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60m - out of band tx possible

DrTeeth Member ✭✭
edited December 2018 in SmartSDR for Windows
I was just on 60m, JT modes and it looks as if I can transmit out of band. The top limit on the UK of the channel in question is 5.358MHz.

Naturally, I could be mistaken, so please let me know what screenshots or anything else you would like to see what is going on. From the recent discussion it looks as if Flex now takes into account the3 TX bandwidth and no longer just relies on the carrier frequency.

73 de Guy G4DWV/4X1LT


  • Tim - W4TME
    Tim - W4TME Administrator, FlexRadio Employee admin
    edited December 2018
    Screenshots were provided via a HelpDesk ticket.

    SmartSDR determines the range of transmitted RF energy as the slice frequency readout plus the bandwidth of the TX filter.

    For example, the UK 60m Channel 1 has a frequency range of 5.258,5 to 5.264,0. This channel has a 5.5 kHz bandwidth.

    If the slice frequency is 5.258,5 and the USB transmit filter is 3.0 kHz wide then the frequency limit of the transmitted RF emission is 5.261,5 which is less than the upper-frequency limit of the channel (5.264).

    Now , keeping the transmit filter bandwidth at 3 kHz, if you change the slice frequency to 5.262, when transmitting, the radio would be putting out RF energy from 5.262 to 5.265. Clearly 5.265 is outside the upper limit of the UK 60m channel 1 frequency range, and this results in a transmit out of range interlock violation and the radio will not transmit.

    You can vary the parameters of the slice frequency and the bandwidth of the transmit filter so that the RF emission fits within the channel bandwidth. It is also easy for the upper-frequency range in USB (and consequently the lower frequency range on LSB) to exceed the limits my tuning the slice within the channel too.

    I hope this explanation clears things up.
  • DrTeeth
    DrTeeth Member ✭✭
    edited August 2016
    It does indeed. Thanks again Tim.

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