Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Cursitor Doom Newsgroups: sci.electronics.design Subject: Re: Distorted Sine Wave Date: Sun, 2 Jun 2024 10:32:58 -0000 (UTC) Organization: A noiseless patient Spider Lines: 48 Message-ID: References: <3lcf5jd7li0a3c0fgddt7o8lnfocvls2pr@4ax.com> <48bd78e1-7da8-3bba-2879-d22962203fa3@electrooptical.net> <9olh5j9al34fhrebr4grqq8h6c8javjpp1@4ax.com> <1n0i5jh257hiinlj2dhaatlo11s33m5n0e@4ax.com> <9k2i5jpfhu3ncfpm28ukusrok4hugal80s@4ax.com> <9tok5j9p388ookujrtbsofskjlbekfuhjb@4ax.com> <60rk5jti9l5154hqaqicohmj3u1lfd16g3@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Sun, 02 Jun 2024 12:32:59 +0200 (CEST) Injection-Info: dont-email.me; posting-host="40a1d383888994c45f6bff6cd4b36ba9"; logging-data="3487737"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18stTdLcWeKnOrhraQM8RJrqncNxH/hXIk=" User-Agent: Pan/0.149 (Bellevue; 4c157ba) Cancel-Lock: sha1:FuBdhifw7i4fQL6GeKVQ+zSWVp8= Bytes: 3670 On Sat, 1 Jun 2024 22:00:58 -0000 (UTC), piglet wrote: > Cursitor Doom 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!!)