Author Topic: Economical option for precision frequency reference?  (Read 155303 times)

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Offline Vgkid

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Re: Economical option for precision frequency reference?
« Reply #225 on: August 09, 2015, 10:59:09 pm »
I got it powered, using the db15 connector.
Unless i've messed up, do not try connecting the external comms connectors(rs422) to the db9 on the data/power connector unit.
sparks will fly.
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Offline cncjerry

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Re: Economical option for precision frequency reference?
« Reply #226 on: August 09, 2015, 11:04:18 pm »
Today around noon I tripped the breaker powering my ref-0/ref-1 pair.  Prior to this happening my ref-0 was active and transmitting the 15Mhz signal. Ref-1 was in standby. Upon powering the units back up, ref-0 is showing a fault (after the blinking light test) and now ref-1 is active. Ref-0 is remaining in fault state.  Ref-1 is running the survey again.

I looked in the error log and around the time of the failure a "15Mhz output failure" was logged.  Stupid me I cleared the log so I can't read the correct error text.  So I guess what happened is that the ref-0 (which was active) saw the power failure first?  transferred to ref-1?  and now ref-1 will be active until the next failure?  I power cycled them right after the failure so they came up at the same time.  I would have thought ref-0 would have taken over again.  And if ref-1 is active I would have thought ref-0 would be in standby, not fault, no?

Is there a way thru Satstat to have them switch back or is there another way to test the fail-over?  Also, Since the 10Mhz output is on ref-0, does that remain sync'ed when ref-1 is active?

Lastly, I see there is a power-on setting to either have it rerun the survey or use the last known position.  I don't see a way to set it.  Querying the device shows it defaults to rerun.

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Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #227 on: August 10, 2015, 02:21:44 am »
Today around noon I tripped the breaker powering my ref-0/ref-1 pair.  Prior to this happening my ref-0 was active and transmitting the 15Mhz signal. Ref-1 was in standby. Upon powering the units back up, ref-0 is showing a fault (after the blinking light test) and now ref-1 is active. Ref-0 is remaining in fault state.  Ref-1 is running the survey again.

I looked in the error log and around the time of the failure a "15Mhz output failure" was logged.  Stupid me I cleared the log so I can't read the correct error text.  So I guess what happened is that the ref-0 (which was active) saw the power failure first?  transferred to ref-1?  and now ref-1 will be active until the next failure?  I power cycled them right after the failure so they came up at the same time.  I would have thought ref-0 would have taken over again.  And if ref-1 is active I would have thought ref-0 would be in standby, not fault, no?

Is there a way thru Satstat to have them switch back or is there another way to test the fail-over?  Also, Since the 10Mhz output is on ref-0, does that remain sync'ed when ref-1 is active?

Lastly, I see there is a power-on setting to either have it rerun the survey or use the last known position.  I don't see a way to set it.  Querying the device shows it defaults to rerun.

thanks

I don't think any special command is required for it to switch back. For sure it should go back to REF-0 after power cycle. Double-check your interface cable (J5) and really make sure it's screwed in tight. I saw several reports of people having issues with that cable caused by some of the pins being shorter than normal.
 

Offline cncjerry

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Re: Economical option for precision frequency reference?
« Reply #228 on: August 10, 2015, 02:32:36 am »
Wrt my lengthy post above, the fault light on ref-0 never went out.  Ref-1 worked as expected and ref-0 continued to output 10Mhz but not the 15Mhz which continued to be supplied by ref-1.  The 'on' light was lit on ref-1;  ref-0 posted a fault light.

For the heck of it, I pulled the power on ref-1.  The 'no gps' light was lit on ref-0 which continued to display 'fault'.  I would have expected ref-0 to go into hold over and output the 15Mhz, but it didn't.  It seems like it outputs 10Mhz all the time. 

I then power cycled both units. After going thru the blink test, the 'on' light on ref-0 lit and it started to output 15Mhz.  I would have expected it to do this when I pulled the power on ref-1 forcing a fail over, but it didn't.  Also, I had changed the power on default to use the last position so it wasn't doing a survey again.

After about 10 minutes of ref-0 outputting 15Mhz with the 'on' and 'fault' lights lit (prior to full gps lock), ref-0 posted errors in the log:
15Mhz Failure Set
Failed Mode Entered
At that point, ref-1 lit its 'on' light and started outputting 15Mhz.  So I guess ref-0 saw a failure and it failed over to ref-1.

I then cycled the power again.  The errors are still in the log, but ref-0 is now doing a survey and acting OK.  Both units have the 'no gps' and 'fault' lights lit (prior to the survey which is normal) with ref-0 also having the 'on' light lit and outputting 15Mhz.

So if you can follow the confusing sequence above, the questions are:

1) If you pull the power on the active unit ('on' light lit), shouldn't it transfer to the other?  If the unit you pull power from is ref-1 with the gps, it should go into hold-over;  if you pull ref-0 (without gps) shouldn't ref-1 just take over and not go into hold over?  You would lose the 10Mhz from ref-0, of course.

2) Based on the sequence above, I suspect my ref-0 which is posting the '15Mhz failure set' errors to have a problem.  It transferred twice to the ref-1 unit.  At first I thought it was because of the power failure but now I suspect not.

3) Does anybody know how it monitors the 15Mhz output to be able to tell when it has a failure?

4) It seems like the 10Mhz is always running.  Is this gps locked?  If so, I would not expect to see it if the gps wasn't up.

5) Under normal operation, what lights are lit on your units?  Which of the two is the default for 15Mhz?   I thought when my set were working correctly, ref-1 was in standby and ref-0 had the 'on' light lit and was outputting both 10Mhz and 15Mhz.

I am using 19.6V to drive both of them.  I had seen posted that the DC-DC converter takes anything from 18 to like 36V.  I plan to build a better power supply but I am starting to think maybe I am too close to the 18V.

Sorry for the long confusing posts.

Jerry
 

Offline Vgkid

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Re: Economical option for precision frequency reference?
« Reply #229 on: August 10, 2015, 03:26:29 am »
I had the same issue earlier today in which the xo stayed offline, while the rb remained online. Similiar to your a bad piwer connection caused the xo to lose power while the. Rb stayed online. A power cycle fixed that.
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Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #230 on: August 10, 2015, 03:33:52 am »
I am using 19.6V to drive both of them.  I had seen posted that the DC-DC converter takes anything from 18 to like 36V.  I plan to build a better power supply but I am starting to think maybe I am too close to the 18V.

19.6V is fine, but the lower the input voltage, the more amperage is required. There are some LEDs near rear left of the unit (looking down from above), just to the right of the DC-DC converter. If power is OK, you should see one green LED blinking at a rate of about once per second. If you see anything else, there is a power fault. Can you check this, especially during start-up sequencing (it draws more power during that phase)?
 

Offline cncjerry

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Re: Economical option for precision frequency reference?
« Reply #231 on: August 10, 2015, 04:10:19 am »
Moto, the internal power lights are fine as you stated, slowly blinking green.

I came down after dinner where before I had recycled the power.  Ref-0 (where I had the fault) was now ok, no fault, and 'on' putting out 15Mhz;  ref-1 was in 'standby' mode.  So it looks like a couple of power cycles plus some  waiting time fixed it.

So not being able to leave well enough alone, I switched the front panel Output level from 17 - 23 on ref-0.  The 'on' lights started blinking in both units and they logged an error that the setting were different.  Ref-0 then failed over to ref-1.  So I set them both back to the same 17 level setting.  I then recycled the units and ref-0, the one I've been having trouble with, is now showing fault again and ref-1 is in 'on' mode.  It posted another 15Mhz failure.

I'm wondering if you have to have the 15Mhz unloaded when it boots?  I'll attempt that next as I try to clear the fault on ref-0.  It might just clear itself.  It shows that it is GPS locked which usually is what clears the fault.

I don't know if I am adding to the wealth of knowledge on these boxes or confusing the subject...

 

Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #232 on: August 10, 2015, 04:36:01 am »
Moto, the internal power lights are fine as you stated, slowly blinking green.

I came down after dinner where before I had recycled the power.  Ref-0 (where I had the fault) was now ok, no fault, and 'on' putting out 15Mhz;  ref-1 was in 'standby' mode.  So it looks like a couple of power cycles plus some  waiting time fixed it.

So not being able to leave well enough alone, I switched the front panel Output level from 17 - 23 on ref-0.  The 'on' lights started blinking in both units and they logged an error that the setting were different.  Ref-0 then failed over to ref-1.  So I set them both back to the same 17 level setting.  I then recycled the units and ref-0, the one I've been having trouble with, is now showing fault again and ref-1 is in 'on' mode.  It posted another 15Mhz failure.

I'm wondering if you have to have the 15Mhz unloaded when it boots?  I'll attempt that next as I try to clear the fault on ref-0.  It might just clear itself.  It shows that it is GPS locked which usually is what clears the fault.

I don't know if I am adding to the wealth of knowledge on these boxes or confusing the subject...

The output level alarm is well-known. One of the pins on J5 indicates the level setting. How long have you waited to see if the fault clears? I'd wait at least 10 minutes to see if things return to a normal state.

 

Offline cncjerry

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Re: Economical option for precision frequency reference?
« Reply #233 on: August 10, 2015, 06:13:23 am »
I power cycled them again and all is back to normal.  If I had to point to anything I would think the problem is inconsistent application of power.  We'll see if the 15Mhz failure comes back.

Thanks for the pointers.

