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6400M Full Duplex Operation Question

Wayne Member ✭✭
edited October 2018 in FLEX-6000 Signature Series

The description of the 6400M states it is a Single SCU capable of 2 slice receivers.

The Manual states the following:

Page 101 of the 6400M manual states All Flex-6000 Series are capable of full duplex operation.

FDX is only possible if the two Slice Receivers are using separate physically isolated antennas.

When the radio is switched to transmit the transmitting Slice Receiver will no longer emit audio but the other receiver will continue to receive.

Now under FDX Requirements this is stated as bullet item 4

The signal level of the received transmit signal coming into the receive antenna must be below the overload threshold of the Spectral Capture Unit.

So this is what I am not understanding:

How does 1 Spectral Capture Unit with 2 receiver slices on different antennas not block RF from both slice receivers when transmitting? Maybe I don't fully understand the SCU and where it fits in the block diagram of things since I have not seen a block diagram.

My understanding is ALL received rf travels through the SCU to the slice receivers and if this is the case if I have 2 slice receivers on different antennas 1 on 20m and 1 on 40m and I am transmitting on 40m and utilizing 20m for receive in a crossband QSO configuration why would both slice receivers not be protected when I transmit on 40m if all RF comes thru the 1 Spectral Capture Unit.

Maybe you could explain this to me. If I could see a block diagram maybe it would be a little more clear.





  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited January 2018
    There are two independent RF signal paths; one for RX that uses the SCU (ADC) and the other one TX which does not use a wideband analog to digital converter; it is a digital up conversion (DUC) to RF.

    So in single SCU radios, if the RX and TX antennas are not the same while transmitting RF can be received via the SCU and it's independent RF signal path.

    Multiple slice receivers use the same SCU.  If there is a single SCU, then all slice receivers have the same RX antenna.
  • Wayne
    Wayne Member ✭✭
    edited June 2018
    Thanks for the explanation.
  • Veiko Värk
    Veiko Värk Member
    edited October 2018
    Is it possible to add second SCU unit inside to FLEX6400M? Is there are place to put it?
  • Bill -VA3WTB
    Bill -VA3WTB Member ✭✭✭
    edited October 2018
    The cost of doing so would be more than the difference in price between the 6600 and the 6400. It would mean at least replacing the complete board the SCU is on.
  • Getrik Getrik
    Getrik Getrik Member
    edited October 2018
    Then it's easier to buy a 6600.

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