Make your own free website on Tripod.com

SATELLITE TVRO

Satellite Television Recieve Only

[My Technical Notebook]


A VHF folded dipole construction Coaxial cable Velocity test Stacking Colinear 3 x 3/4 A Duplicated Boomer Yagi antenna for 2 m Transmission lines problems This Page
Page 4 of 4


In fact the Palapa Satellite and other satellites that can be viewed from Indonesia retransmitted various standards and types of Video signals, such as utilizing a ½ or full 36 mHz Transponder beside PAL, NTSC, and SECAM video standards. In order to be able receiving various standard of Satellite TV, I was force to design the Receiver appropriate as close as possible to those various parameters.

  1. Base Band bandwidth

    If the Base band bandwidth is to wide the picture quality will be poor full with black or white sparkling noises, if the bandwidth is too narrow then in every change of the pictures intensity it will be accompanied with a course white sparkling noise and the sound will be disturbed by a rattling noses. I couldn't found a suitable 70mHz IF filter with an 18mHz bandwidth for the ½ transponder signals. To meet the required bandwidth I use a full transponder 70 mHz BP7019B1 Sansen filter and at the front end of the 70 mHz IF amplifier I use an adjustable trap filter to adjust the bandwidth to an appropriate bandwidth.

  2. De emphasis circuit

    I use two type of de-emphasis circuit and video filter that is for the PAl and NTSC.

  3. SCPC

    Particularly for receiving the Thai TV a SCPC sound unit is required. For this pupose we need a sound receiver system and I use the Signetic TDA7000 single chip FM receiver as 70 mHz IF receiving unit.

  4. ANTENNA POLARITY

    Another problem is the polarity of the signals. Since there are vertical/horizontal and circular rigth/left polarity. To be able to received those types of polarities was done by inserting in the feed horn hole a small piece of teflon board 45° against the antennaprobe.

 

Ternyata Satelit Palapa dan beberapa satelit lainnya yang bisa diterima di Indonesia, memancar ulang bermacam macam standar siaran TV, seperti menggunakan ½ dan 1 transponder dengan standar PAL, NTSC dan SECAM. Agar bis menerima siaran TV yang beragam jenis itu saya terpaksa mengadakan penyesuaian untuk itu.

  1. Lebar ban Baseban

    Baseban yang terlamapu lebar akan menyebabkan gambar dipenuhi dengan bintik hitam atau putih yang halus namun yang terlalu sempit akan menyebabkan disetiap perubahan terang gambar timbul bintik-bintik putih yang kasar dan suara akan terganggu oleh suara merepet. Untuk menyesuaikan lebar ban yang dibutuhkan Saya tidak mendapatkan filter yang sesuai untuk menerima isyarat ½ transponder, dan karena itu saya memakai Filter 70 mHz Sansen BP7019B1 dengan di bagian muka penguat IF 70 mHz saya memasang filter jebakan untuk mengatur kelebaran bannya.

  2. Rangkaian de-emphasis

    Saya hanya memakai dua macam rangkaian de-emphasis dan filter video yakni untuk PAL dan NTSC.

  3. SCPC

    Untuk menerima siaran Thailan dibutuhkan Penerima suara SCPC. Untuk ini kita membutuhkan sebuah penerima SCPC yang saya buat menggunakan IC Signetic TDA7000 sebagai IF 70 mHz.

  4. Polaritas Antenna

    Masalah lainnya adalah polaritas pancaran karena adanya polaritas vertikal/horizontal dan circuler kiri/kanan. Untuk bisa menerima polaritas circulair biasanya digunakan sekeping teflon yag di masukan didalam rongga feedhorn sehing membuat sudut 45° dengan probe antena.


Circulair polarity enable

70 mHz Trap Filter

C1 = 1000 pF
C2 = 1000 pF
C3 = 22 pF
C4 = 10 pF

COIL

L1 Close wound
L2 Close wound
enamel 0.6mm

Coil Ø

5mm
5mm

Turns

10 t
9t

SHANSEN 70 mHz IF Filter



Type ABC
BP70B3 61 mHz73 mHz82 mHz
-3 dB58 mHz - 82 mHz
BP70B1 57 mHz68 mHz82 mHz
-3 dB54 mHz - 85 mHz
BP70I9B1 55 mHz67 mHz87 mHz
-3 dB49 mHz - 91 mHz

I've tested 3 types of Shansen 70 mHz filter, apparently all types has 3 peaks, the above chart indicades the 3 peaks of each type and -3 db bandwidth.

Schematic Diagrams

TVRO SCHEMATIC DIAGRAM

.

 


A VHF folded dipole construction Coaxial cable Velocity test Stacking Colinear 3 x 3/4 A Duplicated Boomer Yagi antenna for 2 m Transmission lines problems This Page
Page 4 of 4


Updated March 2000.-

Still Under Construction