Minimal digital signal source

[djrm]

Greetings everone,
I'm a new member just starting on a Portsdown build. My objective has been to get s system working to co-operate with SDR transmitters and receivers. Ive been experimenting (playing) with SDR recentley and when I discovered the BATC Portsdown project it fitted nicely into my realm of activities.

I have a miniml system comprising of an ADF4531 and Modulator board driven by a Raspberry Pi3 with 7 inch touchscreen. Yesterday I added a vMix source on my laptop streaming through WiFi to the RaspberryPi.

For reception I have an old Dreambox500 and a more recent Dreambox800HD. The Dreambox800 seems quite suitable for the Portsdown, I have managed to get it to receive at various sybol rates down to 250k / sec using both Mpeg2 and H264. The old Dreambox500 can only manage Mpeg2, and it cannot lock onto signals with symbol rates below 1000k / sec.

I have been using some SDR radio receivers together with a software DTV decoder which is part of the Sdrangel project, I have struggled with this on some of my reeivers but I ca now decode transmissions from the Portsdown most of the time with some receivers. Things are starting to come together now and I'm waiting to receive a LimeMini SDR in the next day or two and expect this will give better results.

Here is a picture of the minimal system

IMG_20181104_153554a.png (693.74 KiB) Viewed 1250 times

Up until now I'be been powering the Raspberrypi and Modulator from seperate power supplies. I've been looking in my parts boxes for a suitable power supply for the complete system, so far I have not managed to power the raspberrypi and display with anything except the 5.2V microUSB mains supply, I was hoping to use a small LM2595 module fed from the same input to the modulator but this is not able to supply the LCD and display without problems, this may be a problem withthe bench suply I'm using or the module itself - more inverstigation needed. In the meantime I'm successfully powering the frequency synthesier and modulator from the raspberry pi GPIO bus.

It has been very rewarding learning about these systems, I'm very impressed by the software and its integration with the touchscreen and menus. I have a lot to learn yet though. In the future I'm hoping to be able to receive signals from the new Es'hail-2 but to do that I'll need to get a dish and LNB.
Kind regards, David