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TX signal on waterfall - accurate?

DrTeeth Member ✭✭
edited June 2020 in SmartSDR for Windows
How accurate is the display of one's TX signal on the waterfall? As I am at it, how accurate is the display on the panadaptor?

I guess I am trying to find out if they are reliable enough or sensitive enough tools for monitoring signal quality.



  • K6OZY
    K6OZY Member ✭✭
    edited December 2018
    The display of TX on the waterfall is a recapture of RF from the transmitter.   It is a real representation of the signal.   I am unsure if there are any improper artifacts due to the fact that there is so much power so close to the RX.   I'm sure a Flex Employee may know more regarding that.
  • DrTeeth
    DrTeeth Member ✭✭
    edited August 2016
  • Al K0VM
    Al K0VM Retired Member ✭✭✭
    edited December 2016
      Yes there can be a few false signals appearing the the panadapter during transmit..  It takes looking at the TX signal by another means to be sure which is real and which is an internal artifact.  The broad humps are real as well as the signal directly on the dial frequency and the opposite sideband signal.   The false artifacls tend to be >80 db down. 

    AL, K0VM
  • Steve-N5AC
    Steve-N5AC Community Manager admin
    edited June 2020
    When the PA is on, the receiver can see the transmitter signal and can display it on the panadapter. The coupling between the transmitter and receiver varies by frequency and antenna selection. In some situations, the receiver will be slightly overloaded by the transmitter signal and so you may see the results of this in what would look like IMD in the pan adapter. Because of this, you should only use the display as a rough, relative idea for the on air signal, but should not be used to measure transmitter spectral purity. You can use two FLEX-6000s with a substantial pad to measure signal purity. During design of SmartSDR and the FLEX-6000, suppressing the panadapter or providing the exciter signal instead of the receiver were discussed, but each of these options had clear disadvantages we felt outweighed the minor overload artifacts that may appear.
  • Bob N7ZO
    Bob N7ZO Member ✭✭
    edited December 2016
    Hi Steve,

    The use of what appears to be a leakage path still baffles me.  Since the radios have a tap that will be used for adaptive predistortion in the future, why isn't that being used now for the transmit monitor?   What am I missing?
  • DrTeeth
    DrTeeth Member ✭✭
    edited August 2016
    Steve, thanks for your comments. Personally, I do not like having a measuring system and not being able to rely in what I see. "Why have it in the first place?" is a question that springs to mind, hi hi.
  • Ken - NM9P
    Ken - NM9P Member ✭✭
    edited December 2016
    If you are looking at your SSB spectrum and EQ results within your receive/transmit filter bandwidth, I have found it to be fairly accurate, having compared it to the display on my 1500 when monitoring myself. Outside the RX filter is not as trustworthy and varied greatly with frequency band, as has been said.

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