(meteorobs) [radiometeoren] Backscatter RADAR

Jay Salsburg jsalsburg at bellsouth.net
Mon Jun 2 18:39:46 EDT 2014


Hello

 

Thank you for the input.

 

The advantage of CW RADAR is its simplicity featuring low interference,
narrow bandwidth, simple filtering, no modulation, limitless velocity
determination with zero ambiguity, and any range; not to mention ease of
licensing. Disadvantages are spillover or direct leakage of the transmitter
into the receiver. There is a technique used in the early days of RADAR or
what may be the original RADAR set. These early RADARs were quickly replaced
with FMCW, and then Pulse RADAR to detect range. However Static or CW RADAR
is the Mother of electromagnetic motion detection. A similar technique is
used in those Microwave Motion Detectors that open the sliding doors at the
Grocery Store, these microwave motion detectors use a single balanced mixer.
I am not saying that my idea will work but I should try it.

 

Using a Continuous Wave transmitter on one antennae, an identical receiving
antennae is placed a quarter wave apart or multiple 90/270 degree intervals
apart, even an array of 90 degree antennae. Using quarter wave length coax,
the two coaxial cables feed the two inputs of a Double (Doubly) Balanced
Mixer. This unique device uses 3 balanced transformers; Local Oscillator
input (LO), Radio Frequency input (RF), and Intermediate Frequency output
(IF). The unique arrangement of the antennae places the wave of the receiver
at 90 degrees from the transmitter wave. By adjusting the balance of the
various transformers, the 90 degree relative arrival of the two waves of the
transmitter and receiver on the inputs of the mixer produces greater than
100 db suppression of the carrier outputting the upper and lower sidebands
of the mix at the LO output to be amplified by a simple audio amplifier
after a low pass filter. If the Antennae and Mixer are designed with care,
no other amplification is needed other than audio amplification of the IF
output of the Mixer. Use of modern signal processing can suppress the
undesired sideband.

 

http://www.radio-electronics.com/info/rf-technology-design/mixers/double-bal
anced-mixer-tutorial.php

http://en.wikipedia.org/wiki/File:Bsp2_CW-Radar.EN.png

 

 

From: radiometeoren-bounces at ls.vvs.be
[mailto:radiometeoren-bounces at ls.vvs.be] On Behalf Of Jean-L. RAULT
Sent: Monday, June 02, 2014 7:49 AM
To: radiometeoren at ls.vvs.be
Subject: Re: [radiometeoren] Backscatter RADAR

 

Hi Jay

1) Don't forget to ask for an radioamateur licence if you want to transmit
on the 50 MHz amateur band

2) If you plan to use close TX and RX aerials, you will have to use pulse
modulation (CW would desensitize and/or overload your receiver).
 I'm afraid pulse modulation such as used in radar techniques is forbidden
on amateur bands (because of the broad band needed by pulse transmissions
techniques)

Jean-Louis Rault F6AGR
IMO radio commission

Le 31/05/2014 19:46, Jay Salsburg a écrit :

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?






_______________________________________________
radiometeoren mailing list
radiometeoren at ls.vvs.be
http://vps.vvs.be/mailman/listinfo/radiometeoren

 

  _____  

No virus found in this message.
Checked by AVG - www.avg.com
Version: 2013.0.3480 / Virus Database: 3722/7610 - Release Date: 06/02/14

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.meteorobs.org/pipermail/meteorobs/attachments/20140602/fa702a54/attachment.html 


More information about the meteorobs mailing list