K3EXREF and Trimble Thunderbolts
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K3EXREF and Trimble Thunderbolts
 
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Those of you considering a GPS-disciplined oscillator for use with the
K3EXREF may be interested in this: I recently purchased two Trimble Thunderbolts on the surplus market to compare against my HP 58540A and Brandywine GPS4 units. After several days of testing, I'm retiring the HP and Brandywine units. All devices have exceptionally good stability, but the Trimble units consume far less power, run substantially cooler, and the monitoring interface provides much more status information than the prior units. In recent discussions with John, KE5FX, he has performed phase noise measurements across several GPS-DO units and even various oscillator brands within the Trimble Thunderbolt model. http://www.thegleam.com/ke5fx/tbolt.htm Early Thunderbolts use a Piezo Corp. OCXO and when combined with GPS correction, its phase noise performance is good but not exceptional. By contrast, the Trimble-branded OCXO offers phase noise performance several degrees better than most other GPS-DO units near Fc. The area between 1 Hz and 100 Hz is usually a good indicator of the overall phase noise performance. It's not easy getting good numbers that distance from Fc. Although the phase noise performance will not carry over to the K3, it's an important parameter if the GPS-DO will be used in other applications or other transceivers that phase lock onto the 10 MHz external reference. Some suggestions: 1) Look for Thunderbolts with a year 2004 Rev. E stamp. These use the better quality OCXO units with the Trimble-branded label. KE5FX has sampled several from this batch. As noted, early units with the Piezo-branded OCXO are worse in terms of phase noise performance. I do not know the OCXO quality of recent units; 2) You will see Thunderbolts in a high quality case where an internal DC-DC converter is used. My recommendation is to avoid being tempted by the nice looks and what may be perceived as a "better" unit. I can almost guarantee that the switch-mode converters will present noise problems with your K3 receiver -- and seen on your panadapters. I've been down that road with other GPS-DO units and ultimately, I scrapped the converters and fed them with linear supplies. Stick to the basic ugly OEM Thunderbolt module and feed it from a triple-output linear supply; 3) Power supplies: I like OEM/off-board supplies by PowerOne, Condor, and International Power. They offer excellent performance and low noise. I am using an International Power IHBAA-40W. Also look for HBAA-40W. The user must add a fuse, power cord and wiring harness. It's a little more work, but you get a lot of performance for the money; 4) Look for sellers who will accept offers. Both my Thunderbolts were purchased for USD $70 ea and a small shipping change. Even if you have no plans to use K3EXREF, get one anyway as a precision frequency reference for your station. Paul, W9AC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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Paul, > 3) Power supplies: I like OEM/off-board supplies by PowerOne, Condor, > and International Power. They offer excellent performance and low > noise. I am using an International Power IHBAA-40W. Also look for > HBAA-40W. What are the power requirements? Would it not be possible to build a basic linear supply relatively inexpensively and avoid all of the switcher issues? 73, ... Joe, W4TV On 4/5/2011 8:43 AM, Paul Christensen wrote: > Those of you considering a GPS-disciplined oscillator for use with the > K3EXREF may be interested in this: I recently purchased two Trimble > Thunderbolts on the surplus market to compare against my HP 58540A and > Brandywine GPS4 units. After several days of testing, I'm retiring the HP > and Brandywine units. All devices have exceptionally good stability, but > the Trimble units consume far less power, run substantially cooler, and the > monitoring interface provides much more status information than the prior > units. > > In recent discussions with John, KE5FX, he has performed phase noise > measurements across several GPS-DO units and even various oscillator brands > within the Trimble Thunderbolt model. > > http://www.thegleam.com/ke5fx/tbolt.htm > > Early Thunderbolts use a Piezo Corp. OCXO and when combined with GPS > correction, its phase noise performance is good but not exceptional. By > contrast, the Trimble-branded OCXO offers phase noise performance several > degrees better than most other GPS-DO units near Fc. The area between 1 Hz > and 100 Hz is usually a good indicator of the overall phase noise > performance. It's not easy getting good numbers that distance from Fc. > Although the phase noise performance will not carry over to the K3, it's an > important parameter if the GPS-DO will be used in other applications or > other transceivers that phase lock onto the 10 MHz external reference. > > Some suggestions: > > 1) Look for Thunderbolts with a year 2004 Rev. E stamp. These use the > better quality OCXO units with the Trimble-branded label. KE5FX has sampled > several from this batch. As noted, early units with the Piezo-branded OCXO > are worse in terms of phase noise performance. I do not know the OCXO > quality of recent units; > > 2) You will see Thunderbolts in a high quality case where an internal DC-DC > converter is used. My recommendation is to avoid being tempted by the nice > looks and what may be perceived as a "better" unit. I can almost guarantee > that the switch-mode converters will present noise problems with your K3 > receiver -- and seen on your panadapters. I've been down that road with > other GPS-DO units and ultimately, I scrapped the converters and fed them > with linear supplies. Stick to the basic ugly OEM Thunderbolt module and > feed it from a triple-output linear supply; > > 3) Power supplies: I like OEM/off-board supplies by PowerOne, Condor, and > International Power. They offer excellent performance and low noise. I am > using an International Power IHBAA-40W. Also look for HBAA-40W. The user > must add a fuse, power cord and wiring harness. It's a little more work, > but you get a lot of performance for the money; > > 4) Look for sellers who will accept offers. Both my Thunderbolts were > purchased for USD $70 ea and a small shipping change. > > Even if you have no plans to use K3EXREF, get one anyway as a precision > frequency reference for your station. > > Paul, W9AC > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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Joe,
Sure. One could build a clean supply using 1A regulators from a well-filtered supply. The requirement is +12, -12, and +5. So, one could use 7812, 7912, and 7805 regulators -- or their low drop-out LM2940 equivalents. I believe the max current needed during oven warm-up is about 0.75 amp from the +12V supply and that tapers off to quite a bit less afterwards. The trouble with many homebrew power supplies is lack of attention paid to filtering before and after the regulators -- and sizing the voltage drop across the regulator to account for brown-out conditions but no more. Probably the majority of builders neglect the inclusion of film caps and discharge diodes around the regulators. I believe the latest ARRL handbook includes good information about power supply construction and how to go about matching up the transformer to adequately hit the regulator input target voltages based on rectifier type. OTOH, new-old-stock supplies (e.g., PowerOne, Condor, International Power) can be found on-line at a cost comparable to what one would pay to build a supply using new components. I paid about $35 for a NOS triple-output supply made by International Power. Paul, W9AC ----- Original Message ----- From: "Joe Subich, W4TV" <[hidden email]> To: "Paul Christensen" <[hidden email]> Cc: <[hidden email]> Sent: Tuesday, April 05, 2011 10:05 AM Subject: Re: [Elecraft] K3EXREF and Trimble Thunderbolts > > Paul, > >> 3) Power supplies: I like OEM/off-board supplies by PowerOne, Condor, >> and International Power. They offer excellent performance and low >> noise. I am using an International Power IHBAA-40W. Also look for >> HBAA-40W. > > What are the power requirements? Would it not be possible to build > a basic linear supply relatively inexpensively and avoid all of the > switcher issues? > > 73, > > ... Joe, W4TV > > > On 4/5/2011 8:43 AM, Paul Christensen wrote: >> Those of you considering a GPS-disciplined oscillator for use with the >> K3EXREF may be interested in this: I recently purchased two Trimble >> Thunderbolts on the surplus market to compare against my HP 58540A and >> Brandywine GPS4 units. After several days of testing, I'm retiring the >> HP >> and Brandywine units. All devices have exceptionally good stability, but >> the Trimble units consume far less power, run substantially cooler, and >> the >> monitoring interface provides much more status information than the prior >> units. >> >> In recent discussions with John, KE5FX, he has performed phase noise >> measurements across several GPS-DO units and even various oscillator >> brands >> within the Trimble Thunderbolt model. >> >> http://www.thegleam.com/ke5fx/tbolt.htm >> >> Early Thunderbolts use a Piezo Corp. OCXO and when combined with GPS >> correction, its phase noise performance is good but not exceptional. By >> contrast, the Trimble-branded OCXO offers phase noise performance several >> degrees better than most other GPS-DO units near Fc. The area between 1 >> Hz >> and 100 Hz is usually a good indicator of the overall phase noise >> performance. It's not easy getting good numbers that distance from Fc. >> Although the phase noise performance will not carry over to the K3, it's >> an >> important parameter if the GPS-DO will be used in other applications or >> other transceivers that phase lock onto the 10 MHz external reference. >> >> Some suggestions: >> >> 1) Look for Thunderbolts with a year 2004 Rev. E stamp. These use the >> better quality OCXO units with the Trimble-branded label. KE5FX has >> sampled >> several from this batch. As noted, early units with the Piezo-branded >> OCXO >> are worse in terms of phase noise performance. I do not know the OCXO >> quality of recent units; >> >> 2) You will see Thunderbolts in a high quality case where an internal >> DC-DC >> converter is used. My recommendation is to avoid being tempted by the >> nice >> looks and what may be perceived as a "better" unit. I can almost >> guarantee >> that the switch-mode converters will present noise problems with your K3 >> receiver -- and seen on your panadapters. I've been down that road with >> other GPS-DO units and ultimately, I scrapped the converters and fed them >> with linear supplies. Stick to the basic ugly OEM Thunderbolt module and >> feed it from a triple-output linear supply; >> >> 3) Power supplies: I like OEM/off-board supplies by PowerOne, Condor, >> and >> International Power. They offer excellent performance and low noise. I >> am >> using an International Power IHBAA-40W. Also look for HBAA-40W. The >> user >> must add a fuse, power cord and wiring harness. It's a little more work, >> but you get a lot of performance for the money; >> >> 4) Look for sellers who will accept offers. Both my Thunderbolts were >> purchased for USD $70 ea and a small shipping change. >> >> Even if you have no plans to use K3EXREF, get one anyway as a precision >> frequency reference for your station. >> >> Paul, W9AC >> >> >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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What are the advantages / disadvantages of this type of frequency standard over the Efratom LPRO-101 which is a rubidium standard?
Julian, G4ILO
Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com * KComm - http://www.g4ilo.com/kcomm.html * KTune - http://www.g4ilo.com/ktune.html |
Re: K3EXREF and Trimble Thunderbolts
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In reply to this post by P.B. Christensen
Thanks Paul. Good summary and reference info.
The K3EXREF certainly works as advertised. I've already used two different Rb sources, and it's solid as a rock. Using a TIA over the weekend,, saw a 1 to 2 Hz wander at 28MHz, however the Rb clocks have a little start-up drift and the wander might have been due to that. And of course, the TIA is based on Rb, itself. I bought a Rev E Thunderbolt GPS-DO from a vendor on eBay. It's still training (< 24 hours), and there was a 1 Hz per 10 minutes upward drift after two hours of operation, in the REF*CAL indicator. Is this normal? Will check it again at around 24 hours into the experiement. Even though I work in the GPS industry, I've never used a GPS-DO before. I've tossed my original Wellnav OCXO-based freq source. We use these as a time base here in our GPS simulators, but they're far from phase noise free and there is significantly more drift (might also be age). Was seening 5 to 6 Hz of wander, and sampling it showed a textbook [but skewed] Gaussian distribution. The wander should not generally even be detectable with conventional ham equipment, but it was. Cool stuff. Just to reinforce Paul's comments, the Trimble software is quite impressive. I work in the industry, and I've never seen even in our own Pro products, so much monitored statistical and operations data in a control program. It certainly was worth the price (see Trimble's web site under Support). Free that is. I'm running the Tbolt on a linear supply. It's a three-output Topward lab-grade PS. Monitoring the current consumed, I see the following: +12V: 700-750 mA for startup (warming the OCXO), 40-50 mA steady state -12V: < 20 mA continuous +5V: 370 mA continuous Add all this up, and steady state power consumed comes to about 2.7W. This is perfect for use in a solar-powered station. My K3 and general station power comes from two 50W Siemens PV panels on the roof. These feed a charge controller and 110AH 12V AGM battery in the shack. The lower power consumption of the GPS-DO is compatible with this set up. I had borrowed a Brandywine unit from a buddy that works there, and it consumed about 35W steady state. Not good for this installation. 