Jerry

btw:  when ref-0 faulted with the 15Mhz error, I waited about an hour for it to clear without luck.   The good news was it failed-over.  I'd still like to know what the 15Mhz error means and how they track it. 
« Last Edit: August 10, 2015, 02:57:08 pm by cncjerry »
 

Offline cncjerry

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Re: Economical option for precision frequency reference?
« Reply #234 on: August 11, 2015, 12:56:55 am »
Once the survey is complete and the units have been running for a while, how many sats does it have to lock to maintain its best sync?  I can get 4 sat reliably with my antenna outside my shop;  If put it on my railing three stories up I can get 8.  Just wondering if 4 sats are enough for long term operation.

thanks

Jerry
 

Offline Dragon88

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Re: Economical option for precision frequency reference?
« Reply #235 on: August 18, 2015, 04:35:01 am »
Jerry,

I'll try to answer some of your questions. I've been working on these units quite a bit the past couple weeks, with the goal of getting the two boxes (REF-0 and REF-1) to operate independently of each other. I have been successful in this, and have learned a lot about them in the process.

- Each unit knows the status of the other unit using pins on the interface connector. There is no sophisticated signaling. The logic level of three pins in particular tell the REF-0 to initially turn its outputs on. Either by command or through a fault, the REF-1 can take over and turn its own outputs on. I do not know what your own fault is, but I would recommend removing and re-seating the interface cable several times. There may be corrosion on one of the pins which is causing an intermittent connection.

- The 10MHz output on the REF-0 is a test point, and is not a primary output. It is disciplined in that it is generated from the 5MHz OCXO in the unit, which is disciplined to GPS. However, it's status (on or off) is not controlled like the 15MHz primary output is. It's actually buffered by the same chip that generates the clock signal for the processor. A "test point", nothing more. The signal is quite "dirty" compared to the 15MHz output.

- The REF-0 send no commands at all to the GPS. In fact the serial Tx pin from the REF-0 isn't even connected. The REF-0 monitors the GPS strings (and PPS signal) sent from the Oncore GPS to the REF-1, and looks for key fields to know that the GPS lock is good. If it detects that GPS status is degraded, it will enter holdover mode, and recover on its own when the lock is good again. The REF-1 does not guide this process. All the two boxes exchange between each other is "I'm ok and my outputs are on" or "I'm not ok you turn your outputs on". Again, this is merely done with pins on the interface connector for reliability.

- You should always achieve the best antenna position possible.

If you need any more help with your unit, please PM me.  :-+

Dan
 

Offline SoundTech-LG

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Re: Economical option for precision frequency reference?
« Reply #236 on: August 18, 2015, 01:51:21 pm »
That's great.

So if you have the information about "which" pins, and a truth table for them, it would be helpful to many people to post the information here.

Thanks!
 

Offline TheSteve

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Re: Economical option for precision frequency reference?
« Reply #237 on: August 19, 2015, 07:08:57 pm »
Bought an NTBW50AA from the 'bay the other day, looking forward to firing it up when it arrives. I have read there is a divide by two on the 9.8304 MHz which I plan to remove if possible to output 19.6608 MHz which my Agilent spectrum analyzer can use. It can also use the even second output which should be fun to try. Seemed to be the cheapest option overall that I could find.
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Offline artag

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Re: Economical option for precision frequency reference?
« Reply #238 on: August 24, 2015, 01:44:39 am »

I'll try to answer some of your questions. I've been working on these units quite a bit the past couple weeks, with the goal of getting the two boxes (REF-0 and REF-1) to operate independently of each other. I have been successful in this, and have learned a lot about them in the process.


Thank you for publishing this work (and thanks to the other time-nuts people who have provided information). I wanted to get one of these going but the low price is rather spoilt by the postage to the UK - about 3 times the price of the units iirc !

The more you ship the cheaper it is .. though bulk does tend to make sure the customs and excise people notice it. Despite that,  I've bought several to make it worthwhile and am just about to take delivery - so if you're in the UK or nearby and want to share in the oscillatory goodness at a CMOT price, get in touch.
 
 

Offline TheSteve

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Re: Economical option for precision frequency reference?
« Reply #239 on: September 03, 2015, 06:06:51 pm »
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.
« Last Edit: September 03, 2015, 07:06:04 pm by TheSteve »
VE7FM
 

Offline motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #240 on: September 03, 2015, 07:34:55 pm »
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.
 

Offline TheSteve

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Re: Economical option for precision frequency reference?
« Reply #241 on: September 03, 2015, 08:01:16 pm »
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.
VE7FM
 

Offline DimitriP

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Re: Economical option for precision frequency reference?
« Reply #242 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 motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #243 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 #244 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 motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #245 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 #246 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 #247 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 #248 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 motocoderTopic starter

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Re: Economical option for precision frequency reference?
« Reply #249 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?
 


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