Radar
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Introduction to MARIACHI Radar
MARIACHI Radar
The MARIACHI radar design has Radio Cosmic Ray Scatter (RCRS) stations running concurrently with ground shower detection sites. The RCRS will detect all types of reflected signals. To quantify the UHECR signals we will concurrently begin a parallel program of signal modeling and analysis, simulation and accelerator based experiments. This approach will make possible the confirmation of an UHECR signal, and calibration of this signal to extract maximal information.
The final goal of MARIACHI is to setup 3 antennas in each radar site that are spaced by 10 to 20 meters (several wavelengths), and running synchronously to permit interferometric analysis of detected signal. Monitoring antennas close to the transmitters will provide reference signals. It has been shown that it is possible to perform imaging of the ionized region to an accuracy of ~2 km for one frequency. MARIACHI will use a broadband antenna and receivers, in the range of 50 to 200 MHz, to collect data at different frequencies simultaneously. The use of many transmitted and detected frequencies will allow us to localize and probe the ionization cloud at different depths within the detection area.
MARIACHI will eventually aim to use as many transmitters in the range of 50 to 120 MHz as feasible with the aid of optimized antenna to listen to echoes from continuously emitting radio sources. Within a 1000 km radius from BNL site there are many broadcast TV stations in the lower VHF band (55-82 MHz) providing excellent sky illumination. For the initial phase of this work our goal is to implement 3 receiving stations separated by 10-20 km. The initial site for the RCRS station will be at Brookhaven National Laboratory, Stony Brook, and Suffolk County Community College Ammerman Campus.
Radar Scatter Techniques and Technology used Elsewhere
There is a very nice introduction (by Melissa Meyer) to the use of bi-static radar at the Discussion of the Manastash Ridge Radar Project web site. Click on the "What do we do?" link and read how they use a similar technique to that proposed for Mariachi to image electrical disturbances high in the atmosphere.
Antennas
MARIACHI uses and develops different types of antennas. The basic antenna used is a half wavelenght dipole antenna. We use a fancy Biconical antenna from Agilent Technlogies for exploratory and site evaluation. The biconical has a radiation pattern that is similar to a dipole. Jessica has developed Spida, an omnidirectional antenna that is tuned for 67 MHz. For directional work we use a high gain commercial Log Periodic antenna.
Proper antenna calibration will allow us to determine the signal power detected. With the knowledge of the antenna aperture it is possible to estimate the source power density.
Broadcast TV Frequencies (VHF)
Note that VHF analog TV stations are due to be switched off by Feb 2009. After that all transmissions will be Digital. For now the frequencies we tune are:
| Ch | Video (MHz) | Audio (MHz) |
|---|---|---|
| 2 | 55.25 | 59.75 |
| 3 | 61.25 | 65.75 |
| 4 | 67.25 | 71.75 |
| 5 | 77.25 | 81.75 |
| 6 | 83.25 | 87.75 |
| 7 | 175.25 | 179.75 |
| 8 | 181.25 | 185.75 |
| 9 | 187.25 | 191.75 |
| 10 | 193.25 | 197.75 |
| 11 | 199.25 | 203.75 |
| 12 | 205.25 | 209.75 |
| 13 | 211.25 | 215.75 |
The low VHF band, channels 2 - 6 are the best for meteor detection. Stations are offset by 
10kHZ. Hence, channel 2 can be found at 55.24,55.25 and 55.26 MHz. To find where stations are located, power and frequency consult this database.
Receivers
For the initial part of MARIACHI work we have used PCR 1000 and PCR 1500 receivers from ICOM. They are relatively inexpensive and can be easily setup to detect meteors. The big advantage of PCRs is that they are computer controlled. A second receiver that is better than PCR is the WINRADIO model G313i. We are also exploring the use of GNURadio for our work.
Software
To record data and analyze data we have been using Spectrum Lab written by Wolfgang "Wolf" Büscher. Spectrum lab permits on-line display of events and can be used for offline data processing. We have been using MATLAB for data analysis. R is another package that can be used in the analysis of recorded data and will be explored.
Resources
- Tom Feierabend has suggestions for MARIACHIs that want to get their feet wet.
- This web site, http://www.w9wi.com/, has a database of TV and FM radio stations in the United States. It has the information of many stations and specifics on power, location, antenna type, broadcast frequency, etc. It is an excellent resource that can be used to locate a powerful station you might want to use as a source of RF.
- DTV pilot frequencies. Meteor Echos can also be heard on DTV pilot frequencies that are found at 54.309 60.309 66.309 76.309 MHz for channels 2,3,4,5. More information here http://www.8vsb.com/.
- Giant Metreawave Radio Telescope in India, GMTR, has an array of 45 diameter dishes to look for low frequency radiotelescope observations.
- Reflections of NAVSAPSUR (Texas) radio from the moon seen in the Netherlands.
- To calculate distance and bearing of the radio transmitter this page can be useful.
