Archives for 2012

SDR – where are we today?

Woman looking through a mangifying glas

At the second HamRadioWeb convention in Bolognia, Italy Claudio, I4LEC has given a great presentation about the current status of SDR. In his presentation he starts with SDR principals then analyzes then the strength and weaknesses of available Software Defined Radios (mainly FlexRadio Products) and finishes with a comparison against TS-590 and Elecraft K3. The presentation is entertaining and informative at the same time. Definitely worth having a look at!

Claudio was so generous the grant the permission to show it on my website!

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Evolution of the DG8SAQ VNWA

With his low cost, high precision Vector Network Analyzer, Tom (DG8SAQ) started a revolution in Ham Radio. Thanks to his efforts, amateur (and professional!) enthusiasts have now the possibility to perform measurements which were reserved to well funded HF laboratories before. In this video, Tom explains the evolution and capabilities of his VNWA and why even NASA relies on it now as well!

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A simple broadband 4:1 Balun Transformer

During the summer break it became quite here on my blog. While Instead of chilling at the beach, I spend a lot of time on new Hardware and Software projects. Most of them are done, and now it’s time to document them.
In this blogpost I want to share the construction of a versatile 4:1 Balun. In combination with ladder line and an automatic Antenna tuner you can use any dipol on almost all frequencies.

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How to measure Ground Conductivity

Picture of a Measuring tape
Over the last years I spent a lot of time simulating antennas. One annoyance I encountered over and over was the unavailablity of values for ground conductivity and the relative permittivity. Two figures which have quite an impact on the antenna performance, especially on vertical antennas. This finally led to the conclusion that both figures need to be measured. In early 2012 I built a measurement kit and finally determined ground conductivity and relative permittivity at our contest station ED1R .

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Community Improvement on Tuning wheels

FlexRadio Contest Knob alternative The community of Flex-Radio enthusiasts which select the DJ Console as their main user interface is steadily growing. Community members are sharing pictures how the use and improve their DJ Consoles to make it even better. After several labeling solutions, a recent discussion on the PowerSDR-UI Yahoogroup ended up in an haptic improvement for the DJ Console’s tuning wheels.

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My A73A presentation at the Contest Forum

Last weekend I was invited to speak in the Contest Forum at HamRadio convention in Friedrichshafen, Germany. The presentation was about our Contest Activity from northern tip of Qatar. We participated in the Multi/Multi category and used almost exclusively verticals antennas. For everyone who missed the event, here are the slides!

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DH1TW with new website design

After launching this website 5 years ago the time has come to move to modern design. It took me some time and I had a steep learning curve considering modern webdesign but it was actually also fun to dig deep into CSS3, Javascript and HTML5.

Here are the design criterias I tried to follow:

  • Optimized for mobile devices
  • First class accessibility for disabled and blind visitors
  • Integration of social services
  • Fast loading time
  • Responsive webdesign
  • Lean with good readability

What do you think? I would appreciate your thoughts!

Coax Stubs for 20m and 40m

Where ever I operate contest in a multi transceiver environment interferences between the 40m and 20m are guaranteed. An easy way to reduce interferences are coax stub filters. Dave, K1TTT has a great website with a lot of useful technical resources. One of them is dedicated to coax stub filters. After building up two sets of stub filters (one in Namibia – V55V and the other one in Spain at ED1R) it’s time to document it.

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Quick & Easy: VPN through SSH Tunnel

VPN with SSH tunnels
In untrusted environments like open WiFi Hotspots you want to tunnel your traffic through an encrypted channel to the internet. Last year Firesheep has proven successfully how dangerous surfing in a public, non encrypted hotspot can be. A Virtual Private Network (VPN) can also be used to access internet services with IP Address restictions (e.g. Video or Music streaming services like Netflix, Hulu or Spotify). In this post I’ll show you a VPN solution which can be easily set up and used. The tutorial will work with the Windows and Mac OSX.

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How to set up an Ubuntu Server on Amazon EC2

If you have ever dreamed of having your own server, then I have good news. It has never been easier! In this tutorial I will discuss why you actually want to have your own server, how to setup your own Linux (Ubuntu) Server in less than 10 minutes and how to do this for free!

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