Poor picture quality with new cam

[dma]

I hope this is the correct section but has anyone got any suggestions?
I managed yesterday to set up my tivusat smarcam in my Technomate TM-1500 CI+ super Satellite Receiver. When I did this, it was raining at the time and thought nothing of the poor picture quality which occurs when it is raining. In the evening when it had stopped raining the quality of the picture was the same. I removed the smarcam and the picture (on free to air channels) was perfect. I put the smarcam back in and the picture quality became poor again (just like when it is raining). Hence the smarcam in some way is effecting the picture quality. I am using an 80cm dish with 0.3dB monoblock lnb. The signal strength is c.a. 75%.
Is the signal strength too high or too low? Is the monoblock a problem? I use a dragon cam in my Technomate TM-1500 and it does not effect the picture quality. Any ideas?
Thanks.