(meteorobs) Backscatter RADAR

[James Beauchamp]

Hi Jay, 

I've never really liked the terms 'forward scatter' or 'back scatter' because both are essentially the same thing - reflections of RF energy.  The only difference is the angle, and depending on the receiver/transmitter configuration, it will be mono-static or bi-static.

Your description is essentially a CW mono-static radar, and has been employed in many systems for detection of moving objects.  If you are able to minimize the desensitization challenge, the product will be an audio frequency.  It also eliminates frequency stability concerns.

Just my personal opinion, the biggest challenge is that 100 watts, even with an optimized beam pattern (cosecant squared would be the best, IMHO), would not give enough return energy.  The largest contributor to the signal loss is the distance, becoming 1/R^4.

Just as a reference point, standard terminal ATC radars push 1 MW peak pulse into a 35 dB gain cosecant squared antenna and still are only good to about 70 nm range for aircraft detection.    Long Range ASR's have to push several megawatts, longer pulse widths and HUGE antenna sails to extend their detection ranges to 200 nm.   

The AF Space radar at Lake Kickapoo worked so well for us because the estimated ERP was about 9 GIGA watts and was CW.  

A good starting point for 6 meters would be at least 1000 watts, continuous wave, in an omni-directional (horizontal), cosecant-squared (vertical) pattern.  I think that could get enough ERP for detection by receiving stations in a bi-static configuration.

Waivers COULD be considered by the FCC if enough of a case can be made for research.  

On that note, I noticed that WWV is experimenting with periodic broadcasts at 25 Mhz using kilo-watt or higher ERP.  This could be another possibility.

______________________________
Maybe I have been thinking wrong. While it is constructive to use Forward Scatter RADAR for detection from many different locations distant from the Beacon, this technique requires participation, there is no one participating in Meteor detection in my Region. My idea is to make a Back Scatter RADAR.
 
Using 2 Antennae, one transmitting, the other receiving, it should be possible to mix the transmitter energy with the receiver energy to detect Doppler energy. Utilizing the 50 MHz Armature Beacon allocation at 100 Watts, I should be able to build a test rig for detecting Meteors. By placing two 6 Meter-band Antennae facing upward, three meters apart, mixing the two antennae signals in a Double-balanced Mixer, hopefully Doppler Meteor activity will be detected.
 
Any ideas?


On Saturday, May 31, 2014 4:16 PM, Jay Salsburg <jsalsburg at bellsouth.net> wrote:
 


Maybe I have been thinking wrong. While it is constructive to use Forward Scatter RADAR for detection from many different locations distant from the Beacon, this technique requires participation, there is no one participating in Meteor detection in my Region. My idea is to make a Back Scatter RADAR.
 
Using 2 Antennae, one transmitting, the other receiving, it should be possible to mix the transmitter energy with the receiver energy to detect Doppler energy. Utilizing the 50 MHz Armature Beacon allocation at 100 Watts, I should be able to build a test rig for detecting Meteors. By placing two 6 Meter-band Antennae facing upward, three meters apart, mixing the two antennae signals in a Double-balanced Mixer, hopefully Doppler Meteor activity will be detected. 
 
Any ideas?
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