Nice Stefan - are the two back to back diodes just
before the LPF to catch noise spikes back towards the 7667 or another
Laurence KL7 L
From: [email protected]
Date: Mon, 23 Mar 2015 16:11:08 +0100
To: [email protected]
Subject: Re: LF: TXing WSPR on 630m on a Raspberry Pi, Stefan in
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.
The beacon is running now on 475.685 kHz.
Am 18.03.2015 21:45, schrieb DK7FC:
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.
| 2015-03-18 20:32
| 2015-03-18 20:12
| 2015-03-18 20:06
Does someone have good ears to get a decode from me? :-) It is a
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.