View source for WSPR: RaspberryPi

==Raspberry Pi bareback LF/MF/HF/VHF WSPR transmitter==


[[Image:Raspi-wspr.jpg|center|500px|thumb|Rangkaian RaspberryPi untuk WSPR]]


[[Image:LPF.png|center|500px|thumb|LPF untuk QRP Transmitter dari http://www.gqrp.com/harmonic_filters.pdf]]


Membuat WSPR beacon sederhana dengan RaspberryPi dengan menyambungkan GPIO port ke Antenna (dan Low Pass Filter), dapat beroperasi di band LF, MF, HF, dan VHF dari 0 s/d 250 MHz.

Source yang ada sekarang ini compatible dengan Raspberry Pi dan Raspberry Pi 2.

==Instalasi==

Pastikan kita menggunakan kernel yang terakhir dengan cara mengupdate sistem yang kita gunakan. Kernel terakhir termasuk berbagai perbaikan yang memperbaiki keakuratan pengukuran ppm menggunakan NTP.

Lakukan:

 sudo apt-get update
 sudo apt-get dist-upgrade

Download dan compile code:

 sudo apt-get install git
 git clone https://github.com/JamesP6000/WsprryPi.git
 cd WsprryPi
 make

Baca file BUILD untuk detail lebih lanjut.


==Penggunaan (WSPR --help output):==

Penggunaan

 wspr [options] callsign locator tx_pwr_dBm f1 <f2> <f3> ...

atau

 wspr [options] --test-tone f

Opsi:
 
 -h --help
      Print out this help screen.
 -p --ppm ppm
      Known PPM correction to 19.2MHz RPi nominal crystal frequency.
 -s --self-calibration
      Call ntp_adjtime() before every transmission to obtain the PPM error of the xtal.
 -r --repeat
      Repeatedly, and in order, transmit on all the specified freqs.
 -x --terminate <n>
      Terminate after n transmissions have been completed.
 -o --offset
      Add a random frequency offset to each transmission:
        +/- 80 Hz for WSPR
        +/- 8 Hz for WSPR-15
 -t --test-tone freq
      Simply output a test tone and the specified frequency. Only used
      for debugging and to verify calibration.
 -n --no-delay
      Transmit immediately, do not wait for a WSPR TX window. Used
      for testing only.

Frekuensi yang digunakan dapat menggunakan Frekuensi absolut dari TX carrier, atau menggunakan string berikut. Jika string digunakan, maka pancaran akan dilakukan di tengah-tengah dari wilayah WSPR dari band terpilih. Pilihan string,
 
  LF LF-15 MF MF-15 160m 160m-15 80m 60m 40m 30m 20m 17m 15m 12m 10m 6m 4m 2m

'''-15 menunjukan bagian WSPR-15 dari band'''

Jika kita tidak ingin memancar, atau membuat gap antar satu pancaran dengan pancaran yang lain, kita dapat melakukan dengan menyebutkan frekuensi TX sebagai 0.
  
Note that 'callsign', 'locator', and 'tx_power_dBm' are simply used to fill
in the appropriate fields of the WSPR message. Normally, tx_power_dBm should
be 10, representing the signal power coming out of the Pi. Set this value
appropriately if you are using an external amplifier.

==Radio licensing / RF==


In order to transmit legally, a HAM Radio License is REQUIRED for running
this experiment. The output is a square wave so a low pass filter is REQUIRED.
Connect a low-pass filter (via decoupling C) to GPIO4 (GPCLK0) and Ground pin
of your Raspberry Pi, connect an antenna to the LPF. The GPIO4 and GND pins
are found on header P1 pin 7 and 9 respectively, the pin closest to P1 label
is pin 1 and its 3rd and 4th neighbour is pin 7 and 9 respectively. See this
link for pin layout: http://elinux.org/RPi_Low-level_peripherals Examples of
low-pass filters can be found here: http://www.gqrp.com/harmonic_filters.pdf

The expected power output is 10mW (+10dBm) in a 50 Ohm load. This looks
neglible, but when connected to a simple dipole antenna this may result in
reception reports ranging up to several thousands of kilometers.

