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#31
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mike742 wrote: I've always noted with some curiosity that 77.503kHz, 60.002kHz, and 60.005kHz are off-the-shelf crystals too... used in a direct conversion receiver for DCF/WWV to 3Hz, 2Hz, and 5Hz carrier-detect frequencies maybe? Strange. Maybe another resonance mode? I'd guess the specified frequency is parallel resonance with the specified load capacitance. I have some Digi-Key SE3320-ND 60 Khz xctls (C-2 60.000KC-P). My best try at measuring the series resonant frequency shows 59998 Hz. Perhaps the 60.002 Khz ones are series resonant at 60000 Hz. I don't have any of those to measure. Here are some measurement of a few Epson Type 2 60 kHz crystals I made recently: Fs BW Fp 60001.6 4.6 60009.9 60001.2 4.6 60009.7 60002.2 5.6 60010.6 60001.1 4.4 60009.5 The test setup is shown below. The input signal was produced by my homebrew function generator implemented with an AD9833. The clock for the 9833 is an 10 MHz SG-615B which has a specified frequency stability of 100 PPM. |Vcc | | 20.0k | Vi 0.1++ |-+ 2N5457 -/\/\-+--||-||--+-| | ++ | |-+-- Vo \ \ | / 1M / \ 1.0k \ \ /1k | | \ | | | +---------+----+ | V |
#32
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"Watson A.Name - "Watt Sun, the Dark Remover"" wrote
in message ... Or use the S-meter to see very low freq beats. Check out the latest Atlanticon proceedings, or the upcoming issue of the Homebrewer for a circuit to allow you to see zero beat to within a fraction of a Hz. ... |
#33
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["Followup-To:" header set to rec.radio.amateur.homebrew.]
On Wed, 27 Apr 2005 06:01:02 -0700, Watson A.Name wrote: "John Woodgate" wrote in message ... I read in sci.electronics.design that Tim Shoppa wrote (in .com) about 'wwvb receiver chip needed', on Tue, 26 Apr 2005: Zero-beat to WWV is hard to do better than 50Hz by ear. Have you tried a Lissajou display? Or use the S-meter to see very low freq beats. S-Meter! On 'modern' gear?? All they give you is a bank of eye candy in the form of leds. But, yes -- I've used Real S-Meters to get Real Damn Close to zero best in days past. 73 Jonesy -- | Marvin L Jones | jonz | W3DHJ | linux | Gunnison, Colorado | @ | Jonesy | OS/2 __ | 7,703' -- 2,345m | config.com | DM68mn SK |
#34
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On 27 Apr 2005 16:04:33 GMT, Allodoxaphobia wrote:
But, yes -- I've used Real S-Meters to get Real Damn Close to zero best in days past. Well, ... "best beat" works, too. Jonesy |
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