Johnson's Techworld

 There are several Roll Call and Non-Roll Call HF Nets in VU Land, as can be seen from the QSL NET page of VU2JOS . Today VU3CDK suggested a different type of net: A Technical Discussion Net. It could be a 20-30 minute session on popular HF bands, either on 40m or 20m, to which both amateur radio operators and Short Wave Listeners can tune to. Topics suggested were, radios, antennas, propagation, satellites, new technologies and innovations. Interested hams can directly participate in the discussion while SWLs can mail in their questions in advance. Each session could have a topic announced the previous week and 10 minutes could be alloted for open house discussions. This will not be of the regular checkin-signal report pattern. Discussions will be centered on the theme of the week and net start and end time will be fixed. Potential time slots could be chosen between either 6.30 am or 7.30 pm, on Saturday or Sunday. This will help newbie hams who are trying to setup their stations ...

  Gamma match is an arrangement used to match the impedance in both HF, VHF and UHF antennas, typically for Yagi-Uda type of antennas. As HF Yagi antennas are quite large, I do not have an option to use them on my small terrace. I have homebrewed both VHF and UHF Yagi antennas with Gamma match for impedance matching. Though the impedance of a simple dipole of around 70 Ohms is suitable for usual commercial radios with 50 Ohms impedance, Yagi-Uda antennas with multiple parasitic elements may have much lower impedance in the range of 25 Ohms or lower. This needs matching and Gamma match is a popular method. It derives its name form the similarity to the Greek letter Greek letter gamma, that is the capital letter gamma (Γ).

 As we go higher up in frequency, a GPS Disciplined Oscillator (GPSDO) is needed for good frequency stability. Homebrewers are familiar with the drift of our VFOs in yester years, making it difficult for the receiving station to track our signal exactly! GPSDO will have an antenna to get GPS signals for controlling the local oscillator signal. When the GPS signals are not being received, the stability will depend on the stability of the local oscillator. Higher stability of local oscillators can be obtained by controlling the temperature in a special housing. Crystal oscillators enclosed in a temperature controlled chamber to prevent expansion and contraction of the crystal which could cause frequency fluctuation, is known as Oven Controlled Crystal Oscillator (OCXO). Now lower cost GPSDOs have become available which have high stability so that drifts will be only in the range of one hundreth of a Hz! With these it is even possible to track very small changes in frequency of t...

 Today I was very happy to establish my first two way contact with an amteur radio station in Sri Lanka through the FM Repeater on International Space Station. I was using a Moxon Yagi on my first floor terrace and beaming my signals on VHF to the International Space Station during its pass beyond Sri Lanka today morning. I heard 4S7NDR from Sri Lanka on the downlink frequency on UHF and called back. Soon I got a reply from him with a friendly greeting as well. Though Sri Lanka is not very far from here, there are very few Low Earth Orbit Satellite Amateur Radio operators there. In fact I have not heard anyone other than 4S7NDR from there over the past one year of my LEO satellite operations. We are on the look out for establishing contacts with amateur radio operators from other Island Nations of the Indian Ocean. 73 de Jon, VU2JO

  Welcome to the wonderful world of amateur radio, which also popularly known as ham radio. Ham radio operators have a valid license in their country for two way wireless communication using amateur radio equipment. There are around 7,50,000 radio amateurs in the United States of America, and 3,50,000 each in Japan and European Union. Exact numbers may vary and this is only a rough estimate. All of these licensed radio amateurs may not be active either. Most popular mode of short distance communication in amateur radio is using hand held radios like walkie talkies using either VHF (Very High Frequency) or UHF (Ultra High Frequency) two way radios. Distance covered by these small radios can be enhanced by availabalitiy of Repeaters in the region. Repeaters receive the signals from these radios and re-transmit them on another frequency. As the repeaters usually have higher power and are located at a height, they have range of even several hundred kilometers. The popular mode of lon...