Thank you very much. If the topic is not clear for you, you can guess for me š
Thanks again > Il giorno 7 ott 2024, alle ore 12:16, Larry Haney <[email protected]> ha > scritto: > > Hi Gianni, In reference to your question as to why there will be less static > type noise coming out of the product detector than an envelope detector, I've > not been able to find an explanation from an engineering source, but Don > Stoner writes in his book 'New Sideband Handbook' from 1958 on page 191 in > the Product Detectors section '.... there will be less interference since > output can only occur when a signal beats with the bfo.' > > I believe that with the envelope detector with bfo injection there is no real > limiting effect on what will pass through it, so all the noise on the IF > output goes through. Whereas with the product detector, having the bfo > signal on the control grid has a very limiting effect on what passes through > it. So in a product detector, only some of the noise on the signal from the > IF output will pass through. > > This matches what I see from the testing that I have done. > > Regards, Larry > > > On Mon, Sep 30, 2024 at 3:10āÆPM Ing. Giovanni Becattini > <[email protected] <mailto:[email protected]>> wrote: >> Hi & Thanks. >> >> "Another important 'feature' of using a product detector is its natural >> reduction of interfering noise coming in on your antenna. The amount of >> noise reduction depends on the type of noise it is, but can be from 40% to >> 75%.ā >> >> Would you please explain to me why it reduces the noise? Because the BFO >> signal returns back? >> >> >>> Il giorno 30 set 2024, alle ore 10:24, Larry Haney <[email protected] >>> <mailto:[email protected]>> ha scritto: >>> >>> As already noted, easy clear SSB reception on a 390 needs changes in 2 >>> areas: 1. AGC operation and 2. BFO injection level into the 'envelope' >>> detector. I've done both and have had very good success, but for good weak >>> low signal level SSB reception, a 'product' detector is required (mainly >>> due to the much lower noise level in it compared to an 'envelope' >>> detector). And then with 'product' detectors there is quite a range of >>> noise levels in different designs and implementations. The 6be6 method is >>> ok, but there are better (lower noise) choices. See my doc on our website: >>> Improving Lee Prod Det and SSB AGC.pdf >>> <https://www.r-390a.net/Improving%20Lee%20Prod%20Det%20and%20SSB%20AGC.pdf>. >>> It has a link to this doc: R390A Fix Lankford 2 diode SSB AGC.pdf, which >>> has an improved AGC circuit for much improved SSB reception. >>> >>> Another important 'feature' of using a product detector is its natural >>> reduction of interfering noise coming in on your antenna. The amount of >>> noise reduction depends on the type of noise it is, but can be from 40% to >>> 75%. I'm currently working on a circuit to allow correct use of the built >>> in AM noise limiter circuit (designed by Jacques Fortin) to reduce most of >>> the rest of it. I'm in the final testing stage and it looks very promising. >>> >>> Regards, Larry >>> >>> >>> On Sun, Sep 29, 2024 at 2:32āÆPM Jordan Arndt <[email protected] >>> <mailto:[email protected]>> wrote: >>>> The type and specs of the AGC circuit plays a major role in SSB >>>> demodulation... >>>> I'm not too familar with the 51J4 AGC circuit but some of you are... >>>> >>>> I had an R-390 that already had a 6BE6 product detector with wiring and >>>> switching very similar to the Lee circuit. I had to add a small relay to >>>> switch diodes in and out when the BFO was selected on the front panel... >>>> >>>> It worked quite well and allowed excellent Exalted Carrier reception of >>>> low >>>> power tropical AM broadcast stations on the low bands and did well for SSB >>>> with the diodes added to the AGC ckt... >>>> >>>> 73...Jordan VE6ZT >>>> >>>> >>>> ----- Original Message ----- >>>> From: "Bob Camp" <[email protected] <mailto:[email protected]>> >>>> To: "Ing. Giovanni Becattini" <[email protected] >>>> <mailto:[email protected]>> >>>> Cc: "R-390 Mailing List" <[email protected] >>>> <mailto:[email protected]>> >>>> Sent: Sunday, September 29, 2024 3:18 PM >>>> Subject: Re: [R-390] Tuning SSB >>>> >>>> >>>> > Hi >>>> > >>>> > A BFO is not typically set up to provide great audio. A āproduct >>>> > detectorā >>>> > is optimized for lower audio distortion. Yes, there are other >>>> > differences, >>>> > but they get into the āhow did they do itā side of