I am putting a European standard Pal video signal over a cable that can be anything between 100 and 200m (300 and 600ft) in length. The video signal is in baseband and has a bandwidth of 4.5 MHz.
The cable I am using acts as a low pass with an edge frequency of 1 MHz @ 200m.
Shorter cables will have a higher frequency for their 3dB point.
I am using a circuit like this to equalize the frequency response of the cable.
I know it is an approximation, but as long as the zero in my circuit coincides with the pole of the cable it works out well enough.
The problem is that I have to hit the right frequency. And the frequency of the cable´s pole depends on the length of the cable. I would like to make my circuit adjustable so I can trim it to match the individual cable. I´d use a sweep generator and scope for that.
The only thing that comes to my mind is a capacitor-trimmer. Maybe in parallel with a fixed capacitor.
Is there another way to move the pole/ zero pair of an equalization amplfier?
Thanks.
The cable I am using acts as a low pass with an edge frequency of 1 MHz @ 200m.
Shorter cables will have a higher frequency for their 3dB point.
I am using a circuit like this to equalize the frequency response of the cable.
I know it is an approximation, but as long as the zero in my circuit coincides with the pole of the cable it works out well enough.
The problem is that I have to hit the right frequency. And the frequency of the cable´s pole depends on the length of the cable. I would like to make my circuit adjustable so I can trim it to match the individual cable. I´d use a sweep generator and scope for that.
The only thing that comes to my mind is a capacitor-trimmer. Maybe in parallel with a fixed capacitor.
Is there another way to move the pole/ zero pair of an equalization amplfier?
Thanks.
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