Test Equipment Anonymous (TEA) group therapy thread

[mnementh]

Looks like a GPSDO is not in the budget just yet.

Does anyone have some creative ideas on how to check 10MHz sine waves to some level of accuracy?

Before we had al this modern stuff it used to be WWV.

https://en.wikipedia.org/wiki/WWV_(radio_station)

You need to wrap [ URL ] tags around anything ending with a paren; eevBlog will truncate the URL if you don't. Then your link takes you weird places... 

https://en.wikipedia.org/wiki/WWV_(radio_station)

mnem
Verticalness is highly overrated.

[mnementh]

Don't listen to dat assh'o; he's not awake yet. 

mnem
*buggering off to make a mess in his cold-ass garage*

[mnementh]

In Australia, we had VNG - but that all shut down in 2002.

Yeah, WWV is supposed to celebrate its centennial in October; 100 years of continuous broadcast by the NIST. It is supposedly funded through 2019, so that may actually happen. Of course, they may padlock the doors the day after. 

mnem
Cynic...? Isn't that where you wash the dishes-nic after your picnic?

[Kosmic]

Looks like a GPSDO is not in the budget just yet.

Does anyone have some creative ideas on how to check 10MHz sine waves to some level of accuracy?

You could also buy one of those cheap Bliley OCXO from ali or ebay. Put it in an enclosure with a quiet power supply. Then send it to "beanflying cal lab" for calibration. you should get back a decent 10Mhz source.

[ArthurDent]

"You could also buy one of those cheap Bliley OCXO from ali or ebay. Put it in an enclosure with a quiet power supply. Then send it to "beanflying cal lab" for calibration. you should get back a decent 10Mhz source."

That probably wouldn't give you the results you want. Powering down an OCXO then reapplying power is not the way to get maximum stability (accuracy is another subject). I have one crystal frequency standard that has been powered (except for battery changes) for over 35 years so I have pretty good info on how that oscillator behaves. Here is what one manufacturer says:

 "What does all this mean in practice? First, an ovenized oscillator should be continuously powered if at all possible. If power interruptions are unavoidable, be aware that the oscillator will take some time beyond normal warm-up to return to the prior aging rate and, because of aging and hysteresis, is unlikely to return to exactly the same frequency. Hysteresis for AT-cut resonators is unlikely to be much better than a few parts in 10-8. Frequency adjustment during the re-stabilization period is not a good idea."

A rubidium standard has almost no retrace but for maximum stability and accuracy should be powered on for at least a day. It is best for both rubidium and crystal standards to calibrate them in place after they have been powered for quite some time and a GPSDO is one of the best and cheapest ways to do this.

Here's a couple of photos of some frequency standards and a couple of GPSDOs. Note the error on the GPStarplus is -8.56E-13 after running for a day.

[mnementh]

In Other News...


https://www.immersionrc.com/fpv-products/rfpowermeter/

I've had one of these for several years; it's pretty much essential gear for anyone serious about RC, and absolutely necessary if you fly FPV with other pilots. It was their first version; and as such, was a bit buggy. While they did a good job with the device itself, and the testimony of people a lot more knowledgeable than myself says that the meter is pretty accurate (this is a relative statement; but 0.1-5% of scale is probably right), there were some issues. Because of a poor choice in attenuators included with the device, accuracy in the now-critical 5.6-6.0GHz range was pretty much out to lunch thanks to poor absolute accuracy and steep VSWR Slope due to the atten operating right at the upper limits of its design.

I discovered this, and published to the RC community some pretty extensive testing which showed that with the substitution of a decent 18GHz Avionic-grade atten, results were much more linear and useful. As you might imagine, that revelation made a bit of a mess in some circles. *   My "hindsight is 20/20" assessment is that at the time they were designing the thing, 5.8GHz video was pretty new, so they expected the thing to be used primarily in the 1.2-2.4GHz range and testing at 5.8GHz was probably not as thorough as it could have been. However, as the device was more than accurate enough once upgraded with a decent atten, I considered the point moot and moved on with my life, so I never did acquire the expensive gear needed to test its absolute accuracy.


https://www.immersionrc.com/fpv-products/rfpwrv2/ - $79 "Introductory Pricing"

Fast-forward to today, and I find myself reading up on the v2; I'm planning to get back into FPV, and I've known they were going to release this new version for a while; it's been out almost a year now. I'm actually pretty impressed with what they've stuffed into this little thing; looks like they've incorporated some of the LaForge FPV VRX spectrum analyzer code, and according to the specs, the meter is calibrated at 35, 72, 433, 868, 915, 1200, & 2400MHz plus at 5600-6000MHz in 50MHz steps. Also interesting is that they've incorporated a CDC stack; you can actually do logging with this little beast. 

