Saturday, January 9, 2016

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.

FT-817 "dummy" IF filter

In this case, I get up to around 10 kHz without equalizing in DSB (Double Side Band), +/- 10 kHz at RF. But DSB is not usually a problem with Graves.

With this setup I recorded 4 days during the Quadrantids peak looking for head echoes over 3 kHz. And I found a few:

A 5 kHz head echo. Click to enlarge

I found no more than 10 traces of head echoes over 3 kHz during the whole 4 days, do I can conclude large doppler head echoes are quite rare, although quite useful to determine the meteor trajectory (more about this in a later post).

Also, I made an histogram of received meteors:

Histogram of Quadrantids 2016 using Graves radar

For me using Graves the peak was around 13-14 UTC on January 4. It is interesting to see the peak is visible every day at the same time.

Miguel A. Vallejo, EA4EOZ

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