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Crystal phasing & single signal reception
"Ian Jackson" wrote in message
... Ian, with your greater experience than mine, it is the concept of single-signal reception in which I am interested. Have you any clues about that, please? The only clue I can offer is that 'single-signal reception' is vague - but presumably self-explanatory, ie the filtering is very narrow, enabling you to receive only one signal (unless you have more than one on or very close to the same frequency). It's a term that I recall being around when I were a lad, but I can't say I've heard it much since. I guess it's been replaced by more scientific descriptions of how good the filtering is. Thank you, Ian. I have a vague memory of something in BadCon from about 40 years ago which related to setting up for single signal reception, which involved no further adjustments to phasing or BFO once it had been set. I am fairly sure, hence my enquiry that it involved phasing out the audio image as well as involving the peaking that comes from a single series resonant crystal. Hence my assumption that the BFO frequency must lie half way between the peak and the notch. I've no experience of such things. The HRO I had in my possession 20 years ago did not posses the crystal filter, but in an effort to speed up development of my RX project, it seemed to me that a single crystal filter would be an easier starting point than a ladder filter. |
#2
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Crystal phasing & single signal reception
In message , gareth
writes "Ian Jackson" wrote in message ... Ian, with your greater experience than mine, it is the concept of single-signal reception in which I am interested. Have you any clues about that, please? The only clue I can offer is that 'single-signal reception' is vague - but presumably self-explanatory, ie the filtering is very narrow, enabling you to receive only one signal (unless you have more than one on or very close to the same frequency). It's a term that I recall being around when I were a lad, but I can't say I've heard it much since. I guess it's been replaced by more scientific descriptions of how good the filtering is. Thank you, Ian. I have a vague memory of something in BadCon from about 40 years ago which related to setting up for single signal reception, which involved no further adjustments to phasing or BFO once it had been set. I am fairly sure, hence my enquiry that it involved phasing out the audio image as well as involving the peaking that comes from a single series resonant crystal. Hence my assumption that the BFO frequency must lie half way between the peak and the notch. I've no experience of such things. The HRO I had in my possession 20 years ago did not posses the crystal filter, but in an effort to speed up development of my RX project, it seemed to me that a single crystal filter would be an easier starting point than a ladder filter. You're not confusing SSB generation (and reception) by the 'phasing method', are you? That requires something quite different from the action of the elementary single crystal filter we're talking about. While a single crystal filter can provide a fair amount of selectivity (combined, if you choose to use it, useful suck-blow or blow-suck frequency response), it is not really suitable for 'serious' SSB filtering. Its frequency selectivity characteristics don't really use clever phasing out of the audio image. The passband peak is really too sharp for either the generation or reception of good quality SSB, and you usually need a 'proper' flat-topped filter, a 'proper' SSB phasing TX or RX (which also does exist in a direct-conversion form) - or if you're really clever, a 'third method' phasing TX (or, I suppose, RX). That said, I'm sure that 'KISS' transmitters and receivers have been made using a single-crystal filter - albeit having a somewhat limited performance. -- Ian |
#3
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Crystal phasing & single signal reception
"Ian Jackson" wrote in message
... You're not confusing SSB generation (and reception) by the 'phasing method', are you? Neither that nor Weaver's Third Method. While a single crystal filter can provide a fair amount of selectivity (combined, if you choose to use it, useful suck-blow or blow-suck frequency response), it is not really suitable for 'serious' SSB filtering. Its frequency selectivity characteristics don't really use clever phasing out of the audio image. The passband peak is really too sharp for either the generation or reception of good quality SSB, and you usually need a 'proper' flat-topped filter, a 'proper' SSB phasing TX or RX (which also does exist in a direct-conversion form) - or if you're really clever, a 'third method' phasing TX (or, I suppose, RX). Actually easier to set up for the Third Method, because all the phasing is done at a single audio frequency. But that's not what this thread is about. That said, I'm sure that 'KISS' transmitters and receivers have been made using a single-crystal filter - albeit having a somewhat limited performance. It's not for SSB. CW forever! However, ISTR G3VA (RIP) in his TT column discussing Stenode correction when trying to resolve voice through a single-Xtal filter. |
#4
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Crystal phasing & single signal reception
In message , gareth
writes "Ian Jackson" wrote in message ... You're not confusing SSB generation (and reception) by the 'phasing method', are you? Neither that nor Weaver's Third Method. While a single crystal filter can provide a fair amount of selectivity (combined, if you choose to use it, useful suck-blow or blow-suck frequency response), it is not really suitable for 'serious' SSB filtering. Its frequency selectivity characteristics don't really use clever phasing out of the audio image. The passband peak is really too sharp for either the generation or reception of good quality SSB, and you usually need a 'proper' flat-topped filter, a 'proper' SSB phasing TX or RX (which also does exist in a direct-conversion form) - or if you're really clever, a 'third method' phasing TX (or, I suppose, RX). Actually easier to set up for the Third Method, because all the phasing is done at a single audio frequency. But that's not what this thread is about. That said, I'm sure that 'KISS' transmitters and receivers have been made using a single-crystal filter - albeit having a somewhat limited performance. It's not for SSB. CW forever! However, ISTR G3VA (RIP) in his TT column discussing Stenode correction when trying to resolve voice through a single-Xtal filter. That is indeed true, where 'Stenode' is a fancy name for lots of HF boost to compensate for what otherwise would be very bassy audio. -- Ian |
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