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A low power FM transmitter with your Raspberry Pi

23 March 2013 | by Tim G4VXE | Leave a Comment (1)

After seeing the piece about making the Raspberry Pi into a WSPR transmitter, I was also intrigued that it could be made to be an FM transmitter using the PiFM code.

Sure enough it can! I followed the instructions on the Imperial College Robotics website then downloaded the code and compiled it up. The default sound file that’s transmitted is a simple tone, but you could easily record a WAV file announcing your callsign!

What a clever bit of code by Oliver Mattos and Oskar Weigl! I’m not a bad programmer, but I wouldn’t have known where to start with this!

I didn’t even bother putting an aerial on the GPIO pin – I wasn’t looking for DX! The RF signal was strong enough to be detected by handheld receivers on the desk.

Great fun! Just the sort of thing for a snowy March day.

I am so pleased with the Raspberry Pi. What fun I have had with it, since I got it at Christmas. Unwisely, I have agreed to do a talk about ‘Life of My Pi’ at the Harwell Amateur Radio Club on April 9th. I’d better get around to preparing it, but there’s certainly going to be plenty of material.

Tim Kirby, G4VXE, is a regular contributor to AmateurRadio.com and writes from Oxfordshire, England. Contact him at [email protected].

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Is this progress?

22 March 2013 | by Juilian G4ILO | Leave a Comment (0)

The home improvements have overrun. The shack is still full of the contents of two other rooms. I won’t regain access to the PC and radios until early next week. I am typing this slowly and with considerable difficulty on the touch screen of my Android tablet.
Is this progress? Give me a computer with a proper keyboard any time.

Julian Moss, G4ILO, is a regular contributor to AmateurRadio.com and writes from Cumbria, England. Contact him at [email protected].

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Do You Google+ ?

22 March 2013 | by Alex G7KSE | Leave a Comment (4)

Do you Google+ ?

After an initial flurry on interest in Google+ I couldn’t quite decide what it was for. Like many people I keep contact with friends and family on facebook and it servers a purpose, I can’t say I actually like the platform but it does keep me in contact. Google+ is a similar swervice but for a while I couldn’t understand what it was actually for. If nobody I knew was on it then what use is it to me?

Over the past few months a number of different additions have been made to it. There are now communities that seem to be well populated including several for Ham radio.

Again I wasn’t really sure how these things would benefit me, especially as time seems to disappear very quickly at the moment. But yesterday it struck me that you get out what you put in. Not exactly innovative thinking but I posted a question on one community and was pleasantly surprised to see the responses came quickly and they were relevant. Having tested the water I think its time I used it a bit more, not just a personal news service from various blogs and sites now that Google Reader is going to be shut down.

So if you fancy dipping a toe into the various communities I can recommend it. I struggle to actually explain what the service is but as a geek I’ve found it useful in keeping myself up to date with my interests.

Alex Hill, G7KSE, is a regular contributor to AmateurRadio.com and writes from Cumbria, UK. Contact him at [email protected].

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One Mo’ Time !

21 March 2013 | by Larry W2LJ | Leave a Comment (1)

Fox Hunter’s Code of Conduct

I will listen, and listen, and then listen again before calling.

I will only call if I can copy the Fox station properly (so that I will know for certain that he is calling me and no one else).

I will not interfere with the Fox station nor anyone calling and will never tune up on the Fox frequency or in the QSX slot.

I will double check to make sure I am operating split, if necessary.

I will use full break-in if at all possible.

I will wait for the Fox station to end a contact before I call.

I will always send my full call sign.

I will call and then listen for a reasonable interval. I will not call continuously.

I will not transmit when the Fox station calls another call sign, not mine.

I will not transmit when the Fox station queries a call sign not like mine.

When the Fox station calls me, I will send only the required exchange of RST – S/P/C – Name – Power out

I will be thankful if and when I do make a contact.

I will resort to attempting duplicate contacts only if I am very certain that I was not heard the first time.

I will respect my fellow hams and conduct myself so as to earn their respect.

72 de Larry W2LJ

QRP – When you care to send the very least!

Larry Makoski, W2LJ, is a regular contributor to AmateurRadio.com and writes from New Jersey, USA. Contact him at [email protected].

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A Raspberry Pi as a WSPR beacon

21 March 2013 | by Tim G4VXE | Leave a Comment (2)

Thanks to the Southgate Amateur Radio news, I’ve just seen that Guido, PE1NNZ has turned a Raspberry Pi into a 10mW WSPR transmitter that works up to 250MHz. Just a low pass filter and an antenna are required in addition to the Raspberry Pi and the software.
The code is available here
The Readme file at Github says the following:
Makes a very simple WSPR beacon from your RasberryPi by connecting GPIO
 port to Antanna (and LPF), operates on LF, MF, HF and VHF bands from
 0 to 250 MHz.

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 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.

  [1] PiFM code from http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter

To use:
  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 to GPIO4 (GPCLK0) and Ground pins on your
  Raspberry Pi, connect an antenna to the LPF. The GPIO4 and GND pins can be
  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
  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.

  This software is using system time to determine the start of a 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. Reception reports are logged on Weak Signal Propagation Reporter
  Network: http://wsprnet.org/drupal/wsprnet/spots

  As the WSPR band is only 200 Hz wide, some frequency calibration may be needed
  to ensure that the transmission is done within the WSPR band. You can correct
  the frequency error manually in the command line or adjust CAL_PLL_CLK in the
  code.

Usage:
  sudo ./wspr <callsign> <locator> <power in dBm> <frequency in Hz>
        e.g.: sudo ./wspr K1JT FN20 10 7040074

  WSPR is used on the following frequencies (local restriction may apply):
     LF   137400 – 137600
     MF   475600 – 475800
    160m  1838000 – 1838200
     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

Compile:
  gcc -lm -std=c99 wspr.c -owspr
 
This looks amazing! Congratulations to Guido and also to Dan Ankers, MD1CLV whose work led to Guido’s enhancements.

Tim Kirby, G4VXE, is a regular contributor to AmateurRadio.com and writes from Oxfordshire, England. Contact him at [email protected].
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Gotta love those senior moment!!

21 March 2013 | by Mike VE9KK | Leave a Comment (8)

On Tuesday of this week Julie and had plans to go out for a nice dinner. When I got home from work it was time to the make lunches for the next day, have a shower and feed the cat. To have all this done before Julie got home meant we could just head out for dinner once she got in. It was a nice dinner and we took our time relaxing and talking. It was shaping up to be a great evening until we came home and our neighbour called out to us..."I think I hear smoke alarms going off in your place" As we got to the front door I could hear them and then it HIT ME...one of the steps to making our lunches was to boil some eggs!!! I forgot 6 eggs that were on the stove cooking on hi. The house was full of smoke, no fire, cat was hiding under the bed and all six eggs exploded and were EVERYWHERE!!!
I will say Julie was very understanding but I was very very upset with myself!! So no radio at all for the next week or so as I have to do some major cleaning! Our insurance has a deductible of 1,000 and I figure I can get things back to normal for 1/8 that cost. Lesson learned I am now looking for an automatic egg steamer that cooks the eggs and then turns off on it's one if I happen to have another senior moment.

Mike Weir, VE9KK, is a regular contributor to AmateurRadio.com and writes from New Brunswick, Canada. Contact him at [email protected].

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Handiham World for 20 March 2013

20 March 2013 | by Patrick WA0TDA | Leave a Comment (0)

Pat Tice, WA0TDA, is the manager of HANDI-HAM and a regular contributor to AmateurRadio.com. Contact him at [email protected].

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