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LF: WSPR sidebands

To: <[email protected]>
Subject: LF: WSPR sidebands
From: "Markus Vester" <[email protected]>
Date: Sun, 27 Mar 2016 21:59:26 +0200
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References: <CAA8k23SspjCU6=UJ2EcXXFNUY-QUnzBwzpyuyBedCBvdW27BJA@mail.gmail.com> <094E96255B2D4EE9886317C115E7E5D9@Clemens0811>
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Hi Clemens,
 
the 1.465 Hz spaced lines around the strong WSPR signals are "clicks" from the periodic frequency switching, they are supposed to be there. But as the switching is phase-continuous, these FSK sidebands fall off much more rapidly than Opera's AM key-clicks.
 
The 100 Hz lines should normally disappear if a properly regulated ripple-free power supply is used for the TX. Has DJ0ABR rechecked the voltage ripple after the change?
 
But there may be other subtle causes for low-level 100 Hz modulation both in the TX and RX chains, e.g.
- hum injection into PLL oscillators causing phase modulation,
- ground impedance modulated by the rectifier diodes in the power supply,
- modulated scatter from traditional flourescent tubes (more at VHF though), 
- noise blanker acting on periodic interference (eg. SMPS or PLC),
- hum injection into the audio chain.
 
Spurs from the DDS would not be impossible but usually at lower level, and unlikely to exactly hit 100 Hz.
 
Best 73,
Markus (DF6NM)
 

Sent: Sunday, March 27, 2016 8:47 PM
Subject: RE: Cheap and nasty sources - was LF: DK7FC WSPR bad quality problem

Hello all,

I've been watching the 100Hz sideband WSPR multi-decodes also from the other two strong stations on MW,
DH5RAE and DB0ABR.They are located about 65km from me and generate  S9++dB signals here.
The deoded sidebands are also about 40dB down.
DB0ABR has tried a different power supply to no avail and both believe that the DDS synthesizer is the culprit.
It is a AD9859,see
http://www.dj0abr.de/index_english.html
I have added a perseus screenshot with a bin width of 0.24Hz showing strange lines in their signal.
I'm not sure if this is the DDS spectrum what we see here.

73
Clemens
DL4RAJ
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