In a message dated 6/17/04 2:41:52 PM Eastern Daylight Time, [EMAIL PROTECTED] writes:
> The present day LSB - USB band "standards" have their roots > from years ago in the availability of 9 Mc crystals / filters - when > SSB was experimental and you had to build your own. 9 Mc plus a VFO > running at 5.0 to 5.5 Mc gives you 20m USB. Subtract the VFO frequency > and you tune "backwards" on 75/80m and you get LSB. No, that's just not true. Urban legend. I believed it for years but when I did the math the truth could not be denied. The only way you get sideband inversion is if the heterodyne oscillator is above *both* the input and output frequencies of a mixing process. Yes, the 9 MHz IF / 5-5.5 Mhz VFO scheme was popular, and it does result in one band tuning backwards. But it *does not* result in sideband inversion! Generate USB and 9 MHz and mix it with a 5-5.5 MHz VFO and you get USB on 75 and 20. The LSB/USB convention for hams goes back to before hams used 9 MHz filters to generate SSB. . Now if you use a 5 MHz SSB generator and a 9 MHz VFO you *do* get sideband inversion. If anyone wants the exact math, I have it all written up. 73 de Jim, N2EY _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net http://mailman.qth.net/mailman/listinfo/elecraft You must subscribe to post. Subscriber Info (Addr. Change, Unsub etc): http://mailman.qth.net/subscribers.htm Elecraft page: http://www.elecraft.com
