A Basic NOAA/METEOR Weather Satellite Antenna
Some time ago, on this blog, Adam 9A4QV posted a bit about building a top of the line weather satellite antenna – a straightforward way to get a pretty good NOAA/Meteor M2. It is no secret that the vast majority of antenna builds designed for polar orbiting weather spacecrafts have a foundation in the form of a circularly polarized turnstile or QFH designs. Yet, in this case, the antenna has been built around a fairly straightforward linearly polarized dipole, so building such a thing is pretty easy.
The thing is – if you are going to arrange a dipole into a horizontal V shape, the radiation pattern will be redirected to the sky making a 0 figure pattern. Hence, you will optimize it for satellites that travel around the antenna, in front of it, above it and even behind it. Everyone knows that orbiting satellites travel from North to South or the other way around and we can easily benefit from it by simply pointing the antenna to the right direction – North or South.
The design has yet another pro. The antenna itself is polarized horizontally and any vertically polarized terrestrial signals are being reduced by around 20 dB. The vast majority of terrestrial signals are being broadcasted via vertical polarization and this can lead to a substantial interference reduction. It also reduces your RTL-SDR’s overloading. As you probably know, overloading can become a pretty substantial issue for you if you are trying to get weather satellites. These are transmitting at 137 MHz and this is pretty close to those robust FM broadcast bands. On the other hand, a circularly polarized antenna such as a QFH or even the turnstile will only reduce those vertically polarized terrestrial signals by about 3 dB.
Seeing how most satellites broadcast in circular polarization, you will experience a 3 dB loss in the design by using a simple linear polarized antenna. However, in any case, it may not even be taken into consideration. The designer himself also states that such home-made builds will never reach perfection and you will still end up experiencing at least ~1dB due to inaccurate construction of those antennas as well.