User's Manual

TECHNICAL DESCRIPTION

The output UHF filter is made up of a resonators bandpass filter and two notches. It can be regulated on all

the channels of UHF TV band (470 - 8690MHz) and according to all world-wide standards (intercarrier 4.5

- 6.5MHz). The bandpass section is composed by the three middle resonators, while the two resonators

apart are the notches. The filter is symmetrical, therefore the choice of lowest and highest notch is indifferent.

The bandwidth and the notch depth are predetermined, so they don’t need any regulation.

The input/output coupling are regulated by means of the two screws which are in position opposed to

every connector. The regulation is carried out with a screwdriver, considering that when the screw

lines are parallel to the longer side of the filter the coupling is maximum, otherwise if orthogonal it is

minimum. The twist friction of the couplings can be set acting on the hexagonal clamps with a no. 12

key.

TUNING INSTRUCTIONS

The advised sequence is the following:

1. Set the instrument state as follows:

- C.F. = (V.C. + S.C.) / 2

- SPAN = INTERCARRIER * 5 (E.G. 27,5MHz std. B/G)

- TRANSMISSION SCALE = 5dB/div.

- REFLECTION SCALE = 5dB/div.

2. Turn the bandpass section on the required channel, and match input and output until a correct response

is achieved. During this step keep the tunings of the two notches well far away from the response. Fit the

curve at the center of the screen, so as to get the same attenuation at the borders. The input/output

couplings can influence the external resonators, therefore it will be necessary to repeatedly fix the

former after the latter in small steps.

3. Tune the two notches to P.V.-INTERCARRIER and P.A.+INTERCARRIER frequencies. This will

vary the response and matchning.

4. Adjust the bandpass external tunings. The lower notch side tuning shall be a little unscrewed, whereas

the upper notch side tuning will have to screwed.

5. Enhance a little the lower notch side coupling (the coupling screw toward the filter lenghth). Improve

the calibration alternatively acting on two sides according to this sequence: regulate the couplings, re-tune