(meteorobs) Backscatter RADAR

[Cliff Sojourner]

this is a great conversation.

I am surprised no one has yet mentioned John Felding ZS5JF's book 
"Amateur Radio Astronomy" - chapter 7 details a 50MHz meteor radar system!

he uses a 60 degree corner reflector (horn) antenna, which is a great 
choice.  it takes a lot of power, 1kW or more if you can get it, and it 
takes a very good (quiet) preamp.

also check out chapter 12, "The Science of Meteor Scatter"

Cliff K6CLS

On 2014-05-31 21:43, James Beauchamp wrote:
> 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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