Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
¿ªÔÆÌåÓýHi Jacques?? I also had a similar concern/thought, but since the alignment had indicated too much capacitance, both were in general agreement, so not so much need to ask. I think the original sweeps were mostly intended just to get some sort of look at the response. I would not want to expect accuracy unless the probe does not disturb the circuit . ??It would be good to understand how much error can creep in. and¡I hope your slide-rule is well lubricated too. Mystery continues. ? From: [email protected] [mailto:[email protected]] On Behalf Of Jacques_VE2JFE via groups.io
Sent: Saturday, February 22, 2025 2:33 PM To: [email protected] Subject: Re: [HallicraftersRadios] S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak! Importance: High ? Hello Emanuele, One time again, I performed some calculations from your test results below. IF there is no error in the C7A capacitor and L3 sections measurements, your test results constantly shows an effect of EXCESS capacitance in the tested antenna circuits. Could that be induced by the test setup you use ?? The attached .pdf contains the calculated ¡°excess capacitance¡± values (that are not constant, btw). And also the kind of test setup I will use to perform such tests. ? Maybe I missed something from the (very) long thread of exchanges about this problem, but the test setup you used is still not clear to me. I just want to mention that measuring the resonant frequency of a parallel circuit requires high impedance from both the RF source used and the instrument displaying the result. ? As one of my colleagues already mentioned: ¡°Nothing is more useful than a good theory¡±. And I still believe that it is true. ? Let us know ! ? 73, Jacques, VE2JFE in Montreal -- don??? va3drl |
don Root