bg7tbl gpsdo master reference

[hax129]

My BG7TBL 2015-09-17 seems to be a bit different...

- The OCXO is a Morion MV89A
- The PCB date code is older (2015-06-25)

My battery measures 2.48V

Does anyone know if this version has the same "frequency offset" as some of the earlier versions?

[catnip]

I need to replace diode D11 on a Trimble 57963-C board and am not able to determine the specs.  The markings don't lead to any relevant part on Google.  Does anyone have any info on this diode?

[FlyingHacker]

Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.

Thanks.

[motocoder]

I am trying to change the baud rate and sentence types sent by the receiver, but nothing changes or sticks.

Probably because the CPU driving the GPSDO is configuring the u-blox on start-up.

[Vgkid]

Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.

Thanks.

only about 10-15 of the star4 models were on the 'bay'. I saw them when they came out, but missed out. Even tried to buy a bare board from the 168 electronics guy, and was turned down. Didn't even appear on taobao.

[tcomm9]

I can't seem to find the command to set the Trimble 57964-80 in the BG7TBL GPSDO to use UTC Time as its output instead of GPS Time.  Does anyone have that handy?  Any help would be most appreciated!

[usagi]

Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.

Thanks.

none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.

bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.

[motocoder]

Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.

Thanks.

none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.

bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.

Agree with this. I would also get the unit with the u-blox gps chip.

[FlyingHacker]

Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.

Thanks.

none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.

bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.

Agree with this. I would also get the unit with the u-blox gps chip.

Which one is the one with the ublox gps chip? (What markings on the unit?) Sorry, I am having trouble locating it.

Thanks.

[FlyingHacker]

I assume you mean the BG7TBL 2015-09-17 .

Anyone have a line on one of those? I do not see any on ePay.

[usagi]

Wow. Lots of info! Anyone know what the best model to get for use in a basement? It sounds like the Oscilloquarz would have been the way to go, but these do not seem to be available anymore.

Thanks.

none of them are likely to run from the basement. you'll need to run an antenna outside. so it won't really matter which one you get.

bg7tbl has a newer revision of the morion/ublox, which may fix the counter bug. but realistlcally speaking even with the "buggy" one the error is so small as to be largely irrelevant for hobbyist needs.

Agree with this. I would also get the unit with the u-blox gps chip.

Which one is the one with the ublox gps chip? (What markings on the unit?) Sorry, I am having trouble locating it.

Thanks.

all bg7tbl models except the "2015-07-17" version have the ublox gps in them.

[FlyingHacker]

I see. So you mean the common 2014-12-09 too, right?

What about this guy:

http://www.ebay.com/itm/Symmetricom-Inside-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-GPS-Ant-/181948031179?hash=item2a5cf2a0cb:g:rlcAAOSwyQtVkpxI

Anyone know anything about that one?

[motocoder]

Also, make sure you get one with the type if output you want - square or sine

[TheSteve]

This should be the same board they are using inside the box:
https://www.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-%28ocxo-furuno-receiver%29/

Seems to work fine, uses a boost converter for the OCXO which doesn't seem overly reliable.

If don't mind a larger box and a potentially less sensitive GPS receiver also check out the surplus Nortel NTBW50AA offerings on ebay. They don't give 1 PPS without a mod but they are a very nice unit and they work with LadyHeather.

[jeffsf]

Also, make sure you get one with the type if output you want - square or sine

Not that these are terribly expensive if I get the "wrong" output type, but what would drive one to pick sine- or square-wave output?

I can imagine that phase locking an analog oscillator to the sine-wave output might be more robust. Similarly, generating an integer-ratio digital clock from the square-wave output seems like it might be more accurate as there would not be a need for a comparator to trigger the logic.

There's also the harmonic content of the square-wave output that could either be considered as either an advantage (markers up in frequency, for example) or a disadvantage.

I don't know what test equipment generally requires/desires, such as RF signal generators. I checked what I could find on a Marconi 2022x (for example) and only found that it "accepts a 10 MHz signal of at least 1 V (max. 2 V) into a 100 Ohm nominal impedance. A 5 MHz or 1 MHz signal can be accepted by changing an internal link." Is there any common preference for waveform shape among generators and the like that are newer than the analog boat-anchors?

Is there something that I'm missing about output waveform that I should consider before I commit to one of these?

Edit: Is the "square-wave" unit simply a sine-wave oscillator with a comparator internal to the GPSDO box?
At least looking at http://www.morion-us.com/catalog_pdf/MV89.pdf it looks like the OCXO is sine-wave output.

[bitseeker]

That's a very good question, Jeff. I've wondered the same thing as the external clock inputs on counters that I've seen also specify amplitude and frequency, but not waveform type.

[Vgkid]

Couldn't you run the 10mhz square through a 10mhz filter yo get the sine wave.

[bitseeker]

Yep. Trim off the harmonics.

[motocoder]

Couldn't you run the 10mhz square through a 10mhz filter yo get the sine wave.

