[time-nuts] nuts about position (cheap receiver)
Well, I processed the Lady Heather .raw capture file from the $24 LEA-5T through RTKCONV and submitted it to CSRS-PPP and it worked. Using the less precise instant orbits it says the 95% sigma errors are: lat: 0.169m lon:0.148m alt: 0.399m My antenna is that Chinese L1/L2/Glonass/etc antenna from ebay. I'll re-submit the data next week and see how it changes. Also, I now sort-of have Heather outputting a RINEX 3.02 format .OBS file. Oh, and Bob... Heather can run an external program at a given time or after a specified interval, so could be set up to automatically submit the file... you lazy bastard ;-) ___ 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] nuts about position (cheap receiver)
On Wed, May 2, 2018 at 2:54 PM, Mark Sims wrote: > Well, I processed the Lady Heather .raw capture file from the $24 LEA-5T > through RTKCONV and submitted it to CSRS-PPP and it worked. Using the less > precise instant orbits it says the 95% sigma errors are: lat: 0.169m > lon:0.148m alt: 0.399m > > My antenna is that Chinese L1/L2/Glonass/etc antenna from ebay. I'll > re-submit the data next week and see how it changes. Was the solution using the NRCan hourly's or the IGS Rapid products ? (It should say in the email response or the .sum file: the 'Satellite orbits/clocks' lines seem to have 'emu', 'emr' or 'igs' for the NRCan hourly/UltraRapid, Rapid and Final solutions respectively). Submittals less than a day after the observations in the RINEX file seem to result in the use of the Hourly/UltraRapids solutions. Cheers, Tim ___ 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] Adret 4100 compared to the Tracor 527
Hi all Thank you for the information relating to the Racal 9475 Rubidium I will start work on it at the week end Can any one come back with the advantages / disadvantages of the Adret 4100 compared to the Tracor 527 frequency difference multiplier also how much they normally cost Regards Paul B ___ 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] nuts about position (cheap receiver)
For the orbits is says "Precise", so maybe not even the hourly ones. I could not find any mention of emu, emr, or igs. Heather can now spit out Rinex 3.02 files (at least for GPS/SBAS sats).I am currently feeding Heather the .raw capture file I sent to Canada and outputting a RINEX .OBS file. I'll send that off to them and see if there is any difference in the results from the one from RTKCONV. The RTKCONV processed values for pseudo ranges and carrier phase values seems to have been tweaked from what the receiver sent... they differ by a fractional amount. - > Was the solution using the NRCan hourly's or the IGS Rapid products ? (It should say in the email response or the .sum file: the 'Satellite orbits/clocks' lines seem to have 'emu', 'emr' or 'igs' for the NRCan hourly/UltraRapid, Rapid and Final solutions respectively). ___ 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] nuts about position (cheap receiver)
G... Canada lives in the dark ages and does not accept RINEX version 3... I'm now trying Australia... Version 3 is cleaner and easier to write than Version 2... ___ 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] Racal 9475 Rubidium
Greetings Paul, The Racal 9475 does have some inherent shortcomings, the principal one is due to the power supply and the lack of the purpose-designed heat sink for the FRK module. The unit is built into a “heat-sink case” but to keep the FRK base plate within the specified temperature range Racal had to operate it from a 23.5 V supply. The power supply originally had a magnificent C-core transformer which produced a rather too-high output voltage consequently the raw d.c. supply was rather high. The main supply voltage regulator has a rather weird configuration to facilitate heat sinking the pass transistor to the case and this unfortunately precludes using a battery back-up. What Racal overlooked is that with a linear regulator the total amount of heat dissipated is sensibly constant so the FRK module dissipates less heat than if it were operated at a higher voltage and the PSU pass transistor dissipates more heat. When the case is opened a well-used 9475 usually stinks of “hot electronics”! The problem is compounded by the fact that the 5 V logic supply regulator is not adjustable, it is essentially a high current follower from the tap of the R62/R63 potential divider across the 23.5 V main supply rail. In my experience, FRK modules produce their best performance when operated from a supply voltage between 27 V and 28 V, selected