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Sunday, July 16, 2017

Considerations about the Hiland Adjustable DC Regulated Power Supply Kit‎

My "lab" power supply was a homemade one I made/upgrade some years ago. It was constructed around a LM350K TO-3 regulator and worked very well. But I really missed one function: adjustable current limit.

The LM350K regulator has a fixed current limit around 2-3 amps, but usually that is just too much current for a prototype. Many times, when something went wrong, one or more components went burnt.

Monday, May 29, 2017

Shifting to Linux

Some time ago I received a notification via Twitter about someone who installed XP on his notebook after reading my article about Linux I wrote some years ago. I think the tweet is ironical, but that doesn't matter.

The fact is I didn't remember I wrote that article, but actually I'm using Linux full time in my desktop computer. How can it be possible? How someone who ranted about Linux on the desktop ended using Linux full time?

Friday, May 12, 2017

About the CTS OCXO Board

After some time working 10 GHz with a TCXO based local oscillator I decided to upgrade it to a OCXO because stability was not as good as I would expect. It was ok for a short QSO but after some time I must search in frequency to the other station again. It was not very practical.

I decided to try a CTS OCXO Board from ZL2BKC. It is a small board with a brand new 10 MHz OCXO made to complement the ZLPLL board, and it is available in kit form for just $20: a bargain!

Sunday, April 10, 2016

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.

Friday, April 8, 2016

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.

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.

Saturday, November 28, 2015

Simple WGS 84 - ECEF conversion functions.

One of the most unexpectedly complicated things I have found during my research into determining the orbit of a meteor using Doppler measurements is the conversion between geographical coordinates and rectangular, or Cartesian coordinates, also called ECEF (Earth Centered Earth Fixed) coordinates:

At first sight it seems easy: The earth is a sphere, so it only need a few sines and cosines. But later, when you need more precision, you discover earth is not a sphere, it is an ellipsoid, so things start to become problematic.