73, matt W6NIA Upland, CA. On Tue, 05 Apr 2011 08:43:46 -0400, you wrote: >Those of you considering a GPS-disciplined oscillator for use with the >K3EXREF may be interested in this: I recently purchased two Trimble >Thunderbolts on the surplus market to compare against my HP 58540A and >Brandywine GPS4 units. After several days of testing, I'm retiring the HP >and Brandywine units. All devices have exceptionally good stability, but >the Trimble units consume far less power, run substantially cooler, and the >monitoring interface provides much more status information than the prior >units. > >In recent discussions with John, KE5FX, he has performed phase noise >measurements across several GPS-DO units and even various oscillator brands >within the Trimble Thunderbolt model. > >http://www.thegleam.com/ke5fx/tbolt.htm > >Early Thunderbolts use a Piezo Corp. OCXO and when combined with GPS >correction, its phase noise performance is good but not exceptional. By >contrast, the Trimble-branded OCXO offers phase noise performance several >degrees better than most other GPS-DO units near Fc. The area between 1 Hz >and 100 Hz is usually a good indicator of the overall phase noise >performance. It's not easy getting good numbers that distance from Fc. >Although the phase noise performance will not carry over to the K3, it's an >important parameter if the GPS-DO will be used in other applications or >other transceivers that phase lock onto the 10 MHz external reference. > >Some suggestions: > >1) Look for Thunderbolts with a year 2004 Rev. E stamp. These use the >better quality OCXO units with the Trimble-branded label. KE5FX has sampled >several from this batch. As noted, early units with the Piezo-branded OCXO >are worse in terms of phase noise performance. I do not know the OCXO >quality of recent units; > >2) You will see Thunderbolts in a high quality case where an internal DC-DC >converter is used. My recommendation is to avoid being tempted by the nice >looks and what may be perceived as a "better" unit. I can almost guarantee >that the switch-mode converters will present noise problems with your K3 >receiver -- and seen on your panadapters. I've been down that road with >other GPS-DO units and ultimately, I scrapped the converters and fed them >with linear supplies. Stick to the basic ugly OEM Thunderbolt module and >feed it from a triple-output linear supply; > >3) Power supplies: I like OEM/off-board supplies by PowerOne, Condor, and >International Power. They offer excellent performance and low noise. I am >using an International Power IHBAA-40W. Also look for HBAA-40W. The user >must add a fuse, power cord and wiring harness. It's a little more work, >but you get a lot of performance for the money; > >4) Look for sellers who will accept offers. Both my Thunderbolts were >purchased for USD $70 ea and a small shipping change. > >Even if you have no plans to use K3EXREF, get one anyway as a precision >frequency reference for your station. > >Paul, W9AC > > > >______________________________________________________________ >Elecraft mailing list >Home: http://mailman.qth.net/mailman/listinfo/elecraft >Help: http://mailman.qth.net/mmfaq.htm >Post: mailto:[hidden email] > >This list hosted by: http://www.qsl.net >Please help support this email list: http://www.qsl.net/donate.html Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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In reply to this post by Julian, G4ILO
I would say the main disadvantage is that you need a suitably positioned
GPS antenna. I understand that the GPS satellites use Caesium resonators so in theory could be more accurate than Rubidium. Another alternative is an off-air frequency standard controlled by the Radio 4 transmission on 198kHz at Droitwich, Burghead and Westerglen which is accurate to 2 parts in 10^11. One such device by Quartzlock is currently on eBay (item 180648121165). I can confirm that in field test trials the Quartzlock Model 2A locks the K3 okay. 73 de David G4DMP In a recent message, "Julian, G4ILO" <[hidden email]> writes >What are the advantages / disadvantages of this type of frequency standard >over the Efratom LPRO-101 which is a rubidium standard? -- + - - - - - - - - - - - - - - - - + | David M Pratt, Kippax, Leeds. | | Website: http://www.g4dmp.co.uk | + - - - - - - - - - - - - - - - - + ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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In reply to this post by Matt Zilmer
Several folks have inquired about the Thunderbolt's $70 price. The big
on-line auction place. Seller name: "svcompucycle" Paul, W9AC ----- Original Message ----- From: "Matt Zilmer" <[hidden email]> To: "Paul Christensen" <[hidden email]> Cc: <[hidden email]> Sent: Tuesday, April 05, 2011 11:40 AM Subject: Re: [Elecraft] K3EXREF and Trimble Thunderbolts Thanks Paul. Good summary and reference info. The K3EXREF certainly works as advertised. I've already used two different Rb sources, and it's solid as a rock. Using a TIA over the weekend,, saw a 1 to 2 Hz wander at 28MHz, however the Rb clocks have a little start-up drift and the wander might have been due to that. And of course, the TIA is based on Rb, itself. I bought a Rev E Thunderbolt GPS-DO from a vendor on eBay. It's still training (< 24 hours), and there was a 1 Hz per 10 minutes upward drift after two hours of operation, in the REF*CAL indicator. Is this normal? Will check it again at around 24 hours into the experiement. Even though I work in the GPS industry, I've never used a GPS-DO before. I've tossed my original Wellnav OCXO-based freq source. We use these as a time base here in our GPS simulators, but they're far from phase noise free and there is significantly more drift (might also be age). Was seening 5 to 6 Hz of wander, and sampling it showed a textbook [but skewed] Gaussian distribution. The wander should not generally even be detectable with conventional ham equipment, but it was. Cool stuff. Just to reinforce Paul's comments, the Trimble software is quite impressive. I work in the industry, and I've never seen even in our own Pro products, so much monitored statistical and operations data in a control program. It certainly was worth the price (see Trimble's web site under Support). Free that is. I'm running the Tbolt on a linear supply. It's a three-output Topward lab-grade PS. Monitoring the current consumed, I see the following: +12V: 700-750 mA for startup (warming the OCXO), 40-50 mA steady state -12V: < 20 mA continuous +5V: 370 mA continuous Add all this up, and steady state power consumed comes to about 2.7W. This is perfect for use in a solar-powered station. My K3 and general station power comes from two 50W Siemens PV panels on the roof. These feed a charge controller and 110AH 12V AGM battery in the shack. The lower power consumption of the GPS-DO is compatible with this set up. I had borrowed a Brandywine unit from a buddy that works there, and it consumed about 35W steady state. Not good for this installation. 