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Re: SLF: Sidebands arround ZEVS in 1 mHz

To: [email protected]
Subject: Re: SLF: Sidebands arround ZEVS in 1 mHz
From: DK7FC <[email protected]>
Date: Wed, 19 Jun 2019 14:10:56 +0200
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Hi Markus,

Thanks. Seems you are right. The problem seemed to occur when generating the spectrogram from a stream. But now i've extracted the same time period from the database and produced the spectrogram from a (timestamped) .wav file. Fortunately it looks perfectly sharp!
I'll investigate... I'm trying if a stage  'vttime -m none'  stage will help...

73, Stefan

Am 18.06.2019 22:43, schrieb Markus Vester:
Hi Stefan,

it seems these sidelines are about 10 dB down at +- 6 mHz. If they were real, we'd surely see them in 424 uHz at DL0AO, but there's nothing there.

What is strange ist that the main carrier is shown 2 mHz below the 82 Hz tick, wheras in reality ZEVS is only 10 uHz below nominal. So I suspect that the real input samplerate is around 24 ppm higher than what SpecLab thinks it is. This may cause periodic buffer overflows, where samples are lost and phasejumps occurs. The sideline spacing indicates that this is happening every 1000/6 seconds (~ 3 minutes). 

73, Markus

-----Ursprüngliche Mitteilung-----
Von: DK7FC <[email protected]>
An: [email protected] <[email protected]>
Verschickt: Di, 18. Jun. 2019 17:53
Betreff: SLF: Sidebands arround ZEVS in 1 mHz

These days i'm calibrating the colours and angles in my ELF...VLF
spectrograms. The colour of ZEVS is now calibrated to deviate less than
3 deg. However producing a spectrogram in 1 mHZ FFT bin width, i can see
sidebands of ZEVS.
Did someone else observe a similar effect?
In a first thought i would assume it is my timing system that causes the
problem. But maybe it is ZEVS itselfe? Or even propagation?

73, Stefan

PS: Capture attached.

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