Royal SRS - Direct 13 to 18 channels failing to operate using Spektrum DX20 transmitter

  • I am totally new to Powerbox. I only just recently purchased (a week ago) a ROYAL SRS to install in a CARF P-47. Initial impressions of the Powerbox Royal SRS system are good. A very capable unit especially with the internal IGyro. I am looking forward to flying it.

    Now to my problem (and I hope it could be a “newbie” finger problem). As I use a SPEKTRUM DX20 radio, my problem is that the “extra” Direct 13 to 18 channels fail to work/operate on the Royal SRS.

    On the DX20 I initiated the X-plus option and I am able to see the extra X+1 to X+8 channels on the DX20 “monitor” and see/verify the operation of the DX20 switches I assigned to operate on the X-plus channels.

    On the Royal SRS, TX-System selection I choose the “DSMX 18K” option and then carried out the “Bind”.

    When I am in the “Output Mapping” mode I am able to access and assign all the available Direct 1 through 18 Channels - no problem.

    Everything that is connected to Direct 1 to 12 channels works/operates correctly BUT anything connected to Direct 13 to 18 channels do not.

    I have carried out a few “Resets” via the Reset menu but all to no avail.

    I must be missing something. If anyone can help me it would be very much appreciated.


    P.S. On switch-on of the Powerbox the firmware/software is V11.7.

  • Richard

    On the DX20 transmitter to energize the X-PLUS function all I can do is to go to System Set-Up/Frame Rate/scroll down to XPLUS and ACTivate it. Then the 8 extra channels become available. Very similar to the DX18.

    So if the Royal SRS doesn’t support 20 channels but only 18 Channels, can I not just use the 16 channels that I require using the DX20?

    Are you saying I cannot use my DX20 transmitter with the Royal SRS due to compatibility problems by saying the above i.e. “The Royal SRS doesn’t support 20 channels only 18”?

  • We don´t have a DX20 here so I cannot test what is the signal difference to a DX18. If they just split another channel to make 4 slow/low resolution channels out of one it´s a new protocoll.

    But I had another customer using a DX20, just don´t remember what he did.

    Spektrum only transfers 12 channels with full resolution, if you use the xplus 8 option it´s only 10 or 8 - don´t remember.

    Do you need 20 channels? The Servomatching feature gives you a lot of options to reduce the channel count from the radio. Maybe you can get it working without XPLUS

  • Richard,

    Yes your are correct in saying the Spektrum on transfers 12 channels with full resolution. Looking at the DX20 Users Manual there is a caution note with the X-Plus Input configuration description. It reads the following:

    CAUTION. Do NOT connect throttle or any primary control surface to the X-Plus channels. The X-Plus channels are intended to be used for auxiliary functions only. X-Plus channels have a resolution of 512 and variable latency from 22ms to about 88ms. When X-Plus is active, the first 10 channels default to 22ms.

    Not sure what that all means but I understand what the caution is warning the user about.

    No! I don’t need 20 channels. As I say I am new to the Powerbox Royal SRS (not up to speed with it yet, keep pressing the wrong buttons LOL) so with regards to the Servomatching feature (to reduce the number of transmitter channels) I will have to look into that - to see how it works - to reduce the number of channels used by the radio.

    So with my DX20, on the Royal SRS I can only play around with 12 Direct signals/channels from the radio? Correct?

    Any further assistance would be helpful.

    Thank you.

  • Hi 28Squadron,

    I have a Carf P47 running on a mercury - same principle just slightly less capable. I run 12 channels but that's only because I've been lazy. As Richard says, you can double up the controls on to a single channel. It's a little challenging to start with but once you understand the PB way of doing things it all becomes very easy. Loads of willing support on this forum - not least from Richard who appears not to sleep very much given his speed of response!

    Good luck with the project - you'll love the 'Jug'!



  • Hi Bob,

    Yes Richard has been very quick with his replies. Much appreciated.

    Being new to PowerBox system - as you say - I will have to get up to speed with Servomatching. I have already started to reduce the number of channels as used on the radio. I will start practising using the Servomatching on the Rudder/Tail wheel steering before I go onto the Aileron and Flaps.

    Yes I did add a few extra functions in the “Jug” i.e. Canopy Open/Close, Lighting (formation and landing lights), etc hence the requirement for the extra channels.

    Certainly looking forward to getting the big “Jug” in the air and by all indications (guys that I have talked with) it is a good flier.



  • Hello,

    actually we are not working on that. From my side I think Spektrum has to develope more capable radio/telemetry link for playing in the Pro range including a modern bus system which has servodata and telemetry on one wire. The development the last years at HH has shown that they want to exclude 3rd parties more and more. It started with the discontiouing of the TM1000 which was needed to have access to the telemetry link.

    We will see what the future brings, have a look to the Core - this is definitely the future!