Re: [time-nuts] TrueTime AL-AK GPS receiver help
Hi If you want to dig into something like this to learn and to maybe fiddle with a downconverter design - sure, that’s a great thing to do. It’s a hobby and (hopefully) you are set up to handle the task. You probably are already a member of a list (or three) where you have access to info on your project. Since we have zero info about the original requester, I am indeed guessing here. That can often be a bad thing to do. My *guess* is that this is somebody who simply wants a working device. If so, there are a lot of bumps in the road that they need to understand. If the answer is “I want a simple NTP server that is setup and forget”, this is probably not the way to go. Bob On May 1, 2015, at 9:55 PM, paul swed paulsw...@gmail.com wrote: Bob brings up all the additional details that are the reality of dealing with teh older gear. Especially the date offsets because of the 1024 week cycle. That is a real pain. But the reason to spend time on something like this is to understand something and to learn. I picked up the austron 2000 gps because it was a useful rack mount box. Then realized some of its unique qualities. That was the driver for reviving it. I was lucky that I was able to obtain some operational data and then later schematics. BUT it was still a heck of a reverse engineering and adapting process. I am pretty sure I shared that on time-nuts and will guess that must be 5 years ago now. Regards Paul WB8TSL On Thu, Apr 30, 2015 at 5:58 PM, Bob Camp kb...@n1k.org wrote: Hi I guess the first question would be: Are we sure it’s an AL-AK and not an XL-AK? Past that it becomes a fairly involved process of, is it worth real money to get this up and running? If we are talking about a $20 eBay find that is worth another $5 to have somebody else get it running, the conversation is a real short one. If the AL-AK has some inherent value (it’s a working GPS disciplined Cs maybe) then putting a few hundred dollars into checking it out and getting it running might make sense. If it’s like most of the parts from that era, the delta between getting it checked and getting it running is pretty small. Once you *do* have it running, what do you have? 1) Leap second problems 2) GPS year rollover problems 3) Tracking issues 4) A noisy receiver with very few correlators 5) Software support issues This is an unusual box that is at least 20 years old. It *will* have at least some of the listed issues and may have all of them. Fixing them will be impossible. Why bring up all of the negatives? I for one have been sucked into this kind of thing a *lot* of times in the past. Just a few more this or that and it’ll be running fine. Much better to figure out the likely cost and outcome first. That’s *very* hard to do, and even harder to follow through on. If you can’t do the work yourself, the cost isn’t just lost time. This can cost real cash. Bob On Apr 30, 2015, at 12:50 PM, Tom Van Baak t...@leapsecond.com wrote: I received this email. Anyone have a good answer? Thanks, /tvb -- Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites. This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ... -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TrueTime AL-AK GPS receiver help
Hi Remember - a number of these boxes go *way* back in time GPS wise. Often the basic guts were a mix and match affair and this or that sub-system was frozen for a decade or more. At this late date, figuring out why they did that, or why they had multiple sub-systems is going to be tough. I suspect that it goes something like - this one works with 1500’ of RG-58, that one works with 300’ of RG-58. In answer to your basic question - I’d bet it has the IF to a GPS receiver and the tuned front end is up at the antenna. I have never seen one of these that was an either or as installed. If you wanted a downconverter, that’s what they built into the box. If you wanted a full receiver, that went in instead. They flipped a few dip switches on the main board to tell the firmware what it had and moved on. Bob On May 2, 2015, at 12:10 AM, Al Wolfe alw.k...@gmail.com wrote: Does this AL-AK have a real GPS receiver in it? Does the unit have a board with a crystal of 16.368MHz. that is multiplied by 96 up to 1571.328, the mixing frequency to get to the GPS freq of 1575.42? Since the down convert-up convert is offered as an option perhaps TrueTime used an actual GPS receiver in all their units. It stands to reason (at least to me) using a stock off-the-shelf GPS receiver in all their boxes would be simpler than having to do a custom kluge to work at 4 mhz. If this user can find out if his box has an actual GPS receiver then the converter section could probably be bypassed. FWIW, the TrueTime XL-AK used an external up converter and down converter, model 142-6150. Says it's good for up to 1500 feet of RG58. Its manual is on line. It uses the above mixing scheme. Al, retired, mostly AKA k9si Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites. This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ... snip ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TrueTime AL-AK GPS receiver help
