I need to test the antennas to make sure they will function as reasonable as can be expected. I’m secretly hoping that it can comfortably transmit/receive at a distance of at-least 10 km. This is probably realistic, remembering that the range of these XBee transmitters is about 20 km (as per specs).
A picture of the test range is below.
Details of the testing is below.
Testing on 16-June-2013
I set up the payload on a stool up the road from where I lived and mum watched over it. It was aligned so that from Taylor point it would be roughly 45 degrees. i.e. minimal loss. Taylor point is 4.5 km away. I was able to get lots of data from the payload while sitting on the beach. I also got 1/4 of an image before it froze. I then waited a few minutes for the payload transmission to give-up…which it did. Then I was able to receive data. I then put the earth station into test mode…it requested test mode and the payload accepted and responded accordingly. This is good. This means that at 4.5 km the communication both ways seems to work relatively well. The next test is from Yorkey’s knob ~8km away.
Testing on 23-June-2013
I set up the payload on a stool up the road from where I lived again…this time left it all by itself. I drove to Yorkeys Yacht club and was able to get some packets from a few rocks, just up from the sand. I wasn’t able to get a picture transfer starting very well.
I then drive around the corner to the top and found a perfect area to test! It was a patch of grass with uninterrupted view back to the hill where the payload was. I was able to get through about one quarter of a line of dots (4 1/2 lines of dots = whole file). So…not able to get an image unfortunately, but a lot better.
When I got home, I found that about 24 minutes after I had set up the payload on the stall, the wind had blown it down. Fortunately the antenna was not damaged. Amazingly I was still able to receive the signal. This suggests a fairly resilient system.
I still need to make file transfers a bit more robust. currently it just stalls…no more dots. I had an idea just was I was leaving that I should enable debugging in the xmodem library. I think I’ll also examining the xmodem code to try and guess where things are playing up and see if there is some retry/timeouts that can be adjusted. Even though I have my sights on RFS900 modem, I think xmodem enhancements are a good thing to look at.