Author Topic: Economical option for precision frequency reference?  (Read 117785 times)

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Offline DimitriP

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Re: Economical option for precision frequency reference?
« Reply #250 on: September 04, 2015, 01:31:39 am »
I recently needed to buy a GPS antenna for my gpsdo and after touring ebay found item 181420921843.
I received it yesterday and can highly recommend it for anyone looking to get a very nice outdoor GPS antenna for a good price.
The listing isn't too great but what you are really getting is a new waterproof Trimble 5 volt 26 db gain antenna, part # 28367-70 and a 5 meter RG316 cable made by Huber Suhner with a TNC on one end for the antenna and an SMA on the other. The cable is very highly quality - no cheap chinese parts.
Pretty tough to beat this combo for 15.99 USD shipped for those in the US.

I have no affiliation with the seller, just like a good deal and this kit is ideal for many gpsdo owners.

edit - aww, they just put the price back to 19.99 for them, still a good deal but not as good.

The antenna is waterproof, but what about the connector? On the Symmetricon antenna that I have, the connection is made inside a tube, the top of which is sealed with a gasket. So unless you mount it upside down, water can't get in. As you say the listing isn't too good, but based on the picture that's there it looks like water could get into the connector.

I'd recommend any outdoor antenna connection be properly sealed in vulcanizing/Self-amalgamating tape.

Well crap, now the price of vulcanizing/Self-amalgamating tape will go up too....
   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 

Offline motocoder

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Re: Economical option for precision frequency reference?
« Reply #251 on: September 04, 2015, 02:54:10 am »
I recently needed to buy a GPS antenna for my gpsdo and after touring ebay found item 181420921843.
I received it yesterday and can highly recommend it for anyone looking to get a very nice outdoor GPS antenna for a good price.
The listing isn't too great but what you are really getting is a new waterproof Trimble 5 volt 26 db gain antenna, part # 28367-70 and a 5 meter RG316 cable made by Huber Suhner with a TNC on one end for the antenna and an SMA on the other. The cable is very highly quality - no cheap chinese parts.
Pretty tough to beat this combo for 15.99 USD shipped for those in the US.

I have no affiliation with the seller, just like a good deal and this kit is ideal for many gpsdo owners.

edit - aww, they just put the price back to 19.99 for them, still a good deal but not as good.

The antenna is waterproof, but what about the connector? On the Symmetricon antenna that I have, the connection is made inside a tube, the top of which is sealed with a gasket. So unless you mount it upside down, water can't get in. As you say the listing isn't too good, but based on the picture that's there it looks like water could get into the connector.

I'd recommend any outdoor antenna connection be properly sealed in vulcanizing/Self-amalgamating tape.

Well crap, now the price of vulcanizing/Self-amalgamating tape will go up too....

LMAO. Yes, seems all it takes is to post a brand name on here and the eBay prices skyrocket.
 

Offline Lightages

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Re: Economical option for precision frequency reference?
« Reply #252 on: September 04, 2015, 03:22:16 am »
I was just wondering, was the OP question actually answered? ;D

What is the best economical option for a precision frequency reference?
With my experience so far, the FE5680B seems to be it.

What is the easiest to use and have running and have accurate without worrying about being off because of age drift?
IMHO the bg7tbl GPSDO on ebay, any flavor, is the best bet.
 

Offline motocoder

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Re: Economical option for precision frequency reference?
« Reply #253 on: September 04, 2015, 04:02:52 am »
I was just wondering, was the OP question actually answered? ;D

What is the best economical option for a precision frequency reference?
With my experience so far, the FE5680B seems to be it.

What is the easiest to use and have running and have accurate without worrying about being off because of age drift?
IMHO the bg7tbl GPSDO on ebay, any flavor, is the best bet.