As the Raspberry Pi does not attenuate ripple and noise components from the
5V USB power supply, it is RECOMMENDED to use a regulated supply that has
sufficient ripple supression. Supply ripple might be seen as mixing products
products centered around the transmit carrier typically at 100/120Hz.

DO NOT expose GPIO4 to voltages or currents that are above the specified
Absolute Maximum limits. GPIO4 outputs a digital clock in 3V3 logic, with a
maximum current of 16mA. As there is no current protection available and a DC
component of 1.6V, DO NOT short-circuit or place a resistive (dummy) load
straight on the GPIO4 pin, as it may draw too much current. Instead, use a
decoupling capacitor to remove DC component when connecting the output dummy
loads, transformers, antennas, etc. DO NOT expose GPIO4 to electro- static
voltages or voltages exceeding the 0 to 3.3V logic range; connecting an
antenna directly to GPIO4 may damage your RPi due to transient voltages such
as lightning or static buildup as well as RF from other transmitters
operating into nearby antennas. Therefore it is RECOMMENDED to add some form
of isolation, e.g. by using a RF transformer, a simple buffer/driver/PA
stage, two schottky small signal diodes back to back.

==TX Timing==

This software is using system time to determine the start of WSPR
transmissions, so keep the system time synchronised within 1sec precision,
i.e. use NTP network time synchronisation or set time manually with date
command. A WSPR broadcast starts on an even minute and takes 2 minutes for
WSPR-2 or starts at :00,:15,:30,:45 and takes 15 minutes for WSPR-15. It
contains a callsign, 4-digit Maidenhead square locator and transmission
power.  Reception reports can be viewed on Weak Signal Propagation Reporter
Network at: http://wsprnet.org/drupal/wsprnet/spots


==Calibration==

Frequency calibration is REQUIRED to ensure that the WSPR-2 transmission
occurs within the narrow 200 Hz band. The reference crystal on your RPi might
have an frequency error (which in addition is temp. dependent -1.3Hz/degC
@10MHz). To calibrate, the frequency might be manually corrected on the
command line or a PPM correction could be specified on the command line.

===NTP calibration===

NTP automatically tracks and calculates a PPM frequency correction. If you
are running NTP on your Pi, you can use the --self-calibration option to
have this program querry NTP for the latest frequency correction before
each WSPR transmission. Some residual frequency error may still be present
due to delays in the NTP measurement loop and this method works best if your
Pi has been on for a long time, the crystal's temperature has stabilized,
and the NTP control loop has converged.

===AM calibration===

A practical way to calibrate is to tune the transmitter on the same frequency
of a medium wave AM broadcast station; keep tuning until zero beat (the
constant audio tone disappears when the transmitter is exactly on the same
frequency as the broadcast station), and determine the frequency difference
with the broadcast station. This is the frequency error that can be applied
for correction while tuning on a WSPR frequency.

Suppose your local AM radio station is at 780kHz. Use the --test-tone option
to produce different tones around 780kHz (eg 780100 Hz) until you can
successfully zero beat the AM station. If the zero beat tone specified on the
command line is F, calculate the PPM correction required as:
ppm=(F/780000-1)*1e6 In the future, specify this value as the argument to the
--ppm option on the comman line. You can verify that the ppm value has been
set correction by specifying --test-tone 780000 --ppm <ppm> on the command
line and confirming that the Pi is still zero beating the AM station.


==PWM Peripheral==

The code uses the RPi PWM peripheral to time the frequency transitions
of the output clock. This peripheral is also used by the RPi sound system
and hence any sound events that occur during a WSPR transmission will
interfere with WSPR transmissions. Sound can be permanently disabled
by editing /etc/modules and commenting out the snd-bcm2835 device.