Does this AL-AK have a real GPS receiver in it? Does the unit have a board with a crystal of 16.368MHz. that is multiplied by 96 up to 1571.328, the mixing frequency to get to the GPS freq of 1575.42? Since the down convert-up convert is offered as an option perhaps TrueTime used an actual GPS receiver in all their units. It stands to reason (at least to me) using a stock off-the-shelf GPS receiver in all their boxes would be simpler than having to do a custom kluge to work at 4 mhz. If this user can find out if his box has an actual GPS receiver then the converter section could probably be bypassed. FWIW, the TrueTime XL-AK used an external up converter and down converter, model 142-6150. Says it's good for up to 1500 feet of RG58. Its manual is on line. It uses the above mixing scheme. Al, retired, mostly AKA k9si Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites. This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ... snip ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TrueTime AL-AK GPS receiver help
Bob brings up all the additional details that are the reality of dealing with teh older gear. Especially the date offsets because of the 1024 week cycle. That is a real pain. But the reason to spend time on something like this is to understand something and to learn. I picked up the austron 2000 gps because it was a useful rack mount box. Then realized some of its unique qualities. That was the driver for reviving it. I was lucky that I was able to obtain some operational data and then later schematics. BUT it was still a heck of a reverse engineering and adapting process. I am pretty sure I shared that on time-nuts and will guess that must be 5 years ago now. Regards Paul WB8TSL On Thu, Apr 30, 2015 at 5:58 PM, Bob Camp kb...@n1k.org wrote: Hi I guess the first question would be: Are we sure it’s an AL-AK and not an XL-AK? Past that it becomes a fairly involved process of, is it worth real money to get this up and running? If we are talking about a $20 eBay find that is worth another $5 to have somebody else get it running, the conversation is a real short one. If the AL-AK has some inherent value (it’s a working GPS disciplined Cs maybe) then putting a few hundred dollars into checking it out and getting it running might make sense. If it’s like most of the parts from that era, the delta between getting it checked and getting it running is pretty small. Once you *do* have it running, what do you have? 1) Leap second problems 2) GPS year rollover problems 3) Tracking issues 4) A noisy receiver with very few correlators 5) Software support issues This is an unusual box that is at least 20 years old. It *will* have at least some of the listed issues and may have all of them. Fixing them will be impossible. Why bring up all of the negatives? I for one have been sucked into this kind of thing a *lot* of times in the past. Just a few more this or that and it’ll be running fine. Much better to figure out the likely cost and outcome first. That’s *very* hard to do, and even harder to follow through on. If you can’t do the work yourself, the cost isn’t just lost time. This can cost real cash. Bob On Apr 30, 2015, at 12:50 PM, Tom Van Baak t...@leapsecond.com wrote: I received this email. Anyone have a good answer? Thanks, /tvb -- Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites. This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ... -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] TrueTime AL-AK GPS receiver help
I received this email. Anyone have a good answer? Thanks, /tvb -- Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites. This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ... -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TrueTime AL-AK GPS receiver help
Very interesting that the signal is down-converted to 4.092 MHz to match the ancient XL-AK receiver. They are intended to be sold as pairs, but it may be possible to get only the down converter. The source of the 16 MHz LO seems to be on the down side, which is OK, A separate power cable is required. So is some discussion of the application with the manufacturer. Bill Hawkins -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Alex Pummer Sent: Thursday, April 30, 2015 12:56 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] TrueTime AL-AK GPS receiver help I am not so sure that it is applying to that case, but there are GPS antenna cable extenders which converting down the incoming GPS signal to frequencies at which the cable attenuation see here: http://www.microsemi.com/products/timing-synchronization-systems/accesso ries/government/l1-gps-antenna-down-up-conv http://www.gigatest.net/symmetricom%20TTM/GPS%20%20Time%20Code%20Instr umentation/ds_gps_antenna.pdf 73 KJ6UHN Alex ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TrueTime AL-AK GPS receiver help
