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FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
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Johnny B Good:

--- Quote from: rhb on March 21, 2019, 02:05:37 am ---There were 3 signal sources,  The 6600, the 33622A and Leo's 100 ps impulse.  The DSO sinc(f) issue is *only* visible on the 100 ps signal when the DSO is sampling at 1/10th of the pulse duration.

I have one of Leo's two  channel GPSDOs which has been extremely satisfactory.  The single channel version is cheaper.

I bought a 6 output 10 MHz GPSDO from Roadrunner, but have not yet gotten around to testing it.

--- End quote ---

 I realise it's been over three weeks since you posted this but I was just reviewing the last page of this forum after checking out ebay for cheap GPSDOs and reading the other EEVBlog BG7TBL forum discussion so your remarks about Leo's GPSDO units rather caught my attention this time round.

 After what I'd read about the BG7TBL units and the fact that they seem to be based on an FLL rather than a PLL (accounting for the almost insignificant 0.15Hz frequency error in these units), I decided to take a fresh look at alternative "cost effective" GPSDOs and landed up on Leo's web site, scrutinising his GPSDO offerings which looked rather nice for the money.

 However, the big turn off for me is the use of a VCTCXO rather than a VCOCXO, so as nice as they looked for the money, they don't quite meet my expectations. They might stay locked to GPS time, unlike those BG7TBL units, but, again unlike the BG7TBL units, won't have the short term stability of a half decent VCOCXO based unit.

 I was only browsing on the off chance of finding a cheap bargain basement unit to tide me over the next fortnight before I get my chance to pick up a  VCOCXO or two at a radioham rally (along with a few other bits 'n' bobs needed for my GPSDO project). I'm seriously thinking of having a go at building that diy-gpsdo-with-arduino-and-1ns-resolution-tic designed by the late Lars Walenius who, rather sadly, passed away on the 28th Dec last year.

 <https://www.eevblog.com/forum/projects/lars-diy-gpsdo-with-arduino-and-1ns-resolution-tic/>

 I'd already (rather speculatively) bought myself an Arduino Nano module when I bought the GPS module, both purchases inspired by Scully's youtube tutorial videos <https://www.youtube.com/watch?v=lbns-FvpzK4>.

 The Lars version will put the Arduino Nano to a less demeaning use than the one it was fated for in the Scullcom GPSDO project which was basically just a cheap 'n' cheerful frequency calibration standard offering no better performance than the bare NEO M8N module I'd bought.

 It's taken me several weeks of pissing around with the GPS module, a sig genny and a 'scope to realise that the heart of any decent GPSDO is its VCOCXO module. That comes first and foremost in the BOM. The rest of the BOM is just the after-market paraphernalia required to bolt whatever choice of GPS that happens to conveniently suit the task (virtually any of the more recent units possessed of a 1PPS output signal) and, optionally, provide "Das Blinken Lights und Switchen"(tm).

 Between my own experiences with TCXOs (the one I'm using in the Feeltech and the one in the u-blox M8N module) and from what I've read on the subject, I know that VCTCXOs aren't in general a good substitute for the VCOCXOs normally used in GPSDOs. That being said, I'm wondering whether you've had a chance to compare that Bodnar unit against any other GPSDOs, possibly that Roadrunner unit you hadn't gotten round to using as of  three weeks ago.

 I know that testing the performance of GPSDOs can be rather time consuming but I reckon it's something worth doing with that Bodnar unit even if it's merely to satisfy idle curiosity about the VCTCXO versus VCOCXO debate in their use as a GPS disciplined oscillator reference source for driving (to keep it on topic) a modified FY6600 for example.  :)

 I just did a quick search for reviews of these Bodnar units and discovered this interesting document file:-

<http://leobodnar.com/files/Informal%20Evaluation%20of%20a%20Leo%20Bodnar%20GPS%20Frequency%20Reference.pdf>

<https://tinyurl.com/y4fgs8oz>

 It gives a fair assessment these TCXO based units with no surprises. A couple of months back, I might have bought the single channel version. I guess my naivety which had led led me to believe I could maybe knock up a poor man's GPSDO version sans the expense of a VCOCXO for a fraction of the price must have put me off buying one.

 TBH, I was seriously considering ordering the £99.99 one just now since, in spite of the compromised phase noise performance, it's still a well made handy little test and calibration unit for very little money but sense prevailed after reading through that report. At the end of the day, it isn't quite up to the standard I'm hoping to ultimately achieve with my own DIY GPSDO project.

 Don't get me wrong, it's a vast improvement over what I'd been hoping to initially achieve but now that "I've seen the light"(tm), I don't want to take any prisoners in my quest to assemble a home brewed GPSDO of my very own manufacture. I've just got to sit tight for the next two weeks in the hope that I'll be able to do a face to face deal at the radioham rally on a used but good quality VCOCXO module or three (and likewise for the other bits needed to glue it all together).

JBG
rhb:
OK, this tops it all!!!

I just got the May/June 2019 issue of QEX.  On the front page is an FY6600 which was converted into a WSPR transmitter by the author.  The article references this thread, so hopefully he'll see this and share some details of the project for readers who don't have access to QEX.

He did the TXCO, output amp and mains cord modifications.
2N3055:

--- Quote from: rhb on April 17, 2019, 04:43:22 pm ---OK, this tops it all!!!

I just got the May/June 2019 issue of QEX.  On the front page is an FY6600 which was converted into a WSPR transmitter by the author.  The article references this thread, so hopefully he'll see this and share some details of the project for readers who don't have access to QEX.

He did the TXCO, output amp and mains cord modifications.

--- End quote ---

That article is free sample on arrl.org

http://www.arrl.org/files/file/QEX_Next_Issue/May-June2019/Steber.pdf
rhb:
Very cool!
Miti:

--- Quote from: Johnny B Good on April 15, 2019, 02:15:07 am --- After what I'd read about the BG7TBL units and the fact that they seem to be based on an FLL rather than a PLL (accounting for the almost insignificant 0.15Hz frequency error in these units), I decided to take a fresh look at alternative "cost effective" GPSDOs and landed up on Leo's web site, scrutinising his GPSDO offerings which looked rather nice for the money.

--- End quote ---

If you're looking for cost effective GPSDO take a look at this
https://www.eevblog.com/forum/projects/my-u-blox-lea-6t-based-gpsdo-(very-scruffy-initial-breadboard-stage)/msg929949/#lastPost

I tested it on a breadboard and it works really well.
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