Here's a little more info on the Q of caps used in the R390. Jordan Arndt sent me a file from 1966 on the specifications of Elmenco caps made then. It states that their SM caps were made to the MIL-C-5 specifications at that time. I could not find it from around 1960, but did for 1975. It states that the SM cap Q must be greater than 1,333.333 for those caps with a value between 75pf and 1000pf. I suspect that this spec did not change since the 60's.
If someone could find the MIL-C-5 spec from that period and send it to me, I'd appreciate it. This information agrees with what Jacques Fortin measured and posted to this forum on *Apr 6 23:49:53 EDT 2024:* I have also run some tests with my HP 4192A Impedance Analyser. The best 100pF ceramic cap I have in my bins scores a Q of 220 at 1MHz. A 100pF EL-MENCO from a R-390A RF deck scores a Q of ~1800 at 1MHz A 100pF EM dipped silver mica pushes the instrument to it's maximum reading: Q of 2000 at 1MHz ! Since previous information posted here says that the best ceramic cap Q is around 1,000, this information about ceramic and SM caps indicates that only good SM caps be used as replacements in the hi-Q circuits of the R-390. Regards, Larry ______________________________________________________________ R-390 mailing list Home: http://mailman.qth.net/mailman/listinfo/r-390 Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
