A Video Amplifier for boosting the output level of satellite receivers.
(and anything else that needs a bit more oomph!)

Most ATV stations use domestic satellite receivers for frequencies  above 1GHz. They are cheap and easy to buy but have one serious drawback, low  video output level. This isn't due to a deficiency in the receiver, it is  because the modulation index of amateur TV transmissions is much lower than  domestic TV uses. A lower modulation index means less video is recovered from  the incoming signal.

Almost all receivers have a built-in level controls  which are adjusted by their manufacturer to give the correct output level for a  standard satellite input signal. In some cases this control can be advanced far  enough to lift ATV signals to the same output level but most receivers will need  this design adding to assist them. There is a penalty to pay for winding an  amplifiers gain up, given that the gain x bandwidth is a constant, the bandwidth  is proportionately narrowed which results in poorer picture quality. Adding  extra gain, such as this device does, will always be a better solution.

By  using a split and isolated supply, the input and output capacitors normally used  in this kind of amplifier are eliminated. Bandwidth goes from DC up to more than  10MHz.

The  PCB is small enough to fit upright inside most satellite receivers. Connect  "A" to the old video output point and use "C" or  "D" as the new output point. The two outputs can be loaded simultaneously. VR1 sets the gain, try leaving it set half-way and adjust the  receivers original gain control for the desired output level. If possible, keep  both controls below their maximum settings.

Parts list:

R1 - 1K
R2 - 220 Ohms
R3 & R4 - 75 Ohms
RV1 - 470 Ohms
IC1 - EL2020        note that ordinary '741' type op-amps will NOT work in this application!
IC2 - NMA1212
C1, C2 & C3 - 33uF / 16V
C4 - 100nF (0.1uF)
L1 - 100uH

Click HERE for downloadable PCB files.