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Mar 07, 2018, 04:51 PM
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Discussion

External XJT vs Internal XJT module latency


Hi, about 6 months ago I did the antenna mod to my X9D+, at the beginning everything was fine, more range than stock antenna and everything worked perfectly. But I started losing range and now I have poor range, I tested with the same receiver and in the same position a QX7 and the RSSI was 95 while in my Taranis it was 60. I've doing a lot of test more and definetly my internal XJT doesn't work properly.

Now I have to decide if I replace the internal XJT module or just use an external one. I would prefer the external one as it's cheaper and I'm afraid the internal one starts to lose range as happened with the previous one. But my question is, will the external XJT module have more latency than the internal one?

Thanks!
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Mar 07, 2018, 05:02 PM
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You might have a problem with your SMA connector wearing out. I would replace the SMA / cable again and see if your range returns.
Mar 07, 2018, 05:07 PM
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Quote:
Originally Posted by Volt_Ampere
You might have a problem with your SMA connector wearing out. I would replace the SMA / cable again and see if your range returns.
Hi, I thought the same, so I ordered another cable and SMA connector specifically for the mod and replaced. RSSI values where nearly the same, not any improvement in range I'm afraid. Also tested with different antennas and getting the same results.
Mar 07, 2018, 05:21 PM
No bounce, No play.
davidmc36's Avatar
Sounds like you may have overcooked the RF Final with the Mod.

If you go new internal I would be leery of using the Mod.
Mar 07, 2018, 05:28 PM
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Quote:
Originally Posted by davidmc36
Sounds like you may have overcooked the RF Final with the Mod.

If you go new internal I would be leery of using the Mod.
I think I'm going external for this reason, what I would like to know is if the External has more latency over the internal module
Mar 07, 2018, 05:58 PM
No bounce, No play.
davidmc36's Avatar
I read something where Jim Drew was testing and mentioned an extra 5ms for external.
Mar 07, 2018, 06:14 PM
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Quote:
Originally Posted by davidmc36
I read something where Jim Drew was testing and mentioned an extra 5ms for external.
Mhh I guess that wouldn't make much of a difference, even for FPV racing right?

The only thing I read when researching for this before asking is this topic
https://www.rcgroups.com/forums/show...atency-testing

But he compares his external module with the internal one, getting less latency with his module. But didn't saw any test with the FrSky XJT module.
Mar 07, 2018, 06:20 PM
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Quote:
Originally Posted by WireW0lf
I think I'm going external for this reason, what I would like to know is if the External has more latency over the internal module
I would expect them to be identical. It's basically the same hardware running the same firmware for the same protocol using the same PXX interface to communicate with the radio. Any significant difference in latency would be surprising.
Mar 07, 2018, 06:26 PM
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Quote:
Originally Posted by pressalltheknobs
I would expect them to be identical. It's basically the same hardware running the same firmware for the same protocol using the same PXX interface to communicate with the radio. Any significant difference in latency would be surprising.
That's what I was willing to read, thanks a lot!
Mar 07, 2018, 06:49 PM
Registered User
For each model ...

You should turn off the internal module and select XJT for the external module otherwise telemetry may not work properly.

Use the XJT Mode setting for the external XJT. Don't use PPM or you will get a latency hit.

For the best latency with D16, explicitly limit the Channel Range to 8 channels eg. CH1-8 unless you actually need more than 8. That applies to both the internal and external XJT modules.


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