Go Back   Home > Forums > >

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

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
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools
Old 13th June 2021, 11:22 AM   #3901
Thom is offline Thom  Sweden
diyAudio Member
 
Join Date: Jan 2003
Location: Sweden
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, 164 views)
File Type: jpg switchboard_coilnotgrounded.jpg (489.0 KB, 159 views)
File Type: jpg switchboard_groundedcoil.jpg (480.4 KB, 154 views)
  Reply With Quote
Old 13th June 2021, 12:10 PM   #3902
Joseph K is offline Joseph K  Hungary
diyAudio Member
 
Join Date: Dec 2004
Location: gran sasso
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
  Reply With Quote
Old 13th June 2021, 12:36 PM   #3903
Joseph K is offline Joseph K  Hungary
diyAudio Member
 
Join Date: Dec 2004
Location: gran sasso
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.
  Reply With Quote
Old 13th June 2021, 01:07 PM   #3904
Thom is offline Thom  Sweden
diyAudio Member
 
Join Date: Jan 2003
Location: Sweden
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?)
  Reply With Quote
Old 13th June 2021, 01:20 PM   #3905
andrea_mori is offline andrea_mori  Italy
diyAudio Member
 
andrea_mori's Avatar
 
Join Date: Jan 2005
Location: Italy
The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillator
Yes, it should terminated to ground with 50R.
  Reply With Quote
Old 13th June 2021, 01:28 PM   #3906
Thom is offline Thom  Sweden
diyAudio Member
 
Join Date: Jan 2003
Location: Sweden
Ok, thanks Andrea.
  Reply With Quote
Old Yesterday, 02:09 PM   #3907
Thom is offline Thom  Sweden
diyAudio Member
 
Join Date: Jan 2003
Location: Sweden
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, 80 views)
File Type: jpg switchboard_moddedboardmeas.jpg (581.4 KB, 80 views)
  Reply to this post

Reply


The Well Tempered Master Clock - Building a low phase noise/jitter crystal oscillatorHide this!Advertise here!
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
low jitter crystal oscillator IC beta tester needed. yizhou Digital Line Level 4 28th April 2013 05:13 AM
Circuit wanted for a Low Phase noise 100MHz Clock JohnW Digital Source 58 26th June 2012 08:28 AM
New Ultra Low Phase Noise Oscillator from Crystek wktk_smile Parts 7 25th August 2011 07:16 AM
Low jitter 30MHz crystal oscillator? Kuro Parts 2 1st April 2010 12:27 AM
Tube Crystal Clock Oscillator poynton Everything Else 3 25th August 2008 05:32 PM


New To Site? Need Help?

All times are GMT. The time now is 09:42 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki