Hi MF,
I've added a simple ICL7667CPA MOSFET-driver to the GPIO of the
Raspberry. It's power supply is 5V coming from the GPIO itselfe. This
leads to a 5V rectangular signal with lower output impedance. I've
coupled the output matching circuit so that the output power is now 50
mW / 17 dBm, i.e. 7 dB more power then in my previous test.
Iamge:
https://dl.dropboxusercontent.com/u/19882028/MF/17dBm%20RPI%20WSPR.jpg
The beacon is running now on 475.685 kHz.
73, Stefan/DK7FC
Am 18.03.2015 21:45, schrieb DK7FC:
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.
|
|
