Can I throw one more option in the mix to make it an even four? While Googling the other day, I came across VCTCXO that is "just" about pin compatible, is output compatible (PECL), voltage compatible (3.3v) has the same frequency range as the XO (max=300MHz), has the same or a little better phase noise numbers and is an order of magnitude better in stability (+/- 20 ppm).
http://greenrayindustries.com/library/ZT620.pdf I asked Gerald to look at it and he replied... "This is a very interesting part that I have never seen. I look all the time for good oscillators but never came across this one. To make it work, you would have to: 1) Cut all the center pins. 2) Move the jumpers on the TRX to single ended mode. 3) Bias pin 1 to Vdd/2. The precision of this reference will set the frequency since this is a voltage controlled oscillator." Now an EE, I'm not, but the modification listed in item #3 don't seem too unreasonable. It might even be a good XO option for the external board option listed below. I am inquiring about cost and hopefully will have price and availability info in the next day or two. Comments & opinions? -Tim --- Tim Ellison ( [EMAIL PROTECTED] ) Integrated Technical Services ( http://www.itsco.com ) -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Eric Ellison Sent: Monday, January 02, 2006 6:25 PM To: 'John Ackermann N8UR' Cc: [email protected] Subject: Re: [Flexradio] Software taming the wandering oscillator - a thought John et.al. Dang this is Great! It gives me a hard.... er.. well.. This is the way to go for three projects. Pardon my ignorance, but is the V-F Osc a pluggable part? This is the best of all worlds. Unmodified, the SDR works just as it does now. Modification kit we can move the osc chip off the board at the expense of an external board with all sorts of isolation. Software solution, put the V-F osc on the external board, count it, discipline it and send it to the radio as well as corrections the software. SMA connectors and a little glue should marry it for the guys who want Accuracy to Microwave. Looking forward to the TAPR Reflock solution! We are all just really noodling, but getting closer! If Jim Lux says we should be countin' the 200 mhz to determine the 'software correction' (as he did in a message further up) I'm with him and you. Jim: Thanks for the answer to my question of a 'full count'. And counting only to the worst case. I think you have mentioned that before but I forgot. Anyone want to sketch this into a schematic? Eric John Acermann said: I've suggested to Gerald that the "right" answer to the mechanical issues around the oscillator could be to build a small board with a single ended to differential buffer/converter and an SMA connector that would plug in where the oscillator now goes. That would provide a clean interface for whatever oscillator you might want to use. The other half of the equation would be to make an external board to hold the current oscillator with an SMA connection for the output. That setup would make it very easy to add thermal control, and also to tap the signal for other purposes. The oscillator interface board could well be part of the final version of the TAPR Reflock solution for the SDR-1000, but no promises yet as we're still noodling the design. 73, John ---- _______________________________________________ FlexRadio mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
