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Canon 600EX II-RT drops link- HELP!


Scenarios I have tried: 


Using Canon Transmitter ST-E3-RT as the master and (2) 600 EX II-RTs as slaves.

Using A 600EX as master and B 600EX as slave.

Using B 600EX as master and A 600EX as slave. 


I get the same result of the slave dropping link. The time varies. Sometimes it drops link in 4 mins, sometimes 10mins, sometimes 20 or more minutes. The only way to relink them is by turning everything off and back on.


All channels are the same. Yes, I have scanned for the best connection as well as every other channel and AUTO.

All IDs are the same. 


Not near a wifi-router or airport, I'm in a row home in Philadelphia. 


Using NiMh rechargeables and using freshly charged batteries for every test. Batteries are about 2 years old. 

I have spoken to 2 Canon service reps and neither of them has any idea what the problem is. I really don't have the money to spend on sending everything in for "repair". 


Any help is greatly appreciated, thanks!





Sadly I couldn't resolve the issue and Canon insisted they couldn't find a problem. I ended up buying new flashes - not an ideal outcome! 

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199 REPLIES 199

I also found that using the suggested channel of an Android app, not the transmitter scan, worked well. There's a lot Canon can do though:

1) Improve the channel scan algorithm and auto set channel and ID
2) Fix the transmitter to recognize when link has been lost
3) When link has been lost, re-scan for a clean channel/ID and re-link

Thanks for this.  I've switched the rechargables to alkalines in units that delinked, and that helped one unit but made no difference in another.  I switched to channel 14.  That improved things a little but not a lot.  Also, it seems some units are more sensitive than others.  Although, I have some now going strong for a half hour with no problems.  I'm now going to try WiFiman and setting the ideas to 4 of the same digits as you suggest.  Things are improving, just not fully there yet.  Appreciate all the helpful advice that has been provided.

After further testing, it's definitely NOT the batteries.  The suggestion of using the I.D. numbers to 0000, or 1111 or 2222 etc. and using a less frequently selected channel was the best solution.  After doing that, I only had one delink over the course of an hour using four 430EX RT flashes being triggered by the wireless master transmitter version 2.  The next test will be to try it with 10 slaves and see how that goes.  

Trying this this week for testing. I am so furious with the drops in 2022. My house is for sure one of the culprit locations I’ve run into. 

What variable are you guys looking at when using something like Wifiman? I downloaded it and don’t understand what function to use to find a free channel. 

On the Wireless tab (bottom, center), you'd be looking at the 2.4 GHz band and some clear space.  I have no idea where Canon gets 15 channels.  There are only 14 total in the 2.4 GHz band and only 11 are technical usable in the North America.  Godox has even more (higher numbered) channels.  Who knows?

I only ever use channel 15.  I also bookend my IDs to either 0000 or 9999 (this is where I think the issue is because there are so many and the tolerance -- distance between IDs -- is probably low).

There is no panacea in the 2.4 GHz band, unfortunately.

I tried channel 15 with no difference


Shame on you Canon for not addressing this. I have called into CPS on the issue and it’s treated like “wow we’ve never heard of this issue before”. Really disappointing for someone who just invested in 3 new EL1’s for 2022. Now I’m STUCK. 

I don't know if you ever watch Bob Davis -- who is a Canon Explorer of Light -- YT videos.  He rave(ed/s) about Canon's RT system (which is a big reason I gave up on 3rd party solutions and went pure Canon) but then readily admits to using RadioPoppers (which operate at ~902-928 Mhz) as a backup for when the RT system, "...isn't quite adequate."

When I first saw this -- searching around for a fix after experiencing drops -- it kinda pissed me off.


P.S. Canon -- whatever that means -- knows about it.


Canon needs to do two things:

1) redesign the transmitter/flash so if link is lost, the user from the transmitter can reset them remotely… or have a setting in the flash that re-seeks connection every minute, 5 minutes, 10 mi utes, etc based on user input. This way, as wifi standards update, it will extend this feature tpinntge flash.

2) offer past canon flash users either an upgrade price or a priority on new refurb models.  This will at least allow users some reason for brand loyaty. These flashes are 5x the Price of the knockoffs… don’t make me think going knockoff was the smarter way.