Digital Mode Transmission Distortion

  • 2
  • Problem
  • Updated 5 years ago
  • Not a Problem
I recently constructed a cable to put my Flex-6700 on the digital modes with my Tigertronics SignalLink USB modem. I have been able to make a number of JT65 and JT9 contacts with this setup, but have noted when transmitting, the waveform (including the baseline) on the panadapters will randomly jump perhaps 30 or 40 dB and then quickly returns to normal. I have not noted a glitch in output power when this problem occurs.

This anomaly probably occurs at least once per 50 second transmission and lasts less than one second. It appears similar to what one would see from a lightening strike somewhere nearby when receiving. In this case, however, there is no lightening and it is the transmitted waveform that I am viewing rather than the received one.

SSDR 0.12.17 running under Win 7/32, DIGIU mode.
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Ed, K0KC

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Posted 5 years ago

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George Molnar, KF2T, Elmer

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Same issue which does not appear to affect transmission.
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Tim - W4TME, Customer Experience Manager

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That is the question I had too. Is this just a visual anomaly or is it being transmitted as RF. I suspect it is just a visual FFT display anomaly.

Ed can you verify this?
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Ed, K0KC

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Tim,

I suspect that is a visual anomaly. I never listen to JT65 or JT9 signals off the air or via a monitor, but yesterday, I did engage the monitor and there was no clicking, noise or other indication that the RF signal was affected by the display jumping around.

If I do not hear anything in the monitor, I think that it is a good assumption that the RF is clean, especially since I also observed an external power meter and could not see an output power "glitch".

I have had no problems making contacts either.
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Tim - W4TME, Customer Experience Manager

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That is what I suspected. We will be doing some things to clean up the spectrum display on TX in future versions of SmartSDR.
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Ed, K0KC

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Another data point...when I use the tune button in WSJT-X (transmits a single tone), the display jumps around. It did not seem to do that when I used the tune button in SSDR.
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Tim - W4TME, Customer Experience Manager

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This is just another manifestation of the FFT display issue I mentioned above.
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George Molnar, KF2T, Elmer

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Seems much better in 0.13.10
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Ed, K0KC

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I agree...seems much better in 0.13.10.