Jim- Do you need to tune it? The 571 is the VCXO - but if you're feeling adventuresome you could drive the 570 as an NCO (numerical) via its i2c interface.
NS On Tuesday, November 18, 2014, Jim Lux <[email protected]> wrote: > On 11/18/14, 11:19 AM, Orin Eman wrote: > >> I have one of these: http://sdr-kits.net/PA0KLT_Description.html >> >> built with the CML output Si570 that goes to 1417 MHz (!) >> >> There is a schematic in the assembly manual that's linked to from that >> page. They use 100n and 1n capacitors in parallel on Vdd and 4K7 pullups >> on SCL/SDA. They have 100n DC blocks directly on the output pins. >> >> Into a 50 ohm load, the CML outputs produce about 4dBm as I recall. >> Obviously, the CMOS output will be different. >> >> There is a review of a different Si570 kit on the Clifton Labs site: >> >> http://www.cliftonlaboratories.com/si570_kit_from_k5bcq.htm >> >> I got similar results comparing my kit against an HP 8640B. The Si570 >> beats the 8640B close in just as shown on the Clifton Labs site. >> >> Some Softrock SDR radios also use the Si570. They use a single 10n >> capacitor on Vdd and 2K2 pullups...: >> >> http://www.wb5rvz.org/ensemble_rxtx/03_lo >> >> I have the Softrock Ensemble RXTX. It works fine on RX, but unfortunately >> I have not been able to get satisfactory image rejection on TX. I suspect >> the FST3253. >> >> So, it looks like decoupling isn't that critical - 10n or 100n||1n in >> these >> examples. 1K pullups on SDA/SCL seem to be overkill and anything >> reasonable <= 4K7 should work. >> >> Orin. >> >> >> thanks... looks like it's time to stop analyzing and go find a piece of > copper clad to stick this thing down on. I see a lunchtime project coming > up, > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
