Taranis X9E

[GONZO]

Just for info.There are two types of plastic aerials one type slightly bigger than the other. The smaller ones are just center feed PCB dipoles. The bigger ones, generally used on the L9R have a low noise amp. I posted some pics a while back.

[Chris Bott - Moderator]

Posted by Paris Skoutaridis on 23/09/2015 13:47:41:

I stumbled across this thread and since I have been thinking of getting a Taranis it grabbed my attention.

Being a communications engineer I thought I'd lend a hand to help with the power and loss calculations.

The formula for path loss is 20*log(4*pi*d/lamda) were d is the distance in metres and lamda is the signal wavelength calculated as the fraction of the speed of light (3*10^8) over the signal freequency (2.4 * 10^9 Hz in this case)

At a max "useful" range of 1500m you get a path loss of 103.5dB.

If you then reduce your transmit power by 10dB, the result is that you can maintain the link (i.e. maintain receive lock) at a distance that corresponds to 10dB less path loss than the original range of 1500m. I.e. you can maintain the link with a maximum path loss of 93.5dB.

At a frequency of 2.4GHz, the range at which the total path loss is 93.5dB is about 460 metres.

Keep in mind the above is quite simplistic as it only takes into account free space loss. The receiver will also have to contend with multipath fading (i.e. several delayed versions of the same signal arriving from different angles at the receiver), block and absorption from surroundings and the model's structure and so on.

Hope this helps somewhat

I'm afraid I only just got to see this first post awaiting approval in the back office. I thought it worthy of quoting, just so folk spot it.

Welcome to the forum Paris.

[Geoff S]

Posted by Peter Christy on 23/09/2015 19:09:57:

I have a sneaky suspicion (and it is only a suspicion!) that the problem is more likely related to those plastic encapsulated aerials that come as standard on the current receivers. I suspect they are more directional than the basic aerials used previously. If I were a gambling man, I wouldn't mind betting that replacing those with the standard wire ended aerials would make a lot of the issues go away....

--

Pete

I think you could well be right. You don't get owt for nowt and high gain antennae tend to achieve that by tighter directional sensitivity. It's the difference between a simple dipole and a full blown directional yagi array in the days when I was involved in TV sales/service in the 1950s. The yagis were a lot trickier to get right.

In any case, those lumps of plastic are harder to position than the simple antennae.

Geoff

[Frank Skilbeck]

Posted by Peter Christy on 23/09/2015 19:09:57:

The added complication is "coding gain" resulting from the spreading and de-spreading of the signal. It could be that they are talking about a reduction in the coding gain, or even a reduction of the total path budget. I suspect that the answer lost something in translation, because as it stands, it doesn't make a lot of sense.

--

Pete

 

I remember reading about the recent pluto probe, as the signal is so weak they have to send the data back very slowly or it can't be picked up. As the data is basically an on or off (binary) if the data is too compressed then it gets harder to detect the on's and off's, so you've either got to space out the signal (longer off and ons) or increase the strength. In this case you can't increase the transmission strength (EU limits) and the time to transmit the data has been reduced using the new EU medium utilisation limits, the only thing that can give is the receiver sensitivity which is maybe what has happened. To restore the sensitivity with these limits you'd need to send less data so you can increase the binary on and off time (isn't that what Frsky did on the LR rxs), but that would be a major re-coding of the digital transmission protocol. It maybe that Frsky transmit much more data than their competitors hence they find the new MU limits more onerous.

Or it could just be the odd faulty Rx, but there does seem to be as many reports appearing these days about Frsky range problems as we used to get on Spektrum lock outs, but that could just be due to the large numbers in use.

Edited By Frank Skilbeck on 23/09/2015 22:25:22

[Peter Christy]

This will have to be a quick reply - I'm about to travel and won't be home until tomorrow night. Don't know if I'll be able to get on line before then.

First: Thanks to Chris for expediting Paris' useful post, and thanks to Paris for the input.

I'm sure Paris will correct me if I'm wrong, but I believe that the equation he quotes, in effect, predicts where the signal drops below the noise floor. For normal modulation techniques (FM / AM) this will provide a useful yardstick of expected range. However, one of the features of spread spectrum is its ability to recover a signal from below the noise floor (one of the reasons for my comment about "Black Magic" earlier in this thread! It defies logic!). IIRC what Paul Beard said to me some years ago, when the Spektrum system was originally introduced, this "coding gain" is very significant - I seem to recall figures of between 10 and 20dB being bandied about. This does make a big difference to the expected "free space" range predicted by Paris' equation. You may not be able to break the laws of physics, but you can stretch them a bit with some mathematical sleight of hand!

