Hi Stefan,

That looks very nice.  Is there a script for generating RF with a pi?
A 500Hz tone is easy but for higher freqs it seems a DDS is needed.


73
Joe VO1NA
On Wed, 18 Mar 2015, DK7FC wrote:

Hi MF,

Today i've got i 3rd Raspberry Pi. I quickly installed the WSPR softaware and since a few minutes i am transmitting WSPR-2 on 630m, my usual frequency 475.685 kHz.

I'm directly using the GPIO output pin, without an amp stage behind! The rectangular 3.3V output voltage is passing a cap and an isolation transformer (FT50-77) as well as a simple pi-filter, because it is a Raspberry pi! ;-)

See: https://dl.dropboxusercontent.com/u/19882028/MF/Raspberry%20Pi%20B%2B%20WSPR%20TX.jpg

I measured an output power of about 10 mW at 50 Ohm. It is now connected to my MF antenna and transmits in a 100% duty cycle. I still have to learn how to reduce it but this will not take long.

With 10 mW TX power i managed decodes by 3 stations now.

3 spots:

Timestamp     Call     MHz     SNR     Drift     Grid     Pwr     Reporter RGrid     km     az
2015-03-18 20:32      DK7FC      0.475684      -21      0      JN49ik 0.01  DH5RAE      JN68qv      345      98
2015-03-18 20:12      DK7FC      0.475685      -24      0      JN49ik 0.01  F1AFJ      JN06ht      667      247
2015-03-18 20:06      DK7FC      0.475683      -27      0      JN49ik 0.01  DL1DBC      JO41bi      217      349



Does someone have good ears to get a decode from me? :-) It is a challenge! :-)

73, Stefan/DK7FC

PS: The signal is so weak that my RX antenna frontend is not overloaded, so at that power level i can transmit and receive to the same time :-)
PPS: A small amp stage will follow soon, i intend to use an BS170 running at 5 V.