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Amateur radioastronomy: dish suggestions

Amateur radioastronomy: dish suggestions


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What kind of amateur radioastronomy can any interested citized do with:

a) A 2 m dish antenna. b) A 2,5 m antenna. c) A 3 m antenna. d) A 5 m antenna. e) A >5 m <10 m antenna (likely I can not afford this or the previous but I just want to know… ).

Of course, space is sometimes a logistic issue for big stuff, but I wondered what kind of objects or sources can someone do with suitable instruments and with aid enough if not an expert. Projects and links would be welcome!


The size of your dish determines two things:

  1. Along with the temperature of your electronics, determines the signal-to-noise ratio of your telescope.
  2. The size of your dish determines the angular resolution you can expect. This has an approximate relationship of $$ R = lambda / D$$ where $R$ is your angular resolution, $lambda$ is your wavelength of light and $D$ the width of your aperture (dish).

Instead of talking about dish size lets talk about interesting things to look at and see what the requirements are:

The Sun

The sun is a good source of radio waves in the 10cm wavelength. Since the sun is around half a degree, we would need a dish at least 11.5 meters before you could expect to see the sun as anything more than a point source.

Jupiter

Jupiter has some magnetic field effects that produce radio waves in the 10-100cm wavelength range. Of course Jupiter is 50 arcseconds across, and would need a dish 412 meters in diameter to do any amount of resolution.

Cosmic Microwave Background

The CMB was one of the earliest measurements of radio waves from space. The strongest peak of the CMB is in the 1mm wavelength. However it is very weak. The original investigators cooled their radio detector with liquid helium, and I imagine something similar would be required.

Terrestrial and Man-made sources

There are plenty of man-made radio sources. Airports have a radio wave emitter in the 10cm range for radar. There are plenty of geosynchronous satellites along the equatorial plane that use the X-band in the ~2-5cm range. These by definition have a strong enough signal to be seen from Earth with even a small dish.

Summary

Resolving power is likely out of the reach of an amateur radio astronomer since the dishes have to be either very large, or you must use a much more sophisticated radio interferometry method to achieve any angular resolution. You can however still see things as point sources in the sky if you are so inclined. An excellent example of what is likely accomplished by most people would be this project here.


I have a used 2.4 metre mesh C band dish that I picked up for free that I will be converting for observing the 21cm hydrogen line @ 1420MHz. I was lucky with this dish as it's in as new condition, but you need to be aware of any rusting and damage to the mesh that will distort your data. I'm mounting mine in my backyard on a 75mm steel pole 2 metres above the ground pointing straight up. This is to do meridian drift scans, so you don't need to have a movable dish, the planet's rotation does this for you.

The hydrogen line can be used to observe deep space objects which emit strong hydrogen line signals. Observing this spectrum from the Milky Way is one example, as well as say, the Cygnus A galaxy and others.

The old large (2 to 3 metres or so) C band dishes once used for satellite TV, now largely replaced by smaller Ku band dishes, can be picked up for about AU$100 or even for free from household backyards. These are used in a number of amatuer radio astronomy projects, especially for the 21 cm line.

Once you have the dish, you will typically need to:

Replacing the Low Noise Block (LNB). The LNB is attached to the top of the dish struts. You will need to replace this with one made specifically for 1420MHz. You can make your own LNB with details at http://www.setileague.org/hardware/feedchok.htm. On that site there is an Excel spreadsheet with variables for adjusting some of the measurements of the LNB.

The LNB for the hydrogen line basically consists of an aluminium tube (waveguide) capped at one end. Inside the tube is the antenna probe, which is just a brass rod - length and placement varies according to the projects I have seen, but the SETI guide above should be OK. The probe is soldered to the centre pin of the coaxial cable connector fitted to the waveguide. Again, refer to the SETI page above.

You can also purchase one ready made from https://www.radioastronomysupplies.com/store/p22/1420_MHz._CYLINDRICAL_FEEDHORN_AND_CHOKE.html

You will need a Low Noise Amplifier (LNA) for 1420MHz. The LNA will need a Gain of > 30dB and a Noise Figure (NF) of somewhere around 0.3dB or lower. The higher the Gain (sensitivity) and the lower the NF the better, though obviously at a price. The LNA should be mounted on the coaxial cable connected to the LNB antenna probe inside the LNB waveguide. The closer the better. I have no connections with Radio Astronomy Supplies, but they also have what appears to be a decent LNA for the hydrogen line:

https://www.radioastronomysupplies.com/store/p9/1420_MHz._HIGH_PERFORMANCE_LNA.html

Another LNA made for 1420MHz

A receiver. The receiver allows you to interpret the signal coming down from the LNA. I have purchased a cheapish (AU$30) Software-defined Radio (SDR) USB dongle for my setup which will act as the receiver. In particular a RTL-SDR Blog R820T2 RTL2832U 1PPM TCXO SMA Software Defined Radio

One example of such usage is at https://www.rtl-sdr.com/hydrogen-line-observation-with-an-rtl-sdr/

More discussion on SDR for observing the hydrogen line is at https://www.rtl-sdr.com/rtl-sdr-for-budget-radio-astronomy/

The SDR dongle connects to the coaxial line from the LNA. You can then plug the SDR dongle into your computer's USB port. Beware of the length of coaxial line as longer lines will lose data. An alternative is discussed below.

