EME, SETI, Radio Astronomy, DSP
and
Radio Amateurs.

The following Pages are dedicated to:

building bridges between the EME, SETI and Amateur Radio Astronomy Interest Groups.
and
the promotion and preservation of Weaksignal Communication.

Introduction

    It is the opinion of the author of these pages, that communication and experimentation in the weaksignal domain represents the future of what will be left of Amateur Radio and that these fields have always been the basis for Amateur Radio from the very beginning, some 70 years ago.

    By using low transmitting power, so called QRP, one can create a situation such as exists in the weaksignal domain, with similar challenges. The communication link between the source of the information and the destination, the receiver, is given by the total budget of gain/loss. It is the noise level at the receiver antenna and the natural noise in the "ether" that needs to be overcome to enable the the exchange of information.

    If we were to lose this weaksignal domain, it would mean the end of our beloved hobby.Other forms of communication are possible and often more reliable than via weaksignal.

    In commercial communication, one tries to avoid or overcome path loss variables as they present uncertainties. Often, commercial signals are such that the receiver is driven in a saturated state as is the case with certain forms of modulation and detection such as FM, PM and the like. Communication in this form represents NO challange and NO magic. It is like using a pair of wires, without having them. Here the emphasis might be on efficiency, throughput and automation. We all like to have the fire department and ambulance services to have solid mobile wireless connections!

    In the areas of radio astronomy, deepspace communication, such as done in space research, SETI, as well as weaksingal in amateur radio, the real weaksignal techniques are applied. Here the propagation properties of the Electromagnetic spectrum are always important factors.

    Weak Signal Communication techniques are under severe assault by a wide variety of conditions and demands of an ever expanding technological and commercialized Society.
    The segments of the Electro Magnetic Spectrum that were historicly allocated to Amateur Radio represent a     large treasure. International and National Commercial Interests are making continuous efforts to chip away frequencies.
    It is wise to remember that the Amateur Radio Community received these bands in the very early beginnings of radio and that there are     no Constitutional Rights to these bands.
    Even the     Internationally Protected Frequency Bands for Radio Astronomy are becoming more and more polluted by spurious signals generated by low orbitting satellites.
    These forms of pollution might affect the ability to execute SETI operations in the future.     Wide Band Spread Spectrum Communication in particular will present an ever increasing threat to weak signal conditions.

    Dish Antenna with Feed

    When Measuring "Weak" or Small Signals in Electrical Circuits, one will eventually reach the point at which such a signal can no longer be Recognized as the Desired Signal. The signal is now of the same order of magnitude as the The Natural Noise in the system.
    The Total Noise has many components such as:

    In Radio Astronomy as well as in Weaksignal, Losses as well as Signals are often expressed as so called Noise Temperatures expressed in Kelvin, temperatures referenced to the absolute zero point ( -273 C = 0 Kelvin ).
    Relatively small changes in either the level of noise temperature or in the signal amplitude, can cause large changes in the so- called     Signal to Noise Ratio - SNR. This in turn can largely affect the ability to Detect a desired signal in the presence of Noise.

    Since the discovery of "Radio", a part of the radio amateur community has been attracted to do their experimenting, communicating and observing under these Weak Signal conditions. It is also in this region of signal amplitude with its Natural Noise Floor where one can observe many interesting phenomena in circuitry and wave propagation.
    In the past and present Radio Amateurs     have explored and discovered new forms of propagation, often by applying Weak Signal Procedures.

    Real Weak Signal Enthusiasts can experience the thrill by participating in these techniques by receiving and monitoring signals generated by nature and mankind at the noise threshold level.

    It is in the weaksignal domain where NEW and PROGRESSIVE Developments occur in changing world of Amateur Radio.

    It is as important to preserve a clean, unpolluted EM spectrum for Radio as it is for other forms of observing such as optical astronomy.

    It is safe to assume and to state that Signals from Other Civilizations, existing or not, will appear as weak signals at best.

    More on Weaksignal by Charles, K4CSO

    EME ( Moonbounce ) This Technique represents to most Radio Amateurs a very special branch of Weak Signal Communication, due to the Limitations in Antenna Size and Transmitter Power Output.
    Radar studies provided the first results of using the lunar surface.
    An early NASA historical paper about EME
    M^2 with Mike, Staal, K6MYC and Taylor Howard, W6HD report on early Amateur Radio EME on 144 Mhz.
    In Moonbounce, the Moon Surface is used as a Reflector for Radio Signals and the echoed signals that return to Earth are often just barely above the Noise Background.
    EME is, as are other forms of Weak Signal Communication such as Meteor Shower(MS), Sporadic E and forms of Satellite Communication, a big Challenge for its Devotees.
    Recently new, mostly DSP based techniques, are gaining in popularity. Examples of these are:
    JT44/65 and Linrad
    Because the technique is often marginal, all components of the system have to operate near to or at peak performance levels.
    Such Components of importance include:

              Antenna and Tracking.
              Feed systems.
              Low NoisePreamplifiers. (LNA's)
              The Connection to and the Input of Receiver.
              The Characteristics of the Receiver.
              The Operator's ability to Copy weak Morse Code in Noise.
              Planning for and Tracking of the Moon.
              Generation of Power and Coupling to the Antenna.
              Frequency Stability of the System.
              The Desire to go out and collect "Items" for the System.
              Knowledge of Radio, Computers and newer developments such as DSP.( Digital Signal Prosessing )
              The ability to test and maintain the system.
              A friendly Neighbourhood and at least some Land around the Residence.
              For Amateurs in a Relationship, an understanding Partner!
              An appreciation for hearing one's own Echo's returning from Outerspace.

