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Why should I use a product from the RAL10 series to build a small amateur radio telescope when I can save money by using a low cost Sat-Finder?

Many people asked this questions, people with some practice in electronic assembly that wish to build an amateur radio telescope using low cost components from the satellite TV market. Assuming that someone who plans to use a Sat-Finder has some familiarity with soldering, we will compare this solution with the one that includes the use of our RAL10KIT.

We remind you that a Sat-Finder is a device used by satellite TV installers of equipment to facilitate the orientation of the antenna towards the satellite. It is, essentially, a broadband detector (900-2000 MHz) amplified and equipped with an analog display of the signal strength and a potentiometer for the sensitivity adjustment. This object is very cheap and available in all electronics supermarkets.

As a first step we will try to find what it takes to build, in the simplest and safest way, our first amateur radio telescope.

It is certainly possible (and advisable) to try and build a small radio astronomy device using low-cost parts and components from the satellite TV market (such as antennas, LNB, Sat-Finder modules, and more). The web provides many good examples and we always encourage this way.

A Sat-Finder can actually represent the basic element for a small amateur telescope, since it converts the power of the signal received by the antenna in an easily measurable voltage. It is a simple, inexpensive approach.

If you are not satisfied by displaying the received signal on the original indicator, and you want to acquire, display and archive the data in graphic form with a personal computer (as required by a "serious" instrument), you must connect to the system an acquisition card, handled by an appropriate software.

The simplest radio telescope achievable with a Sat-finder operates in the frequency band from 10 to 12 GHz and is composed of:

  • Satellite dish antenna and structure for orientation.
  • LNB unity (Low Noise Block) with specific illuminator for the antenna used: it receives the signal at 10-12 GHz, amplifies and converts it in the intermediate band 950-2050 MHz.
  • Coaxial Cable TV-SAT needed to connect the LNB output to the Sat-Finder.
  • Sat-Finder module.
  • Electronic interface circuit which adapts the signal at the Sat-Finder output to the entrance to a capture card for the PC.
  • Acquisition module with ADC (analog-to-digital converter) and output serial channel (RS232 or USB) for the connection to the PC.
  • Software for the management of the acquisition module (graphic visualization of the signal and storage).
  • Power supply.

The various models of Sat-Finder commercially available have equivalent features and performances. The entire passing bandwidth at the LNB output is amplified, with no band-pass filter: this confers sensitivity to the system, but as much instability and susceptibility to interferences.

The device is very sensitive to temperature changes: fluctuations occur in the gain and the characteristic of the detector that produce drifts in the response, making it difficult and confused the interpretation of weaker signals. On the other hand, a Sat-Finder is not intended as a precise and stable power meter, but to provide rapid intensity assessments of the "robust" signals from TV satellites.

RAL10KIT is the ideal solution for amateur radio astronomer who wants to build with certainty of results his first instrument. It is a true radiometer with accurate and repeatable performance, designed taking into account the costs and the ability to use, however, easily available components in the satellite TV market.

All the important functions of a radio astronomy receiver have been integrated. The researcher completes the kit with the power supply and the container, connects the system to the PC via a USB cable and start the observations with the supplied software. There is everything you need, all integrated. Compare the performance: it is easy to see how, in reality, this proposal economic and "secure" is.

 

What do I needed to build a radio telescope with RAL10KIT?

These are the components needed to build your first radio telescope at 10 GHz:

  • Satellite dish antenna and structure for orientation.
  • LNB unity (Low Noise Block) with specific illuminator for the antenna used.
  • TV-SAT coaxial cable to connect the LNB output to the RAL10KIT.
  • Power supply that provides the voltages 12 V and 20 V.

RAL10KIT is a real microwave radiometer: it filters, amplifies and reveals the signal from the LNB, it performs the amplification of post-revelation with gain, offset and constant of integration which are programmable. The LNB power supply is provided directly from RAL10KIT via the coaxial cable, and you can switch the polarization in reception (horizontal or vertical).

The internal microprocessor converts the received signal into a sequence of digital samples (with high resolution, 14 bit) and handles the serial communication with the station PC through a USB port. It is also provided a free software that captures the measures and controls the functions of the receiver.

