Determining the radiant of a meteor using Graves radar (III): the details

In my previous post I explained what we did and what results we got. In this post I'll show you the technical details behind the experiment, with some hints and tips in the case you want to replicate it. As a guide, I'll solve a meteor step by step, from the wav file to the radiant, and then, the final orbit around the sun.

Determining the radiant of a meteor using Graves radar (II)

One year ago, I published my experiences about determining the radiant of a meteor using Graves radar. If you read it (I hope you really did it) a question arises immediately: What about three receivers? Fortunately David, amateur astronomer and ham radio operator also known as EA1FAQ joined the team so we could answer this question.

Figure 1: Transmitter and receivers location

We had some doubts. Could the same meteor head echo be received simultaneously by three different stations? some calculations and simulations were made with many interesting results.

Wideband Quadrantids using Graves radar

Recently I realized one of the most limiting factors while measuring doppler head echoes is the limited bandwidth of SSB receivers. Sometimes you receive a really long head echo appearing at 3000 Hz and going down to 1000 Hz, the rest frequency when you tune 143.049 USB with Graves. And you wonder: how high the doppler can be? To answer that question I made an "special IF filter" for my FT-817. The filter is just a piece of coaxial, so I can receive the whole receive bandwidth. A dummy filter.

Determining the radiant of a meteor using Graves radar

Important
This article has been superseded by this one: http://ea4eoz.blogspot.com/2016/04/determining-radiant-of-meteor-using.html

During the last months of 2014, Iban EB3FRN and me were recording meteor head echoes using Graves. But to make things interesting, we synchronized the recordings using a PPS GPS signal. The idea was to analyze the Doppler from the head echoes and and see if something useful can be extracted from them.

Typical Graves' head echo followed by a large tail echo

Geminids 2013 with Baudmeteors

Last weekend I used Baudmeteors to study the Geminids meteor shower using the Graves radar. I left the computer logging data for more than 120 hours trying to catch the shower peak. And I did it:

FM passive radars as alternatives to Graves

Two weeks ago, on November 13, I left my computer logging meteors on Graves' frequency with the help of Baudmeteors. My goal was to catch the Leonids shower. But on November 15, around 16:40 UTC I detected one meteor and then, only silence for the next two days. Graves was turned off.

You don't realize how dependent the radio meteor detection is from Graves until you lost it. Around 20 UTC I realized there was no problem with my radio or just a very low meteor count. Graves were really off!

Baudmeteors: Capturing meteors with Baudline

I already knew Baudline. I used it some years ago as a simple FFT spectrum display but I didn't use it until last summer, when Iban, EB3FRN sent me a little script to automate meteor capture using Baudline. It turned out Baudline was much more than a simple spectrum analyzer display. Baudline turns out to be a powerful signal analyzer and quickly it becomes one of the most used programs in my computer.

ISS in Graves radar recording

From time to time, while recording Graves' signal with Spectran for meteor head echoes, strange things appear on the screen. Some of them are just "birdies" from the neighborhood, or noises from frequency inhibitors ( 142 - 144.5 MHz is deliberately interfered in some areas of Spain ). But sometimes I detect some "traces" in the spectrogram from unknown origin... until now.

Example of bistatic radar using VOR transmitters

Observing Doppler from airplanes over nearby transmitters is an interesting way to study Doppler from meteors, because the Doppler signature from airplanes is a slow-down version of meteors.

Detecting meteors by radio reflection in 2013

Some years ago I made meteor observations using the low VHF band TV transmitters around here with great success. Even with nearby transmitters I was able to see reflections from airplanes. Analyzing those doppler reflections some interesting info can be obtained. But with time, all those TV transmitters moved to digital at UHF frequencies so nothing can be heard now. I tried some amateur beacons but their low power and modulation are not adequate for this kind of observations.

From time to time as propagation permits I can hear some TV carriers around the usual frequencies: 48.250, 53.750 and 55.250 MHz but no meteor or plane reflections: They are too far away and their signals reach my antenna via multi hop sporadic E or F2 so they are not useful for meteor detection.

So, what are the most suitable signals for this kind of job right now?