I am the OP. I think the answer depends on what your specific needs are. They all stay accurate without drift - that's what the GPS is there for. Here is a breakdown of how I see it:

BG7TBL / 2014-12-09 -
  Pros: Smallest unit, good sensitivity on GPS receiver.
  Cons: Small frequency error. OCXO has a high failure rate in first 30 days. No management interface. Produced by someone who is semi-anonymous and not able or willing to answer questions about his product. No software to monitor. GPS chip is a UBlox non-timing chip, which has more jitter than their equivalent timing chips (like the one used in the Huawei).

Huawei/BG7TBL 2015-07-08 (Star4+ board)
  Pros: Excellent OCXO, Good management interface, excellent GPS sensitivity using UBlox timing application-specific GPS receiver module, coolest running unit. Simple mod to expose second 10M output (square wave)
  Cons: Requires minor change (solder two wires) to fix management interface mis-wiring from BG7TBL. Limited availability now it seems. No software to monitor.

"TRIMBLE"/BG7TBL 2015-07-17 -
  Pros: Good management interface.
  Cons: Insensitive GPS receiver. OCXO quality was on the low end (but still not bad). No software to monitor.

Lucent KS24361
  Pros: Great management interface compatible with Z38XX software. Ties with Huawei for quality of output.
  Cons: Big (two units, but can be hacked into one unit with a special cable and mod to expose the 10Mhz signal). Generates a ton of heat compared to all but the BG7TBL unit which is similarly hot. Poor sensitivity on GPS receiver. Crazy DB9 power connectors with funky latch. RS422 interface instead of RS232. 15 MHz primary output instead of 10. It has 10 MHz output, but it's reportedly relatively poor quality compared to the 15Mhz.

So personally, I prefer the Huawei/Star4+ board, with or without the BG7TBL strap-on hardware. My second choice would probably be the BG7TBL/2014-12-09 unit, because the frequency error isn't important to me, and it does make a nice compact unit and has good GPS sensitivity. My third choice would be the Lucent.

 

Offline DimitriP

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Re: Economical option for precision frequency reference?
« Reply #254 on: September 04, 2015, 04:30:29 am »
For a box with no docs, no specs, no software and an abused looking OCXO to boot, no one should be paying more than $60-$70 for it.
But you know what they say ...opinions are like GPSDOs...everyone has one.....

 
   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 

Offline EV

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Re: Economical option for precision frequency reference?
« Reply #255 on: September 04, 2015, 01:17:50 pm »
Huawei/BG7TBL 2015-07-08 (Star4+ board)
...
  Cons: Requires minor change (solder two wires) to fix management interface mis-wiring from BG7TBL. Limited availability now it seems. No software to monitor.

Can you give details or link for these changes?
 

Offline carpelux

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Re: Economical option for precision frequency reference?
« Reply #256 on: September 04, 2015, 05:18:17 pm »
First: Hats of to your work motocoder (and all other that has given great information on all these devices).

I have followed the other thread about the BG7TBL but failed to really understand what modifications to do on the huawei flavor of the BG7TBL gpsdo to get communication with it. I failed to run ublox u-center, it kept resetting the satellites all the time and didn't show any fix, but I suppose that's because the computer only has read-only access to the receiver. Don't know if u-center will work after these modifications is done?
 
I received my sample of the BG7TBL 2015-07-08 from ebay a couple of days ago, and so far it seems to work very good. Haven't had that much time to evaluate it, but it got GPS lock within about 30 mins and has kept it that way. I have a Racal Dana 1998 (with option 04E) connected to it  and my visual checks shows it has been steady between 10.000000004 and 10.000000039 during the 5 days it has been running. I suppose it's really useless information, but I'm happy with both the gpsdo and the counter.

Anyway, more detailed information on the modifications would be very much appreciated.
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Offline motocoder

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Re: Economical option for precision frequency reference?
« Reply #257 on: September 05, 2015, 06:46:40 am »
For a box with no docs, no specs, no software and an abused looking OCXO to boot, no one should be paying more than $60-$70 for it.
But you know what they say ...opinions are like GPSDOs...everyone has one.....

What option out there is $60-$70?
 

