Re: U3S with TCXO #u3s
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Hans Summers
Hello Mont, all A reminder that curing drift on an Ultimate3S is possible, at least to a large extent, by other methods than a TCXO - and that this was described in an age old App Note I wrote back in the mists of time, AN001 at http://qrp-labs.com/appnotes Yikes... I know that here you have been referring to the QCXPTCXO, but that's not clear in the Synth docs. Yes, the problem is the synth docs were written some years ago, and predate the QCXPTCXO which only came on the scene in mid 2020. When there are hundreds of documents it is hard to keep everything straight between them. THAT WOULD BE GREATLY APPRECIATED. :) It isn't something that is available from a components distributor. The procurement of these was via a tortuous path which is far outside the scope of this post... The only way for people to get these components would be if I sell just the component alone on the QRP Labs shop; but I am reluctant to become a parts distributor, let alone a parts distributor of one-off SMD parts. I already have enough problems being a kit producer! So therefore the best way is to use the QRP Labs TCXO module, http://shop.qrp-labs.com/qcxptcxo which was extensively tested and characterized and found to be a very suitable fit for QRP Labs kits. The cost is also low particularly considering no SMD soldering is needed and that it is a known, tested item, specifically in regard to this "stepping" nature of some TCXOs, which is a performance characteristic of great importance to low bandwidth weak signal mode operations like WSPR, but is not something available in any datasheets. For reference, attached are some of the charts from my testing. The derived specification from my testing: Accuracy at 25C: 25,000,000 Hz +/- 5Hz Output: 1.05V peak-peak Temperature stability: +/- 0.25ppm over 4-65C tested Supply voltage: 1.6 - 3.3V Current consumption: 1.25mA It doesn't constitute $million laboratory testing but, I did put some reasonable time and effort into it and believe the results justify calling it a 0.25ppm TCXO and suitable for our purposes (no sudden frequency stepping during a 10's of C temperature test). 73 Hans G0UPL http://qrp-labs.com
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