==Example usage==

Brief help screen

 ./wspr --help

Transmit a constant test tone at 780 kHz.

 sudo ./wspr --test-tone 780e3

Using callsign N9NNN, locator EM10, and TX power 33 dBm, transmit a single
WSPR transmission on the 20m band using NTP based frequency offset
calibration.

 sudo ./wspr --self-calibration N9NNN EM10 33 20m

Transmit a WSPR transmission slightly off-center on 30m every 10 minutes for
a total of 7 transmissions, and using a fixed PPM correction value.  sudo

 sudo ./wspr --repeat --terminate 7 --ppm 43.17 N9NNN EM10 33 10140210 0 0 0 0

Transmit repeatedly on 40m, use NTP based frequency offset calibration,
and add a random frequency offset to each transmission to minimize collisions
with other transmissions.

 sudo ./wspr --repeat --offset --self-calibration N9NNN EM10 33 40m

Contoh lain untuk station YB0NNN dengan antenna tri-bander 40m, 20m, 15m

 sudo ./wspr --repeat --offset --self-calibration YB0NNN OI33 33 40m 0 0 0 0 20m 0 0 0 0 15m 0 0 0 0




 sudo ./wspr <[prefix]/callsign[/suffix]> <locator> <power in dBm> [<frequency in Hz> ...]
        e.g.: sudo ./wspr PA/K1JT JO21 10 7040074 0 0 10140174 0 0
        where 0 frequency represents a interval for which TX is disabled,
        wspr-2 or wspr-15 mode selection based on specified frequency.

WSPR is used on the following frequencies (local restriction may apply):

     LF   137400 - 137600
          137600 - 137625 (WSPR-15)
     MF   475600 - 475800
          475800 - 475825 (WSPR-15)
    160m  1838000 - 1838200
          1838200 - 1838225 (WSPR-15)
     80m  3594000 - 3594200
     60m  5288600 - 5288800
     40m  7040000 - 7040200
     30m  10140100 - 10140300
     20m  14097000 - 14097200
     17m  18106000 - 18106200
     15m  21096000 - 21096200
     12m  24926000 - 24926200
     10m  28126000 - 28126200
      6m  50294400 - 50294600
      4m  70092400 - 70092600
      2m  144490400 -144490600

==Credits==

Credits goes to Oliver Mattos and Oskar Weigl who implemented PiFM [1]
based on the idea of exploiting RPi DPLL as FM transmitter.

Dan MD1CLV combined this effort with WSPR encoding algorithm from F8CHK,
resulting in WsprryPi a WSPR beacon for LF and MF bands.

Guido PE1NNZ <pe1nnz@amsat.org> extended this effort with DMA based PWM
modulation of fractional divider that was part of PiFM, allowing to operate
the WSPR beacon also on HF and VHF bands.  In addition time-synchronisation
and double amount of power output was implemented.

Peroulas <james@peroulas.com> added several command line options, a
makefile, improved frequency generation precision so as to be able to
precisely generate a tone at a fraction of a Hz, and added a self calibration
feature where the code attempts to derrive frequency calibration information
from an installed NTP deamon.  Furthermore, the TX length of the WSPR symbols
is more precise and does not vary based on system load or PWM clock
frequency.





==Referensi==

* https://github.com/JamesP6000/WsprryPi
* https://github.com/threeme3/WsprryPi
* https://github.com/DanAnkers/WsprryPi
* http://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
* http://www.scribd.com/doc/127599939/BCM2835-Audio-clocks
* http://www.scribd.com/doc/101830961/GPIO-Pads-Control2
* https://github.com/mgottschlag/vctools/blob/master/vcdb/cm.yaml
* https://www.kernel.org/doc/Documentation/vm/pagemap.txt
* http://www.gqrp.com/harmonic_filters.pdf