# Month: April 2020

## Step to the neutron stars 13. A new attempt

At the beginning of February, I again made new attempts to catch the pulsar. Once it was a fail (cable disconnected from the antenna and I had noticed it too late), the result of another attempt is here. I had changed the observation place to quieter and I had increased the observation time to 1h5. […]

## Step to the neutron stars 12. First attempt to receive the signal

So all the components of the radio telescope are ready and its time to assemble them together and try them in practice. The first version of the amplification/filtering module is in the picture below: Here I will tell you about the first but wrong configuration. Anyway, a bad experience is also an experience, and I […]

## Step to the neutron stars 11. RF bandpass filter

In the case of artificial radio interference (Radio Frequency Interference), the external filter is a necessary part of the radiotelescope. Let's start with the basics. In the simplified case, the bandpass filter has two parameters: main frequency and bandwidth. The bandwidth is measured at -3dB, ie when the signal is twice weaker. The frequency in […]

## Step to the neutron stars 10. Noise

A step back to the radiometer equation There some points which bother me and I think it is important to mention. The RMS value of noise power (thermal noise) in the bandwidth of is: where is system temperature, and Boltzman constant. So, the noise of the system can be described by the value of temperature. […]

## Step to the neutron stars 9. How RTL-SDR works

The best article I have seen on the principles of the RTL-SDR receiver operation is described here. Here is a brief synopsis of this article. In a few simple steps, I will try to tell you how this receiver works. Step 1. Simple demodulation Let us assume that we have a signal with amplitude modulation […]

## Step to the neutron stars 8. Assembly and test of antenna

The construction of the antenna took time. But it ready and it wiggly fit in my apartment. The construction of the antenna I start with linking of the boom sections. I will remind the reader that I make the boom of three parts. Each part is a 1m long square tube (10x20x1000). For their connection, […]

## Step to the neutron stars 7. Some practical questions

Here I summarize some questions, which I had asked myself and on which I had found the answers. Why the impedance of the antenna is 50 Ohm when the open dipole has 73 Ohm? An antenna that has multiple elements also has an impedance that is different from the impedance of the dipole. The same […]

## Step to the neutron stars 6. Antenna theory in practice

In this note, I will progressively explain some basics of antenna theory and will present the results of antenna modeling. I had already used a few terms (directivity, impedance), which I had not introduced yet. So I think it is a good time for this. Lets will be normalized on peak value radiation pattern. The […]

## Step to the neutron stars 5. Antenna simulation

As any creative project have the turns in the wrong way, the same happens to me when I had considered an in-phase antenna array. The problem of this antenna is not only in matching but also in high mechanical complexity. The mechanical structure should be made from dielectric material. If I would be in my […]

## Step to the neutron stars 4. The choice of antenna type

So to be able to detect pulsar in reasonable observation time, the minimum gain of the antenna should be at least 14dB at 400 MHz. I choose a linear polarization for the antenna because it is the most simple configuration. The choice of antenna type is guided by several factors: budget and construction time, compactness, […]

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