Anytime!

Pete

"ShortwaveMan" wrote in message
ink.net...
Thanks for the explanation

God gives Peace not war +

"Pete KE9OA" wrote in message
...

"Pete KE9OA" wrote in message
...
That is correct. Another thing that can cause that (2 X 2nd I.F.) image
is 2nd LO leakage coming back into the input of the 1st mixer. Once the
concept of mixer theory is understood, things become clear. I know that
many, if not most of the folks on this group understand this, but for the
new folks, I will repeat it.
A mixer is a three port device. It doesn't matter if it is used as an SSB
detector or as the first stage in a superheterodyne receiver; the
concepts are the same. In the first stage of a receiver, the antenna
input is applied to the RF port of the mixer, the tuning oscillator is
applied to the LO port, and and the resultant signal is taken from the IF
output port. Here is where it gets a little tricky (not really!). If you
could see the IF output of the mixer on a spectrum analyzer, you would
see three distinct signals. You would see a lower sideband signal, the LO
signal (suppressed by a certain amount, depending on the LO feedthrough),
and an upper sideband signal. Both the lower sideband and the upper
sideband will be separated from the LO feedthrough signal by the
intermidiate frequency. This means that if you have a 455kHz I.F., the
lower sideband will be 455kHz BELOW the LO signal, while the upper
sideband will be 455kHz ABOVE the LO signal. If you have now preselection
ahead of the mixer,

Sorry folks, that should be "if you have NO preselection ahead of the
mixer"

Pete