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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
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Old 13th June 2021, 11:22 AM   #3901
Thom is offline Thom  Sweden
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Quote:
Originally Posted by gionag View Post
one or two things that may be worth checking.
better to switch the coil with positive voltage and keep one side grounded.
the positive side can be bypassed with a cap also to gnd.

that ensure a path towards ground and let the coil act as a shield.

an RF relay, while more expensive, can ensure proper impedance matching.
I confirmed today that the grounding of the coil indeed makes a big difference

the sine in was 11.29 MHz, 5.5 Vpp

with open relay, on the output I measured:

coil not grounded, 7 mVpp (58 dB isolation)

coil grounded, 0.3 mVpp (84 dB isolation)
Attached Images
File Type: jpg switchboard_measurement.jpg (611.9 KB, 489 views)
File Type: jpg switchboard_coilnotgrounded.jpg (489.0 KB, 468 views)
File Type: jpg switchboard_groundedcoil.jpg (480.4 KB, 457 views)
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Old 13th June 2021, 12:10 PM   #3902
Joseph K is offline Joseph K  Hungary
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Nice.
Then, just wanted to signal, that Anders Wallin has an open hardware project of an 8 channel RF mux.
Maybe worth a look. And, for people for ~ABX testing like Doede, could serve as it is!

Projects / RF Multiplexer 8ch 1GHz * Open Hardware Repository
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Old 13th June 2021, 12:36 PM   #3903
Joseph K is offline Joseph K  Hungary
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Thom,

I see from the waveform that You are doing it un-terminated.. Maybe it would be, generally better to use Andrea' s clock always properly terminated.
Then, if it is 5Vpp unterminated.. that seems a bit low for me.. Maybe Andrea can correct.
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Old 13th June 2021, 01:07 PM   #3904
Thom is offline Thom  Sweden
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Hi Joseph,
Thanks for your comments. Don't know if I understand you correctly but the signal is now terminated with 100 ohm to ground when relay is open (would be better with 50 ohm resistor perhaps?)
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Old 13th June 2021, 01:20 PM   #3905
andrea_mori is offline andrea_mori  Italy
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Yes, it should terminated to ground with 50R.
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Old 13th June 2021, 01:28 PM   #3906
Thom is offline Thom  Sweden
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Ok, thanks Andrea.
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Old 14th June 2021, 02:09 PM   #3907
Thom is offline Thom  Sweden
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new test,

As suggested here, I soldered a 0.1 uF MLCC between coil pin and ground plane at the 3.3V side at each relay and re-measured, and this gave nice results, direct coil grounding not needed anymore I think.

I measured only 0.16 mVpp leakage in the best case.

I changed termination from 100 to 75R (did not have 50R at home at this time) and the waveform looks better. Something that looks like approx 100 MHz is riding on the waveform, picked up from something nearby I guess?
Attached Images
File Type: jpg switchboard_modded.jpg (389.1 KB, 390 views)
File Type: jpg switchboard_moddedboardmeas.jpg (581.4 KB, 387 views)
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Old 15th June 2021, 12:12 PM   #3908
gionag is offline gionag  Italy
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The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Quote:
Originally Posted by Thom View Post
new test,

As suggested here, I soldered a 0.1 uF MLCC between coil pin and ground plane at the 3.3V side at each relay and re-measured, and this gave nice results, direct coil grounding not needed anymore I think.

I measured only 0.16 mVpp leakage in the best case.

I changed termination from 100 to 75R (did not have 50R at home at this time) and the waveform looks better. Something that looks like approx 100 MHz is riding on the waveform, picked up from something nearby I guess?
in my experience, one side solidly grounded and the other bypassed by a cap performs best.
By switching the coil "high-side", extra care (filtering) must be taken on the psu that act upon the coils (if shared with other electronics..)
but mileage may vary based upon the type of signal/relay/layout.
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Old 16th June 2021, 09:19 PM   #3909
Thom is offline Thom  Sweden
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Yes, that makes sense.

I have tested the switchboard + STS-DX squarer board in my DAC now. Input is Driscoll 11 and 12 MHz + doublers. Sounds good, will make some listening comparisons later when the build is more final.

Output from the squarer mounted in DAC looks like this.
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File Type: jpg squarer 10x.jpg (67.1 KB, 115 views)
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Old 19th June 2021, 11:39 AM   #3910
minionas is online now minionas  Lithuania
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I recently received my 5/6mhz Drixo plus doublers to have final 11/12mhz. Powered it with 16V Andrea's TWRPS-pp.
Earlier i had 45/48mhz Crystec 957 and Andrea's Driscoll v1.
To imagine better: jump of sq from Crystec to Driscoll was less prominent, than Driscoll to Drixo.
Most obvious: better resolution with more details and stronger bass. More focus needed: bigger space, fuller sounds extension, less strain, better PRaT. Just less digital, more natural music reproduction.
Im happy Big thanks to Andrea for developing such fine products! It was worth the wait!
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