Frank's point about the Pluto probe also raises this matter. The typical power output of transmitters on these probes is in the region of tens of watts. OK, so high gain antennas are used at each end, but even so I think this demonstrates how clever modulation techniques and coding systems can extend the range of an RF link well beyond that normally expected. Now I know our systems aren't *that* sophisticated, but I think it illustrates a point.

The problem is that we only have partial information here. What we've heard from FrSky appears to have lost something in translation, or is otherwise incomplete. Not everyone is suffering from the problem, which would be the case if it were a simple matter of the change of protocol.

I do believe there are other factors at work in the reported cases, and without a lot more information, we are all involved in something of a guessing game!

--

Pete

 

Edited By Peter Christy on 24/09/2015 08:53:36

[Paris Skoutaridis]

Thank you Chris, good to be here.

 

Peter, your assumption is very close to the mark, but not quite there. Spread spectrum and most other digital communication systems can still maintain a link even if your "useful" signal is below the noise floor, to differing degrees. However, if your original max range is, say, 1500m with a clear line of sight, then this is simply the limit of signal loss between Rx and Tx that your link can be maintained under. This already takes into account any fade mitigation your system may be using, such as the spreading gain (coding gain is something different) that results from using a spread spectrum air interface.

Therefore, all else being equal (meaning no change in the surrounding environment, local interference etc etc) if you loose 10dB of transmitted power and your original range is 1500m then your range will be reduced to 460m.

With regards to receiver sensitivity, bear in mind here I haven't read the specs, it may either refer to the received signal power or the ratio of that power over the power of the noise picked up by the receiver, at which signal lock can be maintained. Either way, a lower value for this parameter is better as it means your link can be maintained with reduced Tx power, or increased noise, or increased path loss.

So, if Taranis has reduced the Tx power by 10dB, but also reduced the Rx sensitivity by 10dB then the two changes should cancel each other out, in principle.

Paris

 

 

Edited By Paris Skoutaridis on 24/09/2015 09:42:17

[Andy48]

At the end of the day, one really does not need the complex theory. Firstly there is the built in RSSI warning, and then as the Taranis has built in telemetry, all that is needed is to enable logging this telemetry and after a day's flying one should be able to download the telemetry from the SD card onto a computer and see the RSSI signal at any point in the flight.

Job done and peace of mind.

[Mike Blandford]

Back in February, when the EU firmware was new, I did some tests, posting the results here: **LINK**.

I haven't repeated these tests with more recent (EU) firmware, I'll see if I can find time to do so.

Mike.

[Kevin Wilson]

So, Has anyone bought an X9E yet?

[Martin Harris - Moderator]

Posted by Andy48 on 24/09/2015 12:00:17:

At the end of the day, one really does not need the complex theory. Firstly there is the built in RSSI warning, and then as the Taranis has built in telemetry, all that is needed is to enable logging this telemetry and after a day's flying one should be able to download the telemetry from the SD card onto a computer and see the RSSI signal at any point in the flight.

Job done and peace of mind.

 

I think there's a possibility of a bigger issue here. It seems that there's a possibility that the LBT solutions adopted by some manufacturers may have an effect in particularly intense 2.4 GHz noise areas - such as a flying site in urban Los Angeles (Sepulveda Basin) which is surrounded by industrial and residential areas. As EU compliant firmware is uncommon there, it isn't likely to affect many users, but as usage of the 2.4 GHz band increases, this could become more significant over here - especially in more urban areas...

As an example, Andy, you might take your model to a fly in at a different site and encounter a totally unexpected problem, despite a ground based range test being OK.

Edited By Martin Harris on 24/09/2015 12:56:39

[Martyn K]

Posted by Kevin Wilson on 24/09/2015 12:34:27:

So, Has anyone bought an X9E yet?

I am going to wait until the problems (real or imaginary) have been resolved, so probably early in the new year. I do like the idea of a tray transmitter - as I have modified my X9D to sit in a tray.

M

[Andy48]

Actually Martin, just the opposite. I had a lot of problems with my Spekky kit in two distinct areas (and height) in our field which would appear to be a microwave link. The Taranis has been fault free in this respect.

How would I encounter a problem at a different site? There is a spoken warning for low and critical RSSI values, so on hearing the former, one simply turns closer to get a better signal.

In any case is Los Angeles relevant, this firmware is for the EU only.

[Phil Green]

Posted by Andy48 on 24/09/2015 12:00:17:

At the end of the day, one really does not need the complex theory.

