Author Topic: Ghetto 10MHz GPSDO  (Read 2102 times)

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Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #25 on: January 25, 2021, 01:28:53 pm »
Justanothername,

That resistor is going to the led. I lost the smd part in the carpet!

I just separated the pcbs, powering the multiplier with its own supply and things are looking as they were.

I'll work on a pcb layout and share if it improves things.
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #26 on: January 25, 2021, 01:41:23 pm »

Nope, you won't but nor would I, I tend to build things like that to get a job done and then chuck them in a box or tear them down.

SMA connectors between boards and some shielding may improve matters but I wonder how good the 2MHz input looks on that spectrum analyser and if it shows the same pattern 'divided by 5'?

If you want to explore and experiment more it's worth thinking about what you intend to achieve and how the different approaches work, all the various 'frequency standards' have advantages and disadvantages, some are great short term, some are pretty awful.

FWIW, it's not that much more difficult to 'discipline' a cheap OCXO and get a really clean signal.

It is however considerably more difficult to discipline it well :)

CJay,
I'm just a cheap tinkering old man. I just love to mess around.
I'm going to reinstate all the connectors and start spectrumizing for your delectation... hold my beer.

I know the scope likes 2Mhz, but I never shoved the spectrum on it.
The scope hated the 5X signal until I loaded it with 50R, but I'll get busy with a forthcoming slide show.

Cheers
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #27 on: January 25, 2021, 01:46:32 pm »
Is this a GPSDO?
Afaik, those Ublox modules have a TCXO in them, where the 24MHz is not disciplined ( derived/compensated ) with the GPS signal.
The 1 PPS signal is, and you need to use that with the usual controller to make it 10MHz.

I'm just farting around, Mr. NANDblog and you just made me poop. I may as well throw it in the dog.
 

Online NANDBlog

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Re: Ghetto 10MHz GPSDO
« Reply #28 on: January 25, 2021, 02:06:03 pm »
Is this a GPSDO?
Afaik, those Ublox modules have a TCXO in them, where the 24MHz is not disciplined ( derived/compensated ) with the GPS signal.
The 1 PPS signal is, and you need to use that with the usual controller to make it 10MHz.

I'm just farting around, Mr. NANDblog and you just made me poop. I may as well throw it in the dog.
What's with the attitude? I think I was civil when asking the question.
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #29 on: January 25, 2021, 02:18:31 pm »
It was an attempt at humour. Obv failed miserably.
 

Offline justanothername

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Re: Ghetto 10MHz GPSDO
« Reply #30 on: January 25, 2021, 06:55:19 pm »
Justanothername,
I just separated the pcbs, powering the multiplier with its own supply and things are looking as they were.

I guess the PLL can work with 3V3, so a low noise LDO like the TPS79333 may be used. A small pcb layout would be a nice thing to share! If you want to put something in just because you can, then go for a small battery charger to make it a portable device. The MCP733811T is an easy part to put in. VBAT is the input for the regulators then.
 

Offline shakalnokturn

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Re: Ghetto 10MHz GPSDO
« Reply #31 on: January 25, 2021, 07:08:40 pm »
Best I can do, I'm afraid.



Ohhh...!
Ali-patch-art-work!
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #32 on: January 25, 2021, 07:26:49 pm »
C'est vrai.
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #33 on: January 25, 2021, 07:41:06 pm »
justanothername,
Battery power was my first thought. Leaving off the ftdi and putting on a programming header for it, was another, but my ftdi has just given up, so might have to get another type in to try.

cheers
 

Offline justanothername

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Re: Ghetto 10MHz GPSDO
« Reply #34 on: January 25, 2021, 07:55:26 pm »
I'd say put it in, you can always choose not to solder it in. Looking forward to the result.
PM me if you need schematic design snippets for the ublox receiver with supercap instead of the battery.
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #35 on: January 25, 2021, 07:58:51 pm »
Will do.
 

