Wow, even located outside it is having some issues. The survey has now been suspended because it no longer has 4 satellites tracking. Really piss-poor GPS in this thing, I guess. I guess I'll have to get the antenna up on the roof to use it.
Wow, even located outside it is having some issues. The survey has now been suspended because it no longer has 4 satellites tracking. Really piss-poor GPS in this thing, I guess. I guess I'll have to get the antenna up on the roof to use it.
What signal strengths are you seeing for the satellites? How do they compare to the screen capture I posted back on page 4? I have a VIC-100 Timing Antenna with about 38 db gain + 100 ft. of RG-59 coax (about 11 db loss @ 1.5 GHz) plus a few couplers and short cables, so call it 25 db gain to the receiver.
Ed
Wow, even located outside it is having some issues. The survey has now been suspended because it no longer has 4 satellites tracking. Really piss-poor GPS in this thing, I guess. I guess I'll have to get the antenna up on the roof to use it.
What signal strengths are you seeing for the satellites? How do they compare to the screen capture I posted back on page 4? I have a VIC-100 Timing Antenna with about 38 db gain + 100 ft. of RG-59 coax (about 11 db loss @ 1.5 GHz) plus a few couplers and short cables, so call it 25 db gain to the receiver.
Ed
Here's a screen capture of the signal strength window. I'm not sure what units those are - something proportional to dBm I suspect. Looks like my signals are not as good. Looks like you are farther north than me, so I don't think it's my latitude. Maybe antenna, the adapters I have on both ends of the cable, or the coax itself.
Here's a screen capture of the signal strength window. I'm not sure what units those are - something proportional to dBm I suspect. Looks like my signals are not as good. Looks like you are farther north than me, so I don't think it's my latitude. Maybe antenna, the adapters I have on both ends of the cable, or the coax itself.
Those levels are just fine. C/N stands for carrier to noise level. I don't remember what the reference is. Levels above 50 are unusually good. Above 40 is good. Above 30 is okay. You'll find that those levels will change from satellite to satellite and if there are any trees or buildings around, the level from a particular satellite will change as it moves across the sky and is either blocked or has multipath problems.
You should do just fine with those signals. I didn't notice how long mine took to do the survey. I'm guessing it was only a few hours at most. If it has to stop and start the survey, it will obviously take longer. I have an absolutely clear view of the sky from east to south to west so it has no problem here.
By the way, that same signal level info is in the output of the :SYST:STAT command. That's where Z38xx gets it from.
Ed
Do you know what the receiver is inside the gps box?.
Do you know what the receiver is inside the gps box?.If you send this command via the RS422 Diagnostics port:
:DIAG:IDEN:GPS?
It reports this:
"COPYRIGHT 1991-1997 MOTOROLA INC.","SFTW P/N # 98-P36848P ","SOFTWARE VER # 2 ","SOFTWARE REV # 2 ","SOFTWARE DATE APR 24 1998","MODEL # R5122U1152 ","HWDR P/N # 5 ","SERIAL # R05582 ","MANUFACTUR DATE 9D12 "," "
Here's a screen capture of the data displayed by the Z38XX program. There's a big gap in the charts because my computer went to sleep last night. The stability looks similar to that shown in Ed's chart - it bounces back and forth between +/-40ns. HUD was very high, but after running with a GPS lock for some time, it finally dropped to 8.7us.
Here's a screen capture of the data displayed by the Z38XX program. There's a big gap in the charts because my computer went to sleep last night. The stability looks similar to that shown in Ed's chart - it bounces back and forth between +/-40ns. HUD was very high, but after running with a GPS lock for some time, it finally dropped to 8.7us.
I'm glad you were able to calibrate your counter. If you decide to leave your GPSDO online permanently, you could consider using it as the external reference for your counter. The short-term jitter might be a problem. I haven't tried that.
The EFC on mine was wandering up and down, which caused the HUP to do the same. Your EFC looks much nicer. Your HUP will likely keep dropping. As that happens, you should see a decrease in the peak-to-peak excursions on the time interval graph.
Ed
I found out why my RFTG-0 unit was AFU, turns out I must have damaged a resistor causing the EFC voltage to wonder from one extreme to another. Replaced the damaged part and it seems to be working again
From a cold start it takes less than 20 minutes for the NO GPS to go off using a decent outdoor antenna.
Stability seems ok for my needs. After running overnight and sitting directly under a ceiling fan and the AC cycling the short term frequency deviates less than .0004Hz according to my 53131A.
Still getting gibberish from com port. Tried several different Prolific RS232 to USB adapters on 2 different PC's, Win 7 and XP. Must be something real obvious that I am missing and just dont see it ?
