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Should the panadapter show signals at the same level as displayed on a spectrum analyzer

Jeremy_W2JG Member ✭✭
edited October 2020 in FLEX-6000 Signature Series

Should the panadapter show signals at the same level as displayed on a spectrum analyzer? My 6700 is not doing that for the RXA and RXB inputs. I do not have anything connected to Ant1 or Ant2

I have a DEMI 2MLDPA amp connected to the 6700 RXB port and a Q5Signal L432 transverter connected to the 6700 RXA port. I measured the output of both boxes with a spectrum analyzer. The 6700 displays the signal on the RXB port -23dB LOWER than that of the spectrum analyzer, while the RXA port displays the signal -13db LOWER than that of the spectrum analyzer. Note, the panadapter displaying the signal on the RXA port is in WIDE mode.

Why are the panadapters showing different signal levels from that of a spectrum analyzer and is it a coincidence that the signal displayed in WIDE mode is closer to the actual value? Is there a way to have the 6700 display the signal levels closer to that of the signals going into the 6700?

Thank you for any help you may have on this matter!




  • Jeremy_W2JG
    Jeremy_W2JG Member ✭✭

    UPDATE: I apologize, I have the levels SWAPPED above! When the receiver is in WIDE, the difference is GREATER, its over -20dB LOWER!

    I have also tried swapping the inputs, 2MLDPA going into RXA and L432 going to RXB, the differences TRACK. The the L432 still goes into a WIDE receiver and is LOWER by -27dB. The 2MLDPA now has about a -10dB LOWER difference.

    SUMMARY levels are at least -10dB LOWER than shown on a spectrum analyzer and when in WIDE mode, the difference increase to at least -20dB LOWER. This occurs when the input goes into RXA or RXB.

  • Jeremy_W2JG
    Jeremy_W2JG Member ✭✭

    Three more pieces of information for people:

    1). I am using SmartSDR version 3.1.12

    2). I have the 2MLDPA set to EXTERNAL LNA, meaning the unit does not provide any gain, in fact it appears to have about a 3dB loss

    3). I measured the gain through the L432 transverter and typed THAT VALUE into the Gain setting on the transverter setup tab. I appreciate the documentation states that the panadapter uses that value as an offset on the display. In addition, it is the transverter path that shows WIDE and is an additional 10dB lower, for a total of over 20fB lower than the spectrum analyzer measurement.

    Adding to my questions: are these differences between what the spectrum analyzer measures and the panadapter displays true additional losses or is it purely a display offset. This is probably the most important question of them all...

  • Jeremy_W2JG
    Jeremy_W2JG Member ✭✭
    edited October 2020


    PLEASE NOTE: There was a BIG misunderstanding on my part on what the panadapter is showing! SmartSDR displays what it thinks is the ANTENNA output NOT the signal level into the Rx input!!! As the documentation states for transverters, the Gain field gives an offset for the gain of the Transverter and any loss for switches after. One is supposed to set that level and then the panadapter scale will show the antenna output signal level. The offset had NOTHING to do with being in WIDE Mode!!! THIS ANSWERS the issue with Transverters, there is NO issue! Just set the Gain to the proper offset. (I didn't quite measure that exact value, but it was within repeatability). I APOLOGIZE FOR MY CONFUSION!

    THERE STILL REMAINS AN ISSUE WITH 2m! There is no way to change display axis level offset for 2m! SmartSDR appears to make an assumption for the gain of the external amp/LNA box. I have set the USB cable for the 2MLDPA to EXTERNAL and the gain display is about -10dB offset per the panadapter side display scales. Making matters more confusing, if one clicks on the S Meter to change into dBM levels, the stated value appears close to what I measured with spectrum analyzer, within 3dB! This level is DIFFERENT from the levels on the panadapter axis! It would be helpful to give the user the ability to change the display offset for both with and without the internal LNA enabled.

    If anyone has questions about my statements , feel free to ask. I am still looking for information about why the 2m panadapter scale is off by about 10dB and why the dBm meter shows a different value, but closer to the actual spectrum analyzer value.




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