Well, the world's favorite search engine has several hits for a TrueTime XL-AK. There is a manual for the XL-AK 600 receiver. The PDF does not include the schematic. A down converter is listed as an option, to be mounted within a foot of the antenna. There is no discussion of the down converter beyond mounting it close to the antenna. The manual says the unit was designed in 1994 and is capable of acquiring six satellites. If the receiver input is 4 MHz, it requires the down converter at the antenna. This allows use of inexpensive cable in 1994. I'd expect this receiver to be as useless as the TrueTime GOES receiver. Antenna and converter will be hard to find, as they were probably junked separately. I would not expect the receiver to be set up by changing some dip switches. Now, if someone had the RF skills to build a GHz to MHz converter, it might work. Bill Hawkins -Original Message- From: Tom Van Baak Sent: Thursday, April 30, 2015 11:51 AM I received this email. Anyone have a good answer? Thanks, /tvb -- Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites. This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ... -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TrueTime AL-AK GPS receiver help
I am not so sure that it is applying to that case, but there are GPS antenna cable extenders which converting down the incoming GPS signal to frequencies at which the cable attenuation see here: http://www.microsemi.com/products/timing-synchronization-systems/accessories/government/l1-gps-antenna-down-up-conv http://www.gigatest.net/symmetricom%20TTM/GPS%20%20Time%20Code%20Instrumentation/ds_gps_antenna.pdf 73 KJ6UHN Alex On 4/30/2015 9:50 AM, Tom Van Baak wrote: I received this email. Anyone have a good answer? Thanks, /tvb -- Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites. This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ... -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TrueTime AL-AK GPS receiver help
I can add some insights to way-ward receivers that are missing the down converters. You can indeed fabricate replacements or like I have done for several units like Austrons adapted Odetics downcoverters in. This is not at all easy you have to be time-nutty to do this. It takes reverse engineering and than almost always a mixer and local oscillator to shift the signals around. Some of the old rockwell and other gps receivers had nice IF frequencies at 35 Mhz. Easy to work with. However the more integrated a receiver is the less likely you can access what you want like IFs and LOs. One key thing I ran into is that the receiver you want to make work has to control the first LO. So that means as an example in the Austrons case using its 10 MHz LO to multiply up and that same signal had to replace the rockwell 10 MHz crystal.This required a TTL to PECL conversion and some really small wires. You could actually go a more direct route these days and build a LO chain to 1.5 GHz using PLLs they seem pretty reasonable. Most of the converter schemes I have reversed engineered seemed to produce a 74 MHz IF or 35 Mhz. Good luck and if the receiver is going to be scrapped I might want to tinker. Good luck if you move forward. Regards Paul WB8TSL On Thu, Apr 30, 2015 at 1:55 PM, Alex Pummer a...@pcscons.com wrote: I am not so sure that it is applying to that case, but there are GPS antenna cable extenders which converting down the incoming GPS signal to frequencies at which the cable attenuation see here: http://www.microsemi.com/products/timing-synchronization-systems/accessories/government/l1-gps-antenna-down-up-conv http://www.gigatest.net/symmetricom%20TTM/GPS%20%20Time%20Code%20Instrumentation/ds_gps_antenna.pdf 73 KJ6UHN Alex On 4/30/2015 9:50 AM, Tom Van Baak wrote: I received this email. Anyone have a good answer? Thanks, /tvb -- Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites. This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ... -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TrueTime AL-AK GPS receiver help
Hi I guess the first question would be: Are we sure it’s an AL-AK and not an XL-AK? Past that it becomes a fairly involved process of, is it worth real money to get this up and running? If we are talking about a $20 eBay find that is worth another $5 to have somebody else get it running, the conversation is a real short one. If the AL-AK has some inherent value (it’s a working GPS disciplined Cs maybe) then putting a few hundred dollars into checking it out and getting it running might make sense. If it’s like most of the parts from that era, the delta between getting it checked and getting it running is pretty small. Once you *do* have it running, what do you have? 1) Leap second problems 2) GPS year rollover problems 3) Tracking issues 4) A noisy receiver with very few correlators 5) Software support issues This is an unusual box that is at least 20 years old. It *will* have at least some of the listed issues and may have all of them. Fixing them will be impossible. Why bring up all of the negatives? I for one have been sucked into this kind of thing a *lot* of times in the past. Just a few more this or that and it’ll be running fine. Much better to figure out the likely cost and outcome first. That’s *very* hard to do, and even harder to follow through on. If you can’t do the work yourself, the cost isn’t just lost time. This can cost real cash. Bob On Apr 30, 2015, at 12:50 PM, Tom Van Baak t...@leapsecond.com wrote: I received this email. Anyone have a good answer? Thanks, /tvb -- Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites. This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ... -- ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
