[time-nuts] SRS FS710 spurs at 50Hz and harmonics?

John Miles john at miles.io
Thu Oct 1 10:44:42 UTC 2015


SRS likes to isolate their RF connectors from ground, it seems.  This is almost never a good idea.  When measuring PRS10 Rb standards, I've seen similar line spurs that went away when I grounded one side of the balanced 10 MHz output at the point where the DC supply was connected to the unit.   

Looking at the schematic that Orin posted earlier, it seems they've done the same thing with the FS710.  Try bonding the insulated BNC input jack to ground at the point where it enters the chassis, and I'll bet those spurs get a lot better.  (That is, unless you actually do have a bad filter capacitor.)

-- john, KE5FX
Miles Design LLC

> > I seem to get very strong spurs at 50Hz and harmonics with an old
> > second-hand SRS FS710:
> > http://www.anderswallin.net/2015/09/srs-fs710-noise-measurement/
> > feature or bug? Anyone looked at the powersupply and figured out what parts
> > to change?
> 
> If you live in a country with 50 Hz mains network then this sounds like
> a dead capacitor in the power supply...




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