Dumb question abt FRSKY telemetry

[Redbrickman]

OK I will probably end uo in the corner with a hat labelled with a big D on it but here goes...

I have the FRSKY DJT and DBRII receiver and understand the concept for telemetry but don't see anything that describes how the data gets back from the receiver?

Is there a low power Tx inside the receiver to send back the data?

Told you it was a dumb Q

[ShowMaster]

Yes, same power both ways, same chip I believe. Just guessing, but it is 2 way TX and RX.
SM


ShowMaster
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[gohsthb]

They are transceiver chips, so both transmitter and receiver at the same time. What they actually do is divide up the time between transmitting and receiving. So one transmits and then listens for a short while while the other transmits. But we really don't need to know how that works, just that it does.
-Gohst

[Redbrickman]

Thanks for the replies. I guessing maybe the receiver power output would be less as you don't need so much power on a non critical downlink. The DBRII receiver draws just 100 ma for instance.

As Gohst say we don't need to known but curious minds often need stimulation

[Kilrah]

The TX module doesn't draw more power

Both the module and receiver have just the same components apart from the inputs/outputs.

[Redbrickman]

Actually the Tx module draws 50ma and the receiver 100 ma!

[Scott Page]

Ok -- while were at it.. could I use a receiver antenna on a transmitter module?

[ShowMaster]

Actually the Tx module draws 50ma and the receiver 100 ma!

Correct, but the 4ch only draws 60ma and the 8ch draws 100 ma so is it the rf IC drawing different currents or the decoding ic's?
SM


ShowMaster
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[ShowMaster]

Ok -- while were at it.. could I use a receiver antenna on a transmitter module?

Yes, but...
I've not taken a Frsky 2dbm TX antenna apart to see if a counterpoise or decoupling sleeve has been added to the coax to add some gain. Being that it's labeled as a gain antenna it's got to be more gain then the RX antenna I think.
So yes the RX antenna will work but should be less gain.



ShowMaster
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[Kilrah]

Actually the Tx module draws 50ma and the receiver 100 ma!

Correct, but the 4ch only draws 60ma and the 8ch draws 100 ma

Did you measure them for real or just used the specs?

There will be a difference for sure because the RXs use a linear voltage regulator, while the TX modules use a switching one. So the current consumption of the TX module will vary (the higher the supply voltage the lower the current) while the RX's current consumption will be constant whatever the voltage.

[Redbrickman]

I just looked at the specs as I have no means of measuring.

[ShowMaster]

Just used the posted specs but I'll measure them next "lab time"
SM


ShowMaster
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