How or When to use 'RxNum' in a Model Setup?

[Flying Dutchman]

I have both ACCESS and ACCST receivers (mostly GR8's), and a single QX7 ACCESS radio. I have never entered a number in the 'RxNum' field on the Model Setup page of any of my models, so they're all at the default '00' value. This has never caused a problem, but I wonder if there is some functionality I'm missing out on, or a potential problem to worry about.

The description in Lothar's OTX manual doesn't clear it up for me either. It appears to be primarily a way to limit the number of Rx's and Tx's that can be bound to each other, which I have no need for. As it is, I can swap Rx's between planes without problems or need to re-bind etc., which I find convenient.

* Am I taking a risk by not assigning RxNum's to all my Rx's? If so, what is the nature of that risk?
* If I were to get an additional radio (likely an X9D-2019), will that require RxNum's?

 

[Miami Mike]

The receiver number feature is there to keep you from trying to fly with your radio set to the wrong model. It's analogous to Spektrum Model Match. You should assign a different receiver number to each of your models so that if your radio isn't set to the model you're trying to fly then the model won't respond to commands from your radio.

So yes, you're taking a risk by not assigning unique receiver numbers to all your receivers, and the nature of that risk is that you could launch your model and find that some of your controls are working backward, or the wrong control surface is responding to a stick input, all because your radio is set to the wrong model. If that happens then it's very likely that you'll crash.

When two model setups have the same receiver number then that number generally shows up in red when viewing the otx file with Companion. That's a warning, but there's one case where you might want to have multiple setups with the same receiver numbers: It's okay in cases where the setups are meant to control the same model. You might have a new version of your setup that you want to evaluate, but you're keeping the former version in your radio as a backup.

 

[jseyfert3]

Do you set up models on your radio or on a computer with Companion? I noticed when setting up a model on Companion, it automatically fills in an Rx number for you, and the number it uses is the model number you're setting up. So if setting up model #6, the Rx number will be pre-filled with "6".

Example from companion on a blank model setup, with a newly created model in slot 6 that I've modified no settings for other than select the internal radio to be X16 protocol. I'm running OpenTX 2.3.15.

 

[jure]

The receiver number feature is there to keep you from trying to fly with your radio set to the wrong model. It's analogous to Spektrum Model Match. You should assign a different receiver number to each of your models so that if your radio isn't set to the model you're trying to fly then the model won't respond to commands from your radio. .....

Anecdote:
I can tell from experience what happened to me when two different plane receivers bound to the same Tx had the same model number and protocol.
One of the model settings was copied from the other , bound and modified as needed , mixes , directions , throws , etc. Model number was not changed . - FIRST MISTAKE - .
Both were electric sport planes.
So , I fly the first model for the pre-designated time, land , but accidentally forget to unplug the flight battery ( BAD ! ) . - SECOND MISTAKE - .
Then , I decide to fly the second model .
Change the models in the TX, check the surface deflection , all fine and dandy ( but no throttle test on the ground ) . - THIRD MISTAKE - .
Launch , but then there are two models spinning their propellers !
Panic arises , as the supposedly idle model started to taxi. Luckily a friend ( thanks , you know who you are ! ) caught it safely.
I promptly cut the throttle and dead stick landed the airborne plane.
Never again !

PS: I think that the model number feature does not apply in the D8 protocol.

 

[jseyfert3]

PS: I think that the model number feature does not apply in the D8 protocol.

Companion backs that up, the receiver number field only shows up in D16 or LR12 protocols, it is not an option if D8 is selected.

 

[jure]

Companion backs that up, the receiver number field only shows up in D16 or LR12 protocols, it is not an option if D8 is selected.

perhaps telemetry is required for the model number feature ?

 

[Flying Dutchman]

Thanks for all your feedback, guys. I do understand the potential for problems due to selecting the wrong model, although I can't imagine doing that (I haven't thus far, anyway). I do occasionally move Rx's between planes, and having to keep track of their numbers seems like a hassle (another spreadsheet!), but you're right, I should. I think I even will!

BTW, will one type of ACCESS Rx (e.g. GR8 in a glider) respond when another (e.g. SR8 in a power plane) is selected? I assumed that it won't, as the specific Rx type is selected on the model setup page.

@jure That exact same thing happened to my flying buddy (with a Hitec radio) a few days ago: he had left his Tundra on and started flying another plane; I caught the Tundra as it started to taxi through the pits. Apparently that Hitec radio doesn't give you a warning when you select another plane while another is still connected (like FrSky does).

No, I don't use Companion, I do everything on the radio (QX7). I never got comfortable with Companion - once made a mistake and picked the wrong sync button, which caused me to wipe out all models on the Tx and had to start over. Yeah, I know it's a useful tool and I should just spend some time learning it well, but thus far I have not felt the need.

 

[jseyfert3]

No, I don't use Companion, I do everything on the radio (QX7). I never got comfortable with Companion - once made a mistake and picked the wrong sync button, which caused me to wipe out all models on the Tx and had to start over. Yeah, I know it's a useful tool and I should just spend some time learning it well, but thus far I have not felt the need.

That's fair. It's not needed, though I think it makes it easier to set up new models. Faster to navigate than using the radio, but the radio interface is very good.

Note if you ever use Companion again, your first step after setting your radio settings on Companion to match your radio should be to "Backup Radio to File." This will grab all your models and settings and save them to a file on your computer. If something happens to the models on your radio for whatever reason, you can restore this backup file to the radio and all your models and settings will be back on the radio again.