Offline Shock

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Re: Economical option for precision frequency reference?
« Reply #258 on: September 05, 2015, 08:22:10 am »
FYI the LUCENT/SYMMETRICOM Z3810AS, KS24361 has gone up to $200 now. 9 left.
Soldering/Rework: Pace ADS200, Pace MBT350
Multimeters: Fluke 87V, 117, 27/FM       >>> WANTED STUFF <<<
Oszilloskopen: Lecroy 9314, Phillips PM3065, Tektronix 2215a, 314
 

Offline motocoder

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Re: Economical option for precision frequency reference?
« Reply #259 on: September 05, 2015, 05:11:13 pm »
Huawei/BG7TBL 2015-07-08 (Star4+ board)
...
  Cons: Requires minor change (solder two wires) to fix management interface mis-wiring from BG7TBL. Limited availability now it seems. No software to monitor.

Can you give details or link for these changes?

Here are the details for the two simple mods that I have done to the Huawei.

The Huwai/"BG7TBL" 2015-07-08 is actually a Star4+ board from Oscilloquartz that BG7TBL has strapped onto a PCB of his design and jammed into an enclosure. The BG7TBL PCB is a nicely designed board that allows him to connect a variety of 3rd-party GPSDO and provide consistent front panel connections. He includes a MAX3232 chip in there so that internal TTL-level signals can be converted to RS-232 levels before connecting to the DB9, connection points for power, LEDs, and the BNC connectors.

In this post I will show you how to reconfigure the DB9 connector to connect to the actual RS232 management interface on the Star4+ board, as well as how to add a square wave output to the front panel. Since the actual GPSDO is a Star4+ board, the first thing I would recommend is to download the user manual for that which usagi links in this post:

https://www.eevblog.com/forum/testgear/bg7tbl-gpsdo-master-reference/msg740339/#msg740339

If you look near the bottom of this manual, you will see a diagram for a connector on the Star4+ board. THis is where we are going to be tapping into the various signals. Let's discuss the management interface first, as I think that's the mod most people will be interested in.

As the board comes from the eBay seller, the front panel DB9 is a "talk only" interface and is connected to an RS-232 level version of the Tx interface from the uBlox GPS chip. This will sort of let you run the uBlox u-center software. I say "sort of" because this software gets confused by the interface being effectively read-only, and it has some issues sometimes and much of the functionality doesn't work. However, it's enough to see the satellite strength and some basic stats. If having this sort of nice graphical interface is important to you, stop here, because you won't get that after the mod. If you proceed with this mod, you will (until some nicer software is available) just be able to use a serial terminal to connect to the board. However, you will have access to more information, including the state of the actual GPSDO, and the ability to set parameters such as the antenna delay. The board has a set of commands that are documented in the aforementioned manual; take a look at those to see what's possible.

On the Star4+ board is a Xilinx FPGA, which has inside it a soft-core processor. This processor is what actually implements the control logic of the GPSDO. It talks to the uBlox chip via a serial connection  on the uBlox, which is why BG7TBL was not able to route the uBlox Rx pin out to the DB9 connector. This soft-core processor has its own serial connection which we can talk to send commands and view status.

To proceed with the mod, remove the 4 screws from the front panel and slide out the board. The picture below shows a top-down view of the Star4+ board sitting on top of the BG7TBL adapter board. Note the black connector that the red arrow is pointing to. THis is where we are going to make our connections. Also note the arrow pointing to the uBlox chip. This is where the uBlox Tx connection is being made.


The next picture shows a detail view of the connector. The yellow wire is the connection to the management Tx pin, and the green wire is the connection to the management Rx pin. Solder some suitable wire there, and route these wires around to the bottom of the board. If you're interested in also adding the square wave output, you can also see the connection for that here.



Here is a close-up of the bottom side of the BG7TBL adapter board. Note the yellow and green wires, and the dangling red wire. The red wire is coming from the uBlox Tx pin, and used to connect to where the yellow wire connects now. These connections go through the MAX3232 chip, and then onto the front panel.