    The existence of Large Super Stations makes it possible for startup and smaller stations to participate in Moonbounce with Satellite Class setups.

    Listen to the world of Weak Signal Sounds.

    Because many of the Equipment Requirements and Observations overlap in Amateur Radio Astronomy, SETI and Amateur Radio, it makes sense, in the opinion of this author at least, to learn and experiment in these fields as well.
    An Example of such an Integrated Environment, both Educational and Professional, can be seen at Radio Science at Stanford.

    Microwave Frequencies for Weaksignal Frequency bands for Weaksignal Communication are most frequencies assigned to the Amateur Radio Service. From 1.7 MHz to 28 MHz conditions exist at times and areas where communication is possible very close to the natural noise floor. The 50 MHz band presents many opportunities with many devotees. When going up in frequency, the properties change and Space Communication Applications become an important field.
    Microwave Bands from 1.2 GHz and up are rapidly becoming in demand for commercial applications. The radio amateur community is at great risk of losing the assigned frequency bands. Microwaves present lots of possibilities for Weaksignal work, EME, SETI and Radio Astronomy.

    Very Low Frequencies An new part of the spectrum is emerging as a domain for experimentation with advanced weaksignal methods and procedures. The monitoring of beacons and often low speed cw transmissions form and exciting field.

    Radio Astronomy is the Science of Astrophysics in the radio spectrum from Low Frequencies to as high as 300 GHz. Many bodies radiate in addition to signals in the Visible, signals over the total Electro-Magnetic Spectrum. Bodies appear as sources of noise in the frequency domain. The measurement of the type, quantity and location of these sources of radiation form the observational part in Radio Astronomy.

    Early Radio Astronomy - The Connection with Amateur Radio

    Amateur Radio Astronomy has become more popular with the advent of more sensitive receivers and surplus Antennas. Many participants in radio astronomy are also involved in one or more aspects of Weak Signal in Amateur Radio. Some will be drawn from amateur radio into astronomy and vice versa.

    SETI or the Search of Extraterrestrial Intelligence is the Science of Detecting Intelligent Signals from other Civilizations. This science forms a controversial subject in certain circles. Whatever your views are, the Search efforts are right in line with Advanced Weaksignal Detection and Techniques. A large body of Scientific Literature is available on the Internet.
    Interesting Reading material forms     SETI Pioneers by David W. Swift.
    Bottom line is that many Weaksignal stations could utilize their sophisticated stations in SETI and get more return on effort and investment.
    By participating in the Search one would be part of a World Wide Network of mainly radio amateurs, searching in the Universe for Weak Signals.

    Digital Signal Processing is a way of Detection Enhancement. Analog Techniques exist side by side with digital techniques.

    The advent of powerful home computers and dedicated processing units has made DSP more and more important in weak signal work.
    The Utilization of Computer Based tools for copying and detection of weak signals presents, at times, a subject of heated discussions.
    Very powerful     Multiple Channel Spectrum Analyzers and pattern recognition engines are used in SETI. These instruments are all DSP-based.
    An example of a Software Based MCA that can be used for Amateur SETI, MS Meteor Scatter, Beacon Monitoring and EME Carrier Detection.
    For regular cw code detection the MCSA may not be optimal due to the time requirements even for low speed cw ( 5 wpm ). For those tasks a matched DSP Filter can be more useful.
    You are encouraged to participate in a Research Project on Receivers and Noise by W8MQW
    A new project for a DSP Based Receiver for Weaksignal and Microwaves is on its way.
    A well balanced approach to DSP and Moonbounce Communication could be a MCSA for detecting the presence of weak Keyed Carriers in the IF Passband. This information could then be used to fine-tune the receiver, so that the Beatnote Frequency matches the Passband of the Matched Filter.
    A preliminary Report on use of the Matched Filter on real EME Signals by VE7BQH.
    The Assembly Files for this Filter.

    The Antenna performs a vital function in coupling the Receiver, Digital Signal Processor, Readout Device and Transmitter to the Electro-Magnetic Universe and its frequency domain.
    The design, construction and properties of an antenna, the noise and gain characteristics as well as the coupling of the antenna to the first modules in the detecting or other signal processing equipment play a vital role in the overall system performance
    Reflectors (Dish Antennae) represent a Dominant Group among the different types of Antenna Systems that are used in space communications.
    Much Design, Engineering, Research and Science go into these Systems.
    Many forms and structures have been tested, constructed and used over the years and the development of newer systems remains ongoing .

    Some Examples are presented here:

    If you like you can submit your Antenna for Display here:

    You can upload anonymously FTP to: nitehawk.com/pub/upload/rasmit/

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W6/PA0ZN

Charter Member.

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