Junk on 80M tune on Flex 6400.

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  • Updated 3 weeks ago
80M tune and or transmit, dummy load or antenna, generates all these junk sideband's. In the attached photo the tune power is set for 10 watts. This does not show up on any other band. Anyone have an idea on what is going wrong?
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Craig Williams

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Posted 3 weeks ago

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Jay / NO5J

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Craig
First off, keep in mind that the panadapter in the image is a RX panadapter image. There isn't any true TX panadapter. Would you mind posting another screenshot of the entire SSDR window during a 10 w tune. the signal trace in your image is internal signal leakage thru the TX/RX relay. Normally with my 6500, 10 w of tune power will read as high as -40 dBm, but more often around -60 dBm, and I often see fairly weak harmonic peaks on either side of the carrier during transmit, but, not the garbage your seeing. Also with your screenshot I can't see the dBm scaling values, so I can't tell how strong the garbage is in relation to the carrier. Also the signal trace of the TX carrier should be a single carrier which is all the tune button should be generating, clearly yours isn't, but it could just be that the RX panadapter is zoomed in to much. Also since it's a RX panadapter the rigs preamp settings may contribute to that garbage in the image, could you set the preamp to off or  0 dB when you create the next screenshot. The panadapter display, speed and averaging settings might also be making it appear uglier than it really is. 

I agree it looks bad, but it might be fine, and just an artifact caused by the panadapter setup.  

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(Edited)
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Craig Williams

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Thanks Jay. No, it's really ugly ha ha. Here is a full screen capture. The "grunge" pulses up to 20dB higher than you see it here.
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Craig Williams

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Here it is showing on a SDRPlay SDR receiver.
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Jay / NO5J

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Craig
Thanks for the new screenshot, I still don't see anything definite, that's likely to be the problem.
Just as an experiment, try first changing the RX antenna selection to RXA, unless you either don't have that option on the 6400, or do and have something connected to it. RXA is usually a cleaner choice. which of course won't be of much use for normal operation, I'm just curious about what effect it might have.

 Ok, my second guess, and something I don't usually use, is you have PC Audio enabled, but you have Mic selected as the TX audio source. Which might have nothing to do with the garbage at all, I just don't have any experience on what might be in the PC Audio TX audio. Tune should not be using any of the audio sources, it ought to be a pure carrier generated by the radio. 

Third guess, There is always the possibility of a 60Hz hum from a ground loop between the PC and the Radio, Ground Loop Hum looks a lot like that garbage. Is the PC case single point grounded with the Rig? Ground Loops can be a pain to eliminate sometimes. They were for me, with my setup. Anything physically connected to the radio, that has a different path to ground than what the rig is grounded to, can be causing a ground loop, and adding in the 60 Hz Hum into the TX signal. Changing the input source might make a difference. But I don't really know how a loop would affect TX when your using PC Audio.

If it is Ground Hum, I'd expect when using, LSB, and TX EQ enabled, and PROC enabled that any of the hum getting into the TX signal might be even uglier after being EQ'd and processed, than without a Ground Loop.

If you listen to your transmitted carrier on another radio, does it sound clean, no distortion or hum, or it also ugly sounding?

I'll assume you've rebooted the radio several times without success.  

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Craig Williams

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Great ideas but , it only does it on 80M. All other bands have a very clean, narrow, carrier. Any grunge is down almost to the noise. Will do further based on your input. I am voting for a bad 80m transmit bandpass filter. 2 bad we are not given a schematic.