GPSDO  with big LCD related question - Page 1
Forum section: electronics / testgear

author: Commander_Spock
author_rank: Contributor
timestamp: July 03, 2019, 09:22:21 pm
content: Yes it is looking like a newbie question but this is my first try at gpsdo techno... and want to avoid to make a mistakeI found on ebay this gpsdohttps://www.ebay.com/itm/Trimble-LCD-GPSDO-10MHz-1PPS-OCXO-GPS-Disciplined-Oscillator-2019-5-8/312599997545and i plan to buy one of them as a 10Mhz time ref for my oscilloscope, frequencemeter and signal generators... yes that mean i will have to also buy from ebay one of these boxeshttps://www.ebay.com/itm/OCXO-benchmark-frequency-standard-8-port-output-10MHz-Distribution-amplifier/172311880978i particularly like the big screen giving me all info i need and allowing me to avoid to use probably lady heather program ...i can see on this gpsdo it offer one 10mhz sine sma connector and two 10mhz hcmos ...1/ what are the diff between these two kind of signal ?2/ which one is the best to use for me ?3/ anybody tried this gpsdo ?4/ as the same gpsdo design propose various components, what is best between trimble ? Symmetricom ? SAMSUNG (STP2878LF) ?Thanks in advance for your help

author: Electro Fan
author_rank: Super Contributor
timestamp: July 03, 2019, 10:18:18 pm
content: I can't answer your specific questions but I think you are headed in a good direction.I purchased the same model distribution amp (from a different eBay seller) and I'm very happy with it.I also purchased a different (BG7TBL 2018-06-05) LCD GPSDO that doesn't display as much info on the LCD as the model you are considering. In general I think it's advantageous to be able to see some info at a glance without depending on the Lady Heather/a computer. Most people here will likely tell you that LH is more useful than any info you can see on built-in display. I think it's desirable to be able to use both when/as needed. My main interest in using a GPSDO (in addition to learning about GPS) was in getting the 10 MHz Ref output from the GPSDO as an input to various pieces of test equipment, and the status of the 10 MHz signal is primarily what I observe on the GPSDO LCD. I have another GPSDO (a Star 4+) without an LCD and it shows more/different info in LH, but I haven't been able to get either GPSDO to display anything regarding the 10 MHz Ref signal in Lady Heather, so I like having the Ref signal display in the LCD.I think you will find if you use a GPSDO with LH that different models support/expose different levels of functionality with LH. I don't have a Trimble-based GPSDO but it's my impression that a Trimble-based model is likely to support a relatively high amount of features and functions in LH, so that's a good thing.As for the components you will get lots of suggestions but I think you should break it down in terms of the receiver, the oscillator, and the overall integrated package. The oscillator gets a lot of attention (and very rightfully so) but I think the receiver and the integration will also help determine the features and functions as well as the performance you ultimately get. Depending on far you want to take it you might also want to look at the power supply (switched vs. linear). I think with LH you can see some differences with a linear supply but I haven't been able to detect the impact of the power supplies on the 10 MHz Ref signal - but that might be because I can't really see/determine how my equipment performs beyond about 1 Hz or maybe .1 Hz on 10 MHz.I'm sure others here will have more info regarding your specific questions.One thing I'm sure of is that with a good GPSDO and that distribution amp you will like seeing how your various pieces of test equipment snap into good timing and good alignment. When you see a collection of test equipment that could in some cases previously be 10 Hz or more out on 10 MHz all start displaying the same 10,000,000.0 or close to it (plus or minus a few tenths) it's kind of neat. And when the entire system (antenna, GPSDO, and dist amp) all run continuously even if your computer reboots, you start to look at LH as very interesting but maybe but not essential to the timing and synchronization of your test equipment. LH is averycool program and you should definitely try it but you can keep your gear well timed and synchronized without relying totally on it.

