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Beiträge zum Thema: ADS-B Receiver

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In unserem Blog möchten wir Ihnen wertvolle Beiträge zu Themen in Bereichen wie ADS-B, Mode-S, MLAT, Flight Tracking, Antenntechnik und 1090 MHz geben.
Wenn Sie Interesse an speziellen Beiträgen haben, lassen Sie es uns wissen: support@jetvision.de

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Explaining Noise Figure and Gain

Gesamten Beitrag lesen: Explaining Noise Figure and Gain

We do see various offers for any kind of preamplifiers that are promising wonders, so let me give an explanation for the true important factors when using such devices. During my active time at ham radio I was very active in earth-moon-earth communication, that is sending signals to the moon and getting the echo back, up to 5.6 GHz, far beyond the ADS-B frequency of 1090 MHz. This is one of the most sophisticated operational modes in amateur radio, and needs high transmission power as well as most sensitive receivers. This knowledge was brougth into the receiver design of the Mode-S Beast as well as the Radarcape.

Now we do see a lot of preamps on the market. Most of the time gain is given for them, but the more important value of noise figure is missing. There are synonyms for both that can be understood easier:

  • Gain is like brightness of a monitor
  • Noise figure is contrast or somehow the minimum black level

You may quickly understand by these synonyms, once you have destroyed the black level of your picture into a kind of grey, you no longer never can see the small nuances of weak black symbols on your screen. It is the same with radio signals: Once you have destroyed the noise figure, you never will get it back. Even turning the brightness on (= adding gain), you never will recover the true cold black on your screen but instead simply amplify your grey even more.

This brings me to the cable: A cable is attenuation. With our video screen, this is similar to a milky glass in front of it. So you don't see the nice pure black any more but a little bit of grey. Of course, your bright symbols still appear readable. If now you insert an amplifier, the bright symbols will become brighter, but also the grey becomes brighter. But the weak nuances of black are lost.
However, if you amplify before passing the lossy section, you will amplify the nuances of black we're talking about, and they may be still readable behind the attenuation.

Even worse, electronic devices may become overloaded by the shiny bright parts. So this means with an amplifier after the cable and in front of the receiver, you may make things even worse. Only if your device is really deaf or has a lot of internal losses, an amplifier in direct front of the antenna input will improve the situation.

Our Active Diapason antennas for 868MHz (FLARM) and 1090 MHz (ADS-B) are equipped with an amplifier directly connected to the antenna element, which is the pure optimum. Their noise figure is somewhat 1 dB, a quite reasonable value for an antenna that partly sees warm earth within its diagram (less than, say 0.8 dB, only makes sense for space pointing antennas). They are sold with 20 m cable because the gain should not overdrive the receiver, and because this cable attenuation is completly knocked out due to the low noise figure.

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How do I find my Radarcape

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Do you have one of the following problems?

How do I access my Radarcape in my local network?

My Radarcapes’ IP-Address changed and I do not know the new address.

How do I get an overview of all my local Radarcapes?

I don't want to use the roundabout way over my router everytime the IP changes.

 

One easy solution: CapeFinder

We created a small tool to offer you a quick and easy way to get information of all Radarcapes in your local network. CapeFinder works out of the box, you just need to download and start it.

 

What does it do and how does it work?

CapeFinder automatically detects all network interfaces. Then it starts scanning to find connected Radarcapes. In addition, it gathers some information like the current IP-Address, Hostname, Software-Version and the MAC-Address.

 

Where to get and how to use?

Simple as that: download the latest version, open it on your PC and allow network access if asked.
Use our wiki page to download the latest version:http://wiki.modesbeast.com/Radarcape:CapeFinder

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The Development of Our Flight Tracking Products

Gesamten Beitrag lesen: The Development of Our Flight Tracking Products

Ham radio experience

My motivation of this project comes from a more than 25 years ham radio experience, mainly weak signal and GHz operation, a lot of interest in signal processing, and a professional background as an electronic development engineer.

I managed to combine all my knowledge in this project, and was able to fill some gaps with the special knowledge of some friends with special know-how in microwave and digital electronics.

It all began around 1995 when I mainly participated in radio contests on 144 MHz up to 2320 MHz with always good success. However, on the upper bands there was always one that was better. I heard that part of his success was his efficiency in aircraft scatter, a method when on 1296 MHz and 2320 MHz an aircraft is used as passive reflector. I also used this mode, mainly to the Netherlands, but wasted a lot of time waiting for aircraft passing the hot spot. A flight tracker called SBS-1 was the key for my competitor, which showed that there are aircraft in the scatter zone. However, for that time, this unit was far out of reach within my budget. Also, the thought of a closed system never attracted me very much.

ADS-B Receiver

Around 2007 I found more about ADS-B Receiver, 1090 MHz antennas and Software like Planeplotter, the miniADSB receiver and the PIC decoder and brought it into work. Back to ham radio thinking, I was surprised about the bad performance and started tweaking. The first result was the floating comparator, which adjusted the digitial comparator automatically to the signal level, thus avoiding the awful donut effect of this set-up. Driven by an "is that all?" thinking, I asked how reception could be done without the bottlenecks of a PIC, using an FPGA as decoder. Not knowing anything about FPGA, I started teaching myself. I avoided some weaks of the existing designs and brought in my experience from Earth-Moon-Earth communication. After some time, the ADS-B Mode-S Beast was born, which was even at the early stages outperforming all existing units.

By the way, why is it called Beast? Well, at that time Planeplotter only had some devices like SBS-1 and PIC decoders as frontend, and their weak performance resulted in only a few frames per second. With the Beast, Planeplotter suddenly had to handle much more messages and went into a stall. "Hey, what a little ugly beast", I thought, and so the name was born. Those early devices did have so less performance that even a hexdump "AVR format" or CSV protocol (Port 30003) was enough for data transmission, and I introduced the Beast-Binary protocol.

MLAT

A few years later I sat together with some friends, talking about aircraft not yet localized and had the idea to catch them with multilateration (MLAT). At around the same time little Linux based boards grew on the market, mainly Raspberry Pi and Beaglebone. This matched to our need of remote operation and LAN interface, transporting the data to a central server - the Mode-S Beast only had USB and a not handsome and expensive LAN solution based on Xport. I decided to use the Beaglebone because it has connectors that allow an easy integration into a metal case and because of power supply problems of the Raspberry Pi. For easy and accurate multilateration I choose a GPS module as timestamp. The add-on boards on the Beaglebone are named "capes", and so my ADS-B flight decoder was named "Radarcape".

Flightradar24 asked for the Radarcape as backbone for their own network with their proprietary software in order to provide updates for their flight tracking app. They showed me an ADS-B antenna which was hardly worth the name. Due to my ham history, I found a manufacturer in Italy who makes very good antennas which really proof the given technical data. Our portfolio widened up and so the web shop warehouse increased to a whole set up.

Jetvision

In 2014 I joined the activities of existing jetvision, who had some solutions with RTL-SDR and USB DVB-T dongles, and my meanwhile founded company took over the brand "jetvision". In May 2016 my company took over the whole business of these and Planevision Systems offers rack solutions based on the Radarcape only. We now are a team of around 8 people working for the development, marketing and sales with a great support by friends and other companies in all themes.

(Günter, CEO)

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