Trimble thunderbolt or HP Z3805A - Page 1
Forum section: electronics / testgear

author: AlfBaz
author_rank: Super Contributor
timestamp: September 17, 2015, 01:49:33 am
content: Let me start by saying that I am a complete noob at this time nuttery stuff, so be patient with meI have the opportunity to purchase a GPSDO. Unfortunately there are quite a number of options.I have considered some of the BG7TBL units but SHMBO has given me permission to splurge, so now I'm looking at either aTrimble thunderboltorZ3805ASo far, from what I've been able to find, the major difference between the two is configurability. Lady heather and the thunderbolt provide oodles of adjustable paramaters where as the Z3805A is more a set and forget unit.Also the Thunderbolt seems to have a better GPS front end so it may be able to find and track more satellites. Is this a factor worth considering?The OCXO in the Z3805Alooksto be the better of the two but I am not certain what, if any, are the overall effects on the final reference output. I've also read that disciplining good OCXO's can actually degrade their performanceWhilst long term stability is important to me, phase noise and jitter are equally important to me and to that end I'll end up using the GPSDO to cal a decent OCXO somewhere down the trackIf given a choice between the two units what would some of the more time nutty members here choose?

author: Deathwish
author_rank: Unknown
timestamp: September 17, 2015, 01:51:38 am
content: Im not a time nut, but I think you answered it for yourself, thunderbolt.

author: TSL
author_rank: Regular Contributor
timestamp: September 17, 2015, 05:37:46 am
content: This is a question that has been asked many times before on various forums and often on the TimeNuts list.The common answer is archived here...http://ko4bb.com/dokuwiki/doku.php?id=precision_timing:comparing_thunderbolt_and_z3805a_gps_stabilized_crystal_oscillators

author: TSL
author_rank: Regular Contributor
timestamp: September 17, 2015, 05:52:39 am
content: Quote from: AlfBaz on September 17, 2015, 01:49:33 amI should ask - If you're only going to cal an OCXO why is phase noise and jitter important to you ? neither will really affect the ability to cal an OCXO.FYI... jitter is the integral of phase noise and there's plenty of calcs on the net for you to covert between the two. Both are short term quantities, one in the time domain the other in the frequency domain.Phase noise becomes important for local oscillators used in microwave radios since it affects the MDS. Stability at those frequencies becomes the other important quantity.Knowing what you want to do beyond cal of an OCXO will help to point you in the right direction.All this being said, both the Z and the Tbolt are exceptional units with exceptional specification and it would be hard for most people to get themselves into a situation where neither was adequate !

author: AlfBaz
author_rank: Super Contributor
timestamp: September 17, 2015, 09:34:38 am
content: Quote from: TSL on September 17, 2015, 05:37:46 amI have read that one. Assuming it's the same Bob, he goes a littler further the 3rd post I found here, putting the thunderbolt slightly in fronthttp://comments.gmane.org/gmane.comp.time.nuts/4403QuoteSorry, I didn't make myself clear. I am lead believe that a good OCXO has less phase noise and jitter than a GPSDO. If this is true then I can use the GPSDO as an accurate time base and the OCXO if I need low jitter and phase noiseQuoteYes, I still need to read up on phase noise specs, at a glance they don't seem intuitive, to me at leastQuoteThe "what do I want to do with it" question is inevitable however it is difficult to tell at this point as I dabble more in the high speed digital and RF world. It would be nice if a few months down the track I don't say "damn I should of gotten the other one". This is why I ask what would you get if you had the choice

author: DimitriP
author_rank: Super Contributor
timestamp: September 17, 2015, 11:27:04 am
content: The TB will be more fun to play with.Granted you can only change the antenna, software parameters and the OCXO but that should provide many days (weeks/months/years) of fun .Chances are if you buy or build one GPSDO, you'll probably end up buying /building one more.http://www.ke5fx.com/gpscomp.htmhttp://www.ke5fx.com/tbolt.htm