Offline TheSteve

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Re: Ghetto 10MHz GPSDO
« Reply #36 on: January 25, 2021, 09:15:07 pm »
Is this a GPSDO?
Afaik, those Ublox modules have a TCXO in them, where the 24MHz is not disciplined ( derived/compensated ) with the GPS signal.
The 1 PPS signal is, and you need to use that with the usual controller to make it 10MHz.

Lady Heather would not be impressed, we all know she loves to discipline :)
Maybe this is more of a "GPS Derived Output" device.

purpose - btw, not knocking it all, I love DIY projects. It might be "Ghetto" as you call it for now, but overtime you can grow/improve it into very nice device.
VE7FM
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #37 on: Yesterday at 12:38:39 am »
Very encouraging, Steve. I'll have to get busy.
 

Offline rfclown

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Re: Ghetto 10MHz GPSDO
« Reply #38 on: Yesterday at 03:08:27 am »
Very encouraging, Steve. I'll have to get busy.

ot not. I would never discourage you from turning this into some super duper mind bending oscillator, but... I like the fact that this is simple and cheap. I've got a GPSDO, and I'm even waiting on a second one (eBay, China, don't hold my breath). But for most applications of mine, I don't need that combination of long term and short term accuracy. I like the idea of a relatively cheap reference that I know has good absolute long term accuracy.  I'd be interested in characterizing what the phase looks like in time. Does it jump occastionally to keep it in line with the 1pps?
« Last Edit: Yesterday at 04:12:31 am by rfclown »
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #39 on: Yesterday at 01:16:50 pm »
Does it jump occasionally to keep it in line with the 1pps?

Can't say I've noticed it, but how long would I have to stare at the scope to discover such behaviour? Cough.
It does however have a 20mV, or so amplitude modulation that I'd like to iron out.
 

Offline justanothername

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Re: Ghetto 10MHz GPSDO
« Reply #40 on: Yesterday at 01:21:33 pm »
I like the fact that this is simple and cheap.

+1 for simplicity and portability. Make the barrier low for others to reproduce your nice little creation, then they can help you classify it thoroughly.
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #41 on: Yesterday at 01:56:04 pm »
Simple (and cheap) was the goal, justy.
WRT battery...18650, or bigish li-po?
On board patch antenna, or sma in?

I love these design by committee projects.
 

Offline justanothername

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Re: Ghetto 10MHz GPSDO
« Reply #42 on: Yesterday at 02:05:52 pm »
WRT battery...18650, or bigish li-po?

I'd say just a JST connector, you can connect a li-po or a li-ion, the charger won't care.

On board patch antenna, or sma in?

SMA with bias if you ask me. Patch antennas are a little difficult to get good performance out of them, you need a big enough ground plane, had some serious troubles with them.
Furthermore, you mostly want to use it inside a room with the antenna outside. I'll send you a schematic screenshot via PM for a proven solution.

I love these design by committee projects.

:-+
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #43 on: Yesterday at 02:12:05 pm »
CJay's slideshow.

2MHz out of ublox into 50R. Ignore Rigol's counter. Trust me.


Same on the spectrum.


2MHz X5 no load.


2MHz X5 into 50R


10MHz sine post BPF



« Last Edit: Yesterday at 02:26:16 pm by purpose »
 

Offline purpose

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Re: Ghetto 10MHz GPSDO
« Reply #44 on: Yesterday at 02:25:46 pm »
Mr. Justy,
I'd say just a JST connector
So off board? I thought a li-po under the pcb would have been the trick, but a JST makes sense.

I'll send you a schematic screenshot via PM for a proven solution

Send away.
 

Offline geggi1

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Re: Ghetto 10MHz GPSDO
« Reply #45 on: Yesterday at 08:58:16 pm »
These UBLOX gps modules have a clock that runs on 48Mhz.
The frequency on the puls output must be a even number of 48 to get the cleanest square puls out.
Frequencies like (Mhz) 24 , 16, 12 , 8 , 6 , 4 , 3 & 2 are the cleanest frequencies.
 
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