Selecting a 7500 RTG Antenna
It is essential for each and every application and installation to evaluate the right antenna type. The antenna selection depends on the following criteria:

• Type of application (i.e. free space vs. stilling well)
• Installation possibilities (size, location and height of nozzle)
• Properties of the product stored in the tank (vapor pressure, temperature, etc.)
• Accuracy requirements

The 7500 series RTG comes with four basic radar antenna forms that can be divided into the following two groups.

For Stilling Well Applications

7530 RTG - Iit is possible to use a horn antenna on stilling well applications. However, the results will normally not satisfy custody transfer application requirements. The diameter of the horn antenna must match the inside diameter of the stilling well as closely as possible. For products with a low radar reflectivity [dielectric constant (εr)<1.9], a stilling well is always required.

7532 RTG - Planar stilling well antenna is specially designed for stilling well applications only. The emitted circular mode radar pattern is a must for high accuracy applications on stilling wells. This special mode allows the software to compensate for variations of the inside diameter of the stilling well and layering of adhering product. The diameter of the antenna itself fits in 6” (DN150) stilling wells directly. Cone adapters allow installation on larger diameter stilling wells. A good match between well and adapter is essential. The Varec planar antenna with pulsed radar technology allows direct installation, even on tapered stilling wells – a unique feature.

For Free Space Applications

	7530 RTG - It is essential that the horn extends below the nozzle. The general rule for diameter selection is "the larger, the better", as a larger aperture of the antenna generates a narrower beam and has a better gain – signal to noise (S/N) ratio.
	7531 RTG - Rod antenna is ideal for tanks where only small diameter nozzles are available and tanks containing condensing products (or heavy water condensation) or corrosive products, such as sulphur, as the rod is easy to clean and has good "drip-off" properties. The "inactive" length of the antenna should extend below the nozzle.
	7533 RTG - Parabolic antenna is the largest free space antenna with the smallest beam angle. It is ideal for applications close to tank walls, where a manway cover is available. The parabolic antenna is also an excellent choice on products with a low reflectivity, such as asphalt and bitumen.