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From: Cursitor Doom <cd999666@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: Distorted Sine Wave
Date: Sun, 2 Jun 2024 10:32:58 -0000 (UTC)
Organization: A noiseless patient Spider
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On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote:

> Cursitor Doom <cd999666@notformail.com> wrote:
>> On Sat, 1 Jun 2024 15:44:17 +0200, Jeroen Belleman wrote:
>> 
>>> On 6/1/24 14:07, Cursitor Doom wrote:
>> 
>>>> I've taken a shot of the waveform into the 50 ohm input. It's around
>>>> 850mV peak-peak. Hopefully the slight distortion I spoke about is
>>>> visible; the slightly more leisurely negative-going excursions WRT
>>>> their positive-going counterparts. So it's not a pure sine wave as
>>>> one would expect. Does it matter? I don't know!
>>>> 
>>>> https://disk.yandex.com/i/7cuuBimDbOIBZw
>>> 
>>> The shape looks perfectly acceptable to me. This is +3dBm into 50
>>> Ohms.
>>> Is that what it's supposed to be? Canned reference oscillators most
>>> often deliver +13dBm, sometimes +10dBm.
>> 
>> Is it? I only make it about half your figure: +1.65dBm.
>> I admit I'm frequently prone to careless errors, so stand to be
>> corrected,
>> but here's my method:
>> 850mV peak to peak is 425mV peak voltage. Average of that is
>> 0.425x0.636 =
>> 0.27V. Average power is average volts squared divided by the load
>> impedance of 50 ohms = 1.46mW = +1.65dBm.
>> 
>> I shall consult the manual to see what it ought to be - if I can find
>> it, that is, as PDF manuals are a nightmare to navigate IME.
>> 
>> 
>> 
> Use 0.71 for RMS instead of 0.636 ! I make that about 1.8mW or +2.6dBm ?

Thanks, Erich. But there's no such thing as "RMS power" strictly speaking 
IIRC, so that's why I took the average figure; not that it makes much 
difference in practice. it does seem a bit on the low side, but despite 
reading through the most likely sources (the service manual and the 
trouble-shooting/repair manual) I can find nothing stated for what that 
signal level should be! This may be due to the user-unfriendliness of very 
large PDF manuals; I just don't know. Anyway, not very satisfactory! Later 
today I plan to do a direct power meter measurement of the ref osc (since 
none of us here seem to agree on what 850mV vs 50 ohms equates to!!)