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VIEW AM modulation FLEX radio

sdrwow
sdrwow Member ✭✭

Hello tech folks

Is there any way to view the modulation of an AM signal with the FLEX radio like using a O'Scope and what would be called waveform

PLS look toward bottom of wiki page. A familiar waveform view

I find this to be a better view than a trapezoid. I realize that on the right hand side of the display where it comes to a point; that is NEGATIVE and the opening up like a VEE is your pos peaks. And trapezoid is useful to show linearity. Trapezoid is a little more involved to setup using a 'scope

Thanks

FRED KC4MOP

Comments

  • VE7ATJ_Don
    VE7ATJ_Don British ColumbiaMember ✭✭✭

    Hi Fred... I'm not aware of any 'output' from the Flex which would provide what you are looking for. The best we can do on the Flex (as I suspect you've found already) is zoom way in to the signal and view the 'sampled' version. On the Display menu, you could try increasing the FPS (frames per second) and decreasing the AVG (averaging) to get a more accurate display of the instantaneous bandwidth of the signal, but I don't know of any way to turn it sideways :-)

  • Ted S
    Ted S Member ✭✭

    Two methods I can think of, put an RF sampler in your TX antenna line and just view the sampled RF on the O'scope directly. Second you could monitor the RF using the XVTR output and run it directly to the scope input.

    If your looking to monitor both the baseband audio and the modulated wave form you could pick off baseband audio from the Line Out or Headphone jack with the Audio Mon turned on, then your mic audio appears on line out. However, I suspect there is some delay between the line out audio and the modulated RF output so you have to take that into account when analyzing the waveforms.


    Ted WR4T

  • KD0RC
    KD0RC Broomfield, COMember, Super Elmer Moderator

    Hi Fred, Flex radios do not currently have this capability. The only made-for-purpose units that I know of are the TelePost LP 500 and LP 700. They are pricey, but are the gold standard in monitoring RF output.

  • KD0RC
    KD0RC Broomfield, COMember, Super Elmer Moderator

    Hi Fred, a cheaper alternative is CleanRF. It does require an oscilloscope, but does not need much bandwidth, so a cheap scope will do.

    RF Demodulator | RF Sampler | AM Modulation Monitor (cleanrf.com)

  • Geoff AB6BT
    Geoff AB6BT Member ✭✭✭

    I have done this by wrapping several turns of, say 22 AWG, wire around the coax feeding the antenna and connecting the ends of the coil to an oscilloscope.

  • W7NGA
    W7NGA Member ✭✭✭

    Not exactly sure what you are referencing, but you cannot test linearity in the traditional lissajous x-y method due to latency. That is, the modulated RF is delayed from the audio signal. There are workarounds and other methods, but evaluating fundamental AM wellness only requires an RF pickup of some sort, an oscilloscope of suitable bandwidth, and an eye for identifying over-modulation and noise. On-the-air reports will quickly identify any underlying AM issues.

    Come join the AM fun on 21.430 MHz now that the band is opening up.

    73

  • Bill N3HQB
    Bill N3HQB Member ✭✭

    Have you looked at this?

    http://www.radioassociates.com

    Also Telepost LP-500 does a nice job.

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