author: tkamiya
author_rank: Super Contributor
timestamp: July 04, 2019, 03:31:14 pm
content: I am interested in that one as well. My problem is, which color? (ha) Actually, I already have a few of other GPSDO so I will probably not spend more money on it.I don't know about this particular unit but IN GENERAL:10MHz sine is a sine wave output and typically 7 dbm or so.HCMOS output is a square wave output and typically swings 0 to 5 volt.Both has its uses. Currently, my lab standard is sine wave 10MHz.

author: Commander_Spock
author_rank: Contributor
timestamp: July 04, 2019, 07:57:58 pm
content: if i understand you well that mean i should attach a cable to the 10mhz sma connector to get this 10mhz sine signal and then plug the other end of this cable into the oxco amplifier input ?

author: kj7e
author_rank: Frequent Contributor
timestamp: July 04, 2019, 11:44:31 pm
content: Quote from: Commander_Spock on July 04, 2019, 07:57:58 pmYes.

author: Commander_Spock
author_rank: Contributor
timestamp: July 05, 2019, 01:04:58 pm
content: i started looking at my equipment and found that only few of them have connectors for 10mhz external sync signal... My feeltech 6600 has one but nothing on the back of my vc3165 frequence counter.so i try desperately to find good reason to buy now a gpsdo now or alternatively spend this money in better equipment like the SDG1032x (to complement/replace my unmodified feeltech 6600)I looked at the back of my rigol ds1054z and found only a trigger connector...looking around i found very little info but i understood that it is NOT possible to connect the gpsdo 10Mhz sine signal to this connector in order to get a better time ref for my oscilloscope ?anybody is willing to comment ?

author: Electro Fan
author_rank: Super Contributor
timestamp: July 05, 2019, 02:05:09 pm
content: Quote from: Commander_Spock on July 05, 2019, 01:04:58 pmYou are correct. Many entry level pieces of test equipment do not have 10 MHz reference signal inputs. I think the Siglent SDG1032X is the entry point among Siglent counters. 10 MHz Ref inputs have not been included in Rigol 1000 and 2000 series scopes as best I can tell (maybe same for equivalent Siglent scopes?). Even a Tektronix 2467B does not have a 10 MHz Ref input (but a 2247A does).I think only relatively recently has the market been offering relatively low priced GPSDOs with easy to access 10 MHz Ref outputs so there was not much incentive for TE manufacturers to burden TE with the extra cost of a ref input - but maybe now that will start to change. In the meantime this might start to influence some home lab buying decisions for new and used TE. It’s very possible that the improved timing performance is not “needed” but is “wanted” enough that it will start to influence equipment designs.

author: Electro Fan
author_rank: Super Contributor
timestamp: July 05, 2019, 02:36:36 pm
content: It seems like the first place 10 MHz Ref inputs should show up is in entry standalone counters. Anyone who buys a standalone counter would seem to be into countingNext would be equipment that includes internal counters such as scopes and generators. If it’s possible to do this at relatively low incremental cost it will put further pressure on standalone counters.If this were to become an architecture design trend the next step might be to see Siglent or Rigol or GWI etc add a GPSDO to their product family. I’m not sure if the market is big enough or if they can compete with the semi-home brew integration of repackaged oscillators and receivers - but if there is a big enough demand (kind of hard to believe) why work so hard to sell $350 scopes when you could also be selling $100-$150 GPSDO add-ons?It reminds me of the discussions 5-6 years ago about whether it made sense for entry scope makers to include logic analyzer functionality. It took a while but now most scopes makers offer at least basic serial decoding - so I think it’s inevitable that as digital technology expands that improved timing functionality will be a natural extension. Might or might not come via GPSDOs and distribution amplifiers - might be some competing architectures - but for manufacturers addressing the EEVblog market segment a 10 MHz Ref input might be worth putting on the candidate feature list within the overall product roadmap.

author: Commander_Spock
author_rank: Contributor
timestamp: July 05, 2019, 04:30:31 pm
content: QuoteGuess we will all agreeAs a temp conclusion for this post i created, i think now it is for me not a good idea to buy today a gpsdo.will spend this budget on a new SDG1032x signal generator and later when i will have few more equipment with a 10mhz sync connector will look again at buying a gpsdo