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Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Lasse Langwadt <llc@fonz.dk> Newsgroups: sci.electronics.design Subject: Re: Distorted Sine Wave Date: Thu, 30 May 2024 20:56:41 +0200 Organization: A noiseless patient Spider Lines: 37 Message-ID: <v3ai59$1qbu0$1@dont-email.me> References: <v37ncd$17q1d$1@dont-email.me> <nnd$1540c445$35e5ece6@6a11785c39b8fb50> <vi4f5jlua68idhefpgddthl2q08luvtqqg@4ax.com> <v384cn$1a1og$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Thu, 30 May 2024 20:56:42 +0200 (CEST) Injection-Info: dont-email.me; posting-host="ca1853de830f734dc9a338102e539587"; logging-data="1912768"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+jdFY5mIyBTe/qh5wJOtyZAIDQXBrHGWk=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:yR21kQwKRZ2rLbnb4PwFULyCI1Y= In-Reply-To: <v384cn$1a1og$1@dont-email.me> Content-Language: en-US Bytes: 2485 On 5/29/24 22:49, Cursitor Doom wrote: > On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote: > >> On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com> >> wrote: >> >>> On 2024-05-29 19:07, Cursitor Doom wrote: >>>> Gentlemen, >>>> >>>> Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the >>>> 10Mhz reference oscillator is generating an 'unsatisfactory waveform' >>>> which may be causing the device to be unable to lock it's main PLL. >>>> I've come across this waveshape before, but mostly with oscillators I >>>> was building and in the process of trying to iron out the wrinkles of >>>> and certainly NOT a critical reference oscillator from a respected >>>> manufacturer. Can anyone tell what's most likely going on here? >>>> >>>> https://disk.yandex.com/i/z6fYbeVfPRK7aA >>> >>> >>> Looks like reflections in the cable. Try the 50 Ohm termination. >>> >>> Arie >> >> If the drive is a sine wave, a cable can't generate that 2nd harmonic. > > I don't understand how a reflection can account for it either. THe cable's > only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic > disappears. It's just one of those inexplicable mysteries that no one > knows the answer to. :) > maybe the oscillator is source only so without a 50R load there's no sink to do the low side of the sine