I/O Pin Waggling on the RaspberryPi

I have been building more LPF’s to the same design for the RasPi. The only band that has produced no reports was Top Band, 1.9MHz. Taking a look at the signals that I was receiving the power levels seemed to be 5Watts so, with the clatter on 160m my 10mW was lost.

Better luck on 10MHz today.

2013-03-30 14:12 G3ZJO 10.140177 -21 0 IO92ng +10 0.010 DK6UG JN49cm 706 439
2013-03-30 13:28 G3ZJO 10.140167 -24 0 IO92ng +7 0.005 DK3SML JN49sf 806 501

Whilst producing the 1.9MHz LPF I ran on 474KHz, 630m, not expecting any results really, well the 3 stations close and capable of receiving me at really low powers did.

2013-03-29 15:08 G3ZJO 0.475701 -24 0 IO92ng +0 0.001 G4KPX JO02dj 80 50
2013-03-29 15:04 G3ZJO 0.475699 -23 0 IO92ng +0 0.001 G3XIZ IO92ub 46 29
2013-03-29 17:08 G3ZJO 0.475699 -29 0 IO92ng +0 0.001 G0VQH JO02fe 91 57

I now have a 3.6MHz LPF near completion. Later today I will test there.

Edit – its now later today.:)
Not DX but its working nicely on 80m.

2013-03-30 20:34 G3ZJO 3.594094 -20 0 IO92ng +10 0.010 G8JNJ/A IO90hx 148 92
2013-03-30 20:28 G3ZJO 3.594092 -23 0 IO92ng +10 0.010 G7JVN JO00gv 182 113

Fun Stuff WSPR with no TX

A fun project. The Raspberry Pi has a PLL which runs at 2GHz and fractional divider combo built into it which is intended to be used as a general purpose clock.

First a team thought of using the Pi to transmit your IPod music at 100MHz. Then MD1CLV decided to use the idea to send WSPR at up to 1MHz or so. PEiNNZ then ran with the idea and delved further into the fractional divider.

At the moment I am happy with the cleanliness of the signal up to 21MHz, 24 and 28MHz have an image close to the wanted and more spurs than I would like to transmit. However this is work in progress and in theory it could go to 250MHz.

I found that the usual USB power supplies cause 50 and 100Hz sidebands, I had to build a twin regulated 5Volt USB supply fed from a battery or good linear PSU.

All that is needed is an LPF and you have a 10mW QRP WSPR TX.

I ran it for the first time today, one report on 14MHz then on 40m the reports are coming in by the dozen. Best Spot up to now.

2013-03-28 18:26 G3ZJO 7.040071 -22 0 IO92ng +10 0.010 LA9JO JP99gb 2124 1320

GMSK Mode for 630m QSO

I have recently been testing GMSK on 630m. Information and software for the mode are both rare. Gaussian Minimum Shift Keying has been adopted in the Digital radio fields such as the GSM Mobile Phone Network and DStar Ham Radio.

The only Software that includes it as a keyboard mode for Ham Radio to my knowledge is MMVari by Makoto Mori JE3HHT.

Download Here

JE3HHT Software is always of a high standard and MMVari has some superb features, originally a project to use the full Japanese Character set implementing Varicode.
The software shows a warning when first run about use with other languages, this can be ignored, I think the software went through some changes which include adding European Character sets.

Speed and hence Bandwidth is adjustable, the frequency shift is half the Bit Rate. For MF use we can select 15.625Hz, the bit rate is a little slow but represents a comfortable QSO typing speed.

Being a Frequency Modulated mode it is suitable for Non Linear PA’s.

G4GWT has been testing the mode also and his power level enables 100% copy with me, he had had near 100% copy from Germany also. My personal best 2 Way QSO is with G6AVK over 127Km both stations being QRP level.

The G4GWT to G3ZJO path is 188Km.

Finland on 630m almost 2000Km

Overnight last night I had several Spots of my WSPR2 from OH5YW Finland.

2013-03-16 00:32 G3ZJO 0.475627 -23 0 IO92ng +7 0.005 OH5YW KP30ju 1924 1196

The night before produced a Spot from OH6JKN.

2013-03-15 03:52 G3ZJO 0.475638 -27 0 IO92ng +7 0.005 OH6JKN KP22xk 1944 1208

The possibility of over 2000Km now seems closer using QRP and foolishly small antenna.

Throwing a rough circle over the map illuminates some intriguing possibilities, no time to get bored.

QSO Modes for 630m

Several stations have been testing QSO modes on the 630m band.

RTTY 50Baud 85Hz Shift has worked well for the stations that run high ERP. PSK31 has worked well for those with linear PA stages and higher ERP.

For lower ERP guys like me these are too fast a data rate, I think 150Km is a reasonable target during daytime conditions to aim for, so what will make the trip.

CMFSK8 made it but is too critical to tune and has only produced one way copy.

I had hopes for JT9-2 but whist the new release version is better and has been OK with my slight Kenwood TS870 drift on some long sessions, from cold it failed totally on another session. JT9-5 failed totally and has a PTT problem, something that has bugged WSJTX from day one. That leaves JT9-1 as the only mode in the suite which is stable and has been of use for QRP with ‘normal’ HF rigs.

JT4A is not such a nice random message mode as JT1 but does do well, recent tests have produced good results.

This leaves us still looking for a keyboard mode for QRP use on MF, MFSK4 is a little slow but the bit rate is too high, MF guys are patient on the whole, a slowed down version would be worth a try.
It seems that all recent developments are toward getting results on extreme DX with more and more critical parameters. Having to go back 40 years in technology to computer generated RTTY shows that most development has been for HF/VHF.