Inside a Futaba R334SBS

[Brewbud]

I opened up one of my new Futaba R334SBS receivers to conformal coat it. I was surprised to see an internal antenna in addition to the external antenna. I wonder if this is used for improved reception or for the telemetry? My guess is telemetry. Thoughts?

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[dmitry100]

its called "Dual antenna diversity". they only have one atenna in their other older receivers.

[Brewbud]

I am familiar with diversity antennas having looked at designing them into our wireless medical products. However, in this case, I know the telemetry has less range so that is why I was thinking along those lines. Although, after thinking about it, using a different signal path for telemetry may add even more complexity. I am curious why the telemetry distance is less given the usual 2-way implementation (such as error correction) of typical 2.4GHz systems.

[NativePaul]

Futaba FASST surface receivers have model numbers ending in a "F" which are single antenna non diverse RXs.
Surface RXs ending with a "s" are dual antenna models with diversity, although for some reason one of the antennas is internal. All the air RXs have had dual antenna diversity with both antennas external.

While I use the FAST protocol and air radios so am not familiar with that that RX, I van tell you that the FASSTest telemetry RXs just have the usual 2 external antennas and don't have a separate antenna internal for telemetry.

[NativePaul]

I would guess that the lower range for telemetry is either for lower heat in the tiny transmitter on board the receiver, or as it is limited to 10mw to be France compliant, when most people wouldn't want the extra size and weight of a France switch (as can be found inside all their Txs) and 100mw capable transmitter added to their RX when telemetry is a non-critical application.