You dont need it as such, but some of us are genuinely interested in the radio itself and the technology that goes into it. Many of us here are retired comms engineers or electronics techs and this is our bread & butter. It seems there may be a problem, and here we are discussing the symptoms, factors and possible options that Frsky might take. Its not off-topic, Martyn had this in mind when starting the thread.
So theory (its really not that complex...) is cool, its an inherent part of the discussion!

Cheers
Phil

[Andy48]

Yes I appreciate that Phil, and I am interested too (I was an electronics production engineer). Just really pointing out that the Taranis lets you back up any theory with actual data. What, perhaps would be interesting would be to have 2 Taranis systems, one with the updates EU version, and fly the same circuits and compare RSSI values.

I also quite like playing with data. Perhaps one day I will update one of my Taranis to find out.

I would also love some feedback on the X9E...

Edited By Andy48 on 24/09/2015 19:29:29

[Martin Harris - Moderator]

Posted by Andy48 on 24/09/2015 16:32:23:

Actually Martin, just the opposite. I had a lot of problems with my Spekky kit in two distinct areas (and height) in our field which would appear to be a microwave link. The Taranis has been fault free in this respect.

How would I encounter a problem at a different site? There is a spoken warning for low and critical RSSI values, so on hearing the former, one simply turns closer to get a better signal.

In any case is Los Angeles relevant, this firmware is for the EU only.

 

The LA example was quoted because (I understand) a system with EU LBT compliant software has experienced problems at this very high RF noise site which included lower than expected range with telemetry warnings and a sudden lock-out with no low signal or quality warnings. This same system appeared to work perfectly at more rural locations.

Your system may well perform perfectly at your location and low RSSI warnings may well normally give adequate warning to turn back - hopefully not deeper into an affected area during the turn! This extremely interesting and informative discussion is beginning to give me a little more grounding in what I'm increasingly realising is an incredibly complex subject.

If there is an issue with LBT implementations by any manufacturers then open discussion should be of benefit to the whole RC community.

Edited By Martin Harris on 24/09/2015 23:37:48

[Biggles' Elder Brother - Moderator]

This discussion is very interesting.

I have a very large octocopter at work, around 10Kg, controlled from a 9D and with a X8R on board. The aircraft has structural plates made from CF and I had been having some problems with RSSI warnings at ranges of about 250m or so. I put these down to RF shielding of the aerials by the CF plates and tried different locations and arrangements of the antenae to solve the problem. Arranging them on a fabricated plastic 'V' mount on a stalk produced some limted sucess.

Then we went over to the EU implementation of the system. Result - the problem seems to have gone away! I recent had need to fly the UAV at extreme range on one job. I was fully prepared for "RSSI Low" wanings and having to abort, but no. I'd estimate I was at close to 500m based on the site survey we did and the proximity of certain ground datum points, and no warnings and the RSSI strength indicator which may observer was monitoring stayed at 3 to 4 bars.

So that is contary to the experience others seem to be having? Obviously the "jury is still out" and I will continue to proceed with great care at longer ranges for some time. But so far, so good. It's certainly a complex issue to be sure.

BEB

[Peter Christy]

I think BEB's experience confirms what I said earlier: There are other factors at work here. If it were a problem with the protocol, then everyone would be suffering the same effect. The fact that some are and some are not tells me to look elsewhere for a solution.

The first thing I would do would be to try the alternative aerials on the receiver. As Geoff correctly pointed out, the black plastic ones are proper dipoles, and will give better range at the cost of being more directional. Whether these work better or worse than the standard wire ones will be down to a number of factors - not least installation - so to me, it would seem worth experimenting to see if these solve the problem.

To illustrate the point: Back when I was experimenting with 459 MHz, I had a lot of trouble getting it to work in a helicopter. It was OK in my "Lark" (mostly wood!), but not in a Shuttle (metal and plastic). I did finally get it to work in the Shuttle, but it required *very* careful placement of the receiver aerial.

At 2.4 GHz, the wavelength is even shorter than at 459 MHz, so the aerials are more easily obscured, and there is a limit to how much clever modulation methods can overcome this. Spread spectrum is a lot more robust than the previous systems we used, but that does not mean we can afford to take short-cuts with installations.

Noting what Paris has said, I'm pleased that we are coming to similar figures despite approaching the matter from different perspectives. When two solutions provide more or less the same answer, it must be right!

Having looked at the output of my transmitter since updating to EU firmware, I can see no significant difference in the power output levels between any of my 2.4 GHz transmitters. They are all punching out the same power, as close as I can tell.

