Newbie question about FrSky telemetry

nollox · Post by **nollox** » Fri May 06, 2016 11:30 pm

Yesterday, I flew a RC model for the first time in my life. I'm just telling you that to highlight what a noob I am. The model I flew is one that I built, and to fly it, I have been on a spending spree, and accumulated a bit of equipment. I didn't have anything before, so motors, servos, transmitter, receiver, etc. are all new.

I have a Turnigy 9xR Pro transmitter with FrSky XJR Tx module and X8R Rx.

i) What do I need in order to monitor the Rx signal strength? In fact, is this already built in to the module? I see in the manual that it beeps to indicate Rx strength - though I have never heard it beep. Is that only because I have never taken the receiver onto the edge of its range?

ii) What do I need to monitor battery condition in the model? Is this just down to monitoring voltage, or does it require something that will keep track of mA-hours used?

bob195558 · Post by **bob195558** » Sat May 07, 2016 12:31 am

i) RSSI signal strength and SWR should be working for you already, scroll to view your Telemetry Screen.
FrSky XJT module to your FrSky X8R receiver has this telemetry built in.
See here: (https://www.youtube.com/watch?v=0vc7g69 ... pr&index=3).
Some more video instructions: (https://www.youtube.com/playlist?list=P ... fxUB5C-mpr).

ii) See here for X-series sensors: (https://alofthobbies.com/radio-gear/frs ... nsors.html).
Look for: FrSky SP-FLVS - Smart Port Lipo Voltage Sensor.

More info with these manuals
For User Manuals for now use the Er9x Manual find it here: (viewtopic.php?f=5&t=6473).
(Note: Being created is an ErSky9x Manual, it is not ready for release yet.)
Also you can see the 9XR-Pro Manuals for erSky9x: (viewtopic.php?f=122&t=5575#p79483).
Er9x/Ersky9x Video Tutorials: (https://www.youtube.com/playlist?list=P ... qcuIqJXhb9).

Bob B.

Post by **MikeB** » Sat May 07, 2016 9:05 am

To monitor the flight battery you will need a sensor. Have you any idea how much current you flight motor is taking? We need to know this to be able to specify a suitable sensor.

Mike.

nollox · Post by **nollox** » Sat May 07, 2016 2:27 pm

My thanks to Mike and Bob,

My motor is specified at 420W, and for a 3S battery, so with a nominal 12V, I guess its maximum current is 35A. I don't believe the other electronics will amount to more than a couple of hundred mA.

Bob, I'm guessing that SWR isn't Standing Wave Ratio, but whatever it is, you say it's already set up. My transmitter is a Turnigy 9xR Pro, not a FrSky X8R. It does have telemetry capability, but needs a cable from the XJT module to the Futaba port on the Tx. I don't have the cable, but I'll get one when required, but according to the manual, the module itself should beep. The manual says...
Single Beep The signal strength is adequate
Constant double Beeps The model is far, but safe range
Constant triple Beeps The model in near maximum range

Yesterday, I set up the receiver on a tripod with a white flag (made of foam-board), and I could still see it wagging under transmitter control at the limit of my vision with binoculars, but it was only about half a mile. At that point, nothing had beeped. I'm thinking of a better test today with a bigger flag, so I may get closer to the limit.

Post by **MikeB** » Sat May 07, 2016 3:16 pm

You don't need the cable with the XJT on the 'PRO, it connectes internally. What you do need to do is set the protocol to the module to PXX, D16 not PPM. Then the telemetry will be available immediately.
You might also check which revision of ersky9x you have running on the Tx, see the version menu.

Mike.

bob195558 · Post by **bob195558** » Sat May 07, 2016 4:57 pm

Hi nollox,
To clarify, I was not indicating the FrSky X8R to be a radio, as you have a 9XR-Pro radio.
I was clarifying that you are using the FrSky X8R Receiver with your FrSky external XJT module (transmitter) with your 9XR-Pro Radio.
See here for more info about the FrSky X8R Receiver: (http://frsky-rc.com/product/pro.php?pro_id=105).
I believe you can do a Range Check between your X8R and XJT, see the FrSky X8R Receiver Manual.

X8R.zip: FrSky X8R Receiver Manual; (448.13 KiB) Downloaded 318 times

Also for your XJT see here for more info: (http://frsky-rc.com/product/pro.php?pro_id=104).

XJT.zip: FrSky XJT module Manual; (164.91 KiB) Downloaded 313 times

bob195558 · Post by **bob195558** » Sat May 07, 2016 5:21 pm

Yes, SWR dose stands for “Standing Wave Ratio" which is one of the built in telemetry sensors between your FrSky X8R and XJT.
Here is an old quote which maybe some help too:

MikeB wrote:A 'good' value for the SWR is 0, so this is why you might think you are not seeing a reading.
You can try wrapping you hand around the module antenna to see if you can make the SWR read a value other than 0.
Mike.

