Jump to content

Sussex Pete

Members
  • Posts

    57
  • Joined

  • Last visited

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

Sussex Pete's Achievements

1

Reputation

  1. Thanks to all for your input which helped me think clearly about the problem and its limitations. And to find the bug in my alarm code that was triggering warnings way too soon! Doh! But back to the question, Am I receiving good data at the rx?, I have now learned where and when the answer is no and written new alarms for Link Quality low and critical to flag it up. There's a log tests and results here: Important Firmware Update - ACCESS 2.1.x - Page 31 - RC Groups (p. 31 post #460 ff). In parcticular, I have adopted voice alarms for my Archer rx, at these values: Link Quality Low: VFR Low 75% (can be reached sometimes near the 35dB "floor" zone of the RSSI data) or RF Signal Low 34db (i.e. once step below a 35dB floor and 1dB below the FrSky advised limit) Link Quality Critical VFR Critical 65% (reached into the weak zone but some way from link loss) or RF Signal Critical 30dB (before any sudden decline in VFR and 2dB below the FrSky advised limit) with a half-second allowance for dips while circling. My feeling is these will give me comfortable warnings to fly closer. I plan to set the alarm levels for each rx installation separately but expect the numbers to be similar.
  2. Thanks Mike. I do understand antenna radiation patterns - a physics PhD doesn't wear off too quickly! 🙂 I generally hang my tx from a neck strap and fly facing the model with the tx antenna to one side parallel with the top of the tx so the radiated "donut" is maximal directly in front of me with the donut, rather than the antenna, pointing at the aircraft. But it's your point about VFR that lit a bulb in my head and suggests a paradigm shift: never mind the tx shouting about the RF signal level, the only question should be, am I receiving good data at the rx? In other words ignore RSSI, a value calculated in the rx and hence subject to all sorts of rx hardware assumptions and variabiltity, and concentrate instead on VFR, which is not a calculation but a simple counter of valid data received. And lo! And behold! My VFR remained excellent throughout! In the air and on the ground, the logged VFR stayed between 92% and 100% all day. In the flight above with my max altitude and max downwind, VFR stayed at 96% or above and mostly nailed at 100%. I was receiving good to excellent data despite the RSSI warnings. So does this sound like a plan? Ignore FrSky's generic "suggested" levels of 35dB and 32dB and use ground tests to determine an empirical, rx-specific RSSI at which VFR falls. Then set the RSSI alarms to a few dB above that. A bit more effort in setting up each model in exchange for a more reliable set of warnings? In fact I already have a LS/SF combo reporting high lost frame rates which wasn't triggered at all all day. Perhaps I should have heard that silence over the apparently misleading alarms!
  3. FrSky expect 1km range in clear air on 100mW output and colleagues who fly F5J get much better range than I am. The rx is sending telemetry back at the same power (but lower frame rate). The tx doesn't record telemetry signal level but I don't see any loss of telemetry data - much as I have not seen a big dip in valid frames getting to the rx. Though I'm not sure of those last points actually tell me anything except I haven't quite gone out of range! :)
  4. I see your thinking. Any pair of lines defines a plane but you're right that the current arrangement puts the antenna plane parallel to the wing and the CF in it (and indeed the CF boom). That was pretty much my first thought too once I saw the log plots. But other people (on FB) tell me they have the same arrangement of antennae and no RSSI problems, pointing fingers at a duff rx (or at least one duff antenna). This will need some testing to sort. This week I hope as the next round is weekend after next! 🙂
  5. Thanks Steve very useful! Not very new I bought them a while ago with projects in mind. I will check with Richard if I don't get this sorted easily
  6. Yes. And the rx has the latest firmware too
  7. Thanks Denis you confirmed my suspicion: my wing is shadowing both rx antennae as I circle. Below is a plot of altitude and RSSI from a flight in yesterday's FxRES contest in Shrewsbury (where I topped just over 1000 feet 😇). The regular dips in RSSI pretty much coincide with my cirling. The steady decline in mean RSSI as altitude increases looks fine but the dips are HUGE - from 56db to 35 db, effectively a 7-fold reduction in received power and almost 3-fold reduction in range (if I have done my sums right). At 56db the rx is well within range but at 35db it's getting short - as well as annoying hearing repeated verbal warnings from the tx! The good news is that the valid frame rate only dipped from 100% to 97% in those moments of a few log intervals (0.2sec). Both my antennae exit the fuselage ahead of the wing at 90deg to each other. They are also well away from the metal pushrods which testing showed also significantly affected signal. However, in a thermal turn, the banked wing with a CF LE and spar can easily cross the line of sight from tx to rx. I committed the sins of testing the installation with the wing off and conducting pre-flight range checks with the aircraft facing me - both showed good range of course. I don't have a place to put a satellite rx - it's a pod-and-CF boom fuselage with nowhere (obvious at least) to put it. But I am going to rethink the antenna positions to try to ensure there's always one un-shadowed.