Software to observe the data. There are a number of open-source applications for SDR reception. Possibly the most popular for SDR - radio astronomy is SDR#

Using a Raspberry Pi 3 B+ as a server from the dish. Alternative to using coaxial cable from the LNA to SDR at the computer is to have a Raspberry Pi 3 B+ (RPi) act as a server to send the data to computer via Ethernet cable, rather than coaxial cable. This has a number of possible advantages including much less or no data loss depending on the cable and length. I will be using Cat6 cable up to around 20 to 30 metres. The cable plugs into the RPi RJ45 Ethernet port. The SDR dongle plugs into a RPi USB port. The LNA attaches to the SDR dongle directly via the coaxial connectors/adapters.

This setup can be mounted on the mounting pole for the dish contained in a weatherproof and ventilated box, something like this You would then need to think about powering this setup.

Currently I'm looking at Power Over Ethernet (POE) to the RPi 3 B+, possibly using the RPi POE HAT when it's released this year. Then you could take power from the RPi and use boost converter to 9v or 12v to power the LNA of choice. as well as any 5V cooling fans you have in your box.

Then when connect to the RPi from your computer (e.g. using SSH) you should be set to receive data. The other advantage to this setup is that since the RPi is acting as a server connected to the internet, you can access your dish from anywhere in the world with an internet connection. There is some discussion of this here, here and here


A simple 11.2 GHz RadioTelescope (HW part)

Abstract : In this post we describe the construction of a small amateur radio telescope operating at the frequency of 11.2 GHz. The construction of the radio telescope takes advantage of the satellite TV market which has made it easy and cheap to find parabolic reflector antennas with relative illuminator (feed horn) and LNB block (low noise amplifier-frequency converter). The performances of a similar instrument are naturally rather limited, however they still allow to make interesting observations of some of the most intense radio sources.

Introduction

Radio astronomy is a difficult and fascinating science. It requires the use of bulky and expensive antennas, uses sophisticated radio-electronic technologies and sophisticated algorithms for signal processing. At first glance it would seem completely beyond the reach of an “amateur”. In reality it is possible to make interesting radio astronomical observations even at an amateur level.
On our site we have already described some radio astronomy projects for specific applications:

Now we want to try to make an “amateur” radio telescope based on the principle of the radiometer. This is certainly not the place to give detailed information on radio astronomy and radio telescopes (there is a lot of information on the net and specific texts), so we limit ourselves to providing some hints on the main points that guided us in the construction of the radio telescope.

Radio astronomy studies celestial bodies by analyzing the radio waves emitted by objects in the sky: any object emits electromagnetic waves through various physical processes (thermal and non-thermal), these waves are picked up by the antenna and analyzed with appropriate instruments: in general the characteristics of the captured signal are no different from those that characterize a broad spectrum electrical noise. The purpose of the radio telescope is to pick up this radiation and measure the signal strength, such an instrument is called a radiometer. To be precise, we speak of power per unit area and per unit of bandwidth and is expressed in Jansky : 1Jy = 10 -26 W/m 2 Hz.

The range of radio frequencies useful for radio astronomy observations is between 20 MHz and about 20 GHz: below 20 MHz there is absorption by the ionosphere, above 20 GHz there is absorption by of the gases present in the atmosphere.

To choose the most suitable frequency band for an amateur radio telescope we must make a compromise between the observation possibilities and the cost and feasibility constraints. The frequency spectrum of the radio-source emissions depends on the underlying physical process: for “thermal” emissions such as the sun or the moon, the intensity follows the law of the black body with maximums at high frequencies (according to the approximation of Rayleigh-Jeans I ∝ 1/λ 4 ), while for non-thermal emissions (for example synchrotron emission) the maximums are at lower frequencies, as can be seen in the graph below which shows the intensity of some radio sources as a function of frequency.

As we know the dimensions of the antenna are related to the wavelength of the radiation to be received, furthermore our antenna must be sufficiently directive, otherwise it would be practically useless: this means that to receive frequencies below 1 GHz the dimensions of the antenna should be significantly greater than 1m: large antennas are expensive and difficult to move.
Another aspect to consider is external radio interference. The ether, especially in the city, is now saturated with transmissions and RF signals from the most heterogeneous origin: radio and TV broadcasting, cellular networks, WiFi networks, disturbances from power lines, etc …. Not having the possibility to install the radio telescope in “quiet” places we must choose a frequency band that is not too disturbed.

For the reasons described above, the choice is almost obligatory: the 10-12 GHz frequency band is the one that seems most suitable for an amateur project like ours. At these frequencies, parabolic reflector antennas and devices designed for satellite television can be re-used. The costs of the equipment are affordable, the spatial resolution of the antenna is quite good and the interference is low (basically broadcasting satellites) and easily avoidable.
Working at lower frequencies would make it possible to easily receive more radio sources but with a considerable increase in terms of costs, not to mention the problem of interference.

Parabolic Dish Antenna

The antenna we found on the second-hand market is a prime focus dish with a diameter of 120 cm. For radio astronomy applications it is better that the dish is of the prime focus type: in these antennas the feed horn is placed in the focus of the dish. In offset-type dishes, the feed-horn is not placed in the center but on the side, this type has constructive advantages but is more difficult to aim to the source than the prime focus.

