Cheers everyone! I've been experiencing some problems with image rejection at RX (havent test in TX). The problem seems to appear whatever SDR software is used (Winrad, Sdradio, Powersdr). I thought, it may be usefull to begin a thread, not just because I want to know the common problems and propably find the cause for mine, but we might get a good notelist about the common faults?
Here's what I've done to fix the problem so far: 1. Checked that my I/Q vfo really gives I/Q (I'm using solid 74AC74 + crystal inverter (74HC04) oscillator for 75 meters). 2. Checked with scope that the audio output is also in 90 relation to each other. 3. Because I'm using EMU 0404 ASIO audio card, I haven't been sure if the routings from the (super difficult) mixer software patchmix are correct, so I just downloaded a soundcard oscilloscope software and keep my figers grossed that it works with ASIO. I want to check that my PCI card L goes 100% to the left and PCI card R goes 100% right. The software is dual channel so I can see that also my PC is receiving the I/Q audio. My SDR uses RCA connectors, which IMO seem to be really tight producing a good connetion. At the audio card side I have 6.3mm mono plugs. One question that just poppep to my mind: how the cables effect the IQ relation at audio frequencies. I mean, I have about 3-4 meter long cables. Since I'm a musician (hi), I bought two good quality guitar cables when visiting local shop for buying some strings & stuff.I removed the 6.3mm plugs from the other end and put RCA males in. The unneeded lenght of the cable is 'of course' rolled to several turns. How do you guys see this? Might this be the problem? My problem seems a little bit odd, because I can see few db (maybe 10) attenuation for the image, but the phase adjustments don't change it at all. Maybe the phase relation is too far because bad connections etc and that's the reason for this odd problem? Is there any place where I could see the effect of image cancelation visually. It would be nice to see print-screen (Winrad, Sdradio, Powersrd etc.) from zero image rejection and second pic from full image rejection so I can be sure that I'm doin' it right :) Thanks and 73 de Janne, OH1GTF