Here's the pinout of J6 if anyone is interested:
J6 goes to U37, U38, U39 (75176 Differential Bus Transceiver)
J6.1 --- U38.6
J6.2 --- NC
J6.3 --- GND
J6.4 --- U39.6
J6.5 --- U37.6
J6.6 --- U38.7
J6.7 --- GND
J6.8 --- U39.7
J6.9 --- U37.7
FWIW. I have a Thunderbolt GPSDO and a $5 car-top mag-mount amplified antenna from e-bay that looks like a hockey-puck. It's mounted at 25 feet to clear the peak of my roof and fed with about 50 feet of cable TV coax. One hour after a cold start I have acquired seven of eight possible satellites and the 10 MHz output is within +/- .05 ppb according to the T-bolt monitor programme.
Ken
Toronto, Canada
I have a Thunderbird also but its an older version and twice as wide. Its front end isnt too bad, able to pick up 4 birds with an el-cheapo Chinese mag mount inside the house.
Those new GPSDO on fleabay from China are using much newer (AND BETTER) front ends. All 3 of mine will lock on to 4 birds with just a 2" piece of wire stuck into the antenna jack.
On those $5 GPS antennas I found that the round ones have at least 2 units stronger received signal than the squarish types.
Just stuck one of the round ones on a 20ft. pole wich is above my roof so now I will have a CLEAR view of all the birds.
Vidas
I have a Thunderbird also but its an older version and twice as wide. Its front end isnt too bad, able to pick up 4 birds with an el-cheapo Chinese mag mount inside the house.
Those new GPSDO on fleabay from China are using much newer (AND BETTER) front ends. All 3 of mine will lock on to 4 birds with just a 2" piece of wire stuck into the antenna jack.
On those $5 GPS antennas I found that the round ones have at least 2 units stronger received signal than the squarish types.
Just stuck one of the round ones on a 20ft. pole wich is above my roof so now I will have a CLEAR view of all the birds.
Vidas
Can you post a link to the newer/better GPSDO you are speaking of? THere are a lot of GPSDO on eBay.
After I purchased 4 of these he jacked his price up LOL
I really like these units, nice and small AND brand new except for the salvaged OCXO they are using.
They have 2 flavors, sine or square wave output so do a search on them.
One thing I read about these tho is that there is a slight bug in its firmware and they run just a touch on the slow side but its so minute that I cant measure it nor will it make any difference for me. I think its somere in the beginning of this thread ?
http://www.ebay.com/itm/HW-HUAWEI-GPS-DISCIPLINED-CLOCK-GPSDO-OSCILLATOR-Antenna-power-supply-/111716558224?hash=item1a02d36590
Wiss, Let us know how your new toy works when you get it
Your right, these are something new, sorry about that. The ones I got are the ones with the MORION OCXO: http://www.ebay.com/itm/10MHZ-OUTPUT-SINE-WAVE-GPS-DISCiPLINED-CLOCK-GPSDO-GPS-Antenna-Power-supply/181793953652?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3Dc0a0dd3ba68d468a8bd57e5c5a38479e%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D181800366117
After I purchased 4 of these he jacked his price up LOL
I really like these units, nice and small AND brand new except for the salvaged OCXO they are using.
They have 2 flavors, sine or square wave output so do a search on them.
One thing I read about these tho is that there is a slight bug in its firmware and they run just a touch on the slow side but its so minute that I cant measure it nor will it make any difference for me. I think its somere in the beginning of this thread ?
http://www.ebay.com/itm/HW-HUAWEI-GPS-DISCIPLINED-CLOCK-GPSDO-OSCILLATOR-Antenna-power-supply-/111716558224?hash=item1a02d36590
Wiss, Let us know how your new toy works when you get it
Are you sure these are the ones you bought? I've just noticed that there are now three different GPSDOs on ebay that all have this same aluminum+PCB case. The one you posted actually uses an Oscilloquartz 'Star 4' board. I found a datasheet on that, but no user manual. The second is the home-made one that appears to be running slightly slow. The third is a Trimble unit. I bought the bare Trimble unit from somewhere else and just powered it up yesterday. I can't find any data on it, but it uses a command set that is somewhat similar to the Z38xx series. It only took about 10 minutes from a cold start to figure out where it was and lock the oscillator! I didn't even have time to get the PC connected!
Ed
Thanks for the info Moto !
It was my fault that caused damage. I removed the board to look around for a good point to tap off 10Mhz sine output. Anyways, when I was putting the board back into the case I must have hit the resistor on one of the chassis mounting lugs that the board is mounted to.
Off I go to put a little more altitude on one of the GPS antennas.
tnx again 73
Vidas