For this antenna we can calculate the gain and the directivity intended as half power band width HPBW (half power band width) :

G = η*(π*D/λ) = 40 dB

HPBW = 65*λ/D = 1.45°

Where
η : efficiency = 0.5
D : diameter = 120 cm
λ : wavelength = 2.68 cm (correspond to 11.2 GHz)

The images below show the antenna and the metal structure used for manual movement.

The first component of the system is the converter-amplifier block, the so-called LNB. This is the most important component because system performance largely depends on it. Our system receives in the 10-12 GHz band, at these frequencies the use of cables is problematic, for this reason the LNB block provides for a frequency down conversion in a lower band so that normal coaxial cables can be used.
The following image shows the basic scheme of the LNB block: there is a first RF amplification stage, followed by the mixer which multiplies the RF signal with the signal generated by a local oscillator (LO). The resulting signal contains the sum and difference frequencies, the next filter eliminates the high frequency sum components to let pass only the frequencies in the band of interest, called intermediate frequencies (IF), which are further amplified by another amplifier stage. In practice it is a heterodyne scheme, in which the frequency of the local oscillator is fixed.

The LNB block we use is Invacom’s SNF-031 model which has low noise and good stability of the gain parameters with respect to variations in operating temperature. The actual antenna is located inside the waveguide which has a C120 flange on the outside to which the feed horn is fixed, which has the task of collecting the waves reflected by the dish and conveying them to the inside the waveguide.

  • Operating frequency band : 10.7 – 12.75 GHz
  • Intermediate frequencies (IF) : 950 – 2150 MHz, LO = 9.75 GHz
  • Noise Figure NF = 0.3 dB
  • Gain G = 50 – 60 dB

The following images show the LNB block with its feed horn fixed to the focus of the dish.

The Receiver

The receiver consists of the few components, shown in the following image: there is a bias-T for feeding the LNB block, a bandpass filter centered at 1420 MHZ, a wide-band amplifier and the Airspy R2 SDR receiver. The “hardware” part has the function of limiting the receiving band and giving the signal a second amplification after the LNB stage. The signal is then acquired by Airspy and subsequently processed for the determination of the total power using GNURadio software. The radiometer function is practically realized through software.

Features of our receiver :
Frequency Band = 80 MHz
GLNB = 55 dB NFLNB = 0.3 dB
GFilter = 3.5 dB (insertion loss)
GAmpli = 15 dB NFAmpli = 0.75 dB
Gain : GLNB – GFilter + GAmpli = 55 -3.5 +15 = 66.5 dB
Noise Figure : F = FLNB + (FAmpli – 1)/GLNB = 0.3 dB
Te = (F – 1) * T0 = 20.3 °K (Receiver equivalent temperature)

Bias-T

The Bias-T has the function of “injecting” the supply voltage to the LNB block along the coaxial cable. In practice it is a simple circuit with a coupling capacitor to filter the DC component towards the RF side and an inductance at the DC input. Obtained on eBay, it can be easily self-built but attention must be paid to the “RF” quality of the components and the shielding.

1420 MHz Band Pass Filter

This filter is dedicated to amateur radioastronomers interested in the hydrogen line observations. It uses the TA2494A SAW component and measures only 50 x 10mm. It features edge pads for an easy soldering of a RF shield. Insertion loss is typically less than 3.5dB and bandwith 80MHz.

Technical Data :
Center Frequency 1420MHz
Usable Bandpass 1380-1460MHz
Insertion Loss, 1380 to 1460 MHz 3.5dB
Amplitude Ripple, 1380 to 1460 MHz 1.0 dBpp
VSWR, 1380 to 1420 MHz 1.9:1
Rejection referenced to 0dB :
DC to 1300 MHz 28dB
1550 to 3000 MHz 30dB
Impedance 50Ω
Maximum Input Power Level 10 dBm

In the images below we show the unit and its frequency response. We have soldered two wires between the SMA female headers and we wrapped the filter with aluminum tape in order to shield the filter.

Frequency (MHz) Gain (dB)
1300 -50
1420 -3.5
1500 -50

Wideband Amplifier

This unit HAB-FLTNOSAW built by UPUTRONICS is a preamp designed to go between a software defined radio receiver and an antenna. The LNA used inside is a MiniCircuits PSA4-5043. This particular model has the SAW filter removed to cover the 0.1MHz to 4GHz. There are 2 options for powering the unit : either by the USB header or via bias-tee. Devices such as the Airspy can enable bias-tee and power the device. Alternatively any mini USB cable can be used to power the device. We chose to power the unit via USB line.

Technical Data :
Gain 24db @ 100MHz -> 15.2db @ 1415MHz
NF 0.75dB
Supply Voltage USB or Bias tee 5V

In the images below we show the unit and its frequency response.

Frequency (MHz) Gain (dB)
1300 16
1420 15
1500 14

Airspy R2 SDR Receiver

From the manufacturer’s site : The Airspy R2 sets a new level of performance in receiving the VHF and UHF bands thanks to its low-IF architecture based on the Rafael Micro R820T2 chip and a high quality 12-bit Oversampling ADC and state-of-the-art DSP. In Oversampling mode, the Airspy R2 applies analog RF and IF filters to the signal path and increases the resolution up to 16 bits using software decimation. Coverage can be extended to HF bands via the up-converter companion SpyVerter (not used by us). Airspy R2 is 100% compatible with all existing software, including the SDR # scan standard, but also with a number of popular software-defined radio applications such as SDR-Radio, HDSDR, GQRX and GNU Radio. The stability and precision of the clock for the local oscillator, given at 0.5ppm, is also important for our application.

