Have you looked at the 44.545 MHz injection signal with the spectrum
analyzer? What do you see there? Any spurs on it? I'm not exactly
sure how you have it set up...are you saying you have disconnected the
output of the 1st mixer so that it doesn't reached the 2nd mixer? If
so, what does the 44.545 signal mix with to get the 455 KHz 2nd IF?
Also, if the input to the 2nd mixer is simply disconnected, is the input
port of the 2nd mixer terminated somehow? Also, are you feeding the
proper level of 44.545 to it (not overdriving it are you??)? Not sure
what level is required for the SBL-1.

Scott
N0EDV

john wilkinson wrote:
Hi,
If I feed my second mixer into a spectrum analyser, and inject a 44.545MHz
LO, with no power to the first IF stage, I see spurs at about 48-50KHz
intervals on the mixer output, from 0 to the 455KHz normal output freq.

The mixer is an SBL-1.

Any ideas as to where these are comming from?

Best regards,
John