Ok about your interesting test with 0.5 TX Power. Sorry, I cannot copy you
on day time, due to high carrier QRM just on your transmitting QRG. On the way
now, the G3WCB signal is good around 0 dB S/N, at about the same distance as
I am now transmitting 2 or 3 times to see the difference in ON7YD and OR7T
You know that I am always transmitting QRP on MF. Maximum power is 3 Watts
output TX. Now I have exactly the same power as your : 0.5 Watt. On night this
winter I was mostly using below 0.1 Watt.
My large winter antenna (Inv L) is dismounted and I am using a single 25
meters vertical tube without top hat capacitance. The effeciency is around – 20
dB, so the PAR (apparent radiated power) is 5 milliwatt.
If you want to have real QRPP test, you can test WSPR at 500 micro watt
PAR, and still have lucky reports up to 1500 km.
Best 73. Andy F6CNI – JN19QB
Sent: Friday, March 27, 2015 10:29 AM
Subject: RE: LF: TXing WSPR on 630m on a Raspberry Pi, Stefan in
solid signal here, best decode was at -8dB!
73, Rik ON7YD - OR7T
I'm now running the 7667 at 13.8V supply voltage. The MOSFET
driver is easily keyed by the Raspi, directly with its rectangular output. I
measured 0.5 W TX power
at 50 Ohm. This is what i'm running tonite
Not a real PA, just the Raspi and this IC in a DIL-8 case.
Am 23.03.2015 16:11, schrieb DK7FC:
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
beacon is running now on 475.685 kHz.
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.
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! ;-)
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.
Does someone have good
ears to get a decode from me? :-) It is a challenge! :-)
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
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