73, matt W6NIA Upland, CA. On Tue, 05 Apr 2011 08:43:46 -0400, you wrote: >Those of you considering a GPS-disciplined oscillator for use with the >K3EXREF may be interested in this: I recently purchased two Trimble >Thunderbolts on the surplus market to compare against my HP 58540A and >Brandywine GPS4 units. After several days of testing, I'm retiring the HP >and Brandywine units. All devices have exceptionally good stability, but >the Trimble units consume far less power, run substantially cooler, and the >monitoring interface provides much more status information than the prior >units. > >In recent discussions with John, KE5FX, he has performed phase noise >measurements across several GPS-DO units and even various oscillator brands >within the Trimble Thunderbolt model. > >http://www.thegleam.com/ke5fx/tbolt.htm > >Early Thunderbolts use a Piezo Corp. OCXO and when combined with GPS >correction, its phase noise performance is good but not exceptional. By >contrast, the Trimble-branded OCXO offers phase noise performance several >degrees better than most other GPS-DO units near Fc. The area between 1 Hz >and 100 Hz is usually a good indicator of the overall phase noise >performance. It's not easy getting good numbers that distance from Fc. >Although the phase noise performance will not carry over to the K3, it's an >important parameter if the GPS-DO will be used in other applications or >other transceivers that phase lock onto the 10 MHz external reference. > >Some suggestions: > >1) Look for Thunderbolts with a year 2004 Rev. E stamp. These use the >better quality OCXO units with the Trimble-branded label. KE5FX has >sampled >several from this batch. As noted, early units with the Piezo-branded OCXO >are worse in terms of phase noise performance. I do not know the OCXO >quality of recent units; > >2) You will see Thunderbolts in a high quality case where an internal DC-DC >converter is used. My recommendation is to avoid being tempted by the nice >looks and what may be perceived as a "better" unit. I can almost guarantee >that the switch-mode converters will present noise problems with your K3 >receiver -- and seen on your panadapters. I've been down that road with >other GPS-DO units and ultimately, I scrapped the converters and fed them >with linear supplies. Stick to the basic ugly OEM Thunderbolt module and >feed it from a triple-output linear supply; > >3) Power supplies: I like OEM/off-board supplies by PowerOne, Condor, and >International Power. They offer excellent performance and low noise. I am >using an International Power IHBAA-40W. Also look for HBAA-40W. The user >must add a fuse, power cord and wiring harness. It's a little more work, >but you get a lot of performance for the money; > >4) Look for sellers who will accept offers. Both my Thunderbolts were >purchased for USD $70 ea and a small shipping change. > >Even if you have no plans to use K3EXREF, get one anyway as a precision >frequency reference for your station. > >Paul, W9AC > > > >______________________________________________________________ >Elecraft mailing list >Home: http://mailman.qth.net/mailman/listinfo/elecraft >Help: http://mailman.qth.net/mmfaq.htm >Post: mailto:[hidden email] > >This list hosted by: http://www.qsl.net >Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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I should have added that USD $70 was the offered and accepted price.
Shipping was very fast as well. > ----- Original Message ----- > From: "Matt Zilmer" <[hidden email]> > To: "Paul Christensen" <[hidden email]> > Cc: <[hidden email]> > Sent: Tuesday, April 05, 2011 11:40 AM > Subject: Re: [Elecraft] K3EXREF and Trimble Thunderbolts > > > Thanks Paul. Good summary and reference info. > > The K3EXREF certainly works as advertised. I've already used two > different Rb sources, and it's solid as a rock. Using a TIA over the > weekend,, saw a 1 to 2 Hz wander at 28MHz, however the Rb clocks have > a little start-up drift and the wander might have been due to that. > And of course, the TIA is based on Rb, itself. > > I bought a Rev E Thunderbolt GPS-DO from a vendor on eBay. It's still > training (< 24 hours), and there was a 1 Hz per 10 minutes upward > drift after two hours of operation, in the REF*CAL indicator. Is this > normal? Will check it again at around 24 hours into the experiement. > Even though I work in the GPS industry, I've never used a GPS-DO > before. > > I've tossed my original Wellnav OCXO-based freq source. We use these > as a time base here in our GPS simulators, but they're far from phase > noise free and there is significantly more drift (might also be age). > Was seening 5 to 6 Hz of wander, and sampling it showed a textbook > [but skewed] Gaussian distribution. The wander should not generally > even be detectable with conventional ham equipment, but it was. > > Cool stuff. > > Just to reinforce Paul's comments, the Trimble software is quite > impressive. I work in the industry, and I've never seen even in our > own Pro products, so much monitored statistical and operations data in > a control program. It certainly was worth the price (see Trimble's > web site under Support). Free that is. > > I'm running the Tbolt on a linear supply. It's a three-output Topward > lab-grade PS. Monitoring the current consumed, I see the following: > +12V: 700-750 mA for startup (warming the OCXO), 40-50 mA steady state > -12V: < 20 mA continuous > +5V: 370 mA continuous > > Add all this up, and steady state power consumed comes to about 2.7W. > This is perfect for use in a solar-powered station. My K3 and general > station power comes from two 50W Siemens PV panels on the roof. These > feed a charge controller and 110AH 12V AGM battery in the shack. The > lower power consumption of the GPS-DO is compatible with this set up. > > I had borrowed a Brandywine unit from a buddy that works there, and it > consumed about 35W steady state. Not good for this installation. > > 73, > matt W6NIA > Upland, CA. > > On Tue, 05 Apr 2011 08:43:46 -0400, you wrote: > >>Those of you considering a GPS-disciplined oscillator for use with the >>K3EXREF may be interested in this: I recently purchased two Trimble >>Thunderbolts on the surplus market to compare against my HP 58540A and >>Brandywine GPS4 units. After several days of testing, I'm retiring the HP >>and Brandywine units. All devices have exceptionally good stability, but >>the Trimble units consume far less power, run substantially cooler, and >>the >>monitoring interface provides much more status information than the prior >>units. >> >>In recent discussions with John, KE5FX, he has performed phase noise >>measurements across several GPS-DO units and even various oscillator >>brands >>within the Trimble Thunderbolt model. >> >>http://www.thegleam.com/ke5fx/tbolt.htm >> >>Early Thunderbolts use a Piezo Corp. OCXO and when combined with GPS >>correction, its phase noise performance is good but not exceptional. By >>contrast, the Trimble-branded OCXO offers phase noise performance several >>degrees better than most other GPS-DO units near Fc. The area between 1 >>Hz >>and 100 Hz is usually a good indicator of the overall phase noise >>performance. It's not easy getting good numbers that distance from Fc. >>Although the phase noise performance will not carry over to the K3, it's >>an >>important parameter if the