Key Features of the AirSpy SDR Receiver :
● Continuous 24 – 1700 MHz native RX range, down to DC with the SpyVerter option (not used)
● 3.5 dB NF between 42 and 1002 MHz
● Maximum RF input of +10 dBm
● Tracking RF filters
● 35dBm IIP3 RF front end
12bit ADC @ 20 MSPS (10.4 ENOB, 70dB SNR, 95dB SFDR)
● 10MSPS IQ output
0.5 ppm high precision, low phase noise clock
● 10 MHz panoramic spectrum view with up to 9 MHz alias/image free
No IQ imbalance, DC offset or 1/F noise at the center of the spectrum1 x RF Input
● 4.5v software switched Bias-Tee to power LNAs and up/down-converters (not used)
● Operating temperature: -10°C to 40°C

In the configuration of the device (done through the osmocom driver in GNU radio) the RF gain is set to 0 (default setting), while the IF and BB gains are each set to 10 dB. These very low gain values ​​show the effectiveness of the components placed upstream of the receiver : from the antenna to the LNA and Wideband amplifiers. The bias-T option is also disabled.

References

Conclusions

We have described the construction of a small and inexpensive microwave radio telescope. We took advantage of the wide availability of radio components for satellite TV. The radiometer function, ie the actual measurement of the signal strength, will be implemented via software using the GNURadio framework : this will be the subject of the next post.

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Is there a limit to the size of an Argus array?

For example, uneven ground, communication propagation time, curvature of the ground, etc?

Assuming that real estate costs are no problem, what would be some advantages of a very large (tens, hundreds, of km) array?

This and SKA was my first thought too. It is already being done and it spans huge distances across multiple countries.

Very interesting. It occurred to me that putting a thing like that on the Lunar Farside could get some interesting results. Besides being shielded from all Earthly interference, and not having a pesky Ionosphere, it would even be shielded from the Sun for 10 days or so per month. I think it would also be much easier to deploy than NASA's proposal to erect a huge parabolic dish inside a crater using robots.

Indeed, LOFAR already allows for double pointings for observations (so one beam on the target source, one beam on the calibrator). This is nice because we can use the calibrator beam to determine the calibration (and especially clock offsets) and that makes our life so much easier for calibrating on the target.

Also, LOFAR can be upgraded to have more simultaneous beams in the future, and plans are already on its way


Radio Astronomy Antennas

For HF reception of Jupiter Noise storms, the well documented and popular choice is the phased dual dipole. For those of us with a little less space to play with, a single dipole with a low noise amplifier (LNA) before the receiver has to suffice. In addition to the Radio Jove designs in the book “Listening to Jupiter 2nd Edition”, there are many designs for Yagi-Uda's in this wavelength which are freely available on the net but they are quite large. Hydrogen and other spectral line monitoring systems usually rely on parabolic dish collectors for the high gain required. The signal is reflected and focused to a feed-horn or helix to couple signals to an LNA(s) and receiver(s). A 3.0 m diameter dish can provide about 30 dB of gain at 1420 MHz with a beam-width (resolution) of about 4° of the sky. The same size dish will increase in gain and its beam-width will decrease (higher resolution) at higher frequencies, assuming the surface accuracy is adequate.

Antenna Aperture

A receiver antenna aperture or effective area is measured as the area of a circle to incoming signal as the power density (watts per square metre) x aperture (square metres) = available power from antenna (watts).

Antenna gain is directly proportional to aperture and generally antenna gain is increased by focusing radiation in a single direction, while reducing all other directions. Since power cannot be created by the antenna the larger the aperture, the higher gain and narrower the beam-width.

The relation between gain and effective area is

G = 4 * PI * A / L2 or A = G * L2 / 4 / PI

Where G is gain (linear, not dB), A is the effective area, PI is 3.14. and L2 is wavelength squared. Units for A and L2 are not important, but both must be given in the same units. The same area means more gain at a higher frequency, and the same gain means less area at a higher frequency.

Simply increasing the size of antenna does not guarantee an increase in effective area however, other factors being equal, antennas with higher maximum effective area are generally larger.

It seems obvious to optical astronomers that a parabolic dish antenna that is many wavelengths across, will have an aperture nearly equal to their physical area. However other antenna such as a Yagi and Col-linear arrays may not look to be the same at first glance but they do achieve the same result using other means at radio frequencies.

Antenna Polarization

Most natural signals (i.e cosmic sources) are almost always non-polarized (which is the same as "random polarized"), so the use of any single polarization method either linear or circular will achieve the same result. The slight polarization present in such signals do not bring any significant "power advantage" so in practice linear polarized antennas are preferred more in Radio Astronomy as they are more practical to construct for a specific gain over a circular polarized antenna.

Polarization can however carry interesting information about the source, so radio astronomers sometimes want to measure this. However it is quite difficult to do, because the signal characteristics are so weak, and below a few 100 MHz, the polarization information is usually too mixed up by the ionosphere to be of any practical use.

Log periodic Antennae

Broad band 'Yagi' antennae are some times used if there is a need to receive a large range of frequencies with the same antenna, as in the e-Callisto Solar Radio Spectrometer 45-870 MHz.

