[Ground-station] 10GHz Remote Receiver - update, and how best to do the web interface?

Tue May 29 16:22:15 PDT 2018

Hi Michelle,

Can you run a websdr station to talk to the RTLSDR dongle?  That would make the RTLSDR's receiver bandpass accessible/visible to everyone in realtime. 

www.websdr.org if you havent seen this in action. There are other receiver on the web packages too. 

Or am I missing something here?

Regards,
Douglas KA2UPW/5

> On May 29, 2018, at 5:22 PM, Michelle Thompson via Ground-Station <ground-station at lists.openresearch.institute> wrote:
> 
> Attached is a screenshot from rtlsdr_scanner (https://github.com/EarToEarOak/RTLSDR-Scanner) and some other photos of LNB on a Stick. This is a DirecTV LNB mounted on a mast and received on an RTLSDR. The RTLSDR is run by an Odroid which is reachable by WiFi link. 
> 
> LNB on a Stick is intended to be a remote receiver looking for things like balloons and payloads (and people!). Right now, the receiver is pointed at the local 10GHz beacon here in San Diego and is successfully receiving it. The beacon is the spike towards the middle of the screenshot. This is a half-watt 12dB gain beacon 23 miles away over terrain. 
> 
> Yes, you get even more gain with a dish, but then we lose that cool 40 degree beamwidth. Think of this as more like a spotting scope. Additional gain can come on board when remoting, reporting, and processing functions are nailed down. 
> 
> If you're looking at the screenshot and wondering why it's at 618MHz, it's because that's the IF frequency received by the RTLSDR from the DirecTV LNB. The beacon is on 10,368.36 MHz. The IF is 9,750 MHz. The signal sent to the RTLSDR is at 618.36 or so. The beacon does drift. The RTLSDR is not calibrated (yet). The LNB is a PLL version and that does help. Further stability can be obtained by aligning the received bandwidth with a locally generated stable tone. We have several synthesizer boards that can be pressed into that service and are working on that angle as well.
> 
> We want to be able to turn this receiving station around and point it north (or wherever) and ask the SBMS etc. to yell down at it just as soon as a not-completely-janky way of recording/sharing/showing the receiver (on the web) emerges. I want them (and anyone else) to be able to transmit and see whether or not they are heard at the receiver. To hear LA I might have to move the receiver higher than where it is in Carmel Valley, but I think we should try it a couple of times as-is and see. A simplistic link budget and what I know about the stations that have participated in the tune-up parties in SoCal makes it look like the link can close. 
> 
> So - easily seeing the receiver on the web is the pressing question. Currently, in order to see anything at all on this receiver, you log in from the local LAN using VNC (and ssh port forwarding) and start gqrx or rtlsdr-scanner or whatever. This works. However, that’s like a sysop approach. What I’m after is a receiver interface on the web that anyone can reach. 
> 
> rtlsdr_scanner (running on the Odroid) can produce .csv files for scanning runs. With rtlsdr_scanner running, I can stash the scan results in a .csv file and then post that to a website ever so often. But - there’s got to be a more elegant way that gives immediate results along with storing/posting the historical archive of the scanner runs (the .csv files).
> 
> Is there some magical HTML5 approach? Packages we should be looking at? Let me know? This is a solved problem? Adding immediate visual feedback of successful receive is the goal. I wanted to ask around before picking something not-quite-right. 
> 
> This prototype is the foundation of remoting the full-blown Phase 4 radio, so getting the right ideas worked out for simpler or narrower bandwidth applications (like the 10GHz balloon and some satellite payloads) I think will pay off in the long run. 
> 
> So far, the odroid+rtlsdr+LNB+biasT+wifiDongle in a sprinkler box on a mast is hanging in there and working well. Odroids do seem to run hot and being in a box has resulted in temperatures from 65C up to 75C - so far. This Odroid does has a fan and it does run. This box does have downward-facing holes for ventilation.
> 
> The VNC isn't exactly robust (Using Chicken of the VNC here). It drops with "protocol errors" and "rectangular problems" and sometimes it just drops. Also, the entire thing is AC powered and not, say, powered from a solar panel. In other words, it's not off-grid or Burning Man Ready - yet.
> 
> But if it was battery/solar powered, and if the backhaul wasn't wifi, but perhaps cellular or something else, then LNB on a Stick would be very grab-and-go. 
> 
> Future stuff? Tracking an APRS-revealed signal (like a balloon or person or vehicle). Trying phased arrays of LNBs. Receiving live video. Experimenting with adaptive coding and modulation in DVB-S2/X. 
> 
> More soon!
> -Michelle W5NYV
> 
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