Andy J Posted October 1, 2021 Share Posted October 1, 2021 Intend to buy a RB20 hub for a large petrol powered model given that the model has a requirement for 9 or possibly 10 servo outputs. Intend to use the hub with a RX8R Pro Rx as the primary input but what does the group suggest as a secondary receiver? Quote Link to comment Share on other sites More sharing options...
David P Williams Posted October 1, 2021 Share Posted October 1, 2021 I have a similar setup and use an RX4R secondary (as I already had it). Nice and small and tucked away down the back. All 16 channels available via the Sbus connection of course. Quote Link to comment Share on other sites More sharing options...
Andy J Posted October 1, 2021 Author Share Posted October 1, 2021 David does the RB20 give any indication which receiver it is using at any one time? Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 1, 2021 Share Posted October 1, 2021 On a couple of gassers that I have redundancy, I use an R9 and an Rx8R Pro as that gives me frequency redundancy as well. Quote Link to comment Share on other sites More sharing options...
David P Williams Posted October 1, 2021 Share Posted October 1, 2021 Haven't really explored that yet Andy. I have enough to think about just flying models without worrying about telemetry as well. All works fine though. The manual says it does but it looks like you have to convert numbers to binary and examine the bits. Haven't bothered to get my head around that yet. Quote Link to comment Share on other sites More sharing options...
Andy J Posted October 1, 2021 Author Share Posted October 1, 2021 Was going to PM you on that topic Ron as aware of all your past issues on interference caused by the petrol ignition systems. Have you found any secondary issues on the use of dual band RF links. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted October 1, 2021 Share Posted October 1, 2021 Please don't go private PMs while we all try to learn something more about large models, Thankyou Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 1, 2021 Share Posted October 1, 2021 (edited) @Andy JoyceSince I changed over to the redundancy bus with dual frequency RXs I've not had a single issue. So changing to the Pro Rx was obviously the first correct thing that I did, the R9 Rx is just belt, braces, jockstrap etc!. The old X8R RXs are still providing excellent service in my leccy and glow models. To be honest I'm gradually moving to glow rather than petrol now so, for me, it's going to be less of an issue anyway. Edited October 1, 2021 by Ron Gray Quote Link to comment Share on other sites More sharing options...
Andy J Posted October 1, 2021 Author Share Posted October 1, 2021 Is the use of 868MHz legal in the UK for model flying? Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 1, 2021 Share Posted October 1, 2021 Yes! Quote Link to comment Share on other sites More sharing options...
Andy J Posted October 2, 2021 Author Share Posted October 2, 2021 (edited) Well Ron it took me some time to find from the OFCOM site that the 868MHz band is indeed legal for airborne use under "Non-specific short-range devices legislation" but only with a transmitter power of 25mW which the FRSKy module does comply with for 8/16ch with telemetry. Turning off the telemetry increases the output power significantly so the module would then not be compliant with UK legislation. Interestingly the LMS and the BMFA web sites as far as I could find makes no mention of the use of 868MHz for model control. Edited October 2, 2021 by Andy Joyce Quote Link to comment Share on other sites More sharing options...
Dickw Posted October 2, 2021 Share Posted October 2, 2021 35 minutes ago, Andy Joyce said: Well Ron it took me some time to find from the OFCOM site that the 868MHz band is indeed legal for airborne use under "Non-specific short-range devices legislation" but only with a transmitter power of 25mW which the FRSKy module does comply with for 8/16ch with telemetry. Turning off the telemetry increases the output power significantly so the module would then not be compliant with UK legislation. Interestingly the LMS and the BMFA web sites as far as I could find makes no mention of the use of 868MHz for model control. The latest BMFA handbook is now an on-line handbook, and the 868 MHz band is mentioned:- https://handbook.bmfa.uk/annex-b/7-rc-technical-info At least one other (European) manufacturer offers that frequency in its equipment. Dick Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted October 2, 2021 Share Posted October 2, 2021 (edited) 2 hours ago, Andy Joyce said: Well Ron it took me some time to find from the OFCOM site that the 868MHz band is indeed legal for airborne use under "Non-specific short-range devices legislation" but only with a transmitter power of 25mW which the FRSKy module does comply with for 8/16ch with telemetry. Turning off the telemetry increases the output power significantly so the module would then not be compliant with UK legislation. Interestingly the LMS and the BMFA web sites as far as I could find makes no mention of the use of 868MHz for model control. In my case, as the R9 is the ‘prime’ Rx and provides the telemetry it’s not an issue, but how anyone could or would check is another matter. Jeti also operate with this waveband and it becomes even more accessible with the new Tandem FrSky TXs. Edited October 2, 2021 by Ron Gray Quote Link to comment Share on other sites More sharing options...
Andy J Posted October 2, 2021 Author Share Posted October 2, 2021 Well about to order an RB20, Rx8R and a R-XSR as the secondary receiver as moving to 868Mhz is yet another unknown for me. Anyone know if any of these products come with an SBUS cable or does this need to be ordered as a separate item? Quote Link to comment Share on other sites More sharing options...
David P Williams Posted October 2, 2021 Share Posted October 2, 2021 (edited) The RB20 and RX8R connect with 3wire male to male servo type leads, not included, and the RXSR has its own 6 pin connector. This will come with a lead that will connect to the RB20 but will only be about 100mm long. Edited October 2, 2021 by David P Williams Correction - just checked and my RB20 came with one male to male lead, 300mm long Quote Link to comment Share on other sites More sharing options...
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