Hello Don, Very true indeed. Downward conversion is a good cost Vs performance solution for radio targeting at ham band.
Elecraft's selection of downward conversation is clever because both K2 and K3 are targeting ham operators. cheers, Johnny VR2XMC ----- 郵件原件 ---- 寄件人﹕ Don Wilhelm <w3...@embarqmail.com> 收件人﹕ Elecraft@mailman.qth.net 傳送日期﹕ 2010/11/17 (三) 7:47:07 AM 主題： Re: [Elecraft] OT: QST's review of the Yaesu FTDX5000MP Actually, the 9 MHz IF got started and gained momentum from the first SSB phasing generators. Some of the first SSB transmitters were phasing types with the 9 MHz IF - using a 5.0 to 5.5 MHz VFO, one could cover 3.5 to 4.0 MHz and also 14.0 to 14.5 MHz with the same 9 MHz generator. Transceivers were only a dream at that time. Receivers did not normally use a phasing approach. Then McCoy came out with a reasonably priced 9 MHz crystal filter that made filter SSB transmitters possible with the same 9 MHz IF. Transceivers were now possible with that filter, and there were several homebrew designs as well as some commercial implementations of transmitters and receivers and transceivers using a 9 MHz IF. Another observation - sideband suppression and top-notch performance were difficult using analog phasing methods (although Rick Campbell KK7B does have some very good analog designs), the DSP algorithms are a perfection of the phasing method of SSB generation and reception, so we have come "full circle" with the advent of DSP implementations. As far as the advantages of "down conversion" - that was very successfully implemented in the K2, although there were other homebrew implementations. The single conversion down-conversion receiver in the K2 proved its worthiness to many operators while the rest of the world was using up-conversion to obtain full 0.1 to 30 kHz continuous coverage and few 'birdies'. Birdies are inevitable with a down-conversion scheme, and the challenge is to keep them out of the ham bands. 73, Don W3FPR On 11/16/2010 6:11 PM, Ron D'Eau Claire wrote: > Sometime in the 1960's or early 70's one company started offering a 9 MHz > filter at a decent price that was widely used by homebrewers back then and > the subject of many QST and ARRL handbook designs as well as a number of > "commercial" rigs. > > Obviously, those rigs up-converted the lower MF frequency bands and > down-converted the higher MF frequency bands. > > Early M.F./H.F. superhetrodyne receivers all "down converted" to an I.F. in > the low MF range (usually 455 kHz) but designing input filters for the M.F. > range that would adequately reject the image response at 2X the I.F. became > very difficult. Filter technology limited the selectivity available at > higher frequencies, forcing designers to use a low frequency I.F., but the > press was on from the beginning for better I.F. filters at higher > frequencies. > > Like all designs, it's always a compromise. The best designers are those who > make the best compromises using the components available at an acceptable > price. > > Ron AC7AC > > > -----Original Message----- > There is a serious misconception by some true believers that Elecraft > "invented" down-conversion (or at least conversion) to an i-f in the 8 to 9 > MHz range. > > Nothing could be further from the truth, and I know that the folks at > Elecraft would never claim as much. I had a Henry Radio Tempo-1 (Yaesu > FT-200) back when radios warmed up the shack. It was a 9 MHz i-f > transceiver. > > Wes Stewart, N7WS > > --- On Tue, 11/16/10, Benny Aumala<benny.aum...@gmail.com> wrote: > >> When K3 came I told this RX architecture will soon be a >> standard >> (as Rob Sherwood told long time ago). > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
