Support for other GNSSs and a rubidium clock for the GPSDO

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To improve reliability and continuity of operation of the GPSDO - add coverage of all known
GNSSs - and the capability to add others w/o major surgery, and add a rubidium clock as a bonus.  Very compact modules are currently available to do all of this.  GPS-only represents
a glaring single-point-of-failure in a world where geopolitical tensions suggest diversifying one's information sources.
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Alex - KM5YT

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Posted 4 years ago

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Jay / NO5J

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Might be why the GPSDO is a separate optional module, If we can get better coverage with Russian,Chinese, or the future Indian systems, I'm thinking they can offer alternate modules based on the current option.

The day the current GPS system totally fails will probably be a bad day, I'm probably going to be to busy ducking, and swerving to worry about the accuracy of the VFO's or about the nanosecond accuracy of a clock, for a few days when that happens.

Beyond a few days, lets hope I don't survive. DX is likely to be all thats available after that. Band noise might or might not be a factor.

I plan on installing alternate modules if/when they become available.

I can't depend on not surviving, to err is human.     

Jay - NO5J
(Edited)
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Alex - KM5YT

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From surveying gear I have seen, top-end stuff seems to handle the current ones: GPS, GLONASS,
BEIDOU, GALILEO ... (see: http://www.spectraprecision.com/products/gnss-surveying/sp80-43987.kjsp), and I suspect  a) either a common format exists or will evolve, and/or b) the modules will be field-loadable with new info.  So I'd like to see Flex offer that Flex-ibility! The rubidium clocks are wonderfully small modules now; I really don't see a problem here with board real estate. I have badgered Flex about vertical card cage architecture from day zero - which would make upgrades trivial - but have been assured by the clairvoyant multitudes (!) that that ain't likely going to happen.

I suspect Flex will come out with a GNSSDO for the 7000 series.

Yes ... let's hope it doesn't become a critical resource!
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Jay / NO5J

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Hard and expensive to re-engineer and retrofit existing design, thats why I like the fact that the GPSDO is an option and a module and not directly soldered to the circuit board. No one knows what the future will bring, in the future no one will know how to solder. They will just download an update, print it, then open the accessory cover in their foreheads and plug it in and then stick their fingers up their nose and press the reboot button. I think I saw this on Star Trek. Perhaps someone does know what the future will bring. ;0)
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Alex - DH2ID, Elmer

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I found this: http://www.ebay.com/itm/GPS-DISCiPLINED-CLOCK-GPSDO-10M-OUTPUT-SQUARE-WAVE-/111514491254
and I built a atomic clock controlled 10MHz source, but I use it only for measurements, as almost all my TRX are stable enough. Exception is the elecraft KX3, which runs a bit when getting hot.
(Edited)
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Alex - KM5YT

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I actually bought what looks like of those modules (the 'can' only - on the board) or something similar in shape and price on ebay; it's only the rubidium clock module, so I gather the rest of the PCB accepts a GPS signal and uses it to sync the rubidium oscillator?  Does the EBAY gadget include a GPS receiver? Decent price - but I haven't got around to playing with my toy.

Alex/KM5YT
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Alex - DH2ID, Elmer

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Hi Alex, as this eBay gadget has a GPS antenna SMA connector it seems to have a GPS receiver, but I'm not sure about that. As I said, we are lucky to have an atomic clock transmitter here in Germany, which has quite a strong signal on 77kHz, called DCF77. There is a kit at 
http://www.box73.de/product_info.php?products_id=1964
which I have built and which is working very well.
73, Alex DH2ID
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Alex - KM5YT

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Note: The Galileo GNSS constellation has now been (or is about to be) launched, so I have (again) poked flex support (directly) about incorporating all the (4!) GNSSs into a xxxxDO - and was/am directed back here. It's clear it won't be exciting for them unless GPS has more observable intermittencies (availability and/or coverage) - so we can hold for that and I will again suggest that a nice compact rubidium clock be added.  A card cage architecture would facilitate such an upgrade.