author: TSL
author_rank: Regular Contributor
timestamp: September 17, 2015, 11:58:48 am
content: Quote from: AlfBaz on September 17, 2015, 09:34:38 amYes - same Bob - the Thunderbolt is slightly in front because it has many settings that can be tuned to provide truly exceptional performance.QuoteA GPS driving an OCXO maks it an GPSDO - the phase noise is then directly related to the quality of the OCXO being driven. This only relates to the 10Mhz output. The PPS out is often a direct function of the GPS engine although some GPSDO divide the 10MHz down to provide the PPS in an effort to minimize the inherent 20ns jitter in any GPS system.QuoteFair enoughGiven digital, you might want low jitter PPS to form the basis of digital clocking, alternatively you might divide or multiply a low phase noise 10MHz output into the frequency you want.Given RF, you most certainly want low phase noise especially if you are going to use the 10MHz signal to lock a Spectrum Analyzer since that will probably affect the performance of the SA. This depends on the specs of the analyzer though.Likewise if your dabbling in RF into the microwave spectrum both phase noise and stability become the issue.The OCXO in the Z you've pointed at is the venerable HP 10811. This is an exceptional low phase noise oscillator and the HP 10811 can be retrofitted to a thunderbolt.More info and test results here...http://www.ke5fx.com/tbolt.htmFor exceptionally low phase noise and jitter its hard to go past the venerable Rubidium Oscillator PRS-10. This Rb has the ability to be guided by a PPS output of a timing GPSDO. This gives you the best possible outcome for all three quantities of accuracy, stability, and phase noise.The PRS-10's come out of Symetricomm primary standards which couple GPS's with RB. The only thing better than these are Cesium or Hydrogen Maser standards.Time Nuttery is a dangerous path to walk down as you start to become obsessed about pico seconds of difference or phase noise above -100dBcAll in all its a fun thing to play with

author: AlfBaz
author_rank: Super Contributor
timestamp: September 17, 2015, 06:33:19 pm
content: Thanks very much for that post TSLLots of new info in there for me to digest

author: bingo600
author_rank: Super Contributor
timestamp: September 17, 2015, 08:29:45 pm
content: Hi ABI'd go for the Tbolt.Tbolt:http://www.prc68.com/I/ThunderBolt.shtmlSmaller , emits less heat , super tweakable w. Heather , No hanging bridges (by design)PRS10: (But they wear out) , i have onehttp://www.ke5fx.com/rb.htmhttp://www.ebay.com/itm/321861322781Z3805:I don't have a Z3805 , but a Z3801 , and it's quite ok.But it uses 48v and emits a lot of heat.Note that "some" says that the Z3805's sold by "yixunhk" , have "unoriginal" HP enclosures.Indicating that the inside might NOT be corresponding to the "Newer enclosure".Watch out for timenutting, the next you want is a HP-5370B or a SR620.And then a PRS10 to verify your tbolt , and ........./Bingo

author: bingo600
author_rank: Super Contributor
timestamp: September 17, 2015, 08:30:33 pm
content: Re: TboltsIf you get a late Rev E model (Not to be confused with the RED Tbolt E) , you might want to change the temperature sensor chip.I did replace it on my latest two, ith a couple of Rev C chips.Some time-nuts says the new "E" chip doesn't have much influence on the stability though.QuoteThis one i saw a few years back , he might still have Rev C's.QuoteIt's en easy mod/Bingo

author: DimitriP
author_rank: Super Contributor
timestamp: September 17, 2015, 11:43:55 pm
content: QuoteMmmmmm..........

author: AlfBaz
author_rank: Super Contributor
timestamp: September 18, 2015, 06:33:32 pm
content: Hey Bingo, thanks for the tips regarding the tbolt. I never knew about the temperature sensor issue. I think I'll go ahead and order the thunderbolt

author: Xtremexp
author_rank: Regular Contributor
timestamp: January 09, 2024, 06:27:25 am
content: Hi,I am debating myself which tbolt I should buy, blue tbolt E, red tbolt E or the tbolt without labels. by looking date code blue tbolt E is manufactured on 2014, is this good enough for experimenting with GPSDO?Thanks!!