduino UNO CNC Shield based controller]
|[[No rotator]]
|
|[[Antennas|Cross-Yagi]]
|-
|
|[https://community.libre.space/t/ramps-1-4-board-for-satnogs-rotator/3386 RAMPS 1.4 Board for SatNOGS Rotator]
|
|
|-
|}

{{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 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. Sometimes it's useful the ability of [[Antenna switching|switch]] different antennas among observations.

==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.

[[Category:Build]]
[[Category:Hardware]]

Antenna switching

2021-03-15T13:55:12Z

Vittorio: Created page with "Sometimes it is necessary / useful to be able to switch between different antennas. In this way the observations can take place on different bands, or it is useful to have onl..."

Sometimes it is necessary / useful to be able to switch between different antennas. In this way the observations can take place on different bands, or it is useful to have only one feeder, with excellent performance in terms of attenuation, from the antennas to the receiver.

Read carefully the full thread in [ https://community.libre.space/t/antenna-switching-project/2311 ], where it's possible to find different solutions, ranging from "parallel" control exploited via GPIO pins, to "serial" solution via USB connection or via RS485 (under tests) for longer physical connections.

Several parts (software & hardware) are necessary to activate this kind of control. Once the type of control has been established there are some software setting to be done, mainly to write scripts which will be performed before and after the observations.

Firstly, run 'sudo satnogs-setup' , then into "Advanced" section edit the parameter SATNOGS''PRE''OBSERVATION''SCRIPT to <path_''to_script>preob.sh -f <nowiki>{{ FREQ }}</nowiki>.

In the same manner in satnogs-setup set the parameter SATNOGS''POST''OBSERVATION''SCRIPT to <path''_to_script>postob.sh

This, for example, is the content of preob.sh and postob.sh, invoked by the client to switch the correct antenna using an USB serial connection. Pay attention to the exact syntax and to the following described permissions on scripts and users:

 

*'''preob.sh''' : called just before observation starts, set the right antenna and write to the local satnogs log.

 <pre class="">#!/bin/bash
#set the ports up to known state and disable close between calls
stty -F /dev/ttyUSB0 9600 -hupcl

date=`date +"%d/%m/%y %H:%M:%S %Z"`
freq=0

while getopts f: option
do
case "${option}"
in
f) freq=${OPTARG};;
esac

if ([ $freq -ge 399900000 ] && [ $freq -lt 470000000 ]) ;
then
echo "$date --> 399.9 to 470 frequency, ANT0 selected" >> /home/pi/tests/satnogs_log.txt
echo -e "ANT0\n" > /dev/ttyUSB0
fi

if ([ $freq -ge 136000000 ] && [ $freq -lt 150100000 ]) ;
then
echo "$date --> 136 to 150.1 frequency, ANT1 selected" >> /home/pi/tests/satnogs_log.txt
echo -e "ANT1\n" > /dev/ttyUSB0
fi

if ([ $freq -ge 24000000 ] && [ $freq -lt 30000000 ]) ;
then
echo "$date --> 24 to 30 frequency, ANT2 selected" >> /home/pi/tests/satnogs_log.txt
echo -e "ANT2\n" > /dev/ttyUSB0
fi

done</pre>

*'''postob.sh''' : called at observation end, puts RF relays in ‘deactivated’ position and to setup a know switch position.

 <pre class="">#!/bin/bash
# disable all relays... no power waste!

date=`date +"%d/%m/%y %H:%M:%S %Z"`
echo -e "ANT0\n" > /dev/ttyUSB0
echo "$date antenna switch reset " >> /home/pi/tests/satnogs_log.txt</pre>

Please take note about the following mandatory permissions, because the scripts are executed as “satnogs” user:

*<code>sudo usermod -a -G dialout satnogs</code>, to access serial device by satnogs user
*<code>sudo usermod -a -G pi satnogs</code>, to permit execution to satnogs as member of pi group
*<code>touch satnogs_log.txt</code>, to create the log file
*<code>chmod 666 satnogs_log.txt</code>, to permit everybody writing on this file
*<code>chmod +x preob.sh</code>, set script to be executable
*<code>chmod +x postob.sh</code>, set script to be executable

To test the whole stuff try to execute:<pre class="">./preob.sh -f 435000000

./postob.sh

tail ./satnogs_log.txt</pre>and satnogs_log.txt should contain something like:<pre class="">18/02/21 12:15:25 GMT --> 399.9 to 470 frequency, ANT0 selected
18/02/21 12:30:23 GMT antenna switch reset </pre>