Peter has a write up on the construction of a 5 metre long log periodic antenna for this receiver here.

Radio Telescopes

There is so much written about Radio Telescopes by the professionals, it seems silly to try and write another.

The link Radio Telescopes takes you to a series of lectures and courses about Radio Astronomy by the National Radio Astronomy Observatory (NRAO)

Computers and Software You don't need these unless you are going to take the Software Defined Radio (SDR) option but they do come in handy for just about everything you'll ever want to do. The main thing to remember is that whatever hardware platform you choose, if you are going to do digital signal processing (DSP) you're going to want a fast processor because lots of DSP is quite heavy going for the computer. Software is available from many sources and you may even have to buy some, god forbid. However the most popular software is SDR# free software and that's free! It 'talks' to almost everything and you can buy a DVT 'dongle' for under $20 which will get you well and truly into SDR. Most DSP software contains a fast fourier transform (FFT) spectrum analyser, waterfall display spectrograph (frequency & amplitude/time) and audio record/playback function from your radio via the computer's sound card or from files on your selected storage disk. The more exotic packages offer additional capabilities such as auto correlation and other advanced noise reduction techniques. If you are planning to take the SDR option you'll probably get a DSP package with the receiver, then again, maybe not. The USRP is made to work with the GNU Radio suite on a Debian Linux operating system (OS). WinRadio G3xx receivers are primarily made for the various Micro$oft Windows OS and come with standard or optional DSP packages, with limited resources and support for operation under Linux. For other SDR models, check the manufacturers sales information regarding hardware/OS/software requirements. Some links you might find helpful are:

Linux

MacOSX

Receivers

Lots of choices here but they generally fall into the two categories of communications receivers/ scanners and software defined radio (SDR). In the first category, these receivers tend to operate up to several hundred megahertz and are usually reasonably sensitive. If you have an old shortwave receiver, first dust off the spiders, connect it to your new 15 metre band dipole array and you should receive the Sun or even Jupiter if you're lucky. The quality HF communications receivers used by ham radio enthusiasts are a good option, there is quite a lot of software support for the Icom IC-7000 Series and if you look hard enough, quite a few others as well. There are also many ARRL members and enthusiasts developing their own radio hardware which are often better than many commercial models.

Some links you might find helpful are: Rick Campbel KK7B & Bill Kelsey N8ET R1/R2 & Mini R2 Pro Direct Conversion Receiver QPL2000 Project

Software Defined Radio (SDR) is the new toy of choice in the radio world. There are many models appearing not only in the HF and amateur radio bands but wideband models as well as operating well into the gigahertz ranges.

There are also many ARRL members and enthusiasts developing their own SDR hardware.

Some of the more popular models are listed below along with links to their respective websites:

For suitable control software for software define radios of various descriptions see SDR# free software


Amateur radioastronomy: dish suggestions - Astronomy

  • NooElecDVB-T+DAB+FM (R820T) SDR receiver with SDR# V1.0.0.500 showing the solar radio emission.
  • SDR is at 1.2 GHz center frequency and 2 MHz capture bandwidth.
  • The yellow band in the bottom blue spectrogram window is the 6 dB rise in signal strength as the radio dish is moved across the Sun.
  • The blue bottom spectrogram window vertical axis is time and the horizontal axis is frequency.
  • The Satellite Finder and power supply is connected to the first LNB output.
  • The NooElecDVB-T+DAB+FM (R820T) SDR receiver is connected to the second LNB output
  • Click on the above screen for full resolution screen capture.
  • The above screen capture was the first time test of the Itty Bitty Radio Telescope with the SDR.

Itty Bitty Radio Telescope Parts

  • Amazon DirecTv 18-Inch Satellite Dish LNB 18
    • LNB Needs power from the receiver to work
    • Dual output for two receivers
      • LNB output 1 to the Satellite Finder Meter For Directv
      • DC power is provided to the LNB output 1.
      • LNB output 2 to the DVB-T+DAB+FM (R820T) SDR receiver
        • Tuning range 950 MHz to 1.45 GHz
        • 2+ MHz capture bandwidth
        • Center frequency set to 1.2 GHz

        • The finder is adjusted to 1 for the sky overhead
        • The finder reads


        Amateur radioastronomy: dish suggestions - Astronomy

        Below are examples of SDRs and traditional radio receivers that are used for radio astronomy and satellite observing.

        • SDRs based on Realtek RTL2832U and Raphael Micro R820T Digital Video Broadcasting Terrestrial (DVB-T) Receivers using USB
          • Features
            • 2+ MHz capture bandwidth
            • The RTL2832U streams 8-bit I+Q data into the PC using USB.
            • Frequency Range (approximate) 25MHz - 1750MHz
            • Female MCX Antenna Connector
            • Very low cost

            • NooElec NESDR Mini SDR & DVB-T USB Stick (R820T) with Antenna and Remote Control
              • Ham It Up v1.2 - RF Upconverter For Software Defined Radio
                • NooElec cable between the and the up converter Male MCX to Male SMA pigtail cable, RG174, 0.5' length
                • MCX male to F female cable RF coaxial coax cable assembly MCX male to F female 6"
                • Radio Shack FM trap, See the frequency response in the reviews.
                • MCM Electronics FM trap

                DVB-T (R820T) with SDR# V1.0.0.1193 at 28 MHz showing the CB and 10 meter Ham bands using the Scanner Ant-Base 30-1300 Mhz by Antennacraft and Radio Shack FM trap. Notice the CW transmissions at the center-right of the bottom blue spectrogram widow. Click on the above screen for full resolution screen capture.

