DL8KDL, DN1KDL - amateur radio, electronics and computers

After moving my website to a new webspace, I must have forgotten to adjust some essential parts of its configuration. Unfortunately, for about one week many of my articles have not been accessible. Worse than that, I didn’t realize that there was a problem until now. I ask you and all the other occasional readers of this blog to please accept my sincere apologies for the inconvenience.

An interesting article on how to build your own D-Star repeater has been published on eHow.com: How to buy a D-Star repeater. A must-read for each amateur radio operator with a strong leaning towards subtle humor. Selfmade equipment of the 21^st century?

Anyone running his own home server on an Internet connection with dynamic IP addresses has probably experienced pain after trying to send emails from that server. Most providers have configured their servers so that emails coming from a dynamic IP will be rejected. Most providers prohibit using their mail servers as mail relays without prior authentication. The Postfix mail server can be configured to use a foreign mail server as its smarthost. In this case, Postfix will replace the local email address by a “public” one, which is supported by the smarthost and it will provide a username and a password to the smarthost as if it was a regular email application. This works well on single user machines, but with a multi user setup, other problems arise: Different users will use different email providers, have different email addresses and individual login data. Therefore using a single smarthost is not an applicable solution. Luckily Postfix is also capable of using different smarthosts for different local users. Unfortunately, configuration requires root privileges. In this article, I am going to present a short shell script which will enable every unprivileged user to manage his smarthost login data from his home directory. Read more…

More and more cafés, restaurants and hotels offer their customers access to wireless networks for free or for just a small fee. All these wireless networks can be dangerous: They don’t use any encryption. That means that everyone can listen to everybody else’s data just with a wireless card and appropriate software. This in turn means that everyone can read all the user names and passwords you use, if you don’t take any further precautions. Of course, for many internet services, you can use TLS or SSL encrypted connections. But what if you forget to activate TLS? What if that one service, which you have to use urgently, does not provide TLS at all? If you had a VPN gateway, you would have an elegant and simple solution for this problem. Read more…

The iso format is commonly used to store images of CDs or DVDs. Every day PC users are faced with the problem that they urgently need one or two files which are stored inside an iso image. Nobody really would like to burn a CD in this case. While Windows users need to use third party software, Linux users can easily mount iso images into their local filesystem. Read more…

Until recently my notebook, an old Acer Aspire 1520, was running Debian GNU/Linux as its operating system. While Debian was quite easy to install, some configuration files needed to be adjusted. As the Debian project aims to deliver well tested and stable software packages, many programs are only available in older versions. Therefore I wanted to test another Linux distribution and chose Ubuntu version 9.10, codename Karmic Koala. The results were quite promising. The installation is straightforward and can be done without any problems in a very short amount of time. In fact, not much is left to explain in this article… Read more…

This article describes the installation of the free and open source, Linux based router firmware OpenWRT on an old Netgear WGT634U router. The router is configured so that the operating system will boot from a USB stick. Also, a Huawei E160 3G USB stick will be configured. In addition, the APRS software APRS4R will be installed so that the router, in combination with a TNC and 2m transceiver, will act as an APRS gateway or fill-in-digipeater.

WGT634U based APRS gateway

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