WML is continuously striving to provide full satisfaction to customer through reliable & quality products in the area of TV Broadcast. We are already supplying to Doordarshan energy efficient 2 X 50 W UHF TV Transmitter with Class AB MOSFET version technology and VHF and UHF TV transmitting antennae. These products are based on latest trend of technology and consume less power.

Now WML is introducing a "WML - PDA - 6.2 M" model of parabolic dish antenna. It is basically used to down link the DDK program through INSAT series satellite.

Function of the antenna in the TVRO is to receive or collect the weak signals intercepting on it. Main parts of this antenna consists of a prime focused feed and a parabolic reflector. The amount of signal received by antenna is proportional to the effective area of the reflector, which intercepts the electromagnetic wave. The effective area of an antenna is defined as the signal received by the antenna to the power density available at the site. When electromagnetic waves fall on a conductive surface. It gets reflected as light is reflected from a mirror. This principle is used in the parabolic reflector, and if the shape of the reflector is parabolic all the reflected waves will pass through a point known as the focus of the reflector.

Hence a single antenna known as feed, located at the focal point is able to receive, all the singles intercepting on the reflector.

The reflector made of aluminum solid dish able to reflect all the waves to its focus due to surface imperfections or in other words the actual area is more than the effective area of the antenna.

The most important quality of an antenna is its noise temperature, especially when it is comparable with the noise temperature of the LNA/LNBC the system noise temperature is the sum of these two. In a well-designed feed and reflector arrangement, the noise temperature depends on the gain and side lobes of radiation pattern. The antenna noise temperature with 40 degree elevation angle is around 30 degree Kelvin.

Two types of polarizations are in use in electromagnetic propagations viz. linear and elliptical polarization. Low noise block converter is mounted right at the feed to avoid any transmission loss between the feed and LNBC which is housed in a weather-proof enclosure. LNBC contains low noise amplifier, image rejection filter, microwave mixer, voltage tuned oscillator and IF amplifier. I/P connector of LNBC is 229G while output connector is "N" female.

up

The antenna is designed for azimuth angle 0° to 360° rotation & elevation of 5° to 85°. The movement of Azimuth & elevation angle will be done through hand operated screw lock gear box mechanism.

The PDA is made of four main assemblies.

1) King Post assembly.
2) Central drum & trusses.
3) Antenna reflector.
4) Feed support mounting.

1) King Post Assy: - King post assy. is model of steel fabricated, Welded structure ringing facility. For Azimuth & elevation rotation freely rotation of antenna. The rings on kingpost is provided with spherical roller bearing. The steel structure is painted with pu paint for environmental protection. The structure is rigid to with stand the wind load survival speed.

2) Central Drum & Trusses: - The central dram is mounted on kingpost Assy. & 16 Nos. of trusses are mounted on central drum. The trusses & central dram are made from rectangular Aluminium tubs in welded structure for rigid mount.

3) Antenna Reflector :- Reflector structure is made from the aluminium square tubes & angles in 16 sections & it is mounted on trusses. Reflector is made from aluminium purported sheet with 40 Nos. of panels fitted on structure.

4) Feed support mounting: - Feed support is mounted on the central drum with 4 Nos. of support pipe. Feed mounting pipe is mounted centrally & having adjustment facility for height 2480 mm & polarity rotation. The adjustment of feed support can be done from bottom of the central drum.

up

01. Mount : Elevation over Azimuth
02. Dish : Aluminum perforated sheet, sections for PDA and aluminum trusses for back-up structure.
03. Surface Accuracy : 3mm RMS
04. Steerability : 5° to 85° In elevation 360° w.r.t. a ref point in Azimuth.
05. Operating Frequency : 3.7 to 4.2 GHz C-BAND
06. F/D Ratio : 0.4
07. Drive : Manual, Automatic movement optionally
08. Pointing Accuracy : Better than 0.25°
09. Feed : Prime focus (Centrally located)
10. Gain : Better than 45 dB at 4.0 GHz
11. VSWR : 1.3:1.
12. Wind Load a) Operational b) Survival :: 80 Km/H150 Km/H
13. Environmental a) Temperature b) Relative Humidity :: 0-60°CUp to 95% at 45°C

up