Re: Tone or birdie every 500 Hz in USB mode
开云体育
If I disconnect the antenna, the birdies appear in the FT8 waterfall. When I connect the antenna, they disappear, presumably because the atmospheric noise swamps them. Maybe the AGC is a factor as well. I have a 1 meter loop and an active whip. The loop has
much lower output on 10 meters. On 10 meters I see birdies with the loop but not with the whip. I am talking about the 500hz spaced birdies on FT8.
I find it interesting also that Hans mentioned 500hz birdies coming from the ADC built into the microprocessor. They affected his microphone for SSB. I can't make a connection between that and the RX birdies but it keeps rolling around in the back of my mind.
Tony
AD0VC
From:[email protected] <[email protected]> on behalf of Erik Larson via groups.io <kd7ykq@...>
Sent:?Tuesday, April 1, 2025 1:54 PM To:[email protected] <[email protected]> Subject:?Re: [QRPLabs] Tone or birdie every 500 Hz in USB mode ?
I think it can be corrected with filters or settings somehow. When I change to DIGI mode on the QMX, a lot of these noises disappear. In the image below, the bottom portion was DIGI, the top portion USB on the QMX+ (Pressed the Mode button just as green
line appeared to change to USB RX)
Whatever filtering or settings are different between USB and DIGI, the RX looks a LOT better in DIGI. Notice the lines at 750, 1250, 1750, 2250, 2750 are non-existent in DIGI. The lines at 500,1000,1500,2000,2500,3000 appear unchanged by this, but there
is definately something different between RX in DIGI and USB.
?
In this picture, I cycle back through USB to LSB. The bottom half is USB, the top is LSB.
Notice that when I switch between USB and LSB the tone or noise at 1500 and 3k both become more pronounced (stronger signal indicated by line turning red instead of yellow) Also the lines at 500 and 250 get stronger (solid yellow instead of broken yellow).
Earlier today the LSB side was showing a pulsing tone at 750 almost like carrier from CW, but not in any CW pattern.. I did not get a screen shot of that while it was happening, but I now suspect it may have been an external signal. Note that all these signals
I am highlighting are with the radio connected to a dummy load with a 36" piece of RG-8x
|