By Flavio Falcinelli
The RAL10 receivers are versatile and offer many possibilities of use: their input bandwidth, in fact, includes the intermediate frequencies (IF) 900-2000 MHz, a standard for devices Low Noise Block Converter (LNB) used for the satellite TV reception in Ku-band (10-12 GHz) or C-band (3-4.5 GHz). The effective working frequency of the radio telescope will coincide with the input frequency of the selected LNB block.
We remind you that the external LNB unit, often comprising the illuminator for parabolic reflector, is the device placed directly on the antenna focal point. A coaxial cable will transport to our radio astronomy receiver the signal already converted to the IF band. It is a frequency converter (downwards) of the received signal.
The radiometric module microRAL10, common to all RAL10 products, is the "heart" of our receivers for radio astronomy and implements the most important functions. For those who want to deepen its functioning we suggest the reading of the related in-depth documents.
It is a radiometer operated by a microprocessor which amplifies the signal coming from the external LNB module, calculates the power of the received signal, "digitizes" the information and communicates with the station PC through a USB port.
Operating parameters are programmable and all the important functions of a radio astronomy receiver are implemented. The device is sensitive, stable and characterized by high degree of measurement resolution.
Radiometric module microRAL10, the core unit of radio astronomic microwave receivers of RAL family
If the operating frequency of our radio telescope is not too high, you can remove the external block LNB amplifier-converter implementing a direct conversion amplifier. The signal collected by the antenna will be amplified with low noise and filtered to operate at the set frequency, with the desired passband.
In fact, the microRAL10 input amplifier is broadband: it is not difficult to eliminate the original internal filter and insert an outer group of amplifiers with a band-pass filter "cut" to the desired working frequency. Obviously, with this configuration it is difficult to achieve bandpass filters with very narrow window: you must always check the effective "cleansing" of the chosen spectrum portion.
As an example, the following images show an experimental radio telescope, working at the "magic" frequency of 1420 MHz, based on RAL10AP receiver.
Example of direct amplification receiver built "around" the radiometer RAL10AP. It is used an antenna horn (20 dB gain), a low noise amplifier (LNA) with band-pass filter centered on the frequency of 1420 MHz (connected immediately after the antenna), 30 meters of coaxial cable that carries the signal within the station. Before connecting the cable to the receiver RAL10AP a commercial line amplifier for TV-SAT is included.
We propose instruments designed "ad hoc" for the amateur radio astronomer: simple, modular and ready to use, which leave room for constructive imagination of the individual enthusiast and offer many possibilities for expansion.
If you’ll have the patience and the pleasure to follow us, you will find extensive documentation about our products that grows and develops over time. The software that controls our tools will always be available, free and updated, while our pages will host many examples of realizations and experiments based on Total-Power RAL10 receivers, made by us or by our friends who want to share the fascinating experience of amateur radio astronomy research.
Room for imagination!
Using our core modules, the wide range of components and accessories from the Satellite TV market and taking advantage of our support, there are no limits to the customization of your instrument.
Transit of the Milky Way (region of the Swan) carried out with an experimental radio telescope based on the RAL10AP receiver. The system reveals the radio emission of the Galaxy at 1415 MHz (with a theoretical bandwidth of 50 MHz). The radiation includes the continuous component and the neutral hydrogen contribution to 1420.406 MHz, which falls into the "receive window" of the radio telescope. This record does not show the profile of the neutral hydrogen line, but the continuous emission of the Galaxy and of the radio source Cygnus A unresolved because of the wide "field of view" antenna (around 16°).