Re: FSKCW on U3S QRSS 30m in preparation for New Year's Eve
¿ªÔÆÌåÓýHi Al,The edges look to me as being too rapid to be thermal drift, More like as you say RF / Noise induced on the supply rails. (Assuming the receiver audio is clean & without earth loops...) Have you seen Han's & Peters High precision OCXO U3S write up in the hints & kinks:- (In particular, decoupling capacitors around the Voltage Regulators, mounted as close as you can to the device legs. As well as hopefully decoupling RF, and general hash they prevent parasitic oscillation that affects regulators under some load conditions.) Pick your favourite semiconductor manufactures data sheet, and check out their recommendations for values. I also added an additional reservoir cap locally to the U3 for good measure. Alan On 20/12/2017 20:00, Al Holt wrote:
Over the past couple of days I've tried a few things to help clean up my signal. First, I added a small cardboard "Quonset hut" over the Si5351a daughter-board in an attempt to dampen thermal issues. I also improved some of the internal wiring by shortening power supply cables and using miniature coax for the main RF out. I've also added some shielding to the underside of the synth board in hopes it might keep any hash being radiated from the main board out. |
Alan de G1FXB