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Trimble thunderbolt or HP Z3805A
AlfBaz:
Let me start by saying that I am a complete noob at this time nuttery stuff, so be patient with me
I 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 a Trimble thunderbolt or Z3805A
So 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 Z3805A looks to 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 performance :-//
Whilst 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 track
If given a choice between the two units what would some of the more time nutty members here choose?
Deathwish:
Im not a time nut, but I think you answered it for yourself, thunderbolt.
TSL:
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
TSL:
--- Quote from: AlfBaz on September 17, 2015, 01:49:33 am ---
Whilst 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 track
--- End quote ---
I 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 !
AlfBaz:
--- Quote from: TSL on September 17, 2015, 05:37:46 am ---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
--- End quote ---
I 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 front
http://comments.gmane.org/gmane.comp.time.nuts/4403
--- Quote ---I 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.
--- End quote ---
Sorry, 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 noise
--- Quote ---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.
--- End quote ---
Yes, I still need to read up on phase noise specs, at a glance they don't seem intuitive, to me at least
--- Quote ---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 !
--- End quote ---
The "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
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