                • A good overview of the SDR# install process with RTLSDR
                • First use the quick installation script (sdr-install.zip PC bat file) on SDR# downloads to download the files to your pC.
                • Next use Zadig to configure the PC USB driver.
                  • Installing RTL dongle SDR driver using Zadig by M3GHE
                    • The USB ID is needed in Zadig to select the correct USB device.

                    DVB-T (R820T) with SDR# V1.0.0.500 at 1,200 MHz showing the solar radio emission from the Itty Bitty Radio Telescope LNB output. Notice the 6 dB rise in signal strength (yellow band in the bottom blue spectrogram widow) as the radio dish is positioned across the Sun. The spectrogram window vertical axis is time and the horizontal axis is frequency. Click on the above screen for full resolution screen capture.


                    Is it possible to build a DIY radio telescope?

                    Yes it sure is, only thing though it your only gonna get the sun. Here is a link to it. It is real easy and cheep.

                    The first link will take you to the itty bitty dish a simply diy project. The second link is the society of amateur radio astronomers, under the projects tab on the top you'll see a few more sophisticated projects.

                    As far as a used dish goes your limited to what you can do on the cheep without spending a lot more money. At that point you can kit the jove radio project kit or similar.

                    Edited by Allanbarth1, 19 May 2017 - 11:07 AM.

                    #4 starcanoe

                    Way back in the day I got the impression that the equipment to detect Jupiter was not particularly expensive or sophisticated/complicated.

                    #5 Jeff B1

                    Very interesting article, thanks.

                    #6 Allanbarth1

                    You can build a respectively inexpensive antenna for detecting solar storms and storms from Jupiter. The receiver and amplifier can also be done on the cheep, but both require a small bit of electronics understanding. There are lots of different designs for Jove projects that can be easily made in the 20.1 MHz, 15 meter wavelength. A antenna about half that can receive a lot more of the signals from Jove. Even , including detecting occultation's of the moons of Jove because of the Doppler Effect. It's the equipment on the other side of the antenna that gets expensive and complicated. The more that you want to detect and listen to, the more money, time, skill. etc.

                    In all fairness the original posters question was about using a old unused T.V. satellite dish for radio astronomy. For a very little amount of cash out of pocket yes, you can but all that your going to be able to receive is going to be the sun, people who walk close by the dish and trees, yes trees do emit a receivable signals.

                    The MIT link has a few different programs to use depending on your interests.

                    This is the easiest DIY dish conversion and will get your feet wet. It can also be added on to, 2nd dish and even a 3rd dish. You can also use software developed by MIT for just this application and is my favorite be far as far as DIY satellite dish projects go.

                    Edited by Allanbarth1, 19 May 2017 - 09:28 AM.

                    #7 bvillebob

                    The OP mentioned a MINI dish, one of the 30"'ers.

                    The issue you have is that those dishes are designed for receiving strong signals broadcast from nearby (22,400 mile) objects, so they're small and relatively low gain. I saw an astronomer comment the other day that if you were trying to detect a cell phone on the surface of Mars it would be one million times more powerful than the typical source they observe. Astronomical radio sources are weak, very very weak, other than the sun and the reflected sun noise off the moon.

                    Realistically 10' or so is probably about the minimum size I'd fool with. With modern low noise transistors and MMICs, combined with SDR and long integration times, you can detect quite a bit with something that size. I used to have a 24' dish many years ago, and can still remember the thrill of turning it to Saggitarius A* and hearing the noise level come up by 6dB or so.

                    Also, realize that a radio telescope is in effect a one pixel camera. You don't get images, you get data and it's a very different experience.

                    Finally, Jupiter's emissions peak in the upper HF range, 20 MHz or so and they're easy to detect with a shortwave receiver or SDR is even better. Your dish is designed for 12 GHz or so, almost 1000 times higher in frequency, it would be useless for that.


                    Muskegon Astronomical Society

                    Last month we got a 12' satellite dish from Dan Seeley. So the question on everyone's mind: what will we be able to accomplish with this dish? Well, depends on what objects we want to go after and what equipment we can afford. In amateur radio astronomy we could do Solar observations, Jupiter observations, Meteor observations, Galactic observations, or even SETI (search for extraterrestrial intelligence) observations.

                    Solar Observations: We could detect solar flares at the VLF (very low frequency) 30-80 KHz range or in the VHF (very high frequency) 1-30 MHz range. We'd need only simple ham radio equipment. With the satellite dish, we'd be able to pick up solar burst activity at 80-890 MHz frequency range.

                    Jupiter Observations: We could detect radio noise storms from Jupiter. at the 18-24 MHz range These storms are believed to be caused by the movement of the Jovian moons Io and Ganymede through the magnetic field of Jupiter, which in turn causes great electrical storms on the planet, Again, a simple short wave radio equipment and loop antenna.

                    Meteor Observations: By turning into a blank signal, say an marginally received aircraft beacon at 75 MHz, we could pick up in-falling meteors as "ping" sounds. We'd need ham radio equipment and a directional (Yagis) antenna.

