[Elecraft] Elecraft technology

[N2EY@aol.com]

In a message dated 12/31/03 11:31:31 AM Eastern Standard Time, 
w3fpr@peoplepc.com writes:

> Not urban legend, but fact.

I used to think so. But then I did the math. 

For sideband inversion to occur in a mixer, the LO frequency must be higher 
than *both* the signal input and output frequencies. Otherwise the sideband 
does not invert. The K2 uses this to advantage, as did many ham rigs of the past. 
But not those with a 9 MHz SSB generator and 5-5.5 MHz VFO. In those rigs, 
the direction of tuning inverts but not the sideband. 
> 
> It should work the same with either combination of VFO and IF - 5 minus 9 =
> 4 and 9 minus 5 also = 4 (the subtractive mixing inverts the sideband too),
> and 5+9=14 and 9+5 also = 14. 

That's just the tuning range. Sideband inversion is another matter. 

Proof:

9 MHz filter and 5-5.5 MHz VFO

Start with a 9000 kHz USB signal (carrier at 9000, top end of audio at 9003)
Add a 5200 kHz VFO signal for 20 meters
Result is carrier at 14200, top end at 14203 - still USB

Subtract a 5200 kHz VFO signal for 75 meters
Result is carrier at 3800, top end at 3803 - still USB!

But for 5.2 MHz filter and 8.7 - 9.2 MHz VFO:

Start with a 5200 kHz USB signal (carrier at 5200, top end at 5203)
Add a 9000 kHz VFO signal for 20 meters
Result is carrier at 14200, top end at 14203 - still USB

Subtract the 5200 kHz USB signal from a 9000 kHz VFO signal for 75 meters
(9000 VFO - 5200 carrier = 3800, 9000 VFO - 5203 top end = 3797)
Result is carrier at 3800, top end at 3797 - now it's LSB!

73 de Jim, N2EY


--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
The reason this message is shown is because the post was in HTML
or had an attachment.  Attachments are not allowed.  To learn how
to post in Plain-Text go to: http://www.expita.com/nomime.html  ---