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LF: TXing WSPR on 630m on a Raspberry Pi, Stefan in QRPPPP...

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Subject: LF: TXing WSPR on 630m on a Raspberry Pi, Stefan in QRPPPP...
From: DK7FC <[email protected]>
Date: Wed, 18 Mar 2015 21:45:09 +0100
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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! ;-)


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.
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