SATELLITE TVRO

[My Technical Notebook]

	Page 3 of 4

Electronic Construction

Because the satellite frequency is in C band class that consist of serveral transponder, the electronic parts of an TVRO system should consist of 2 units that is the outdoor and indoor unit.

1. The Outdoor unit that consisted of.

   1. The Dish Parabolic reflector that can be aimed to satellites.

   2. A feedhorn for collecting the reflected signals with an ability to select vertical and horizontal polarization transmission signals,

   3. Attach to the feedhorn an LNA for 3.7 ~4.2 GHz (C Band) should be use to amplify the received signal to an adequate level.

   4. Further the frequency must be converted down to a suitable lower frequency to be fed through a coaxial cabel without excessive losses. So a Downconverter is needed.

      There are three generation types of TVRO downconversion methode.

      1. The first generation is the 70 mHz Down conversion type.

      2. The second is the Low block system with an IF down conversion Frequency between 450~ 950 mHz.

      3. The third generation is the High Block system utilized a downconversion IF frequency between 950 ~ 1450 mHz. For this type a LNB is used instead of LNA. (LNB is a LNA with a build in down concerter)

   In building my own TVRO system consequently I,ve tried all those tree down conversion generation. But since the frequency is in the SHF region, there're no spare parts for this purpose available yet in Indonesia, so to made this part was out of the question. I ask a friend to gave me his hand ordering the needed spare parts for this unit. . For the first generation type I've got a Taiwan made Feedhorn LNA and Downconverter. For second I've got an American Gardiner LNA and a Japanese DX down converter unit, And for the third generation type I've got a Gardiner LNB.

2. The indoor unit is the video receiving unit and the television. The receiver unit must capable of deliverng video and audio signal to the televission set. The first stage is the first converter that convert the 450 ~ 950 MHz to a lower frequency with a bandwidth of 1 transponder (± 36 MHz). A Modified UHF Television tuner was used for this. The original IF output was 40 MHz. modified to an IF of 70 MHz. After this a wide band 70 Mhz amplifier followed.