Now, must dash to catch the train home......

--

Pete

[Andy48]

Posted by Martin Harris on 24/09/2015 23:35:54:

Your system may well perform perfectly at your location and low RSSI warnings may well normally give adequate warning to turn back - hopefully not deeper into an affected area during the turn! This extremely interesting and informative discussion is beginning to give me a little more grounding in what I'm increasingly realising is an incredibly complex subject.

Remember that you can change the level at which low and critical RSSI warnings are given, I do set mine a little higher, just in case. You could also add extra levels. Indeed it is a simple matter to set the tranny to give regular spoken RSSI levels throughout a flight. Such a feature early on in the life of an installation (or with a problem aircraft) might give some hints as to how better to position aerials for certain orientations, though I would suggest using a quiet time at the flying field!

Edited By Andy48 on 25/09/2015 10:32:04

[GONZO]

Didn't know where to put this, so mods feel free to move to more suitable location if needed.

Preamble; bought a UHF Tx module and 8ch Rx, EZUHF made by ImmersionRC, from T9 and threw in a couple of XR8 Rx for good measure(they came with the 2015 sticker).

As I'm on pre EU change firmware I expected to have to do some reflashing. Anyhow, I thought I'd have a play to start with and see first hand any effects of mixing the the two firmwares had. Taranis mk1.B set to internal Tx on D8 mode. Now this is not supposed to work with an Rx with the new EU firmware according to the instructions. But, to my surprise binding went OK and the range was v/good, infact the same as a non EU Rx. Shut the Tx in the microwave with door firmly closed, (end of aerial pointing to where I was going to take the Rx) at one end of kitchen and took Rx with servo to other end of house upstairs in model room(at least 40' and several walls and a floor inbetween). Both Rx work fine with no indication of loss of signal or loss of servo control!! Did the binding to both Rx several times and also tried D16 with no change. Others have reported jittering servos, loss of range etc

Whats going on? Have FrSky tweeked the firmware? Have I slipped through a tear in space and time to a parrallel universe?

Answers please, written on £20 notes(to help pay for my RC habit)

[Andy48]

Any chance of posting a vid of your microwave flying?

[GONZO]

All RC flying using 2.4gHz is microwave flying. Or, did you mean the kitchen appliance? The only flying that may do is if I should badly upset the 'guvnor' then its likely to be flying towards me! She's very tollerant really, doesn't mind me using the normal oven to heat up my engines to replace bearings etc.

[Phil Green]

Posted by GONZO on 01/10/2015 14:54:25:

Preamble; bought a UHF Tx module and 8ch Rx, EZUHF made by ImmersionRC, from T9

Is that on the legal 459mhz band Alan (very interested if so) or the ham radio 70cm band? (naughty!)

Cheers
Phil

[GONZO]

Phil,

By flashing different firmware available from the manufacturers site you can put it on a number of frequecy options:

Specifications

Output Power 500mW (high), 200mW (low)

 DC Power Input 6v – 13v

 Current Consumption 250mA @ 12V in high power mode, 85mA @ 12V in low power

 Head-tracker Power Same as input voltage

 Channel Count Currently 12 Max. (16 planned)

 Antenna Connector Standard-Polarity SMA

 Frequency Range 430MHz -> 440MHz, with a UK (459MHz option)

 Frequency Bands 431-433, 433-435, 435-437, 436-438, 430-450 EH1

 Spread Spectrum FHSS, 20 slots from a possible 40, PRBS sequence

1 EH = Extreme Hopping, more robust operation due to a 20MHz hopping range, instead of 2MHz.

Note that when in UK 459 mode it will only transmit @100mW and hop within the band.

Manufacturers site **LINK**

In the past I've tried another UHF LRS whilst monitoring the 70cm band to see if anyone noticed - nothing!

As I posted I got mine(JR module for the Taranis and 8Ch lite Rx) from T9. All working OK but no real life range checks yet. A few 'gotchas' when it comes to checking and changing the firmware but YouTube has lots of vids explaining.

Got to look up a few links of interesting posts re the X9E and X8R that may explain why thing are 'iffy'. Back in a bit.

[Phil Green]

Not wanting to hijack this thread Alan, I'd be very interested to follow your findings if you start an Immersion UHF thread, or a general uhf thread

[GONZO]

Read Alasdair's post re his finding on the X8R **LINK**

Then read pages 7 and 8 of the BARCS thread on the X9E about the RC antenna ('Spoons post with the pictures)

**LINK**