If you're also interested in adding a square wave output, this is what I did there. Remove the front panel, which is a simple matter of removing the nuts from the two BNC connectors and the one SMA connector. Drill a suitable size whole for your BNC. I purchased a BNC connector with a pre-attached pigtail off of eBay. It had an SMA connector on the other end, which I just snipped off. Re-attach the panel, add in your new BNC, and solder it to the location shown in the previous photo. There is a convenient spot to solder the ground/shield right there, so it's a very simple connection other than the fact that the connector pads are very small.



Now before you do this mod, you might want to have a look at the scope capture of the square wave output. It's not the nicest square wave in the world, and in particular note that the duty cycle is not remotely close to 50%. At some point I will probably come back and add a little daughterboard to convert the sine wave to a clean, 50% duty cycle square wave.

« Last Edit: September 06, 2015, 06:50:13 am by motocoder »
 

Offline TheSteve

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Re: Economical option for precision frequency reference?
« Reply #260 on: September 06, 2015, 02:12:13 am »
I was just wondering, was the OP question actually answered? ;D

What is the best economical option for a precision frequency reference?
With my experience so far, the FE5680B seems to be it.

What is the easiest to use and have running and have accurate without worrying about being off because of age drift?
IMHO the bg7tbl GPSDO on ebay, any flavor, is the best bet.

So far I've purchased a Nortel NTBW50AA for 80 USD shipped and a second Trimble unit which is a PCB with no case for 48 USD shipped. I also purchased cables to convert the various connectors on the two units to BNC for another 12 USD shipped. And lastly two Trimble GPS antennas which were 15.99 USD shipped each. I already had power supplies on hand. I have the Nortel unit fired up and running, the Trimble PCB has not yet arrived from china. The Nortel is a little large but is known to work extremely well, it has an even second output instead of 1 PPS but 1 PPS is on the board, a cut trace and jumper and you can have the 1 PPS if needed. In my case I really only care about the 10 MHz. The Nortel also has a DB9 factory installed and directly supports the Trimble diag software as well as Lady Heather. The other unit I will be receiving has a text based user interface, a DB9 just needs to be wired in. I will install it in a box when I receive it and after some aging time I plan to compare the two side by side. I already have both antennas installed on my tower outside with exact length runs of coax in to the shop.
I'd still like a rubidium based reference and when I can find one at a reasonable price I will pick it up. Clearly the rubidium is easier for most people to manage as it doesn't need an antenna however if you receive one off ebay you have no idea if it really is outputting 10 MHz or 1 PPS - they still technically need calibration. Also many of them are 10 to 20 years old. So as an only source I prefer a GPS based solution over rubidium. With a little effort and patience it should be no problem to purchase and setup a nice stable reference in your shop for under 100 USD. The Trimble based GPS units also seem to require less power then rubidium, my Nortel is 5 to 6 watts when warm.
VE7FM
 

Offline motocoder

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Re: Economical option for precision frequency reference?
« Reply #261 on: September 06, 2015, 04:09:06 am »
I was just wondering, was the OP question actually answered? ;D

What is the best economical option for a precision frequency reference?
With my experience so far, the FE5680B seems to be it.

What is the easiest to use and have running and have accurate without worrying about being off because of age drift?
IMHO the bg7tbl GPSDO on ebay, any flavor, is the best bet.

