Is there an advantage to installing the Flex GPSDO option, or is picking up an unit on eBay sufficient?

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  • Updated 5 months ago
Post-purchase GPSDO acquisition options?
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Mike - K6QY

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Posted 5 months ago

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Mark Erbaugh

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At one point several years ago, Flex mentioned the possibility of using the time from the internal GPS to time stamp the data (VITA) packets allowing diversity reception with remote flexes, but to my knowledge this has not been implemented, the GPS is used only as a frequency standard. There been requests to implement a NTP server in the flex, but I don’t think that has been done either. So other than having one less box on the shelf there is no advantage to the internal GPS.
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Ted VE3TRQ

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As I see it, other than cost (an eBay item would be cheaper), there is one other advantage to the eBay GPSDO - they (almost) all have a PPS and RS232 output, allowing you to either keep a PC updated with ntp or NMEATime, or actually create an ntp server (on one of your PCs) disciplined by that GPSDO. You then have the advantage of providing accurate time to all your other PCs on the network (including those at a Field Day or other sites with no Internet).
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Bill W2PKY

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I just picked up this one, antenna works fine in the attic;

https://www.ebay.com/itm/10MHZ-Output-Sine-Wave-GPS-Displined-Clock-GPSDO-GPS-Antenna-Power-Supply-US/123049880474?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

My neighbor has the Flex internal GPSDO unit, we have compared results using WSJT-X FreqCal mode [on WWV & close in AM stations] and both come up with essentially the same data points. This seller in the US so shipping is a few days instead of a month or more from China.

While the Flex radios are more than stable enough for general HF operation, It's amazing how tight the jitter is with a disciplined LO. Can not see how you will be disappointed. 

Bill
W2PKY
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KF4HR

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I bought the same GPSDO that Bill is using (eBay purchase).  It made a major difference in the Frequency Offset Number (under Radio Setup -> RX -> Offset (in ppb).  Without the GPSDO I was seeing numbers in the 900 to 1100 range.  With the GPSDO my Frequency Offset Number typically reads 6.  I seem to remember being told this parameter does not relate to either the transmit or receive frequency stability, but rather the stability of some internal clock function.  In any case, I noticed no difference in operation with or without the GPSDO, even on the digital modes.
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Thomas NE7X

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I purchased a BG7TBL GPS Disciplined Oscillator off eBAY and have it connected to my 6400M, works GREAT !!! Also have it connected to my ICOM IC-7700.
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Steve K9ZW, Elmer

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My take is the VITA-49 packets use the radio-server’s (aka Flex-6x00) timestamp.

The extra accuracy across several Flex-6000s to (hopefully) combine signals will depend on each 6000 being synced to a common time reference.

This clock side of the GPSDO may be what sets it apart from an external frequency reference.

Currently as of April 2019 I’m thinking there is no difference but down the road the timing would look to gain importance.

73

Steve
K9ZW
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Ted VE3TRQ

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If the radio has an ntp client in it (any self-respecting Linux computer should), it won’t make any difference if you have an internet connection or a local ntp server :-) At least if the radio has some way of discovering the ntp server :-(
(Edited)
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John - AI4FR

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Excellent question and lots of good comments in this post. I specifically looked for a 6700 with a GPSDO when I was in the market for one. Bill, W2PKY and I have done numerous tests over the past several months. As he stated, the 6700 is nearly spot on but every once in a while he would spot me a Hertz off which is nothing. Since he built his GPSDO I can not hide from him. Every spot has been perfect on every band. We took this deeper and our radios are the same down to a thousandths of a Hz(0.00X). Now our limiting factor is the software loaded on our PC's. I have nothing that can test a signal more accurate than a 0.000 of a Hz.

If you don't mind the extra features and a tiny box near the radio, what Bill, W2PKY posted about is the way to go. The Flex GPSDO fits inside the case with no extra wires. From what I know now and from what I have seen that Bill has done, I would not hesitate to go with his external unit at a tiny fraction of the cost of a Flex gpsdo.

Good Luck with it.
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Steve K9ZW, Elmer

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Should clarify my take - the precision VITA-49 timestamping would become important when more than one digital data stream is merged. This is when I’m thinking the internal GPSDO would come into play by providing a GPS time reference.

Not certain if the usual net based time servers could provide enough resolution to allow several distinctly recorded digital data streams to be manipulated in the same way.

For the proposes of a frequency reference internal vs external should be insignificant.

For the purposes of running digital mode the usual net based time syncing works.

But if you want to combine and analyze say four streams each recorded at a different antenna site and process them a fifth site, things looks to require better time-stamping carefully synced.

73

Steve
K9ZW
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John - WA7UAR

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Since the topic of VITA-49 has come up here I wanted to share a recent thread with a video and pdf that discusses a (coming?) version 2 of the VRT protocols:

https://community.flexradio.com/flexr...
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Kevin

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I have the 6700 with internal GPSDO. Not really sure why I got it other than I have a terrible time not getting all the options. Thank goodness they didn't offer a racing stripe. And yes, I bought the cover though I never use it.