things. >>>> > >>>> > The R390 came out before SSB was āa thing to useā. Even the 390A was >>>> > right >>>> > at the start of SSB being something the military was looking at. Move a >>>> > few years down the road and the designs did have a ācan do SSBā check >>>> > box >>>> > on the design requirements. >>>> > >>>> > Bob >>>> > >>>> >> On Sep 29, 2024, at 4:50āÆPM, Ing. Giovanni Becattini via R-390 >>>> >> <[email protected] <mailto:[email protected]>> wrote: >>>> >> >>>> >> Hi, >>>> >> I donāt answer ā¦because I āknow", but just because I find the theme >>>> >> intriguing and have similar doubts. This is a picture from the 51J-4 >>>> >> manual, which I think should be good also for the R-390A: >>>> >> <Screenshot 2024-09-29 alle 22.11.58.png> >>>> >> Because we must rebuild something similar to an AM signal but with just >>>> >> one side band, I believe we must keep the BFO 1.5 kHz above the center >>>> >> frequency of the filter for LSB and below for USB. And, obviously, we >>>> >> need to āmoveā the received signal (upper or lower band) to stay >>>> >> centered >>>> >> on the filter using the VFO. >>>> >> >>>> >> In other words: tune the VFO so that the band (upper or lower) is >>>> >> centered on the filter, and move the BFO +1.5 kHz above if the band we >>>> >> want to read is the lower, and vice versa. >>>> >> <What is SSB: Single Sideband Mo dulation Ā» Electronics Notes.png> >>>> >> >>>> >> This interpretation seems to be confirmed by the manual itself: >>>> >> <Screenshot 2024-09-29 alle 22.21.53.png> >>>> >> >>>> >> And this should be true also for SSB. In addition, it lets me think >>>> >> that >>>> >> with the 6 kHz filter, the dial reading does correspond to the carrier >>>> >> frequency of station. >>>> >> >>>> >> All that assumes that the filter is centered on the IF channel, even if >>>> >> not specified by the 51J-4 manual (left), but specified by the R-390A >>>> >> manual (right)) and however rather obvious >>>> >> <Immagineallegata-1.png><Immagineallegata-2.png> >>>> >> >>>> >> I am not sure that I am not saying something wrong, so I hope that some >>>> >> true expert can help us to clarify the thingsā¦. >>>> >> >>>> >> Gianni >>>> >> >>>> >> >>>> >> >>>> >> >>>> >>> Il giorno 29 set 2024, alle ore 19:29, Barry Scott >>>> >>> <[email protected] <mailto:[email protected]>> ha scritto: >>>> >>> >>>> >>> I hope I'm not opening a can of worms but I have some questions about >>>> >>> tuning SSB signals with the R-390/URR. >>>> >>> >>>> >>> I know it works best if the LOCAL or LINE GAIN control is at maximum >>>> >>> and >>>> >>> to >>>> >>> adjust the RF GAIN for a comfortable audio level. What I'm wondering >>>> >>> is >>>> >>> what the proper way is to set the BFO. >>>> >>> >>>> >>> I've always set it +1 for LSB and -1 for USB but I can also just leave >>>> >>> that >>>> >>> at zero and am still able to tune either sideband and now I'm >>>> >>> wondering >>>> >>> if >>>> >>> setting the BFO + or - is mainly to get the dial to reflect the >>>> >>> received >>>> >>> frequency. Is that an over-simplification? >>>> >>> >>>> >>> I'm asking because I'm never really sure what the transmitted frequency >>>> >>> is. If I set the BFO + or -, it's only a matter of how I determine >>>> >>> what >>>> >>> sounds good (e.g. no Donald Duck, etc.) as to what the dial reads. >>>> >>> >>>> >>> I apologize if that's something that should be more obvious but >>>> >>> reading >>>> >>> up >>>> >>> on it on the web doesn't quite make full sense to me. The discussions >>>> >>> seem >>>> >>> to revolve around whether the signal is in the IF's passband, etc., but >>>> >>> like I said, it seems I'm centering the signal in the IF even if I >>>> >>> keep >>>> >>> the >>>> >>> BFO at 0. >>>> >>> >>>> >>> Thanks for any insight on this, >>>> >>> 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] <mailto:[email protected]> >>>> >>> >>>> >>> This list hosted by: http://www.qsl.net <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:[email protected] <mailto:[email protected]> >>>> >> >>>> >> This list hosted by: http://www.qsl.net <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:[email protected] <mailto:[email protected]> >>>> > >>>> > This list hosted by: http://www.qsl.net <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:[email protected] <mailto:[email protected]> >>>> >>>> This list hosted by: http://www.qsl.net <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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