So far I've purchased a Nortel NTBW50AA for 80 USD shipped and a second Trimble unit which is a PCB with no case for 48 USD shipped. I also purchased cables to convert the various connectors on the two units to BNC for another 12 USD shipped. And lastly two Trimble GPS antennas which were 15.99 USD shipped each. I already had power supplies on hand. I have the Nortel unit fired up and running, the Trimble PCB has not yet arrived from china. The Nortel is a little large but is known to work extremely well, it has an even second output instead of 1 PPS but 1 PPS is on the board, a cut trace and jumper and you can have the 1 PPS if needed. In my case I really only care about the 10 MHz. The Nortel also has a DB9 factory installed and directly supports the Trimble diag software as well as Lady Heather. The other unit I will be receiving has a text based user interface, a DB9 just needs to be wired in. I will install it in a box when I receive it and after some aging time I plan to compare the two side by side. I already have both antennas installed on my tower outside with exact length runs of coax in to the shop.
I'd still like a rubidium based reference and when I can find one at a reasonable price I will pick it up. Clearly the rubidium is easier for most people to manage as it doesn't need an antenna however if you receive one off ebay you have no idea if it really is outputting 10 MHz or 1 PPS - they still technically need calibration. Also many of them are 10 to 20 years old. So as an only source I prefer a GPS based solution over rubidium. With a little effort and patience it should be no problem to purchase and setup a nice stable reference in your shop for under 100 USD. The Trimble based GPS units also seem to require less power then rubidium, my Nortel is 5 to 6 watts when warm.

Nortel NTBW50AA goes on eBay, with antenna but not power supply, for exactly the same price as the options I listed above: $159. I do see a few standalone units for $80 in the sold items search, but they are not generally available at that price and that price does not include the nice antenna that the $159 package does.

So I don't think you're comparing apples to apples here. Let's say  you didn't have power supply on hand, but that one could be had for $15. So after looking and waiting on eBay for some time, you finally snag a deal on the $80 Nortel unit. Then you buy an antenna for $16, and the BNC converter for $6. Your at $115. Ok, you saved $54 with some smart shopping and by being willing to wait to find the right deal. Good on you. However, you also got an 8 channel GPS receiver with relatively poor GPS sensitivity. ALso, have you actually verified the Nortel unit supports the software you mention? A brief scan of the time-nuts mailing list shows a few posts saying there is some model of that (it's actually listed as "Symmetricon Nortel NTBW50AA" that does not.
 

Offline TheSteve

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Re: Economical option for precision frequency reference?
« Reply #262 on: September 06, 2015, 04:24:41 am »
I have Lady Heather connected to my Nortel unit as I type this. Started the program and it connected. To build a system for under 100 USD it would take time I do admit. I was more referring to the 48 dollar unit I picked up off ebay. The price has since gone up but they seem to go up/down quite often. They have been as low as 40 USD shipped. The cheaper one also has a newer 12 channel receiver based on posts over on time-nuts, hopefully it arrives soon.

I selected a price of 100.00 USD as to me that seemed to meet the "economical" request. Considering the price of quality test equipment maybe anything under $100 should be considered cheap.

btw, my Nortel/Trimble unit does not mention Symmetricon anywhere on it and is the version with a single PCB.

Maybe we could come up with a list of known working options that includes pictures for people so they can try to acquire the exact same hardware if they really want to get something going as cheap as possible instead of buying one of the ready to go solutions. I am buying various pieces myself as I find it more fun, others may just want to get something that plugs in and runs when it arrives.
« Last Edit: September 06, 2015, 04:39:07 am by TheSteve »
VE7FM
 

Offline EV

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Re: Economical option for precision frequency reference?
« Reply #263 on: September 06, 2015, 05:47:19 am »
Here are the details for the two simple mods that I have done to the Huawei.
...
...

Thanks motocoder!
 

Offline motocoder

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Re: Economical option for precision frequency reference?
« Reply #264 on: September 06, 2015, 06:46:14 am »
I have Lady Heather connected to my Nortel unit as I type this. Started the program and it connected. To build a system for under 100 USD it would take time I do admit. I was more referring to the 48 dollar unit I picked up off ebay. The price has since gone up but they seem to go up/down quite often. They have been as low as 40 USD shipped. The cheaper one also has a newer 12 channel receiver based on posts over on time-nuts, hopefully it arrives soon.

I selected a price of 100.00 USD as to me that seemed to meet the "economical" request. Considering the price of quality test equipment maybe anything under $100 should be considered cheap.

btw, my Nortel/Trimble unit does not mention Symmetricon anywhere on it and is the version with a single PCB.