for individual units but 27.6 V is a good starting figure. At this voltage the FRK module needs the special heat sink if operated at high ambient temperature. More recent versions of the 9475 have a good but lower-quality mains transformer (perfectly adequate for its intended purpose) which has a lower output voltage and this has mitigated the heat dissipation by the PSU pass transistor. The first thing to do is to monitor the voltage of the 5 V logic supply (between TP2 and TP3) and increase the voltage of the 23.5 V main supply rail (R39) until the 5 V rail is as much above 5 V as you care to risk for the 74-series ICs used. A safe starting point is 5.2 V but I am wary of going too close to 5.5 V. I have succeeded in getting several recalcitrant 9475s working properly by this simple ploy of increasing the supply voltage to the FRK module. In my experience an FRK module operated a with a supply voltage lower than 24 V is prone to failing to lock or intermittent locking after long use. The complete cure is to increase the value of R36 to produce 5 V with the voltage measured between TP2 and TP3 with the 23.5 V rail wound up to between 27 V and 28 V. This cures the high internal dissipation problem and considerably improves the performance of the FRK module but the special heat sink is necessary for operation in high ambient temperature or with poor ventilation. There are a few incidental modifications which I like to do to 9475s. They were designed when one could have whatever colour of LEDs which one wished provided that the colour was red! I like green LEDs for the “normal” situation and with the ready availability of LEDs of different colours it is easy to follow the IEC recommendation of orange for “power on” and green for “normal situation”. The “Rb lock” indicator (LP50) is already green but it is worth changing the “Power on” indicator (LP51) to orange or yellow and I consider it essential to change the “1 MHz” indicators (LP52, LP53, and LP54) to green. If 4 greens are showing the unit is locked and the outputs are OK which is perceived with a quick glance. These mods and adjustments are simple and easy to do. Unfortunately it is not nearly so easy to arrange a battery back up facility so it is wise to operate the unit from a UPS. The warm-up frequency drift of an FRK module is still detectable 6 weeks or 1000 hours after starting from cold. The 9475 was apparently intended for supplying the 1 MHz reference frequency for the synthesisers in Naval communications equipment and its drift is sufficiently low for this application within about 2 hours of starting from cold, however Time-nuts are more discerning! At the time of the introduction of the 9475, Racal were the agents for Efratom but went to great lengths to save the cost of the special heat sink for the FRK module and in my opinion “spoiled the ship for a ha’p’orth of tar” (for US readers ha’p’orth is a colloquial expression for a “half-pennyworth” of old UK money, about 1/250th of 1 US$ at the present rate of exchange). False economy is also the reason for the 5 V regulator in the 9475, at the time of its design 7805 regulators cost an arm and a leg! There are not really any other worthwhile mods. The quality of the 1 MHz outputs is remarkably good considering how they are derived. In my experience FRK modules usually work satisfactorily if the “lamp voltage” is above 5 V (it should really be above 8 V but rarely is in disposal units). It is also worthwhile to occasionally tweak the FRK trimmer to keep the oscillator control
[time-nuts] nuts about position (cheap receiver)
I tried submitting Version 3 files to several services... none support Version 3!Heather now creates the uglier/less readable Version 2.10 RINEX, ___ 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] nuts about position (cheap receiver)
On Thu, May 3, 2018 at 9:40 AM, Mark Sims wrote: > G... Canada lives in the dark ages and does not accept RINEX version > 3... I'm now trying Australia... > > Version 3 is cleaner and easier to write than Version 2... > RTKLIB's RTKCONV can convert between RINEX versions. ___ 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] nuts about position (cheap receiver)
The goal is to make it as simple as possible and have Heather do all the receiver configuring, data capture, and RINEX making... with none of that tedious mucking about in RTKLIB Currently all I have to do is fire up Heather and tell it to write a log file with the .obs extension. -- > RTKLIB's RTKCONV can convert between RINEX versions. ___ 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.