So, hopefully, this version will be all that and a bag of chips; at $79 (!!!), it's also about half what my v1 cost. I have one on the way (Actually I got the RotorRiot version for the extra included adapters); should be here in a day or two.

What I wanna know now is... from all you RF HEADS out there... What testing dooya want me to do with it?

Tell me what you want and how to set it up, and I'll do my best. I've attached the latest user manual as a .pdf; you can see specs & tech in there.

Cheers,

mnem
Where is the "kick eevBlog in the 'nads" button on my keyboard; I need it right now!!!

* (If you look at around 00:45 of this J. Bardwell vid, you'll see a brief mention of what I'm talking about, as well as an overview of the device aimed at RC/FPV enthusiasts and discussion with one of the IRC engineers)

[Kosmic]

That probably wouldn't give you the results you want. Powering down an OCXO then replying power is not the way to get maximum stability (accuracy is another subject). I have one crystal frequency standard that has been powered (except for battery changes) for over 35 years so I have pretty good info on how that oscillator behaves. Here is what one manufacturer says:

 "What does all this mean in practice? First, an ovenized oscillator should be continuously powered if at all possible. If power interruptions are unavoidable, be aware that the oscillator will take some time beyond normal warm-up to return to the prior aging rate and, because of aging and hysteresis, is unlikely to return to exactly the same frequency. Hysteresis for AT-cut resonators is unlikely to be much better than a few parts in 10-8. Frequency adjustment during the re-stabilization period is not a good idea."

A rubidium standard has almost no retrace but for maximum stability and accuracy should be powered on for at least a day. It is best for both rubidium and crystal standards to calibrate them in place after they have been powered for quite some time and a GPSDO is one of the best and cheapest ways to do this.

I might be mistaken but i'm not sure Brumby was looking for something super precise.

Overall I agree with you though.

[mnementh]

Or one can go to Italy and drink real coffee.

The Italians may have created the Espresso process but they certainly are not any better at it than others and a lot of the coffee produced is over roasted muck. As to real coffee I prefer to go to my Shacks workbench for 'real coffee' and to the other end to Roast it. 

https://youtu.be/12zGrkHceOM

https://youtu.be/qMrlyEreba8

Speaking of workbenches... I stumbled across this and immediately thought of you. And Aluminum vs Alzheimer's. 

mnem
whuu-we-talkin-about?

[PA0PBZ]

Tell me what you want and how to set it up, and I'll do my best. I've attached the latest user manual as a .pdf; you can see specs & tech in there.

Do you have any kind of calibrated RF source? There's not much you can do without that.

[beanflying]

Speaking of workbenches... I stumbled across this and immediately thought of you. And Aluminum vs Alzheimer's. 

mnem
whuu-we-talkin-about?

Love This Old Tony's channel but maybe go modern instead  I do have several Moka Pots and an old Atomic but I don't like the brew that much.

https://youtu.be/OzfXVH59LjM

[mnementh]

Works for me... and iron is good for my flame. 

mnem
"Horseshoes again mommy? Awww... they taste like pony feet."

[Brumby]

That probably wouldn't give you the results you want. Powering down an OCXO then replying power is not the way to get maximum stability (accuracy is another subject). I have one crystal frequency standard that has been powered (except for battery changes) for over 35 years so I have pretty good info on how that oscillator behaves. Here is what one manufacturer says:

 "What does all this mean in practice? First, an ovenized oscillator should be continuously powered if at all possible. If power interruptions are unavoidable, be aware that the oscillator will take some time beyond normal warm-up to return to the prior aging rate and, because of aging and hysteresis, is unlikely to return to exactly the same frequency. Hysteresis for AT-cut resonators is unlikely to be much better than a few parts in 10-8. Frequency adjustment during the re-stabilization period is not a good idea."

A rubidium standard has almost no retrace but for maximum stability and accuracy should be powered on for at least a day. It is best for both rubidium and crystal standards to calibrate them in place after they have been powered for quite some time and a GPSDO is one of the best and cheapest ways to do this.

I might be mistaken but i'm not sure Brumby was looking for something super precise.

Overall I agree with you though.

What I am after is something I can use to be able to check out the timebase oscillators in my 8656B so I can offer it for sale at an appropriate price.

I'm not going to be able to keep it.

[beanflying]

Doing some playing on the bench over my morning coffee. The setup is fairly horrid but what it shows is the UBlox M8N can generate a 'reasonable' shape and accuracy waveform. Now for the downsides.