Maybe we could come up with a list of known working options that includes pictures for people so they can try to acquire the exact same hardware if they really want to get something going as cheap as possible instead of buying one of the ready to go solutions. I am buying various pieces myself as I find it more fun, others may just want to get something that plugs in and runs when it arrives.

I'll be interested to see what the Trimble is when you get it. I suspects it's teh surplus board that is in the "Trimble" BG7TBL unit I tested. Hopefully not, because that one was at the bottom of my list in terms of features and bang for the buck.

I agree it's fun to assemble stuff. I had a lot of fun playing around with the Lucent unit, but now I really just want the space back on my bench.
 

Offline motocoder

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Re: Economical option for precision frequency reference?
« Reply #265 on: September 06, 2015, 06:51:48 am »
Here are the details for the two simple mods that I have done to the Huawei.
...
...

Thanks motocoder!

You're very welcome. We should both thank usagi for getting the Star4+ manual from OscilloQuartz, and edpalmer42 for numerous helpful posts on this topic.

BTW - you may want to refresh my post; I forgot to embed the picture of the bottom of the board.
 

Offline voltsandjolts

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Re: Economical option for precision frequency reference?
« Reply #266 on: September 13, 2015, 08:04:18 pm »

I'd just like to point out a very cheap and stable reference for anyone like me who has fairly basic accuracy requirements. I only need an accurate reference intermittantly to calibrate my old but reliable OCXO based frequency counter. As has been discussed in this thread, the UBLOX LEA-6T has improved timing specs over some other UBLOX modules, can output a MHz signal locked to GPS atomic clocks and is available $30 on ebay complete with antenna.

http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=lea-6t&_sop=15

Unfortunately, neither of the timepulse outputs are wired outside the unit - so need to add some RG178 and BNC ($3)

OK, this unit has some nasty jitter but is it good enough to calibrate my frequency counter using a 10 second gatetime? I tested it against a (borrowed) Agilent 53230A with UOCXO option (nice!). I set the UBLOX output to 8MHz as recommened in datasheet for minimum jitter.

Answer: Over one hour the frequency spread was mostly within 4ppb and showed the Agilent to be 8ppb off frequency (well, that would need verified I guess).

So, I think LEA-6T is good enough for me.


 

Offline TheSteve

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Re: Economical option for precision frequency reference?
« Reply #267 on: September 14, 2015, 03:26:59 am »
Messed around with my Trimble/Nortel NTBW50AA for a bit today. I converted the Chip Clock/8X output from 9.8304 MHz to 19.6608 MHz and the even second PP2S output to a more normal 1 PPS output that has a positive going pulse.

The 19.6608 MHz clock is useful to me as it is one of the standard reference in options on my Agilent N1996A spectrum analyzer.

The 9.8304 MHz to 19.6608 MHz mod is very simple. The 19.6608 MHz signal is normally divided by two by U18 (74HC74). The divide is bypassed by lifting U18 pin 6 and running a jumper(white wire) from TP30 to TP33.

The PP2S signal is supplied to R82 by an output from the Xilinx chip, it has an input(from the Trimble chip) which is fed a more useful 1 PPS (TP13). I ran a jumper (yellow wire) from the 1 PPS signal going into the Xilinx chip to R82 which was rotated 90 degrees to allow connection to the jumper and disconnect the PP2S input.
The last mod was to lift pin 9 of U18 and run a jumper (blue wire) from pin 8 of U18 to TP29. This inverts the signal so that the 1 PPS signal pulse on the output is positive going.

All of the signals are phase locked to each other and that should be preserved just fine with this mod. The actual delay of the PPS signal would need to be measured but should be a consistent fixed value as I have read the PPS signal going into the Xilinx(from the Trimble chip) is fully corrected.