GPS-DO will be used in other applications or >>other transceivers that phase lock onto the 10 MHz external reference. >> >>Some suggestions: >> >>1) Look for Thunderbolts with a year 2004 Rev. E stamp. These use the >>better quality OCXO units with the Trimble-branded label. KE5FX has >>sampled >>several from this batch. As noted, early units with the Piezo-branded >>OCXO >>are worse in terms of phase noise performance. I do not know the OCXO >>quality of recent units; >> >>2) You will see Thunderbolts in a high quality case where an internal >>DC-DC >>converter is used. My recommendation is to avoid being tempted by the >>nice >>looks and what may be perceived as a "better" unit. I can almost >>guarantee >>that the switch-mode converters will present noise problems with your K3 >>receiver -- and seen on your panadapters. I've been down that road with >>other GPS-DO units and ultimately, I scrapped the converters and fed them >>with linear supplies. Stick to the basic ugly OEM Thunderbolt module and >>feed it from a triple-output linear supply; >> >>3) Power supplies: I like OEM/off-board supplies by PowerOne, Condor, and >>International Power. They offer excellent performance and low noise. I >>am >>using an International Power IHBAA-40W. Also look for HBAA-40W. The user >>must add a fuse, power cord and wiring harness. It's a little more work, >>but you get a lot of performance for the money; >> >>4) Look for sellers who will accept offers. Both my Thunderbolts were >>purchased for USD $70 ea and a small shipping change. >> >>Even if you have no plans to use K3EXREF, get one anyway as a precision >>frequency reference for your station. >> >>Paul, W9AC >> >> >> >>______________________________________________________________ >>Elecraft mailing list >>Home: http://mailman.qth.net/mailman/listinfo/elecraft >>Help: http://mailman.qth.net/mmfaq.htm >>Post: mailto:[hidden email] >> >>This list hosted by: http://www.qsl.net >>Please help support this email list: http://www.qsl.net/donate.html > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Julian, G4ILO
I've got a more basic question than that. What are external, GPS synched freq standards used for? Do I need one for my K1 ?? Seriously, I haven't a clue. 73 Bill K3UJ -----Original Message----- From: Julian, G4ILO <[hidden email]> To: elecraft <[hidden email]> Sent: Tue, Apr 5, 2011 11:09 am Subject: Re: [Elecraft] K3EXREF and Trimble Thunderbolts What are the advantages / disadvantages of this type of frequency standard ver the Efratom LPRO-101 which is a rubidium standard? Julian, G4ILO ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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<quote author="Able2fly">
I've got a more basic question than that. What are external, GPS synched freq standards used for? Do I need one for my K1 ?? Seriously, I haven't a clue. 73 Bill K3UJ
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On 4/5/2011 10:06 AM, Leigh L. Klotz Jr WA5ZNU wrote: > > I've got a more basic question than that. What are external, GPS synched > freq standards used for? GPS relies on very accurate timing of it's signals. Each satellite carries an atomic clock [Rubidium?] and the frequency of the satellite's various signals are thus extremely accurate and stable. With appropriate equipment, they can be used to control a standard oscillator which in turn controls the TXCO in the K3 to the same accuracy. The K2, K1, and KX1 have no such provision. > > Do I need one for my K1 ?? No. 73, Fred K6DGW - Northern California Contest Club - CU in the 2011 Cal QSO Party 1-2 Oct 2011 - www.cqp.org ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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In reply to this post by Julian, G4ILO
I'm a duffer at this time/frequency stuff, but I've scored well enough at the ARRL FMT to get my call in QST, and I gave a presentation on it at the Bay Area Maker Faire last year, and a NIST scientist told me I didn't say anything egregiously wrong, so I'll try to stick to what I understand here. If you want to know more, go to Febo.com or time-nuts and read a bit (before you ask questions) and you'll find people with literally orders of magnitude more experience (and interest) than you ever thought possible. Both an Rb oscillator and a GPS-DO (and for that matter, your own Cesium standard) can provide you with a frequency output, but they're different types of things. A GPS-DO is a managed device with an output, like WWV or the grid 60 Hz (mains 50Hz) frequency. A Rubidium oscillator is like a quartz crystal, but more stable over the long term (modulo a well-defined linear drift), so once it's set, it stays set exceptionally well, though usually the phase noise isn't as good as a temperature-controlled quartz crystal. A Cesium standard is called a standard because it's how we define time; when properly adjusted, it will remain in calibration quite well. A GPS-DO usually contains a crystal oscillator which is controlled (disciplined) to match the data coming in from GSP satellites, which themselves contains Cesium standards which themselves are actively managed by the US government. So it's like listening to WWV or one of the other time signals on HF, but it uses the 1.4 GHz range and averages multiple signals, so you get better results with smaller propagation-induced errors. There are some Rubidium GPS-DO devices as well, some commercial and some done by smart hams, but even those, as far as I know, contain a quartz crystal oscillator which itself is disciplined by the Rubidium bulb microwave resonance. There's arguments about different ways of disciplining all of these oscillators and if you're interested, look for the time-nuts mailing list or read on febo.com, or read about Allan Deviation. But briefly: there are multiple sources of noise, and if you measure the noise on different time scales, you get different answers about how much noise there is. So, roughly, phase noise is at one end of the chart and how far your wristwatch is off at the end of the month is at the other end. What time scale you care about determines what type of oscillator you use and how you measure and take care of it. A Rubidium oscillator does quite well on many of these time scales, better than Cesium in some of them, but worse than a plain quartz crystal in others. Unfortunately, my guess is that buying an Rb standard and using it instead of the quartz TCXO in the K3 would result in worse phase noise which translates into a noisier band RX and noisier TX. Quartz is pretty much the way to go for transceivers given the areas of concern that hams have. (I.e., would you rather have 20dB less band noise or be able to get within 0.1 millihertz of the band edge instead of just 1 millihertz of the band edge?) More philosophically, we define time in terms of what Cesium does. Both Cs and Rb physics packages have knobs to adjust for external magnetic field ("C" Field), so both can be set wrong, but Rubidium bulbs "age" and change frequency (though at an fairly well characterized rate), so you can't substitute a Rubidium oscillator for a Cesium one. According to NIST, gravity is a big effect as well, so