Hello Glen, Any progress on the Anylocker? I’d still like to get two for the FT817, 1pps input first choice, 10 MHz second choice.
Cheers, Steve WB0DBS > On Jul 1, 2020, at 2:30 AM, glen english LIST <[email protected]> > wrote: > > Hello group > > I have an idea that might work, and I wanted to discuss with likeminded that > might already have experience with the problem. > > Shifting a fixed oscillator a few Hz using a image reject mixer. > > background : From time to time I (and others) make lock boards for ham gear, > pulling the internal VCXO (vary from 11 to 55 MHz ish - which are out by a > few Hz ) in against a 10 MHz input. Frequency accuracy is required for narrow > band modes, and low phase noise 10kHz-200kHz is required as not to desense > your ham neighbours. > > I use fast LVDS diff receivers to square stuff up and ADF4157 high res fract > and about 10Hz BW. That's all fine. ....That aside, there are a bunch of > radio that have only XOs, no control facility. Varying the supply voltage as > a means of control is one way, but that doesnt work for the ovenized nor > internal regulator types. > > Other people to solve this problem by applying an external oscillator that > has been disclipined - usually like crappy SiLabs spury synthesiser chips > that can produce the oddball reference frequencies like 31.28234MHz ! > Actually they are pretty good for what they are, but they are certainly not > as clean close in , and particularly poor in spurs far away. they are what > they are. > > Of course the great way is a DDS , and run something like a 400-700 MHz > VCO/SAW/BAW clock. One needs to go that high to get decent oscillator Q , and > of course the DDS needs the high clock. The clock is of course pulled to the > 10 MHz with something like a ADF4002 etc integer synth running high BW like > 200 kHz to kill to close in VCO noise. But that's alot of stuff > > *** I thought in the shower this morning of inserted a block, and shifting > the internal radio oscillator (running at say 31.28234MHz the few Hertz > either side it needs to move.) > > - by using an image reject (full complex) mixer with a +/- 5 Hz oscillator > applied. > > - by using a analog or digital variable delay line to remove or insert delay > as to strecth or contract the period . almost like a phase modulator, but I > think it is going to wrap and cause trouble. Hmm if I play with the high and > low period separately, I might be able to fix it when it wraps. But that > technique will likely insert noise for any soet of small easy implementation. > > - alias to close to baseband using another oscillator (fixed) and then alias > back up. Aliasing technique are very cheap and useful in DSP. Hmm that might > be soemthing I do in DSP for other signal processing tricks, but not on a > small board . > > The cpx mixer is the 1st thought : > > Perhaps a commutating HC-CMOS switch quadrature DBM (like HC4316) with the > complex LO +/- 5 Hz coming from something I can dream up. > > For a single frequency, I would be able to get the quadrature matching at > least -60 over temperature in my experience with something like this.. > > That would be the unwanted sideband down that far. Of course with square wave > drive, the mixer will be sensitive to the harmonic series, but the input is > squeaky clean, so that's no issue. ALTHOUGH hmm the close in noise say + /- > 10 Hz would get a say as it would be aliased in, but the 10Hz noise on those > XOs is usually prety good, and for this purpose, it is the noise at offsets > of 10kHz up to 300kHz that are the most important. Control bandwidth only > has to track thermal drift in the radio, have be fractions of a Hz, so the > system could spend some time calculating and generating the LO. > > Anyone tried this (IE shifting the frequency of the source) ? Comments ? > > Glen > > (VK1XX, AI6UM) > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
