To get VTX options in the OSD you need to use mavproxy to set them up, see OSD based parameter menu — Plane documentation for details. You can see which options are available based on which VTX_* options are available.
thanks, after reading that documentation I think its bit too advance for me at this stage as Im new to Ardupilot, 
With the RC channel (on a 3 pos switch) I can only toggle between two power levels , is that how its meant to be ?
The documentation says it supports 6 power levels! is there a way to get more power levels on a switch or a rotary switch (with a custom curve) ?
What VTX do you have? The power level logic is very imprecise. Did you set VTX_MAX_POWER? Is the VTX unlocked?
Im using rush FPV solo tank , I set the max power to 800mW and yes its unlocked as well
On your radio create a 3 position curve for your switch so you can send different pwm values. I have mine set to 25,200,800 and had to make a custom curve to get 25. Initially without the curve it just sent a request for pit mode. I just adjusted the curve and watched the osd to see when i had the 3 power levels I desired.
thanks. I thought a custom curve might me a solution to this. would u mind telling me the values you used in your curve ?
I just didn’t think that away. I tried this afternoon and it worked. The problem hanging for months and solved today. Thank you. If I use the pot slide. I can get all the power level.
1 Like
This is also the easiest way. First remember the switching points with the pot slide and then use them for a custom curve.
I completed Matek F405 (4.3.1) with VTX JHEMCU 20-600 (IRC tramp) and I set:
VTX_MAX_POWER,600
VTX_OPTIONS,0
VTX_POWER,200
Manually I set on the VTX 25mW.
When I toggle the Tx switch I have on the OSD either 0mW or 1000mW, even if on the VTX still lights up that 25mW, but it is warm like on 600mW.
Please, can be something changed to see a normal behavior?
Tramp tells you the power that is being used - if its 1000mW then it probably is. The issue is that some of the tramp VTX’s simply do not work properly - the Rush Tanks in particular - and it seems like some VTX’s are based on the same design. I have been able to get a genuine ImmersionRC VTX working fine and also an HGLRC, but I could not get the Rush Tank to work at all - I’m guessing the JHECMCU might be one of these designs.
Sorry Rush Tank is Smart Audio - not IRC. So your setup should work, can you send a link to the VTX?
here is the link: https://www.aliexpress.com/item/1005004078526302.html?spm=a2g0o.order_list.0.0.21ef1802eW7YSe
Please, should I see something in the messages in MP regarding to VTX, if it is communicating well with FC?
RushTank VTXs run flawlessly with Betaflight or INAV. Also, in general, the adjustability for SmartAudio capable VTXes via OnScreen Display is much better solved than the only rudimentary power setting in ArduPilot.
What is the reason for this?
The reason for that is that the firmware is different.
You are very welcome to do a github.com pull-request to improve ardupilot’s firmware support of RushTank VTXs.
Why so dismissive? I myself only use ArduPlane and find that good. But I also know the OSD possibilities of INAV or Pitlab and just wonder if this is not also possible with ArduPilot, because such an OSD display for setting all parameters of a VTX is already quite practical.
That there are other firmwares is clear to me. But it is also open source and you can see how it is solved there. You certainly do a good job, but that does not mean that there is no potential for improvement. I do not make any demands, but wishes may be expressed, or is that no longer desired?
Wishes and/or criticism are very welcome. But PRs are even more welcome! 
The main reason is that vendors test their implementations against betaflight rather than against the specification. There are lots and lots of broken implementations out there that work against betaflight’s (different) implementation. There are even implementations that match iNav’s (well-known) bugs. I have made some effort to cater to some of these in the latest release, but I do not have the time or the patience to try and fix every single one. If you find something doesn’t work chances are it is the VTX protocol implementation at fault. If you want to fix you need a logic analyzer and some time.
1 Like
Where can you get the specification for SmartAudio? TBS?
1 Like