Hopefully someone else may find this mod useful and sorry for the crap quality pic, no daylight here right now to get a really nice shot.

edit - there seems to be more then version of this GPSTM around, my board is marked as a "NTBW50AA 10" on the front, on the back it says it is PN 45321-00. It is a single board design that I believe came from a Sprint site. It talks to Lady Heather etc with no problems.
« Last Edit: September 14, 2015, 04:24:38 am by TheSteve »
VE7FM
 
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Offline Vgkid

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Re: Economical option for precision frequency reference?
« Reply #268 on: September 14, 2015, 05:27:11 am »
What is the ocxo on your board?
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Offline TheSteve

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Re: Economical option for precision frequency reference?
« Reply #269 on: September 14, 2015, 05:28:15 am »
What is the ocxo on your board?

34310-T
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Offline evb149

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Re: Economical option for precision frequency reference?
« Reply #270 on: September 14, 2015, 07:19:57 am »
FWIW in case others are interested in my initial experiences so far setting up the KS-24361 LUCENT RFTG-u units, after trying three other locations in the room (that didn't initially work), I was able to get the lucent units to work indoors on the top floor of a two story house using a 28dB gain mag-mount active patch antenna and I was seeing C/N ratios of 31, 31, 35, and 39 for the four satellites being tracked when last I checked.  Another +10 to +20 dB C/N would be nice to attain eventually but for the moment this is minimally adequate.
A location nearer the middle of the room worked better than near the window / corner / outside wall for me.  The initial antenna I have used is this one:
http://www.amazon.com/Waterproof-Active-Antenna-28dB-Gain/dp/B00LXRQY9A

I read: TFOM=3, FFOM=0 with a predicted 7.4us/initial 24 hrs holdover uncertainty was my recent reading after letting the units run for a few days with the poor antenna placement / type and not particuarly good signal quality.
I'll put up a proper timing type of outside antenna at some point to improve the reception.

The RS-422 outputs run between about +0.9V and +4V relative to GND with a 2.4 median level, so I was able to use a 5VDC VDD level MCU / USB-to-UART interface to connect the RS-422 UART / PPS signals to the PC or MCU for a quick test.

The 10VTP appears to be +17dBm relative to 50 ohms so 8.4Vp-p with a distorted sinusoidal waveform, I don't know if it is tracking the "17 vs 23" dBm level switches that affect the 15MHz outputs, I didn't check yet, but my switches are set to "17".

Thanks to all who have recommended these units and who have shared so much good information about them!


 

Offline SoundTech-LG

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Re: Economical option for precision frequency reference?
« Reply #271 on: September 23, 2015, 03:48:07 pm »
Got what I think was a very ECONOMICAL Spectracom SecureSync on the bay. Can't wait to set it up...

Anyone have experience with these???



http://spectracom.com/Desktopmodules/Bring2Mind/DMX/Download.aspx?EntryId=419&PortalId=0


 

Offline SoundTech-LG

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Re: Economical option for precision frequency reference?
« Reply #272 on: September 24, 2015, 01:38:28 pm »
 

Offline motocoder

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Re: Economical option for precision frequency reference?
« Reply #273 on: September 24, 2015, 02:16:51 pm »
New Lucent KS-24361 RFTG-u info...

https://www.mail-archive.com/time-nuts@febo.com/msg74968.html

So to summarize this for people that don't want to wade through the whole document. Someone has figured out how to modify the KS-24361 REF 0 unit to make it functionally equivalent to a REF 1 unit. You just need to come up with a surplus Motorola OnCore GPS unit from somewhere, and do a little SMD rework, and now you have the equivalent of a standalone REF-1 unit with the 10 MHz test-point output
 

Offline Vgkid

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Re: Economical option for precision frequency reference?
« Reply #274 on: September 24, 2015, 03:01:28 pm »
Got what I think was a very ECONOMICAL Spectracom SecureSync on the bay. Can't wait to set it up...
very cool, expecting a teardown. Do you know what options it has?
If you own any North Hills Electronics gear, message me. L&N Fan
 


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