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

To: [email protected]
Subject: Re: LF: TXing WSPR on 630m on a Raspberry Pi, Stefan in QRPPPP...
From: [email protected]
Date: Wed, 18 Mar 2015 21:32:06 -0230 (NDT)
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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.




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