                    Galactic Observations: With short wave equipment and a directional antenna, we could study solar flares. Perhaps we could study some of the more powerful radio sources such as Cassiopeia A or Cygnus A at the 80-100 MHz range. We could also study the galactic arms and the center of the Milky Way.

                    SETI Observations: You heard of the 21 centimeter band? This is the radio wavelength created by an excited hydrogen hydroxyl molecule. At 1420 MHz, it's the hole of silence where almost no Cosmic static is generated. This so-called "water hole" is an ideal place to observe in general (or look for ET). At this frequency, however, we'd need a satellite dish.

                    Oh, FYI. When we talk about the 21 cm Band, it's the wavelength (meters) = 300 / frequency (MHz). Example: 300 / 1420 MHz = .21 meters or the 21 centimeter band. The 21 cm band is also called the L-Band (1420 MHz or 1.4 GHz). Other bands include the 23 cm band (1300 MHz), the 2-meter band (148 MHz), the C-Band (4 GHz), and the Ku-Band (12 GHz).

                    Other Observations: A satellite dish is viable only above 400 MHz. In areas such as the "water hole", it might be possible to observe Doppler shifts in the Milky way or detect HEPs (high energy pulses) from the galactic center. These HEPs are mysterious pulses, possibly generated by flare stars or black hole radiation. Given the right equipment, we could observe pulsars, supernova remnants, gamma ray bursts, or other blackbody radiation (radiation that an object would absorb if it were a perfect absorber).

                    The basic radio telescope has an antenna, a pre-amplifier, bandpass filter, a mixer/oscillator, an IF (intermediate frequency) amplifier, square-law detector, and DC amplifier. The antenna, of course, is the TVRO (TV Receive Only) satellite dish. Signals from the antenna are sent to the pre-amplifier. The pre-amplifier (also called the LNA or low noise amplifier) boosts the weak in-coming signal. The bandpass filter (white box) allows only selected ranges of frequencies to pass to the mixer. The mixer/oscillator lowers the frequency for the IF amplifier (avoids signal feedback to the antenna). The signal is boosted by the IF amplifier (also does some bandpass filtering). The square-law detector allows passage of the signal in one direction by throwing out the other half (otherwise the highs would cancel the lows). The DC processor removes receiver noise and other fluctuations before sending the signal on to either a recorder or an A/D (analog/digital) converter and computer.

                    It'll be up to Dan to assemble our radio telescope. He might obtain the individual components separately. He might opt to get a TPR (total power receiver), an all-in-one receiver that has most of the components built-in. Radio Astronomy Supplies seems to be the main supplier of RA components. They also have $1500-$2500 all-in-one receivers. rfspace.com has an interesting receiver called a SDR-14 which runs about $1000. If Dan assemblies the individual components (gets the signal to the computer), we might be able to get the SDR-14 SpectraView software directly from www.moetronix.com.

                    In radio observations, you aim the dish ahead of the desired object, recording the object as it drifts across your field of view. The hard part is finding the object and getting ahead of it before the observation. If Dan can get four-way control, we'll be able to find objects easier. And if he can train the RA drive to track in sideral time, we'll be able to extend our observing time.

                    But don't hope for images any time soon. I'm told our dish will have a five degree field of view. By optical standards, that's huge and will result in low resolution. Radio astronomy in general is like seeing the sky through a soda straw (and an opaque straw at that). If we can make enough accurate sweeps of a section of sky perhaps we'll be able to create some sort of image. Eventually.

                    So, will we get to observe galactic Doppler shifts or hear ET? Again, depends on the equipment. But you have to start somewhere. And even if we don't see pulsars, at least we'll know why we can't see them. I liken this project to a beginner getting his first telescope. Images off the Internet are a thousand times better then anything you can see in your small scope. But your scope sees the real thing. A picture is like taking someone's word. Same thing with Radio Astronomy. We might end up with just lines on a graph, but they'll be OUR lines.

                    In writing this article, I found several sources of information. "Radio Astronomy Projects" by William Lonc, and "Amateur Radio Astronomy Systems, Procedures, and Projects" by Jeffery M. Lichtman were useful. Also found the following web site helpful:


                    Amateur radioastronomy: dish suggestions - Astronomy

                    This picture is a historic moment, on the 10th of June 2006 Matthias Busch, the Father of EASYSKY installed the ERAC Controler Driver to EasySky and for the first time ever the Radio Telescope Mannheim was no longer only in Meridian Transit mode , it was able to track celestial objects for the first time.

                    The First object to be looked at was of course Cas A and she came in Beutifuly. The next Target was Thermal noise from Jupiter and of course later the Moon. It was for Matthias a whole new feeling moving 2.5 Tones of Steel a Radio Telescope and of Course the seat he was sitting on and all that with his own program .

                    Congratulations and Thanks Matthias you have given us all the tool we need to do Challenging Radio Astronomy

                    A very good source for A.L.L.B.I.N antennas: Dishes upto 3.7 m

                    Contact

                    Starting in October 2006 all discussions are continued in the general ERAC mailing list. You can subscribe to that list on the following website:

                    To send off anything to the group all you have to do is send it off to the address

                    Links

                    • ALLBIN registration form for all who want to participate and support the project
                      ALLBIN registration form
                    • Peter Wright gives a technical overview on ALLBIN ideas and concepts
                      ALLBIN Powerpoint presentation (11 MBytes)
                    • Marko Cebokli describes his SImple Digital Interferometer (SIDI)
                      lea.hamradio.si/

                    Documents

                    It is Basically True that an Amateur Radio Astronomer can not do much with a small dish of say 3 ,5, or 8 meters however that is not true if the Amateur decides to build East West 2 element single site interferometer linked up with cables together to give a collecting area much larger , if the Amateur constructs his equipment well with this simple equipment he gets fantastic results for a very small cost indeed .

