Dave Hopkin Posted April 25, 2016 Share Posted April 25, 2016 A couple of months ago I had a strange session that has never repeated itself so I am curious as to why, let me explain The field was a swamp, standing water on the grass very very muddy - so we flew from a bit we never usually fly from - where we were standing between two rugby posts (about 6 yds apart) I took off and immediately my Taranis was reporting "Telemetry lost" every few seconds (note no "Telemetry recovered" message) - though I had full control of the aircraft at all times - I landed very quickly and did a range check - all fine The plane was one that I had flown many times before and not experienced this problem with (or since) and nothing had been changed So I naturally was worried that my TX may have a fault, open it up and couldn't see anything obvious..... But this undermined my confidence I only flew a couple of cheap foamies for the next few weeks (but not between the rugby posts and not in such wet conditions) - no recurrence of the problem Flew the plan that I had experienced the problem with - no recurrence with that or any other plane So I have built a "blame" picture in my head that the combination of the tall rugby posts and the incredibly wet conditions were causing significant attenuation of the signal and generated the problem and that had I been flying a set up without telemetry I would not have noticed the phenomenon at al Does than make sense? Is there any evidence/experience to confirm this? Quote Link to comment Share on other sites More sharing options...
Ian Jones Posted April 25, 2016 Share Posted April 25, 2016 What are the rugby posts made of Dave? Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted April 25, 2016 Share Posted April 25, 2016 Could it have been reflections from the wet ground creating null spots? Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted April 25, 2016 Author Share Posted April 25, 2016 Posted by Ian Jones on 25/04/2016 11:37:03: What are the rugby posts made of Dave? Steel I assume, certainly metal..... Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted April 25, 2016 Author Share Posted April 25, 2016 Posted by Bob Cotsford on 25/04/2016 12:22:33: Could it have been reflections from the wet ground creating null spots? That was certainly in my mind some sort of attenuation/masking effect caused by a combination of standing water and the rugby posts Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted April 25, 2016 Share Posted April 25, 2016 No RSSI warnings? Only telemetry? I'd concur, we can't know, but the but guess would have to be some sort of unfortunate inteaction between where you were sanding, the metal posts and the extreme wet conditions? BEB Quote Link to comment Share on other sites More sharing options...
Chuck Plains Posted April 25, 2016 Share Posted April 25, 2016 The only thing I can says is, try to replicate it next time the ground's wet. I deliberately set up my RC gear right under some power lines two years ago and everything seemed to work ok. It wasn't a flying location, just on the way to one. But I've also flown near power lines, they were about 100ft behind me while I was flying and I experienced no probs there either. But each situation is different. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted April 25, 2016 Share Posted April 25, 2016 dave-i would say the damp conditions were to blame......one spot at our site over where there is a elecric/transformer box up on poles....used to give me glitches only in the wet damp conditions....on 35/MHZ stuff ... ken anderson...ne....1 glitch dept. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted April 25, 2016 Author Share Posted April 25, 2016 Posted by Biggles' Elder Brother - Moderator on 25/04/2016 12:49:25: No RSSI warnings? Only telemetry? I'd concur, we can't know, but the but guess would have to be some sort of unfortunate inteaction between where you were sanding, the metal posts and the extreme wet conditions? BEB Nope No RSSI alarms at all, only Telemetry Lost messages continually..... Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted April 25, 2016 Author Share Posted April 25, 2016 Posted by ken anderson. on 25/04/2016 13:54:50: dave-i would say the damp conditions were to blame......one spot at our site over where there is a elecric/transformer box up on poles....used to give me glitches only in the wet damp conditions....on 35/MHZ stuff ... ken anderson...ne....1 glitch dept. Well its never recurred and I have regained my trust in Taranis - hopefully it will be a long time before the same passchendale like conditions recur!!! Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted April 25, 2016 Share Posted April 25, 2016 Posted by Dave Hopkin on 25/04/2016 15:56:27: .... hopefully it will be a long time before the same passchendale like conditions recur!!! Optimist! Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted April 25, 2016 Author Share Posted April 25, 2016 Posted by Bob Cotsford on 25/04/2016 16:58:34: Posted by Dave Hopkin on 25/04/2016 15:56:27: .... hopefully it will be a long time before the same passchendale like conditions recur!!! Optimist! I pay good money for foam, wood, motor and batteries then chuck in into to air............ I have to be!!!!! Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted April 25, 2016 Share Posted April 25, 2016 I'd concur with Bob that reflections off the water surface were most likely to blame. This would be a second path for the signal which is slightly longer than the direct path. At specific heights and distances the path difference would be just right for the signals to arrive out of phase and cancel each other. I've always assumed that the telemetry link is less robust than the control link between Tx and Rx. If this is the case, it would explain why the control signal wasn't affected. Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted April 25, 2016 Author Share Posted April 25, 2016 The only other detail I can add, is that the telemetry warnings started almost instantly after take off at something like 4ft, I did a low circuit and brought it straight back in so it probably never got above 30ft or so during the obviously very short flight! Quote Link to comment Share on other sites More sharing options...
AJ Posted April 25, 2016 Share Posted April 25, 2016 Lookup fresnel zones on google. You were in it, the wet ground will have enhanced the effect. Bruce on rcmodelreviews did a good youtube vid on the subject recently AJ. Quote Link to comment Share on other sites More sharing options...
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