It only generates 'reasonable' non horrible jitter at the following frequency steps. 12, 8, 6, 4.8, 6, 3, 2.4, 2, 1 MHz which are all integer divisible from 24MHz. U-Center only allows whole number frequency steps to be sent to the device so it is limiting for higher frequencies without jitter. **Full Bandwidth shown on the Micsig with all the other gear and the screen is 20M filtered.

Setup an RC filter (haven't done any numbers) to generate a Sine wave which should also drop some of the other rubbish too. Take the 10MHz output from your DUT set the UBlox to 8MHz and generate a 5:4 Lissajous on a scope in XY check the drift and for $20 AUpesos you have a reference that isn't horrid. Worth a crack at least.

[beanflying]

Forgot - The other option is you take one of the lower frequencies and feed it into a PLL Multiplier to get a 10MHz. Only a few $ for a lot of them.

[Brumby]

That's OK - I'd already started thinking about a PLL 'fix'.



This is it, isn't it?   This is how time nuttery starts.......

[med6753]

That's OK - I'd already started thinking about a PLL 'fix'.



This is it, isn't it?   This is how time nuttery starts.......

 

[mnementh]

Antidote. 

mnem
Or at least a delaying tactic... 

[Brumby]

They laugh....


... methinks too much.

[Brumby]

Tried looking on Aliexpress for OCXO and GPSDO sources, but some of the descriptions leave a question mark about what I would get.

For example: This is the description on a listing of a $US135 GPSDO
"GPS tame clock module board, this price does not contain detection, can ensure no obvious device damage. Customers who have the intention to contact the customer service and then confirm the order, after the confirmation of the two sides, sold without refund."

Sounds like a crap shoot to me....

[Kosmic]

Tried looking on Aliexpress for OCXO and GPSDO sources, but some of the descriptions leave a question mark about what I would get.

For example: This is the description on a listing of a $US135 GPSDO
"GPS tame clock module board, this price does not contain detection, can ensure no obvious device damage. Customers who have the intention to contact the customer service and then confirm the order, after the confirmation of the two sides, sold without refund."

Sounds like a crap shoot to me....

90$us https://www.ebay.com/itm/NEW-10MHz-Sinwave-PLL-GPSDO-GPS-DISCIPLINED-OSCILLATOR-adapter-GPS-ANT/262038924752?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649&redirect=mobile

This is a bg7tbl gpsdo come with antenna and power adapter. I don't think you can find cheaper than that.

[tautech]

And there's Leo's GPS disciplined modules:
http://www.leobodnar.com/shop/index.php?main_page=index&cPath=107

[beanflying]

What I have eBay auction: #253375324294

From the same seller eBay auction: #254152420977 without the extra outputs. Seems Very Very cheap but might be worth a crack just make sure you use Paypal as belts and braces protection. If it is based on a similar design to mine construction is better than most. The seller does know something about the product too.

Several hours Later and now disconnected from the PC with the 8MHz stored on the boards memory. BORING 

[worsthorse]

90$us

https://www.ebay.com/itm/NEW-10MHz-Sinwave-PLL-GPSDO-GPS-DISCIPLINED-OSCILLATOR-adapter-GPS-ANT/262038924752?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649&redirect=mobile

This is a bg7tbl gpsdo come with antenna and power adapter. I don't think you can find cheaper than that.

I bought one of these a month ago and tested it against an OXCO and my 8640B. Another ham, K7QO, tested another against a rubidium source. We came out in the same place, a drift of less than +/- 1Hz, after it warmed up. Good enough for the kind of stuff I do, especially for 90USD. 

One note: the NMEA string output (on at least some versions) has an inverting buffer. To use the NMEA strings you have to bypass it or add another one in line.

[Brumby]

90$us https://www.ebay.com/itm/NEW-10MHz-Sinwave-PLL-GPSDO-GPS-DISCIPLINED-OSCILLATOR-adapter-GPS-ANT/262038924752?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649&redirect=mobile

This is a bg7tbl gpsdo come with antenna and power adapter. I don't think you can find cheaper than that.

That's veeeery tempting.

[Brumby]

From the same seller eBay auction: #254152420977 without the extra outputs. Seems Very Very cheap but might be worth a crack just make sure you use Paypal as belts and braces protection. If it is based on a similar design to mine construction is better than most. The seller does know something about the product too.

I've put that on my watch list - and I always use PayPal for eBay purchases.  I know I'll probably prefer extra outputs somewhere down the track - but with a decent reference and a decent PLL design, I should be right for a while.



Edit: Bean the enabler, yet again ... but this time I'm in the mood to thank him....?

This rabbit hole is starting to feel comfortable.  Move over Faust.