Alex/KM5YT 



  
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Alex - KM5YT

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Sergey, R5AU

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)))
Alex, what is dfifferent beetwen GPS and GNSS in this case? 1.1GHz-1.6GHz vs 66kHz-77kHz or other short waves transmitters  https://en.wikipedia.org/wiki/Radio_clock ,
looks like GNSS less secure due to ground wave and power limit as well

P.S.
GNSS this is only clock synchronization but not positioning 
a long time already  i use directional outdoor GPS antenna with my 6700 without any issues
https://www.ebay.com/itm/PCTEL-GPS-TMG-40N-40-dB-GPS-Timing-Antenna-with-Collar-Mount-L-Mount/272962...  with RG-316 cable 15 meters long

BTW this item - https://item.taobao.com/item.htm?spm=2013.1.20141003.6.259989c4aXNmwe&scm=1007.10011.70203.100200300000001&id=43019130458&pvid=bc17a35d-c9ad-4ff2-8544-8c019d4bc22c

wiil be good like add-on for 6700 with GPSDO or with https://item.taobao.com/item.htm?spm=a312a.7700824.w4004-11814489530.10.178c7deKFE79u&id=42336500072
(Edited)
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Alex - KM5YT

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GNSS - as I use it above - implies all global positioning satellites/systems.  So I am suggesting - that in view of assorted possible conflicts, one be able to have access to all operational and planned
systems (e.g. GLONASS, GALILEO, BEIDU (sp?), etc.) rather than just "GPS". One sees the beginnings of this in high-end surveying equipment.  The chipsets are out there. No other arcana intended - at this time.
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Sergey, R5AU

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Yeah, I got it Alex and with you, IGNSS like global services always more secure in compare just to unique.
I think with HAM radio one of the issue is ability to make QSO also in the field position that is far away from internet or other services were GPS is universal solution for the time being.
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Alex - KM5YT

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Greetings Sergey:

a funny note on why it's be good to have alternate coverage:

https://www.sott.net/article/373729-GPS-glitches-in-downtown-Moscow-near-Kremlin-are-teleporting-peo...

Ciao,

Alex
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Steve K9ZW, Elmer

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Really uncertain where a multi-system upgrade takes us?  

Usually when you have to "marry" multi-system inputs a device has to prioritize and internally "vote" on a relationship that it then uses as primary anyways. 

Given the present usage-limitations of much of what the present GPSDO could be providing for data time-stamping, and the dissipating/diminishing returns as other calculated limitations limit the achievable accuracy of the core equipment, would the expenditure to do multi-system be worthwhile?

Will an radio amateur be willing to invest many thousands of dollars to "be ready for a post-GPS multi-system possible potential need" rather than wait to swap out the optional GSPDO for some other GNSSDO module in the future?  Remember the Spectra Precision location receiver mentioned is on its own a $12,500 unit, and carries a $3,000 premium over the equivalent GPS-Only unit.

So would a $3,700-plus GNSSDO module be worth it to a ham over the present $700 module?

And that $3,000 increment is extrapolated, as it could well be two-three times more of an increase.

With the present usage, rather unlikely.

---

About 8 years ago I built a Rb-frequency reference for my Flex-5000A  https://k9zw.wordpress.com/2010/04/28/getting-exactly-in-step-adding-a-rubidium-frequency-reference/ and found it useful.  Surplus cell-tower unit interfaced to the transceiver.  Worked awesome after it was on & stabilized, but wasn't anything special for a few minutes when first turned on. 

When my Flex-6700 (#11 BTW) delivered I discovered the Flex-6700 with the GPS "Off" was on par with the externally reference Flex-5000A.  Lacking either the equipment or training to dig deeply into the ultimate performance I've soldiered on with the Flex-6700 with the GPS enabled and the Rb-Reference sits in a box as the Flex-5000A ended up in a cousin's ham shack.

I mention this as I did notice the Rb-Reference had a heat signature - which could be a difficultly putting "under the hood" in a radio not intended to have another heat source added to its cooling load.   I'd have to dig it out to investigate where and why the Rb-Reference gave off heat. 

