Modulator help

[angiodan]

I have a 2 security cameras (with built in modulators) and a 4 channel modulator that is distributed through a video distribution module. I'm not happy with the picture quality, and am not sure what may be causing it. My cameras are on channels 51, 55, and the modulator is using 58,60,62 and 64. I have no analog or digital OTA channels in that range that could be causing it, but you can see these 4" wide white vertical shadows that go across the screen on all my channels, as well as a little graininess. The fact I see them on both the cameras and modulator are making me wonder if it could be an issue with my distribution module, although my OTA feeds are pristine.

Any ideas or things I could try? Or is it really OTA noise?

 

[dishrich]

Yes, it most likely is OTA noise. If you are using any kind of OTA preamp, this only makes things worse with your modulated channels.

What you really need to do is look at what channels all your local OTA digital AND analog stations are on, & then you need to look at getting some sort of low or high pass filter to knock out the noise. By knocking otu this noise, your modulated channels should look good.

For example, in my area, the highest OTA local station we have is channel 55, so I simply use a low pass filter that knocks out everything above 750mhz, which starts at OTA channel 60 - this gives me about 4 "clean" channels that I can modulate on.

At my house, I modulate 6 in-house channels starting on even channels 86+ - since my cable system only goes up to ch. 78 on analog, I use a low pass filter at 600mhz, which still give me another 3-4 channels I can combine with the local cable signal.

 

[angiodan]

I'm not using a preamp per say, but I'm sure the distribution module increases the gain a little. My highest OTA channel in the range of my antenna is 45. I don't have cable at all, so I guess I could do a similar setup as yours, and start my modulated channels at 60.

Thanks for the help.