if you ever move one of your oscillators, its calibration field is toast. And finally, temperature control is of the utmost importance, and those who are serious use multiple nested containers for temperature isolation. For ham use as a frequency standard, in terms of phase noise performance, the algorithm used and the oscillator that's being disciplined (and how often, as part of the algorithm) has the strongest influence. For example, a GPS-DO is additionally affected by what satellites are in view (the "constellation"), and the Trimble units are affected by the changes more so than more expensive units which are designed as frequency references, because they make abrupt changes when the constellation changes, which is pretty much every few minutes as sats pass over. The eBay Trimble units in particular have trouble with this. They were designed for E-911 installations in cell sites, where they were used to calculate distance via speed of light to a mobile unit. My (unfounded, personal) belief is that it was more important that nearby units all had the same idea of the time than that they have reduced noise on the shorter-term. So they make more frequent adjustments to their internal quartz oscillators that are comfortable for a frequency standard, though a number of smart folks have figured out algorithm tweaks to mitigate this effect, making the temperature the dominant factor, for time scales of 1hr - 24 hrs. The K3XREF product that Elecraft is developing is, to my understanding, an external disciplining interface for the TCXO in the K3. It's probably a frequency counter / microprocessor which reads the internal oscillator and the external 10 MHz reference, and when the internal oscillator doesn't produce the right number of cycles in 10 million of the external oscillator's cycles, it adjusts the voltage on the TCXO to bring it back into spec. But if you do this too often, you'll introduce phase noise into the K3 (think of it as FM-ing). Wayne N6KR has said it does this a few times a second an has achieved a trade off between accuracy and phase noise. (I presume he doesn't adjust during TX, for example.) I leave my K3 on most of the time, and I've found that it is seldom off more than +/- 3 Hz. But the K3XREF would let it off +/- 1Hz as soon as you turn it on, provided it's hooked up to your external reference. The actual received frequency is only valid for one mode and one filter, once you calibrate it, since when you shift modes or filters the offets of the various internal IF stages varies. (Keep that in mind if you use the K3 for the ARRL FMT.) Leigh/WA5ZNU |
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In reply to this post by P.B. Christensen
This is very valid question. Each method has advantages and disadvanages. The GPS based reference needs antenna and ability to see satellites. If you lose satellites you enter so-called holdover mode, when your stability depends on local oscillator. In case of Trimble unit this will be free running OCXO - not too bad if the GPS will acquire satellites back in reasonable time. I am not familiar with the Trimble unit and how it handles holdover, I guess our friends with these units can tell us what happens to the frequency if they disconnect GPS antenna from the unit. The LPRO is very stable frequency source and it does not require any antennas. For most of applications it will also give very good phase noise - probably not much worse than the OCXO in the Trimble unit. T he disadvantage of LPRO - limited life. New LPRO units were designed to service life of about 20 years. The units you buy on the web are used - you don't know how much life is left in it, it is quite possible it will fade in year or two if it was operated continuously for many years. It also can be little off frequency - the frequency of LPRO is adjustable (if I remember correctly). 73, Igor, N1YX ----- Original Message ----- From: "G4ILO Julian" <[hidden email]> To: [hidden email] Sent: Tuesday, April 5, 2011 11:09:26 AM Subject: Re: [Elecraft] K3EXREF and Trimble Thunderbolts What are the advantages / disadvantages of this type of frequency standard over the Efratom LPRO-101 which is a rubidium standard? Julian, G4ILO ----- Julian, G4ILO. K2 #392 K3 #222. * G4ILO's Shack - http://www.g4ilo.com * KComm - http://www.g4ilo.com/kcomm.html * KTune - http://www.g4ilo.com/ktune.html -- View this message in context: http://elecraft.365791.n2.nabble.com/K3EXREF-and-Trimble-Thunderbolts-tp6242158p6242619.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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In reply to this post by Leigh L. Klotz Jr WA5ZNU
The K3EXREF uses the 10 MHz standard as it's time base to measure the K3's TCXO and passes
an error value to the K3's MCU every few seconds. No TCXO frequency control takes place, thus no increase in phase noise. Frequency compensation is done in software by automatically updating the REF CAL function. A relatively simple mechanism but effective :) For my installation, I'm using a Thunderbolt, an $11 active antenna from Digi-Key, and a 30' run of RG-6, which works nicely with the F connector on the Tbolt. 73, Rich AC7MA On 4/5/2011 10:35 AM, Leigh L. Klotz Jr WA5ZNU wrote: > ... > The K3XREF product that Elecraft is developing is, to my understanding, an > external disciplining interface for the TCXO in the K3. It's probably a > frequency counter / microprocessor which reads the internal oscillator and > the external 10 MHz reference, and when the internal oscillator doesn't > produce the right number of cycles in 10 million of the external > oscillator's cycles, it adjusts the voltage on the TCXO to bring it back > into spec. But if you do this too often, you'll introduce phase noise into > the K3 (think of it as FM-ing). Wayne N6KR has said it does this a few > times a second an has achieved a trade off between accuracy and phase noise. > (I presume he doesn't adjust during TX, for example.) > > I leave my K3 on most of the time, and I've found that it is seldom off more > than +/- 3 Hz. But the K3XREF would let it off +/- 1Hz as soon as you turn > it on, provided it's hooked up to your external reference. The actual > received frequency is only valid for one mode and one filter, once you > calibrate it, since when you shift modes or filters the offets of the > various internal IF stages varies. (Keep that in mind if you use the K3 for > the ARRL FMT.) > > Leigh/WA5ZNU > > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/K3EXREF-and-Trimble-Thunderbolts-tp6242158p6243171.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Hello group,