---

What does one do with the frequency accuracy and the time-stamping the available GPSDO offers? 

Additional frequency accuracy is always a plus, but only to the limits of the resolution effectively used in amateur pursuits.   

The time-stamping is largely underused/unused but offers future upside potential for signal combining.  Five-six years ago I outlined my thoughts on what the timestamp might do: https://k9zw.wordpress.com/2012/09/05/flex-6700-fantasies-dreaming-what-might-be-series-diversity-re...

Now I doubt an radio manufacturer is going to install a used reference on their add-in module, so I doubt the $200-250 price point of my homebrew unit relates to an all new unit (I know the module I used was about $1500 or so new).

---

In summary, while technologically appealing the migration from GPSDO to GNSSDO has low Return-on-Investment, potentially at costs exceeding the host radio's base costs, and brings complexity to where a simple solution is more than adequate. 

(We also haven't even touched on the sensor antenna differences and other technological differences BTW).

The move to GNSSDO may be theoretically elegant but offers rather little as a practical benefit for the investment.

Internalizing a Reference Source has potential, but loses the commonality of a shared time reference for future SmartSDR signal combining or wide-space diversity with multiple antenna/transceiver set-ups. It also may have a heating issues to be engineered around as a side issue.

The Internal Rb-Reference offers only a subset what the present GSPDO has for capabilities, and has side issues to deal with, while only offering perhaps a cost savings - and maybe not even that.

YYMV of course and a very interesting discussion!

73

Steve K9ZW

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Alex - KM5YT

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A GNSSDO takes us to a place Nassim Taleb called anti-fragility; software people call robustness; I refer to as simply avoidance of single-points-of-failure.  As I noted, the new chipsets are out there - and coming - that will accommodate multiple GNSSs; inexpensive portable "GPSs" already GPS+GLONASS-ready. The internal (rubidium) reference source modules are small and getting smaller (and cheaper) because every cell site has them.  I think your cost estimates and technical obstacles cited are unrealistic - and will be content to wait and see what is offered on the F7000 or other SDRs.

Ciao,

Alex KM5YT
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Alex - KM5YT

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Here's a nice example that will impact the USA:
https://www.zerohedge.com/news/2018-01-26/usaf-begins-massive-gps-blackouts-western-us-during-larges...
... so we'll get a ~realistic test.
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Steve K9ZW, Elmer

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Isn’t the degradation a reversion to civilian accuracy, rather that the privileged (encoded) enhanced or something like that?

The process is supposed to be localized and much less severe than what the recent Russian exercises used. Whether that effect on other countries was spill over or a demonstration is open to debate. And that was both their own system and spoofing of others (like GPS).

Be very certain though dependency on any external timing services has limitations and denial of service risks.

For our hobby’s use as primarily timing regulation one wonders if a combined reference with voting might be useful?

Now of course how do you precisely coordinate three transceivers if one was air mobile, one on top of Mount Lemmon on one at sea level? Or is close enough good enough? And how about that unit on the ISS?

Interesting world!

73

Steve
K9ZW
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Alex - KM5YT

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Further to the issue of wider GNSS coverage in a future GNSSDO (in the Flex ~7000 series):
https://www.sott.net/article/381638-Russia-China-will-merge-satellite-tracking-systems-into-one-glob...

Probably will not be able to get chipsets that   w o n ' t   offer multi-GNSS systems in
the (near) future.  Getting to seem a tad provincial to offer only GPS - esp. for non-US hams.
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Dave Gipson

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This is what I am putting together for another project. I thought I "might" need to tap into it for a "few" other uses hence the distribution amplifier. It worked great spread across the workbench. Now it is almost packaged and ready to go into the rack..... awaiting my 6600M.... which is coming.... sometime.... :)





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Sergey, R5AU

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That i did in the same manner to use with transverters  - transverters/AMP/TRX/LNb everything nearly ANT setup  and LWL  to the shack only )
(Edited)
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Dave Gipson

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I'm up and running with zero issues. It's a beautiful thing :)