  8. Hi Mike-- Can I ask where you found schematics? I just had my first TX Antenna Fault on power-up of an 18-month old Taranis X9D+ 2019 running OTX 2.3.11 and ACCESS. After talking to Richard at T9 (thanks!) I watched the RAS values on the Radio Hardware menu (Relative Antenna Status - was SWR, see user manual p.19, no Rx or telemetry required). I understand from the user manual RAS>51 is a fault to I'm guessing that's what happened. Untouched, RAS varied between 0 and 6. As I moved the antenna by hand, I got it up into the 30s in some holds/positions but it reverted to near zero when I moved my hand away. This essentially shows the impact of external factors on the antenna impedance at 2.4GHz. When I got the fault report last weekend, the tx was on damp grass and I was moving the antenna at the same time. Since then, I have been unable to reproduce the warning. So my guess is the combination of damp and hand momentarily took RAS over 51, but in normal operation, RAS<10 is fine (as Richard suggested). I took the back off the tx and checked the original factory-fitted antenna. Photos below. It looks like the glue blob is supporting the coax. I cannot actually see all of the solder joints but they look well aligned. The nearby SMDs look fine. I have to say Allan's before picture made be wonder if his antenna had been (poorly) repaired in the past. The antenna itself (probably - it's glued in) looks like a standard short FrSky coax antenna stuck into the plastic tube. The coax probably has the last 30.7mm of outer shield stripped back to make a quarter-wave monopole - just like antennae on receivers (and of course, both ends of a telemetry system are really transceivers so you'd expect some symmetry!). When you rotate the plastic tube containing the antenna, the coax is inevitably flexed so it's vital that glue and solder carries that load. That all checked out ok from my standpoint so I'm back to flying after adding "Check and test RAS<10" to my pre-flight procedures. Unfortunately, RAS is not a value accessible to logical switches to write your own warnings with a special function. Maybe we should put that in a a GITHUB request? Thanks to all the other contributors to this thread! Cheers --Pete
  9. Hi-- Can anyone from the magazine - or indeed anyone! - tell me the name of the nice angular headline font used for article titles in the magazine? Just finishing a build from magazine plans (RES-Eagle, March 2018 edition) and I would like to add some decals in the same font. Thanks if you can help! --Pete Edited By Sussex Pete on 04/06/2020 10:00:45
  10. Posted by buster prop on 12/02/2020 10:28:21: George Stringwell’s book about thermal soaring ... Thanks for the lead on that, BP, I didn't know the book before but Amazon just delivered a used copy. Very informative from a first scan through, I think my evening reading is sorted for a while! 8-)
  11. Thanks PatMc - all good knowledge! I've found a nice adjustable tow hook from Hyperflight, maybe a tad too large (metalwork weight 16g) but fits the fuselage and is nicer than I could make myself Edited By Sussex Pete on 17/02/2020 11:51:21
  12. Posted by Andy Stephenson on 16/02/2020 18:05:05: Posted by Sussex Pete on 16/02/2020 13:54:30:... - The whiskers are connected to the on-off switch (recommended in the Wildthing instructions). ... Does this mean you actually connected the whisker antennas to the on-off switch??? I'm intrigued to say the least. A. Don's right, just a piece of fishing line tied to the on-off switch in the middle of the fuselage. I had a Spektrum AR410 rx installed which does not have external antennae.  And hot-glue is great for quick assembly! Edited By Sussex Pete on 17/02/2020 11:26:57 Edited By Sussex Pete on 17/02/2020 11:29:08
  13. Posted by CARPERFECT on 16/02/2020 08:42:45: I know the horse has bolted but, always set fail safe to Zero throttle(yes i know it does not have one ) and off set the rudder, That way it can not get too far away if there is a problem. Or does Spektrum not have fail safe on all channels ?. Only ever used Futaba and they have it on all channels The later Spektrum receivers (eg the AR410 in the lost plane) do have failsafe on all channels though they default to "hold position" unless you follow a slightly different binding procedure. I know it failsafed in this instance as I was in a hard banking turn when it lost contact and leveled itself out.
×
×
  • Create New...