Taranis SWR Survey

Hardware help and support for the FrSky Taranis
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Clivew
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Taranis SWR Survey

Post by Clivew »

I would be really appreciative of results of the following simple test, thanks!
a: switch on Taranis (opentx-r2834 internal module)
b: press page (long)
c: what is SWR? (mine is "0")
d: firmly grip antenna
e: what do you read now (mine still reads "0" on my new Taranis)

My prevous one read "0" and "18"
Just seems a little odd, maybe I am worrying over nothing?
If I fit an external XJT, I get "0" and "18" as expected.

Thankyou,

Clive

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ShowMaster
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Re: Taranis SWR Survey

Post by ShowMaster »

0-18 for me
Dam
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Re: Taranis SWR Survey

Post by Dam »

O, 17!
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Scott Page
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Re: Taranis SWR Survey

Post by Scott Page »

0 is nothing to fret over. High numbers are frightful. I got 0 and 16.
Turbo
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Re: Taranis SWR Survey

Post by Turbo »

Mine says no data !?

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Kilrah
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Re: Taranis SWR Survey

Post by Kilrah »

You need a telemetry receiver bound and powered up for it to show, otherwise you get the NO DATA that shows no telemetry data is available.
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MikeB
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Re: Taranis SWR Survey

Post by MikeB »

But the SWR is always available. On mine, I see a SWR reading just when switching on, no receiver.

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Kilrah
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Re: Taranis SWR Survey

Post by Kilrah »

Badly expressed myself - what I meant is if he has put the SWR display in the bottom bar of the custom telemetry screen (which I usually do) it's hidden by the NO DATA message unless there is telemetry flowing.

So either just display it in the main area or have a receiver on.
Bruneaux
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Re: Taranis SWR Survey

Post by Bruneaux »

Clive,

SWR stands for "Standing Wave Ratio". In a perfect world (and a perfect antenna) all power will be radiated. An antenna is a system and is compiled of may things. When you get you hand close. or on, the antenna you are part of the system. You then 'de-tune' the system, creating a less than perfect radio radiator and it creates standing waves.

The standing waves are basically wasted power. And if that power (SWR) gets really high is can damage the transmitter. Fortunately we are working with very low power so I shouldn't damage the transmitter.

Bruneaux
ImRich
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Re: Taranis SWR Survey

Post by ImRich »

On my radio (manufactured 25/03/2014:

EDITED to update: Depending on how I grab my antenna, I can see an SWR of 0 or 1 or 10 or 16 or 17. So this is very variable (as expected) depending on my hand placement.

But I have to work with my hand to try and find an area where I get the 10, or higher. Often I see 0 or 1.

As others have said, Higher is bad, lower is good. 0 is perfect (unless there is zero output power). Is there a data point where you can see the relative power output, or only the SWR?
Last edited by ImRich on Wed Apr 23, 2014 6:58 pm, edited 2 times in total.
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Kilrah
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Re: Taranis SWR Survey

Post by Kilrah »

"SWR" should always be below 51, or a popup warning will appear and an audio alarm will sound to warn you to check the radio's antenna. The value itself is of little meaning.
It is NOT a real SWR reading, just a very approximative antenna quality indicator that's not meant to be used beyond a pass/fail indication.
Turbo
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Re: Taranis SWR Survey

Post by Turbo »

Update... Swr function had to be invoked on the open tx menu page13 of 13 for me. I chose swr on page one and got it going as someone mentioned above. To get swr 17 I finally found you have to cover the end of the antenna as well as surround it. I grabbed it like a 4 fingered octopus. Palm on the tip and fingers each covering 90 degrees of the antennas sides...bingo 17. So that was a good learning curve. Many thanks for your help :)
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Flaps 30
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Re: Taranis SWR Survey

Post by Flaps 30 »

What does the value actually mean when compared to the Standing Wave Ratio?

Personally I find return loss is more useful (comes from my video days) ---> http://en.wikipedia.org/wiki/Return_loss
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ShowMaster
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Re: Taranis SWR Survey

Post by ShowMaster »

I think as Kikrah posted, the number is a Frsky derived one from the circuit they created. The really good way to test what's going on is to build a tuned 2.4g field strength meter and lock it and the tx down. Then see what the meters change is when messing with the antenna vs the menu value display. For most of us, a value if 0-1 is normal, and with a hand on the antenna, 17-18.
It would be interesting to see what the field strength meter would show for the 17-18 values vs meter drop off?


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Bruneaux
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Re: Taranis SWR Survey

Post by Bruneaux »

Flaps 30,

Being a "Ham" with an Extra class license, Yes. Return loss would be awesome to see. But SWR is easier to measure, etc.

And for those that are holding your antenna in your hand, remember that doing so is stressing the electronics. It will create extra heat (return loss ---> has to go some where!).

ShowMaster has the right idea, but that is also a lot of work/money/time.

I think that the point is to understand that a high value (without having you hand on the antenna) is indicating something is not right. Find the problem before flight.

