Re: [time-nuts] Shielding a DAC line - WWV

2013-09-28 Thread Bob Camp
From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, September 27, 2013 1:11 PM Subject: Re: [time-nuts] Shielding a DAC line - WWV Hi If you already know that the standard is within 50 ppb, then it only can drift 50

Re: [time-nuts] Shielding a DAC line - WWV

2013-09-27 Thread Bob Camp
From: Bob Stewart b...@evoria.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, September 26, 2013 6:13 PM Subject: Re: [time-nuts] Shielding a DAC line Hi Bob, I should have mentioned that I added a new 5MHz output, and the coax ran

Re: [time-nuts] Shielding a DAC line - WWV

2013-09-27 Thread Bob Albert
From: Bob Stewart b...@evoria.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, September 26, 2013 6:13 PM Subject: Re: [time-nuts] Shielding a DAC line Hi Bob, I should have mentioned that I added

Re: [time-nuts] Shielding a DAC line - WWV

2013-09-27 Thread Bob Albert
. What do you think? Bob From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, September 27, 2013 4:30 AM Subject: Re: [time-nuts] Shielding a DAC line - WWV Hi One hertz at 20 MHz is indeed 50

Re: [time-nuts] Shielding a DAC line - WWV

2013-09-27 Thread Bob Albert
. What do you think? Bob From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, September 27, 2013 4:30 AM Subject: Re: [time-nuts] Shielding a DAC line - WWV Hi One hertz at 20 MHz is indeed 50

Re: [time-nuts] Shielding a DAC line - WWV

2013-09-27 Thread Bob Camp
From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, September 27, 2013 4:30 AM Subject: Re: [time-nuts] Shielding a DAC line - WWV Hi One hertz at 20 MHz is indeed 50 ppb. On a practical basis

Re: [time-nuts] Shielding a DAC line - WWV

2013-09-27 Thread Bob Albert
.) Bob From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, September 27, 2013 1:11 PM Subject: Re: [time-nuts] Shielding a DAC line - WWV Hi If you already know that the standard is within 50

Re: [time-nuts] Shielding a DAC line - WWV

2013-09-27 Thread Bob Camp
of precise time and frequency measurement time-nuts@febo.com Sent: Friday, September 27, 2013 1:11 PM Subject: Re: [time-nuts] Shielding a DAC line - WWV Hi If you already know that the standard is within 50 ppb, then it only can drift 50 nanoseconds per second. If you check it every

Re: [time-nuts] Shielding a DAC line - WWV

2013-09-27 Thread Hal Murray
li...@rtty.us said: Anything under 100 ppb relative to WWVB is probably closer than the ionosphere will let you get under normal conditions. You can indeed get a zero beat, but that's not always a guarantee that the carrier isn't moving around at some odd rate. Far better to use WWVB. The LF

Re: [time-nuts] Shielding a DAC line - WWV

2013-09-27 Thread Bob Albert
From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, September 27, 2013 1:35 PM Subject: Re: [time-nuts] Shielding a DAC line - WWV Hi Anything under 100 ppb relative to WWVB is probably closer than

[time-nuts] Shielding a DAC line

2013-09-26 Thread Bob Stewart
I made some minor hardware changes to my GPSDO today and I see that it's locked to a new DAC voltage about 21mV higher.  So, I was wondering about shielding the short run to the OCXO.  I have immediately available RG-174 and I'm putting that in.  But, should this be some sort of steel shelled

Re: [time-nuts] Shielding a DAC line

2013-09-26 Thread Bob Camp
Hi I suspect that you have a ground offset between the OCXO's ground return and the DAC's ground reference. The signal *should* be DC, Shielding it won't hurt, but it really should not help much. If anything is an issue a simple R/C filter at the OCXO pin should nuke it better than coax will.

Re: [time-nuts] Shielding a DAC line

2013-09-26 Thread Bob Stewart
measurement time-nuts@febo.com Sent: Thursday, September 26, 2013 7:54 PM Subject: Re: [time-nuts] Shielding a DAC line Hi I suspect that you have a ground offset between the OCXO's ground return and the DAC's ground reference. The signal *should* be DC, Shielding it won't hurt, but it really should

Re: [time-nuts] Shielding a DAC line

2013-09-26 Thread Bob Albert
, 2013 6:13 PM Subject: Re: [time-nuts] Shielding a DAC line Hi Bob, I should have mentioned that I added a new 5MHz output, and the coax ran within 1/8 of the single DAC wire going to the OCXO.  I don't think anything else changed, but of course there could be some flake of something on the DAC

Re: [time-nuts] Shielding a DAC line

2013-09-26 Thread Bob Stewart
, September 26, 2013 8:24 PM Subject: Re: [time-nuts] Shielding a DAC line This is off topic but I'm unsure how to do it properly. I am trying to 'discipline' a couple of sources.  I zero beat with 20 MHz WWV but can't tell the difference between fading and the beat, so I am stuck in the vicinity of 1