You connect everything and.... you start with observations.

 

How can I improve the signal reception using an commercial SAT antenna?

The sensitivity of every radio telescope mainly depends on the characteristics and the size of the antenna which is the collector of cosmic radiation. The use of large antennas in amateur observations is attractive: there is no limit regarding the size or the kind of the antenna used, if not some economic, space, and installation factors. Obviously, the antenna has to be suited to work in the requested frequency bands. In this field the imagination and the skills of the experimenter are crucial to define the instrument's performance and can make the difference between each installation.

Undoubtedly the RAL10KIT is an optimal starting point for the radio telescope electronics, but the work behind the optimization of the system ensures significant advantages in the performance of the instrument. The first choice is the antenna, equipped with a proper illuminator and LNB, then the coaxial cable that links the external units with the RAL10KIT. If the antenna is far from the receiver and you need to use long cables, you may need to insert an IF amplifier from the TV-SAT commercial line (with a typical gain from 10 to 20 dB). A consistent improvement in the radio telescope performance can be achieved by thermo-stabilizing the external LNB and the RAL10KIT.

If you have any question, doubt or problem regarding particular installations with the RAL10KIT, contact us: let's talk about it.

 

I am no electronics expert but I’m still interested in building my radio telescope: RAL10KIT is within my reach?

This is a good reason to search for “safe” results without sacrificing the experimentation and the pleasure of self-construction: using the RAL10KIT, just created for this purpose, you do not need to be an electronic expert to build an amateur radio telescope. The PDF document "How to build an Amateur Radio Telescope: RAL10KIT" downloadable from our website provides all the information needed.

Moreover, we are always available to solve any problem, also by phone!

 

What can I observe with a small amateur microwave radio telescope?

The answer to this question can be found in the articles “How, what and where to look” and “What future expansions are imaginable with RAL10?”.

 

The acquisition software is available for multiple platforms?

The acquisition and control software provided for free with the RAL10 receivers is all you need to manage the radio telescope. It is constantly updated and is available for all major platforms equipped with at least one USB port: Windows (32-bit and 64-bit), Mac OS X (Intel and PPC), Linux (32-bit and 64-bit ). You can freely use the program without license restrictions and/or number of installations.

 

How do I set the parameters of the RAL10KIT to start a measurement session?

This information is available in the operative manuals of the RAL10 series receivers.

Here we are going to resume the preparatory steps for an observing session end the checking of the proper functioning of the radio telescope. Even if we will refer to the RAL10KIT, the procedure is useful for every RAL10 series receiver.

Once the 75 Ω coaxial cable from the LNB is connected to the RAL10KIT input, you supply the receiver and launch the acquisition program previously installed on your PC. The program will start proposing some default values for the operating parameters, in particular GAIN = 7 for the post-detection gain of the radiometer. During the first test you should leave the default settings unchanged.

To make the instrument operative is essential to initiate the automatic calibration of the radiometric baseline by activating the CAL command. This operation is important, since a Total-Power radiometer measures small changes in the detected signal overlapping a nearly continuous component , with greater amplitude, due to the noise of the system, depending on the total gain of the receiver chain (antenna included), and other parameters. To highlight only the small variations due to the radiation coming from a radio source, you must subtract from the detected signal the contribution due to the background noise: for this scope a voltage offset is generated, which positions the level of the base line to the center of the measuring scale of the analog-digital converter.

 

DataMicroRAL10 software default

 

If after pressing the CAL button you push the ON button for continuous acquisition of the samples, you will notice how the BASE REF parameter varies. When the value of BASE REF stops, the initial calibration procedure is complete: the baseline will be positioned near the center of the scale and you can check the operation of the system by "passing" your hand in front of the illuminator: the received signal will vary significantly.

If you turn off the LNB power to 20V while the tool is running, you will notice a significant decrease in the level of the received signal: the contribution of noise and gain of the antenna and LNB is absent, with the intensity depending on the characteristics of these components and the pointing direction of the antenna. Restoring the power supply voltage of 20 V to the LNB, you will meet the previous record levels. The figure describes this test.