Hardware

Tobias (DH1TW)

2 minute read

One of last years projects was the improvement of our Contest Station ED1R. For the various Yagis we needed smart ways to combine antennas. Instead of buying commercial stackmatches (antenna combiners) I decided to build them up buy myself and adjust them to our needs.

Tobias (DH1TW)

1 minute read

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!

Tobias (DH1TW)

3 minute read

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.

Tobias (DH1TW)

5 minute read

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.

Tobias (DH1TW)

1 minute read

The community of Flex-Radio enthusiasts which select the DJ Console as their main user interface is steadily growing. Community members are sharing pictures]2 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.

Tobias (DH1TW)

3 minute read

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.

Tobias (DH1TW)

1 minute read

It seems that the exchange of GU74b / 4CX800 tubes in Amplifiers like Alpha91b, Acom2000A and Acom1000 is of more interested than originally expected. In my post on how to replace the tubes of an Alpha91b I explained in depth why it is so important to recondition, to “getter”, the tubes at least 24 hours before any other voltage can be applied. Often amplifiers apply automatically HV and grid voltages which makes them unsuited for the gettering process. My Buddy Matthias, DK4YJ built…

Tobias (DH1TW)

1 minute read

A friend of mine recently was very generous and sent me four used 4CX800 / GU74b which he didn’t need anymore. The tubes where traveling a while and through several non-EU countries. Today the parcel finally arrived. I have already heard wild stories about customs, but I didn’t expect this: Customs drilled holes in two tubes and later opened them with a saw. Checkout the pictures.

Tobias (DH1TW)

32 minute read

Image of FlexRadio FlexcontrolI’m a believer in true knob and button radio interfaces… and I’m not the only one. A small team, formed around Stu, K6TU developed the Contest Knob, which is now today manufactured by FlexRadio Systems under the name FlexControl. In this interview K6TU reveals the ideas behind the Flex-Control and describes in detail the steps from the design to the industrial production.

Tobias (DH1TW)

2 minute read

In preparation of the upcoming CQWW 160m Contests my friend Hannes, DK1NO was so kind to give me one of his W7IUV broadband, high IP3 preamplifier. Thanks, Hannes! Without knowing the exact performance data, I ran a few measurements with my Network Analyzer on the amplifier to determine the Gain and it’s operational fitness. Read on for measurement results and additional notes on how to measure active components.