You should be able to view how strong your RSSI signal strength is between your X8R and XJT on your 9XR-Pro telemetry window (screen).

Post by **jhsa** » Sat May 07, 2016 9:41 pm

bob195558 wrote:Yes, SWR dose stands for “Standing Wave Ratio" which is one of the built in telemetry sensors between your FrSky X8R and XJT.

SWR as far as I know, has nothing to do with the receiver. It is the module checking if its own antenna is working well. That means a low SWR value. If this value is high, it could mean you have problems on the XJT itself.

João

Post by **ShowMaster** » Mon May 09, 2016 4:45 am

SWR. RF systems we're using are based on a 50 ohm impedance, AC resistance. The rule is, if the source RF amp is 50 ohms and the coax and antenna are 50 ohms, then all the RF going to the antenna should be radiated. If the antenna is the wrong electrical length and not resonant, not all RF will be radiated. Some of it will be reflected/returned back to the RF output amp. This does reduce the output level and can cause the output amp to overheat or shutdown. Worse case damage It.
The SWR value is a number that can be measured and can indicate a antenna issue.
The perfect # is 0 the way Frsky measures it. In practice, read its value when new and remember it. If it raises to 20 or more and stays there, somethings wrong. Going up and returning to 0 could be normal if you grab the antenna or change its position.
Never point the tip at your plane!
Bend it at 90 works well usually.
Never run the module without the antenna.
I have found that with an XJT module and ersky9x, 12-16 SWR may show up. I think it's a FW issue and not a module/antenna or range issue.
MikeB knows more.

Do a range test, monitor RSSI, check the SWR if these change after a time.

bob195558 · Post by **bob195558** » Mon May 09, 2016 11:52 am

With the FrSky system, when using protocol PXX we have SWR telemetry and when we using protocol PPM we have TSSI telemetry.
Protocol PXX can use the Serial telemetry sensor connections or the newer S.Port telemetry sensor connections.
Protocol PPM only uses the older Serial telemetry sensor connections.

Bob B.

Post by **ShowMaster** » Mon May 09, 2016 10:44 pm

bob195558 wrote:With the FrSky system, when using protocol PXX we have SWR telemetry and when we using protocol PPM we have TSSI telemetry.
Protocol PXX can use the Serial telemetry sensor connections or the newer S.Port telemetry sensor connections.
Protocol PPM only uses the older Serial telemetry sensor connections.

Bob B.

Good post. To help us all out, could you please break it down more?
RSSI as I've used it is with Frsky, is to want to stay above 42 & 43. I've never given it s lot of thought because it all just works and no alarms go off. I look at my SWR value occasional to verify it still hovers at 0-1 and being I don't have any antenna mods or tx's damage, it's always in that range. When doing a range test, I just walk out until I hear radio signal low or lost and note the distance. Mostly X receivers now but maybe 12 various D receivers bought and used over the years with all the 9x, Sky and djt and dht builds.

It should be great to have tssi and RSSI broken down for D and X receivers and ppm and PXX modes and what to look for.

A search for a tssi definition with Google only turned up a few isolated discussions, mostly MikeB, mentioning it.
RSSI had more on it.

Thanks

Post by **MikeB** » Mon May 09, 2016 10:52 pm

RSSI is Received Signal Strength Indication. We use this the the Receiver reporting the signal strength it sees from the Tx. This is really therefore "Rx RSSI".
TSSI is an abbreviation I use for "Tx RSSI", the transmitter reporting the signal strength it sees from the Rx.

Mike.

Post by **ShowMaster** » Tue May 10, 2016 2:36 am

Got it! Thanks as always Mike.

nollox · Post by **nollox** » Thu May 12, 2016 7:27 pm

I have figured out how to set PXX, so now, I guess I have to detect any incoming telemetry and link it to a voice message. I'll get there. More reading required.

Just to let you know, I set up a range test that worked better. I made a setup with the Rx with battery and BEC, controlling a servo that switched a microswitch to turn on a flashlight, and I tested it after dark. It was on a tripod on the beach, and I started walking, turning now and then to test whether I could still operate the light. It was a little single LED flashlight with a focusing lens, and it turned out to be clearly visible from a long way. When I was just over a mile away, the module started making occasional beeps, and at 1.1 miles, it was beeping sporadically, though I couldn't tell whether the beeps were singles or doubles. I think they were singles, but in any case, the receiver was still turning my light on faultlessly. I would have gone further, but I would have had to follow the beach around behind a hill, so I would have lost sight of the Rx. Still, considering that both Tx and Rx were no more than 4ft off the ground, I thought a range of 1.1 miles was pretty good. I had the Rx antennae at approx 90 degrees, stuck to a piece of plywood that was perpendicular to the Tx-Rx line, and I tried the Tx antenna both vertical and horizontal, but it worked either way. At that distance, I doubt I would be able to see my model. The module beeped more meaningfully if I got my body between it and the receiver.

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