Bruneaux
ImRich
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Re: Taranis SWR Survey

Post by ImRich »

Bruneaux,

Extra class here too (the old fashion 20 WPM way) :ugeek:

It's too bad the hardware didn't also have a sensor showing relative power output as well as the 'SWR' value. I think showing SWR by itself doesn't tell you if you have any output power. As you can imagine, if the output power was Zero. the SWR would also be zero. ;)
Bruneaux
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Re: Taranis SWR Survey

Post by Bruneaux »

ImRich,

Yep. Things that may you go "Hmmm"!

Also licensed with the old school - 20 WPM.
csquared
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Re: Taranis SWR Survey

Post by csquared »

I find it interesting that in the Taranis manual from www.frsky.com they show a screen image in the telemetry section with a SWR of 75.
I would love to know what antenna is being used to get this reading. Seems pretty high to me. This image shows up twice in that manual
around page 3 and 17 (the pages are not numbered).
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Kilrah
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Re: Taranis SWR Survey

Post by Kilrah »

It's the value that is shown in the simulator.
On the 9x this value is TX rssi, where 75 makes sense. Wasn't changed for Taran is because who cares ;)

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csquared
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Re: Taranis SWR Survey

Post by csquared »

"who cares"
I guess I care. If I have a SWR of 75 it means one thing to me (get out of the sky).
If I have a RSSI of 75 it has a very different meaning (I am a happy pilot).
xtrmtrk
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Re: Taranis SWR Survey

Post by xtrmtrk »

I have a SWR bouncing between 16 and 17 - should I worry? Could I get better distance if it was lower?
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ShowMaster
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Re: Taranis SWR Survey

Post by ShowMaster »

Have you done any antenna work? What happens if you change the antennas position! Bent left or right seems to give a lower reading.
I believe anything under 20 is normal. As for range, for line of sight your RSSI reading is more important. It should stay above 36 for a solid link, your alarms set for 42. Typically I never get a reading below 51 for edge of line of sight and never a link loss. Antenna to the left or right, never straight out.
Fill in my questions and it may help with a more precise answer.
SM
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Scott Page
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Re: Taranis SWR Survey

Post by Scott Page »

xtrmtrk wrote:I have a SWR bouncing between 16 and 17 - should I worry? Could I get better distance if it was lower?
Way too much is made of SWR. You don't need to worry unless the transmitter refuses to work because it detects the SWR is too high.

Ignore the SWR and pay attention to RSSI.
Carballada
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Re: Taranis SWR Survey

Post by Carballada »

Interesting post.
I moded my taranis for use an external antenna.
If I use stock DJT antenna on my Taranis my SWR readings are like yours (0 and more thant 30 if I touch/cover the antenna)
BUT, if I use the '"FrSky 2.4G V8 Series 5db module Antenna" (better on paper and Frsky product) the better figure for SWR is 16, if I cover the antenna goes to 35.....

any sugestion?
could be a worst antenna just for that?

Crearly I need to test another antennas.

And of course I need to do a RSSI range test and I will tell you something....
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mnementh
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Re: Taranis SWR Survey

Post by mnementh »

Kilrah wrote:
"SWR" should always be below 51, or a popup warning will appear and an audio alarm will sound to warn you to check the radio's antenna. The value itself is of little meaning.
It is NOT a real SWR reading, just a very approximate antenna quality indicator that's not meant to be used beyond a pass/fail indication.
Kilrah -

I remember reading of this elsewhere; that it wasn't a true SWR measurement. Could you direct me to more technical discussion on it? I haven't been able to find the material I read on the subject a while ago.

Now it appears they've done away with this "Reflected power" measurement altogether in the Taranis Plus. I've read posts alluding to the fact this is because they've done a hardware revision that eliminated the circuit entirely; I also can't seem to find any in-depth conversation on that.

Yes, I've read the related material from a week or two back on the RCG Taranis thread; it's JUST detailed enough to make me want to know more!

Is there somewhere that I can see the schematics for the backplane on both TX, and judge for myself what's missing?

Thanks!


mnem
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Kilrah
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Re: Taranis SWR Survey

Post by Kilrah »

AFAIK the circuitry is there on the Plus but is somehow badly tuned and doesn't work.
Haven't seen any pics of the "production" Plus backboard.
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mnementh
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Re: Taranis SWR Survey

Post by mnementh »

Understood.

Shortly I'll have images and video.


Thanks.


mnem
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mnementh
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Re: Taranis SWR Survey

Post by mnementh »

Internal pics of release Taranis Plus are here: http://s1183.photobucket.com/user/mneme ... t=9&page=1

And my short video of the new LCD and peek inside is here: https://www.youtube.com/watch?v=N4cHQTL ... e=youtu.be


Feel free to share as you see fit.


mnem
ZZZzzzZZZzzzZZZzzz...
WZ9V
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Re: Taranis SWR Survey

Post by WZ9V »

I added a connector to the internal module and it bounces around from 0 to 16 depending on position. From what I've read in various forums this is still a good reading. My assumption is the connector introduced a small jump in the losses but it does not seem bad enough to worry about.
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Scott Page
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Re: Taranis SWR Survey

Post by Scott Page »

WZ9V wrote:I added a connector to the internal module and it bounces around from 0 to 16 depending on position. From what I've read in various forums this is still a good reading. My assumption is the connector introduced a small jump in the losses but it does not seem bad enough to worry about.
You're correct. The resolution of the Taranis SWR is only 16 units - so there is no significant difference between 0 and 16.

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