[time-nuts] FSA3011 Frequency Stability Analyzer

[Tom Van Baak]

Yes, I'm evaluating a FSA3011 at the moment. It's a cute little unit. 
Documentation is sparse, the jpg plots are fuzzy, "customer" support is 
nil, but it works. My initial tests show it's ~4x worse than the data 
sheet claims but it turns out the unit is quite dependent on the rise 
time and power of the input signals so YMMV.

With 10 MHz sine inputs from a tee the noise is about 3 ps @1 s. I'm 
checking different frequency and waveform combinations in an attempt to 
obtain the "<1 ps" value implied by the specs.

The output is phase difference, about once a second. Readings look like 
"0.000000000591884\n". Note that last digit is 1 fs, which is 
ridiculous. It's like marketing said, "let's make this go to 15". In 
fact only 11 or 12 digits contain actual information. Then again the 
TAPR/TICC has a similar problem with excessive digits so who am I to 
talk. For the most part, fake digits don't hurt, but realize that 
spitting out 15 decimal places does not in any way imply the device can 
measure to that level.

The block diagram says it's a dual-mixer. It follows a very minimalist 
design. Just two SMA inputs and a 115.2 kbaud serial-over-USB output. No 
switches, no modes, no input commands, no GUI; a couple of labeled LED's 
-- my kind of "do one thing, do it well, and do it quietly" device. 
Startup time (power-up to first reading) is ~1 minute.

Since it first appeared on eBay there are now dozen(s) of clone 
[re]sellers, which often happens these days, especially from far east 
sellers.

My current feeling is if it were half the price and if the documentation 
were better and if they added clean ZCD on the inputs, they'd sell a lot 
of them. Right now, I think they're just reaching for a top price to see 
if it will sell. From the eBay history there have been only a couple of 
sales in several months so that's their answer.

I'll have more info as the evaluation tests continue.

The sad thing to me is that for ten+ years I kept hoping someone on 
time-nuts would make a similar turn-key phase comparator. A number of 
members have mentioned their dual-mixer prototypes but I've never seen 
anyone take it to the level where it's integrated into a 
working-out-of-the-box board or black box like this FSA. A ps-level 
1-100 MHz RF phase comparator would be (would have been) a perfect TAPR 
product. With TAPR, you get open source, good documentation, reliable 
and peer reviewed circuits, and superb support.

/tvb


On 7/26/2019 8:11 AM, timeok at timeok.it wrote:
>  > Hi, > > for some time now on ebay they have been selling the FSA3011 
 > Frequency Stability Analyzer which would seem interesting as a fair > 
compromise between resolution and price. Some have been sold and I > 
would like to know if any of you have had the chance to try it and > 
therefore have an opinion on this instrument. > > Thanks, > > Luciano > 
 > timeok _______________________________________________ time-nuts > 
mailing list -- time-nuts at lists.febo.com To unsubscribe, go to > 
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