I can't say it's made any positive observable difference compared with my 6500. On the negative side, it sometimes is not recognized on start-up and I have to go through a ritual to get it running again. That's just me though.

Would be nice if it could be used to set station time but still doesn't really justify the cost. Geeking can get darn expensive.

73,
Kev K4VD
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KY6LA - Howard, Elmer

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I agree with Kevin.. Bought the GPSDO because I always buy everything fully loaded so I do not have buyer's envy that I did not get everything.

Plus there was an allegation from Matt who talked me into it, that it would be used in the future to time stamp packets for true geographic diversity.  5 years later, and no real geographic diversity...

Since I do not do the Frequency Measuring Tests, its sort of been a waste of money.
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Steve K9ZW, Elmer

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Ah, if everything marketing guys came true in the timeframe they imply we’d have wide area diversity and 500 mile battery packs for our cars that charge in 45 minutes.....

Or maybe both are just around the corner?

Imagination!

73

Steve
K9ZW
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Zack Schindler - N8FNR

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Kevin if you need a racing stripe for your radio I can sell you one. And yes it is V3 compatible.
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Mike - K6QY

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I’m new to the community, a returning ham after 50y! And a new Flex owner. I am simply bowled over by the warmth, openness, and generosity of this community. Thank you all for your detailed responses!
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EA4GLI - 8P9EH - Salvador

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Enjoy the feeling while it lasts. :)
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John - AF3K

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I like the fact that that it's inside the radio and integrated with SmartSDR.  I already have too many "little boxes" that do this and that - each requiring a cable, power, etc. Perhaps not a great value for the $ but didn't want to retrofit if/when more utility is added by Flex, or if I want to get set up to work satellites.







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EA4GLI - 8P9EH - Salvador

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I bought my 6700 with the GPSDO. If I could go back in time I would not do it. Adds no value to my station beside "bragging rights" at a very large price tag. I use it to discipline 440mhz and 1.2ghz transverters, but I could have easily done that with the ebay one and keep accurate time across my PCs to boot. GPSDO, usb dongle, ver 1 maestro,... I have had a lot of disappointments with Flex gear. But that is just me. YMMV.
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Clay N9IO

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Mike,

I ordered a n eBay gpsdo this past weekend From an american vendor. A bunch if the guys in our local club are planning to do the FMT next week, thought I would get in on the fun and compare notes.

I am curious from a comment in this thread if a connected Windows computer can pick up the time from the Flex. I'd appreciate it if someone would answer that for me.
(Edited)
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KY6LA - Howard, Elmer

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No... GPSDO in the Flex definitely cannot send time stamps to a PC
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Clay N9IO

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Thanks Howard.
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John - AI4FR

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Plus it is slightly less than a half a second off from the actual time. In other words you can watch the PC or listen to a legacy receiver tick off the seconds from WWV and the Flex with or without a GPSDO will be about a half a second late.
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Scott Russell - N1SER

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Clay, a club member did FMT and was one of the 5 at the top. His was from the SunSDR2 Pro and an Ebay GPSDO. How did you guys do? I have an Ebay unit as well but missed the event. I was looking forward to it so maybe in the Fall.

Scott N1SER
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Clay N9IO

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Scott,
Was going to start the install the day I received the gpsdo in the mail.
Had good intentions but since I hadn't considered wanting to install the gpsdo at all when I first purchased the radio I didn't realize the SMA connectors did not come installed only if you ordered the factory gpsdo. Hadn't given it a thought.
I get it now and will start the process once I have a better plan and parts required to do a clean installation. I need to know a little more about the 6600's internal connections as I noted below.
Don't know how the guys in my group did but I guess I I'll give the FMT a go next time around. November I think it is.
Bummer...
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Mark WS7M

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I use one of the eBay models.  I just put it into the 10 Mhz input port and I get a perfect lock.

I don't have the lat/long displayed in the radio but I think I know where I am.

I do know the GPSDO is somewhat accessible via the API but not having one I have not done anything with that data.

For me it was a cost issue.
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Clay N9IO

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This is the unit I purchased below on ebay.  It's small around the size of a cigarette pack.

Have never cracked the cover on my 6600 surprisingly so would like a little info before I start.
1) Is the 10mhz input on the 6600 board SMA female?

2) Also asking the group what your take would be to mount this unit inside the 6600 and feed it 12vdc from an external 12vdc source rather than risk sampling from within the radio OR just keep the GPSDO external with a short SMA lead at 10mhz?  Is there a risk of RF interfering with the clock output if it were external.  I run an amplifier so thought I would ask that as well.

Clay N9IO
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Clay N9IO

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Scott you had a post about 4 months back I wish I had seen before the fact would have saved myself a bunch of time.
Anyway figured it out all is good from the 10Mhz RCA Jack in the back of the 6600.
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Clay N9IO

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