Using BLE and Ant+ causing resistance drops

Hi all,

I recently decided I wanted to get the Garmin data for load and training effect from my zwift rides. So I connected my iPad with BLE in the normal way, then connected my FR945 to the ant+ power and cadence channels of my Tacx Flux. The intention being to dual record the workout, then fettle the Garmin distance after.

However, while riding I kept experiencing very short drops in resistance, particularly noticeable while climbing, which is something I’ve never had when just on BLE.

I’ve tried the Fr945 and my Edge 530, both do the same. I’ve tried connecting to the fe-c ant+ and the speed/cadence and power only.

Any ideas if this is something I can solve?


Dual recording is not a problem. Your problem might stem from the trainer broadcasting both resulting in signal interference or it’s inability to adequately simultaneously broadcast both.

What does this mean?

Thanks Lin,

Interference is what I assumed was occurring. I meant that I’d tried dual recording with both my watch and my cycling head unit and that I got the same issue with both.

I am yet to see a technical argument in support of the “interference” theory.

My setting is similar (not identical…) to yours (dual-recording, BLE and ANT+), yet I don’t experience the issue you mention.

Maybe a Flux issue?

Could be, the flux certainly has its fair share of issues. I might keep experimenting with it on rest days. It would be nice to have the data from Garmin, but it’s not the end of the world.

ANT+ is connectionless (broadcast) - the trainer is unaware of anyone monitoring it’s transmission, be if FR or Edge. Nor is there a way I am aware of of controlling said transmission.

Would it be possible for you to eliminate all ANT+ devices and re-examine the situation? (just to take some devices out of the equations…)

Good luck!

Yeah, If I remove all the ant+ devices everything works normally, resistance is stable.

It could very well be a flux issue or it could be signal interference.

If I use my old MacBook Pro Bluetooth for music while connecting via USB ANT+, I get a lot of signal dropouts. If I turn off the Bluetooth, I get zero ANT+ dropouts. If I run Bluetooth and no ANT+, it’s also solid. I surmise that is interference and/or bad antennae design in that particular MacBook. In a newer MacBook Pro, I have never seen this issue.

Bluetooth and ANT+ share the same frequency spectrum (i.e…2.4GHz) along w/many other devices (e.g., 2.4GHz WiFi, cordless phones, etc…) Why? Because it’s unlicensed and free to use. The more devices sharing this frequency band, the more likely you are to experience signal interference. It doesn’t even have to be your own device(s) causing issues. For example, it could be your neighbors WiFi.

It’s not bro science or anecdotal evidence, the above is fact. Hence, you will see recommendations to move WiFi to 5GHz. You will see recommendations of specific channels for 2.4GHz WiFi to avoid Bluetooth. You will see recommendations for USB extension cable to get the ANT+ dongle closer to the trainer and/or bike power meter. Etc…

In addition it depends on your devices as well as environment. Bluetooth may work great while ANT+ sucks or vice versa. Then again, they may both work great or both have issues.

@Kev_Pope3432 What if you go ANT+ only?

I’ve yet to try ant+ only. I wouldn’t be able to use zwift that way because I only have the ipad, but I could do a workout from the Garmin just to see if I have issues. I’ll give that a go next chance I get.

I think my longer term plan is to move to a PC based solution, but there’s no guarantee that’s going to solve this issue. Hopefully give me better graphics though😀