The 2nd xtal oscillator trimmers set amplitude (adjust for max), not frequency. Sorry if everyone knew this but it seemed like it should be said.
Dave Wise > On Apr 10, 2025, at 11:42 AM, Jacques Fortin <jacque...@videotron.ca> wrote: > > Hello Karsten, > > Can you explain how do you probe the oscillator output ? > It is a connection to your frequency meter that use any coaxial cable ? > What is the input impedance of the frequency meter ? > > Sorry to ask, but maybe you did not figure the implications: if any > additional capacitance is introduced in the 2nd crystal oscillator > structure, this will add to the C431H in the V401 circuit, then probably > preventing the oscillator to work on the 3rd harmonic of the crystal. > BTW, to answer a question asked by Larry Haney, the 31MHz band probably > works OK and that is because the stage works in doubler in that band (2 x 17 > MHz). > > Are you trying to "tune" the Xtal outputs to the "right" frequency by using > the frequency meter, or did you use it just to confirm that the oscillator > is working on all ranges during the alignment process ? > From the Y2K-R3 alignment instructions, nothing specifies to do so. > The "trimmer adjustment" instructions in the section 6.2.9 should be > followed without connecting anything, except the 2nd mixer, to the 2nd > crystal oscillator output ! > > 73, Jacques, VE2JFE in Montreal > > I am currently working on realignment: checking and tuning Crystal > Oscillator subchassis. Frequencies measured with an accurate 8-digit > digital counter. Everything appears to be ok. One exception: oscillator > output on band 30 is 22 MHz (2nd harmonic), should be 33 MHz (3rd harmonic). > Active crystal is Y403 (11 MHz). Trimmer capacitor C431H appears to be ok. > Output (pin 3 of T401) is in the range of 3 to 5 volts and can be adjusted > by turning C431H. Band 8 (11 MHz osc. output) is ok. Band 19 (22 MHz osc. > output = 2nd harmonic) is ok. Any ideas why band 30 output is 2nd harmonic > and not 3rd? > Regards > Karsten > > ______________________________________________________________ > R-390 mailing list > Home: http://mailman.qth.net/mailman/listinfo/r-390 > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:R-390@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:R-390@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