It's been many months since I've posted here, much less actually done something new with my K3. This topic has however piqued my interest. Just so I understand fully, am I right in assuming then that the following is correct: 1. Any reference oscillator operating at 10 MHz would work with the K3XREF? 2. All that's needed for this to work is the K3XREF, updated firmware, an accurate 10 MHz clock/oscillator, and a BNC cable? 3. Trimble Thunderbolt seems to be a good, cheap product to try. Any others that are > $100? What are the additional advantages of doing this other than knowing you've pretty much eliminated any frequency drift? 73 de James K2QI President UNARC/4U1UN On Tue, Apr 5, 2011 at 2:32 PM, Rich Heineck <[hidden email]> wrote: > The K3EXREF uses the 10 MHz standard as it's time base to measure the K3's TCXO and passes > an error value to the K3's MCU every few seconds. No TCXO frequency control takes place, > thus no increase in phase noise. Frequency compensation is done in software by > automatically updating the REF CAL function. A relatively simple mechanism but effective :) > > For my installation, I'm using a Thunderbolt, an $11 active antenna from Digi-Key, and a > 30' run of RG-6, which works nicely with the F connector on the Tbolt. > > 73, > Rich AC7MA > > On 4/5/2011 10:35 AM, Leigh L. Klotz Jr WA5ZNU wrote: >> ... >> The K3XREF product that Elecraft is developing is, to my understanding, an >> external disciplining interface for the TCXO in the K3. It's probably a >> frequency counter / microprocessor which reads the internal oscillator and >> the external 10 MHz reference, and when the internal oscillator doesn't >> produce the right number of cycles in 10 million of the external >> oscillator's cycles, it adjusts the voltage on the TCXO to bring it back >> into spec. But if you do this too often, you'll introduce phase noise into >> the K3 (think of it as FM-ing). Wayne N6KR has said it does this a few >> times a second an has achieved a trade off between accuracy and phase noise. >> (I presume he doesn't adjust during TX, for example.) >> >> I leave my K3 on most of the time, and I've found that it is seldom off more >> than +/- 3 Hz. But the K3XREF would let it off +/- 1Hz as soon as you turn >> it on, provided it's hooked up to your external reference. The actual >> received frequency is only valid for one mode and one filter, once you >> calibrate it, since when you shift modes or filters the offets of the >> various internal IF stages varies. (Keep that in mind if you use the K3 for >> the ARRL FMT.) >> >> Leigh/WA5ZNU Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
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Re: K3EXREF and Trimble Thunderbolts
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James,
For most HF operating, a calibrated K3 is about as "right on" as many commercial broadcast stations (even with the normal TCXO), so I don't think it is a great advantage (unless you are a real purist for frequency accuracy). That is for normal HF operating, but the picture changes when one considers a few of the newer digital modes which are quite demanding about frequency accuracy, and also for those who are VHF/UHF advocates and are doing stuff like moonbounce. So for many it is "nice to have", but there are a select few who actually need it. 73, Don W3FPR On 4/5/2011 3:11 PM, James Sarte (K2QI) wrote: > Hello group, > > It's been many months since I've posted here, much less actually done > something new with my K3. This topic has however piqued my interest. > Just so I understand fully, am I right in assuming then that the > following is correct: > > 1. Any reference oscillator operating at 10 MHz would work with the K3XREF? > 2. All that's needed for this to work is the K3XREF, updated > firmware, an accurate 10 MHz clock/oscillator, and a BNC cable? > 3. Trimble Thunderbolt seems to be a good, cheap product to try. Any > others that are> $100? > > What are the additional advantages of doing this other than knowing > you've pretty much eliminated any frequency drift? > > 73 de James K2QI > President UNARC/4U1UN > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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In reply to this post by K2QI
Hello James,
You are correct on #1 and #2, as long as the signal amplitude feeding the K3EXREF is in the range of +4 dBm to +16 dBm. The Thunderbolt 10 MHz output is typically +12dBm (about 2.5V p-p), for example. 73, Rich AC7MA On 4/5/2011 12:11 PM, James Sarte (K2QI) wrote: > Hello group, > > It's been many months since I've posted here, much less actually done > something new with my K3. This topic has however piqued my interest. > Just so I understand fully, am I right in assuming then that the > following is correct: > > 1. Any reference oscillator operating at 10 MHz would work with the K3XREF? > 2. All that's needed for this to work is the K3XREF, updated > firmware, an accurate 10 MHz clock/oscillator, and a BNC cable? > 3. Trimble Thunderbolt seems to be a good, cheap product to try. Any > others that are> $100? > > What are the additional advantages of doing this other than knowing > you've pretty much eliminated any frequency drift? > > 73 de James K2QI > President UNARC/4U1UN > > On Tue, Apr 5, 2011 at 2:32 PM, Rich Heineck<[hidden email]> wrote: >> The K3EXREF uses the 10 MHz standard as it's time base to measure the K3's TCXO and passes >> an error value to the K3's MCU every few seconds. No TCXO frequency control takes place, >> thus no increase in phase noise. Frequency compensation is done in software by >> automatically updating the REF CAL function. A relatively simple mechanism but effective :) >> >> For my installation, I'm using a Thunderbolt, an $11 active antenna from Digi-Key, and a >> 30' run of RG-6, which works nicely with the F connector on the Tbolt. >> >> 73, >> Rich AC7MA >> >> On 4/5/2011 10:35 AM, Leigh L. Klotz Jr WA5ZNU wrote: >>> ... >>> The K3XREF product that Elecraft is developing is, to my understanding, an >>> external disciplining interface for the TCXO in the K3. It's probably a >>> frequency counter / microprocessor which reads the internal oscillator and >>> the external 10 MHz reference, and when the internal oscillator doesn't >>> produce the right number of cycles in 10 million of the external >>> oscillator's cycles, it adjusts the voltage on the TCXO to bring it back >>> into spec. But if you do this too often, you'll introduce phase noise into >>> the K3 (think of it as FM-ing). Wayne N6KR has said it does this a few >>> times a second an has achieved a trade off between accuracy and phase noise. >>> (I presume he doesn't adjust during TX, for example.) >>> >>> I leave my K3 on most of the time, and I've found that it is seldom off more >>> than +/- 3 Hz. But the K3XREF would let it off +/- 1Hz as soon as you turn >>> it on, provided it's hooked up to your external reference. The actual >>> received frequency is only valid for one mode and one filter, once you >>> calibrate it, since when you shift modes or filters the offets of the >>> various internal IF stages varies. (Keep that in mind if you use the K3 for >>> the ARRL FMT.) >>> >>> Leigh/WA5ZNU > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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In reply to this post by K2QI
> 1. Any reference oscillator operating at 10 MHz would work with the
