As you noticed there is a lot of interest from Europe in your LF activities.
If you are able to put 50 .. 100mW ERP in the air I would recommend at
least 30 second dotlength for QRSS, if the signal turns out to be strong
you can always go to shorter dotlengths.
If you prefer not to use a PC to transmit QRSS you can indeed program a
PIC, it will be OK for beacon transmissions but might be a bit complicated
for a 2-way QSO to change the text. Anyway, if you want to make a 2-way
QRSS QSO you will need a PC for receiving the signals.
Another alternative to transmit QRSS is to use a normal memory keyer and
add a large capacitance to the timer of the keyer to slow it down. I
believe G3XDV did this with success.
If you are ready for receiving I would recommend to try to copy DCF39 on
138.830kHz. This commercial station runs about 30kW ERP and is located near
Magdeburg (Germany, JO52WG). It transmits a carrier that is interrupted by
a kind of 'RTTY burst' every 10 seconds. Amateur signals on 136kHz are
about 45 to 55dB weaker (7 to 9 s-points), so you would need to copy DCF39
at 45dB SNR to be able to copy an amateur station in CW. Fortunately we can
win a lot of dB using QRSS, if you copy DCF39 at 30dB SNR you have a good
chance to be able to see QRSS3 signals (QRSS at 3 sec. dotlength), at 20dB
SNR it is worth to try QRSS30 and QRSS120 would require only 14dB SNR.
Regarding TX and RX equipement for 136kHz, there is a lot of information on
the web. I have an overview of these websites at :
73, Rik ON7YD