Starter guide for ADS-B antenna by 9A4QV

Transcription

1 Starter guide for ADS-B antenna by 9A4QV When you get the antenna, you will have a non assembled antenna as on the picture bellow. No extra coaxial cable nor connector, no mounting bracket, just the PCB antenna (one peace FR-4 laminate). To assemble the antenna you will need not more than 5 minutes using the soldering iron and a pair of side cutters. This is the top side of the antenna (logo side) ASSEMBLING THE ADS-B ANTENNA STEP 1. Start assembling by snapping the board on two (yellow line). For a clean cut use the side cutters. Now you have two parts, the vertical monopole (smaller one) and the ground plane with the matching to 50 ohm cable on the bottom side of the PCB.

2 STEP 2. In this step you need to solder prepared coaxial cable to the antenna (bottom side). I prefer to use the Teflon cable as it can be handed easily and it is temperature resistive and it will not melt during the soldering. Solder the coax as per lower picture, the braid should be soldered to the bigger pad (with the grounding vias) and the center wire should be soldered to the smaller pad going to the monopole through the 50 ohm matching line. STEP 3. Insert the vertical monopole (smaller PCB) from the top side (logo side) into the milled holes as on the picture bellow. The PCB will fit tight. Ensure that the monopole is vertical against the ground PCB. The shorter leg should be soldered to the top side (ground side).

3 STEP 4. Turn the antenna up side down and solder the longer leg of the vertical monopole to the matching pad. With the step 4 antenna is ready for the operation. To have more mechanical strength between the monopole and the ground plane you can apply some epoxy from the top side all around the vertical monopole but even without it the monopole will be hard to brake from the antenna. Many questions received how to attach the antenna to the mast or how to use the antenna desktop. If you want to use the antenna desktop, it is handy to attach the self adhesive pads to the all 4 corners of the antenna. This way the antenna will be a couple of millimeters from the desk and the longer vertical monopole leg and the coax braid will not scratch you desk surface. At the same time, if you use the rubber pads as i do, the antenna will not slip off the desk by accidental pulling the antenna cable, it will have a good grip to the desk. For the outdoor use, it is best to use some cheap protective plastic food container. In the same container you can then house the LNA or filter and run just the cable to your receiver. Moreover, there are two marked dots on the ground plane PCB if you want to use a bracket pole mounting. Just drill the required hole size and use the peace of the aluminum L profile to attach the antenna to the mast.

4 What makes this antenna special and different from the other designs that we have on the market? This is one of a DC grounded antenna (GP), efficiently handle the static problems that may occurs on the antenna. This antenna came out as the answer to many s received where the user experience the situations where the ADS-B receivers, DVB-T dongles, low noise preamplifier's were damaged due to static coming from the antenna. There are many sources of the static, like corona discharge, rain static, wind static etc. There are several ways how to cure the problem. The simplest one is to disconnect the antenna, but most of the users are running the receivers 24/7 or remotely positioned antennas where disconnecting the antenna is not an easy option. Most of the users rely on the pair of the protection diodes commonly installed in the equipment they are using. This looks like a good prevention but in reality this is a double-edged sword! This par of diodes are potential source of the intermodulation that can spoil your reception to the levels where the properly installed antenna with the professional preamplifier's may result in poor reception. This is the most common problem if you are close to the strong radio and TV broadcast transmitters, or GSM towers. Setups with the high gain antennas and preamplifier's without the good filtering will amplify already strong out of the band signals routing the same to the pair of diodes at the receiver input. This signals create a so called ghost signals that may interfere with your frequency of the interest. DC grounded antenna will ground also the static and your equipment will be protected. At the same time, the "protection" diodes may be removed, hence the possible cause of the intermodulation. 1. Polarization The signals from the ADS-B transponders are vertically polarized, hence the receiving antenna should meet the same vertical polarization in order to receive the strongest signal for the best reception. The folded monopole antenna is vertically polarized antenna. 2. Efficiency and gain The efficiency of the antenna is better then 99% and the calculated gain is 1.53dB or, for the marketing guys 3.67dBi. The gain was not an imperative when this antenna was designed but it came out from the design. 3. Impedance The antenna has the impedance of 50ohms at the resonant frequency. As the standard widely used 50 ohms is preferred over the 75 ohms due to variety coax lines, preamplifier's and filters that are designed for the same impedance. It is true that there is a large growing community using the simple DVB-T dongles designed with the 75 ohms input impedance but to keep the things simple we stick to the 50 ohms. 4. Voltage Standing Wave ratio (VSWR)

5 The VSWR is quite flat for the frequency range of the interest. If 75 ohm coaxial line is used the VSWR will degrade due to minimal mismatch between the feeder line and the antenna impedance. This should not affect the efficiency of the antenna in large scale. The antenna is made on FR-4 1.6mm laminate and it consist of two parts, the ground plane with the matching line and the vertical hairpin style monopole. The ground plane is 140x140mm in size, while the hairpin is 65mm high. To assemble the antenna it required only to insert the vertical hairpin into the catted slot on the ground plane and to simply solder the hairpin microstrip line to the match on one side and to the ground plane on the top side. Solder the coaxial line to the connecting pads and antenna is ready. If used outside, it is advised to place the antenna into some plastic canister, (cheap food plastic canisters). Such antenna should be placed on top of the metal mast in order to maintain the omnidirectional pattern. Support For info or technical question please to: Where to buy the antenna online Passion Radio Shop -