Feed Horn Antenna Design

Hi all,

I am toying with the idea of building a simple radio telescope and I have most of it figured out. But there is one part of the design that confuses me which is the feed horn. I understand that they typically have a cone shape that eventually feeds into a waveguide but what I do not understand is what the actual antenna is?

Is the feedhorn made of metal and a cable attached to the casing directly or is there some wire inside the waveguide that actually picks up the radio waves.

All the best,
Robin

MitchElectronics said:

Hi all,

I am toying with the idea of building a simple radio telescope and I have most of it figured out. But there is one part of the design that confuses me which is the feed horn. I understand that they typically have a cone shape that eventually feeds into a waveguide but what I do not understand is what the actual antenna is?

Is the feedhorn made of metal and a cable attached to the casing directly or is there some wire inside the waveguide that actually picks up the radio waves.

All the best,
Robin

Click to expand...

As you know nothing about antenna design, find and study a good textbook, like Kraus, J.D. Antennas, and Kraus, Radio Astronomy.

A parabolic-dish antenna consists of the dish plus the primary radiator. This radiator can be a short waveguide horn, with a low-noise receiver like those used for satellite TV. If you need to connect a coaxial cable to such waveguide horn, a transition should be used, no "wire" in the "pipe".

For what frequency your radio telescope is designed? To start, use a discarded satellite TV dish and LNB for Ku-band (11-12 GHz, 1" wave length), and connect to its IF output an "in-line IF amplifier" and a detector. The output detector voltage is proportional to where the antenna is pointed. You can also use a "SAT-Finder" for the same purpose. With the above system you have a simple radio telescope with which you can detect solar radio noise, and more.

As you know nothing about antenna design, find and study a good textbook, like Kraus, J.D. Antennas, and Kraus, Radio Astronomy.

Click to expand...

yes an awesome place to start to learn the basics and more

you also need to decide up front what frequencies you want to receive.
You are only going to use a dish and feedhorn if you are going to be receiving signals above ~ 5GHz. A dish and a dipole feed for 1 GHz to 5GHz.
Below 1GHz say 100 MHz to 900 MHz you can use Yagi antennas.
for lower frequencies you can use plain wire dipoles.

Jupiter noise at ~ 21 MHz is easily receivable on an inverted V dipole
Atmospherics, whistlers and dawn chorus etc are received on large multi-turn loop antennas down ~ 10 to 20 kHz

cheers
Dave