tag:blogger.com,1999:blog-7590176649168185428.post7526765257081786820..comments2024-03-28T18:51:21.655-04:00Comments on SolderSmoke Daily News: But why? Why Can't I Listen to DSB (or AM) on my Direct Conversion Receiver? Bill Mearahttp://www.blogger.com/profile/07662500663603350847noreply@blogger.comBlogger9125tag:blogger.com,1999:blog-7590176649168185428.post-81477928838733914742022-12-06T22:58:58.141-05:002022-12-06T22:58:58.141-05:00There were direct conversion phasing receivers in ...There were direct conversion phasing receivers in the late sixties. One is even in the last ARRL SSB manual, using a B&W audio phasing network.<br /><br />About 1974 there was a better one in Ham Radio. Using a divider for the RF phasing. The author a year or so.later had a matching transmitter.p<br /><br />Gary Breed had a fancy phasing receiver in the late eighties in QST. He even terminated the mixers.<br /><br />Then Rick Campbell had a string of high performance phasing rigs in QST , in the nineties or maybe early 2000s.<br /><br />An SDR is just a phasing rig with the audio phasing done digitally.Michaelhttps://www.blogger.com/profile/13699701261288661640noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-8539800467727455542022-12-06T17:27:24.759-05:002022-12-06T17:27:24.759-05:00Hi Bill - Thanks! So if I understand correctly, ...Hi Bill - Thanks! So if I understand correctly, not only would you need to send the recovered audio through a constant 90 degree phase shift network to obtain a "Q" version, but you would also have to have two mixers, one fed from the LO and another fed from a 90 deg shifted version of the LO? In that case, I can see how that would add enough complexity to throw the project into another bracket entirely.<br />Daveteehttps://www.blogger.com/profile/02743271221936577580noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-81211167536333785902022-12-05T17:01:12.317-05:002022-12-05T17:01:12.317-05:00Dave: Yes anything that would get rid of one of t...Dave: Yes anything that would get rid of one of the sidebands would allow you to tune in the other one without the distortion I describe. That's why I had so much success with my DSB transmitter -- all the other stations were listening with SSB receivers (transceivers really). You could do what you describe with a filter SSB receiver or with the phasing type receiver you describe. I built one of these phasing receivers back in 2015: https://soldersmoke.blogspot.com/2015/12/new-rig-frankenstein-phasing-receiver.html The problem is that these receivers are a LOT more complicated than an ordinary Direct Conversion receiver. They are even more complicated than a filter type superhet. Bill <br /> Bill Mearahttps://www.blogger.com/profile/07662500663603350847noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-55125123714977622772022-12-05T11:10:23.260-05:002022-12-05T11:10:23.260-05:00Bill - just wondering if you derived an I and Q fr...Bill - just wondering if you derived an I and Q from audio output of the DC Receiver, and then sum/subtract them, would this allow you to get rid of one of the "sidebands" ? Can be done in DSP or analog with op-amps - thoughts?<br /><br />https://circuitsalad.com/2015/06/<br /><br />http://www.seekic.com/uploadfile/ic-circuit/200972122276940.gifteehttps://www.blogger.com/profile/02743271221936577580noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-82872325699910465802022-12-04T00:41:38.435-05:002022-12-04T00:41:38.435-05:00DSBsc was never a ham thing until after SSB arrive...DSBsc was never a ham thing until after SSB arrived.<br /><br />GE was interested, hoped to move in with it instead of Collins and SSB. There are advantages, but on ly if you have a synchronous detector. So GE had one in the late forties. And in 1957 or 58, Webb described one in CQ. He worked for GE. But it was at least as complicated as an S38. Webb also had a couple of articles on DSB in general that year.<br /><br />It changed in 1970 when ICs made it feasible. But a lot was about AM. Signetics had a line of analog PLLs, which made AM easy, but needed the carrier. There were some schemes in Ham Radio magazine that did use the two sidebands to place the BFO right between.<br /><br />But it wss Sony's 2010 in the esrly eighties that made sybchronous detectors well known. I have a suspicion it wasn't just about synchronous detection, but it's the same hardware needed for a sideband slicer, like in the fifties. Get decent SSB reception without a narrower filter.<br /><br />So DSBsc was mostly a "cheap way to get on SSB". Lots of mods of AM rig outputs. It allrelied on an SSB receiver at the other end, which converted DSB to SSB. They'd never know. And thus no reception problems, except for AM era receivers without the good selectivity.<br /><br />If you're going to invert audio, you need to look at a better transmitter. Simple phasing works because you can filter the audio before the phasig network.<br /><br />Or SDR.<br /><br />The problem with ham radio is it focuses too.much on simplicity.Doug DeMaw did it endlessly, trying to lure people in. But too often people stay with simple. Got to have that 3 transistor rig, no matter the limitations. <br />Michaelhttps://www.blogger.com/profile/13699701261288661640noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-58199194830735198662022-12-03T06:16:32.229-05:002022-12-03T06:16:32.229-05:00Yes, synchronizing the VFO frequency and(!) phase ...Yes, synchronizing the VFO frequency and(!) phase to the carrier it will make it work. But, you probably ask, how can you sync to a carrier if it is suppressed, not transmitted? Luckily there is a solution: The Costas loop.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-3137449277666197152022-12-03T06:12:08.209-05:002022-12-03T06:12:08.209-05:00A synchronous detector would have a rather hard ti...A synchronous detector would have a rather hard time with DSB stations because of the missing/suppressed carrier. The carrier would have to be extracted somehow from the sidebands.<br /><br />You can listen to another DSB station or have a perfectly fine 2-way DSB-QSO by inverting the audio at RX (or TX) and moving the VFO up or down 3kHz for a standard 300...2700Hz voice channel.RRnoreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-9619914490280771432022-12-02T16:43:37.546-05:002022-12-02T16:43:37.546-05:00Nev: I'm glad to hear that I am not the only...Nev: I'm glad to hear that I am not the only one thinking about this. I'll have to give mixer perfection some more thought! 73 Bill Bill Mearahttps://www.blogger.com/profile/07662500663603350847noreply@blogger.comtag:blogger.com,1999:blog-7590176649168185428.post-49894014067737637142022-12-02T15:36:41.876-05:002022-12-02T15:36:41.876-05:00Bill, I too pondered this some time ago (my first ...Bill, I too pondered this some time ago (my first "rig" was DC & DSB) and I came to the same conclusion as you ... I agree, all should work if the VFO is exactly in the middle of the sidebands. But wait, there's more. I think you also need a perfect mixer.Nevhttps://www.blogger.com/profile/01654805403749706013noreply@blogger.com