Yes, but you will introduce phase noise when you do this. Personally I prefer the sine output, and if I really need to square it up, I can run it through a schmidtt trigger. The two pieces of test equipment I'm using this with don't seem to have an issue accepting a sine input, so I haven't had to do this.

[Vgkid]

I figured that since in the lucent boxes they would run the oscillator through a filter to get the 15mhz. That it should work. Other than that i have seen it used in digibridges to turn the sine approximation into a sine wave.

[motocoder]

I figured that since in the lucent boxes they would run the oscillator through a filter to get the 15mhz. That it should work. Other than that i have seen it used in digibridges to turn the sine approximation into a sine wave.

It does work. What I have read is that the higher the "Q" of the circuit, the worse the problem. So I guess in theory a LPF would be better than a bandpass filter.

[KA1J]

Hi,

My first post to the group. I've been looking to find a reasonably priced GPSDO and I ended up finding this discussion on the BG7TBL and decided to order one. According to some opinions the 2015-07-08 version with the Oscilloquartz "Star 4" was a particularly good one. I searched and couldn't find that version anywhere so I ordered a new one at about the lowest cost I could find.

What I received was this one listed with the 2015-09-17 date (Version) stamped on the front. Ebay # 331800738725 - It contained the GPSDO, antenna and 12V wall wart.

The GPS is a U-blox NEO-6M-0-001 and the OXCO is a Oscilloquartz 8663-XS dual oven. Reading the stats on the stability, it's pretty tight: http://tinyurl.com/h4j58ea

One of the reasons for my posting this is the master chart on the first page reflects the oven to be a  morion mv201 but this one is Oscilloquartz but not the same one pictured in the shots of the "Star 4". The specs on this one are better than the morion mv201.

Thanks for the previous inputs to the discussion, it helped me decide to give the BG7TBL a go.

Gary

[usagi]

Hi,

My first post to the group. I've been looking to find a reasonably priced GPSDO and I ended up finding this discussion on the BG7TBL and decided to order one. According to some opinions the 2015-07-08 version with the Oscilloquartz "Star 4" was a particularly good one. I searched and couldn't find one anywhere so I ordered one at about the lowest cost I could find.

What I received was this one is listed with the 2015-09-17 date (Version) stamped on the front. Ebay # 331800738725 - It contained the GPSDO, antenna and 12V wall wart.

The GPS is a U-blox NEO-6M-0-001 and the OXCO is a Oscilloquartz 8663-XS dual oven. Reading the stats on the stability, it's pretty tight: http://tinyurl.com/h4j58ea

One of the reasons for my posting this is the master chart on the first page reflects the oven to be a  morion mv201 but this one is Oscilloquartz but not the same one pictured in the shots of the "Star 4". The specs on this one are better than the morion mv201.

Thanks for the previous inputs to the discussion, it helped me decide to give the BG7TBL a go.

Gary

do you have pictures you can share?

[KA1J]

Hi,

My first post to the group. I've been looking to find a reasonably priced GPSDO and I ended up finding this discussion on the BG7TBL and decided to order one. According to some opinions the 2015-07-08 version with the Oscilloquartz "Star 4" was a particularly good one. I searched and couldn't find one anywhere so I ordered one at about the lowest cost I could find.

What I received was this one is listed with the 2015-09-17 date (Version) stamped on the front. Ebay # 331800738725 - It contained the GPSDO, antenna and 12V wall wart.

The GPS is a U-blox NEO-6M-0-001 and the OXCO is a Oscilloquartz 8663-XS dual oven. Reading the stats on the stability, it's pretty tight: http://tinyurl.com/h4j58ea

One of the reasons for my posting this is the master chart on the first page reflects the oven to be a  morion mv201 but this one is Oscilloquartz but not the same one pictured in the shots of the "Star 4". The specs on this one are better than the morion mv201.

Thanks for the previous inputs to the discussion, it helped me decide to give the BG7TBL a go.

Gary

do you have pictures you can share?

Hi, I tried to get good ones but can't find my camera so am offering these from my cell phone. It takes lousy close-up photos so these are the best photos I can get right now.
I see the circuit board is a newer date of 2015-11-24 so that means they're now using older covers with newer boards.
 
Can't compare it to other boards/versions but it seems to work just fine. Using the uBlox software from here -> https://www.u-blox.com/en/product/u-center-windows, it seems to be locked on and FWIW, I'm most happy with the frequency stability with my radio in narrow modes.

Next project is to figure out how to use the BG7TBL to keep my computer clock on time in Win 10

[D3f1ant]

Looks nice and tidy on the inside, kinda hate the ones with hacks, it would just bother my OCD to much.

I don't own a gpsdo, dont really have any legitimate reason to have one, but want one anyway. Knowing frequency/timing measurements could be fractionally more accurate, and my scope and SA have 10mhz inputs, all connectors need to be used...must resist.