Re: S-85 refurbish: I've got a problem during the RF alignment of bands 1 and 2 - trimcaps don't peak!
¿ªÔÆÌåÓýHello 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 ? Some additional info: disconnecting BS variable condenser doesn't change things significantly. Here are measurements (ANT circuit only): ? ? I then disconnected C33 from V1 pin4 and moved the probe to C3 but, again, nothing significant happens. Now the ANT circuit is completely alone and ... still resonating too low. I also tried to switch the input connection between; RTMA, a 0.01uF cap, pure induction (air). The signal levels change, but the peak is steady at the wrong values. ? Here you can see the variables: I cannot see any sign indicating not being Halli's originals. ? The last resort idea is to check wiring and all part numbers of my not working ANT circuit against someone else working one. ? -- Emanuele (IU1KNR). |
Jacques_VE2JFE