> K3XREF? The 10 MHz source should have a signal level between +4 dBm and +16 dBm. For square wave sources, 2VDC to 3.3VDC peak is optimum. If the source is a 5V logic level, use a 50-ohm resistor in series with the input. > 2. All that's needed for this to work is the K3XREF, updated firmware, an accurate 10 MHz clock/oscillator, and a BNC cable? Yes. > 3. Trimble Thunderbolt seems to be a good, cheap product to try. Any others that are > $100? Many. For those not affraid of getting a soldering iron hot, I think the Trimble units are pretty tough to beat. Requires making a power cable to a triple-output power supply of your choice. For a while, the HP Z3801A units were very popular. These use noisy DC-DC internal converters, are power hungry, but offer some of the best phase noise peformance of all the GPS-DO units. The Trimble units have been documented to pretty much meet the phase noise performance of the Z3801A. Rubidium is another choice in the USD $100 range but these too will require some creative power connections. > What are the additional advantages of doing this other than knowing you've pretty much eliminated any frequency drift? Really none I can think of, but as the weak-signal V/UHF ops have said, that's reason enough! Paul, W9AC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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Jim,
In case you missed earlier comments, don't worry about phase noise performance of the external reference if you'll only use it with the K3. But, in addition to the K3, a high performance, low phase noise external reference can be distributed around the shack or work bench for other purposes. I use a second output from the Trimble to phase-lock an ADAT transceiver. Paul, W9AC ----- Original Message ----- From: "Paul Christensen" <[hidden email]> To: <[hidden email]> Sent: Tuesday, April 05, 2011 3:36 PM Subject: Re: [Elecraft] K3EXREF and Trimble Thunderbolts >> 1. Any reference oscillator operating at 10 MHz would work with the >> K3XREF? > > The 10 MHz source should have a signal level between +4 dBm and +16 dBm. > For > square wave sources, 2VDC to 3.3VDC peak is optimum. If the source is a > 5V > logic level, use a 50-ohm resistor in series with the input. > >> 2. All that's needed for this to work is the K3XREF, updated > firmware, an accurate 10 MHz clock/oscillator, and a BNC cable? > > Yes. > >> 3. Trimble Thunderbolt seems to be a good, cheap product to try. Any > others that are > $100? > > Many. For those not affraid of getting a soldering iron hot, I think the > Trimble units are pretty tough to beat. Requires making a power cable to > a > triple-output power supply of your choice. For a while, the HP Z3801A > units > were very popular. These use noisy DC-DC internal converters, are power > hungry, but offer some of the best phase noise peformance of all the > GPS-DO > units. The Trimble units have been documented to pretty much meet the > phase > noise performance of the Z3801A. Rubidium is another choice in the USD > $100 range but these too will require some creative power connections. > >> What are the additional advantages of doing this other than knowing > you've pretty much eliminated any frequency drift? > > Really none I can think of, but as the weak-signal V/UHF ops have said, > that's reason enough! > > Paul, W9AC > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3EXREF and Trimble Thunderbolts
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In reply to this post by P.B. Christensen
Julian, and all:
As far as stability and accuracy, I believe the GPS are referenced to a better atomic standard than the Rb, but for ham needs probably not a significant difference (unless you do microwave, like >10-GHz). I have the LPRO Rubidium (5xE-11), an OCXO (5xE-12), a couple Jupiter GPS which I have yet to set up. I chose to run my OCXO 24/7 as my station frequency standard because its phase noise is best (-150 dB/Hz at 1-KHz). The Rubidium is much better for long-term accuracy (the OCXO drifts over months time by a Hz or two). But if you are needing a low phase reference the OCXO is considerably better than the Rb (-119 dB/Hz at 1-KHz). Phase noise is important for good receiver sensitivity. If the Rx uses a PLL phase-locked to an external reference, then that is linked to the phase-noise of the reference. My 1296/28 transverter has a PLL so it is locked to my OCXO with error < 1 Hz. The PLL is rated at -80 dBc/Hz of phase noise so the -150 dB/Hz phase noise rating of the OCXO is overkill. My mw counter has an ext. ref. so I can use the Rb when making critical frequency measurements (in practise, I cannot see a difference using the Rb vs. the internal TCXO in the counter at 1296-MHz). I found that my OCXO had drifted down about 1 Hz in three months since installing the OCXO (it runs continuously on a battery). It implies 2-3 Hz annual drift. If I ran the Rb there would be no drift beyond +/- 5xE-11. But the Rb has a finite life and the ones for sale are used so unknown how much life is left. The OCXO was $39.99 on e-bay. On the other hand the K3EXREF is not a PLL so the reference does not need to have super low phase noise. It does need to be stable and accurate. As Wayne explained it to me they chose not to PLL the TCXO as then the phase-noise spec of the K3 would be subject to whatever a ham used for a reference. By using a method of periodic Frequency correction, the phase noise is only affected during the frequency adjustment that occurs about every 4 seconds. The rest of the time the K3 enjoys the excellent phase noise performance of the TCXO which all the synthesizers in the K3 are locked to. So discussion of best phase-noise reference sources is not really germane to the K3EXREF (Wayne and others correct me if I am misunderstanding this). A OCXO, Rb, or GPS-DO will all work well as external ref. for the K3. You want short term stability and long-term accuracy in the reference. For the record my OCXO keeps the K3 within about 1.5 Hz at 28-MHz: http://www.kl7uw.com/K3EXREF.htm When you monitor the TCXO (CONFIG: REF CAL) you will see the frequency shift over time. That is the action of the K3EXREF shifting the TCXO to match the external reference. I found that my TCXO-3 after a year's use was 36-Hz high at 28-MHz when measured on my counter (with ext. ref off). The ext. ref moved the TCXO to 49.380.074 after about an hour. But with the ext. ref. the K3 was on frequency from the moment of power on. With just the TXCO there is a warm up period when the K3 will drift (about 30-minutes). This is the time that the K3 internal temperature comes up to working level. The amount of drift is much less using a TCXO. And almost non-existent if using a ext. ref. like a OCXO. (sorry, probably way more than you wished to know) 73, Ed - KL7UW ------------------------------ Message: 20 Date: Tue, 5 Apr 2011 08:09:26 -0700 (PDT) From: "Julian, G4ILO" <[hidden email]> Subject: Re: [Elecraft] K3EXREF and Trimble Thunderbolts To: [hidden email] Message-ID: <[hidden email]> Content-Type: text/plain; charset=us-ascii What are the advantages / disadvantages of this type of frequency standard over the Efratom LPRO-101 which is a rubidium standard? Julian, G4ILO 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-1.4kw, 432-100w, 1296-testing*, 3400-winter? DUBUS Magazine USA Rep [hidden email] ====================================== ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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