                    Let us go on a bit further and consider a Radio Linked Interferometer in VHF or UHF or Microwave bandwidth this is also easy as long as both dishes are in an east west Meridian transit mode , things get a bit more complicated however it is still a goal for an experiment that works very well on an amateur budget .

                    Now let us go a step further to imagine a group of Amateur Radio Astronomers spread all over Europe who decide to work together to build up something big . and you have landed by project ALLBIN the basis for the future of Amateur Radio Astronomy well into the future , but how could such a system work ?

                    The first stage is to get an intensity type interferometer up and running using Amateur Equipment then at a later date to upgrade this system to become a phased array but is this dream possible? As president of the European Radio Astronomy Club I say Yes Certainly ! Today we are living in a Society where Technological advances are taking place almost day after day and the computing power available today is gigantic all we have to do is get organised . Today after an idea given to us from Ian Morrison from Jodrell bank using Radio to link up 2 remote stations we have succeeded in making an interferometer from 2 sites with home made equipment . Project ALLBIN is sitting in its start position ready to go and you can most certainly help if you wish to join us ?

                    The System is planned to work like this: A total of 40 Stations are at some stage of construction at the moment by individuals spread all over Europe , we all want to observe at first the Hydrogen line at 1.42 GHz with identical Electronic Equipment in the Meridian Transit Mode Later the Equipment will be slowly upgraded as individual financing allows . Each station gets an e-mail telling him when and at what elevation he or she needs to observe. Now all stations are hopefully up and running and calibrated when a Radio Clock triggers off the computer to sample data at each station , this clock is not however Synchronised does however get everyone started within one second after this start impulse all timing is done using a standard Satellite based clock of high accuracy using the PAL FBAS Signal from the German TV Channel ZDF via ASTRA 1F which gives a signal of 15.625KHz which using a PLL can lock in any other Oscillators to an accuracy of 10 to the power minus 13 to 14, this is not possible with GPS for instance as GPS gives us for each station a local time only . After a run is completed we all meet in the internet in an art chat room for engineering and chat as well as data transfer . this chat room has two levels one for communication and the other to communicate with the group , one station acts as master to pole each station for a sample of data , after all stations have sent in a bit of data the master station calculates the correlation shift for each station individually. This value is sent out to each remote station to let him shift all his data by this value locally so using the computer power of each station rather than at one central hub . Now the sample has been done very roughly and each station can see in the engineering channel what has been Observed roughly , everyone can now decide what needs to be observed in detail which the master station then implements to get depth data of the area of interest , this interactive mode together with modern Data Compression Techniques and the day by day improvement of Computers and Data Highways is the secret of how project ALLBIN will be constructed and will improve its performance in the years to come .

                    Today Project ALLBIN is in the Hybrid stage of early Construction and Development , we need people who are interested in Helping to get the system off the ground , at the end we will be manufacturing a product that will be the basis of a whole new tool for the future and I think that is exiting enough for anyone to help Pioneer the future of Amateur Radio Astronomy in Europe , a later step will be to hopefully work with existing VLBI Groups here in Europe .

                    Q. How can I Help ?
                    A.If you are a Mathematician , Programmer Hardware or RF Man we need you in our team now as training weekends are now being planned to learn how VLBI is being done today and from this how our own equipment will be designed and built for a total of 80 stations spread all over Europe.

                    Q Can I earn money with this project
                    A. No But what you will be doing will be priceless for yourself and others.

                    Q. do I need to own a Radio Telescope to Participate
                    A. No but one day with our help you will that is certain .

                    Q do I need to have my own equipment
                    A No you will be working on of having close contact to an existing ERAC Member in your Area to work together as a central team for development and a local group when implemented .

                    Q. What kind of knowledge do I need to bring with me to work with this group.
                    A. Everyone is a Specialist for something and that is what we need with Project ALLBIN we all help each other to do what we can for others and be helped by others where we have problems .

                    Q. If I choose to build my own station what will this cost me
                    A Every station we get up and running will mean that we get a better view of space and if you wish to build up your own station we will help you to do this the hardware is designed and manufactured by the group so the costs will be very low indeed however allot of work that you will be proud of at the end of the day . The basic Fixed manually tiltable meridian transit telescope will be cheep probably with a donated dish free of charge at a later date the tilt mechanism will need to be controlled via computer and maybe the dish will need to become rotatable but all this is not needed at the start and everything will get upgraded at a slow rate , the basic system may be later used at different frequencies by a simple change of feed and Low noise block down converter .

                    Q How can I join in
                    A. Just Mail us here at Headquarters [email protected] and we will do the rest

                    To close a small word of warning

                    PROJECT ALLBIN IS WORTH GETTING INVOLVED IN AS IT WILL BE A GIFT TO THE WHOLE AMATEUR COMUNITY FOR THE GENERATIONS TO COME