Hi Barry, The common crystal, yes (Y401). The other possible suspect is the silver migration disease in one of the tuning coils capacitors. Meaning in Z213, Z207, Z201, and even T201: all those ones are used on the 0.5 - 1MHz band only. And the prime suspect capacitors are those with a working DC potential (even if it is a small one) across. Like C233, C254...
73, Jacques, VE2JFE in Montreal -----Message d'origine----- De : [email protected] <[email protected]> De la part de Barry Envoyé : 22 octobre 2024 11:24 À : Jacques Fortin <[email protected]> Cc : R-390 Mailing List <[email protected]> Objet : Re: [R-390] High Noise Floor in 0-1 MC Band Hi Jacques, Shorting both antenna jacks eliminates most of the noise; however, there's still a small noise increase when switching from the 1-2 MC band to the 0-1 MC band. I even tried putting the top cover back in place to help eliminate stray noise from getting in through the top but I couldn't notice any difference with it on as opposed with it off. The 6-7 MC band has the same noise level as the other bands. I think you were probably looking at the common crystal for that, right? Given this, perhaps there just a high level of atmospheric or other noise at my location. I experimented a bit with my Grundig Satellit 800 and, while the two receivers aren't nearly in the same class, I don't notice that much difference in, say 600kHz and 1200kHz so still not sure if it's atmospheric. Thanks, Barry - N4BUQ > Hi Barry, > Does it behave the same (higher noise on 0-1 MHz band) when the > antenna input is shorted ? > Just try to understand if it is internal to the receiver or just > dependant on the antenna conditions. > And.. is it also noisy on the 6-7 MHz band ? > > 73, Jacques, VE2JFE in Montreal > > -----Message d'origine----- > De : [email protected] <[email protected]> De > la part de Barry Scott Envoyé : 21 octobre 2024 22:26 À : R-390 > Mailing List <[email protected]> Objet : [R-390] High Noise Floor > in 0-1 MC Band > > For the past few months, I've been trying to determine why the noise > floor on the 0-1 MC band in my R390/URR is so high. If I tune to a > strong station, the noise disappears so, perhaps, "noise floor" might > be the wrong term for it but in places where there's little-to-no > signals, the noise is very noticeable and all but drowns out the weak signals. > > If I switch from 0-1 MC to 1-2 MC (or virtually any other band), the > noise is reduced significantly. The difference can be on the order of > 15-20 dB on the carrier level meter. > > I presume this isn't normal but maybe it is. I think someone > mentioned that the noise on the bands under 8 MC are typically a bit > higher than the other bands but that doesn't seem to account for why > the lowest band is by far the worst of them all. > > There are only passives that change from 0-1 MC to the other lower > bands and I'm wondering if it's even possible for those to be the > problem but I don't know of anything else that could be causing it either. > > I think someone suggested that the 1st crystal oscillator's output > might be low for that band but I seem to recall checking that on the > scope and output for the 1st and 2nd positions seems to be very close > to the same amplitude so I'm thinking that might not be the problem. > > Has anyone seen this and possibly have a cause for it? Like I said, I > presume this isn't normal but I don't know that for sure. > > Thanks, > Barry - N4BUQ ______________________________________________________________ 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
