DUBUS 2022

DUBUS 4-2022 Vol-51

Editorial.
17-Element Ultra Low-Noise Wide-Band LFA Yagi for EME and SatCom
This paper presents an improved design of the LFA Yagi while extended from 15-elements to 17-elements and reoptimized for both low-noise and wide-band performance. The antenna's structural data is provided for the EME and SatCom sub-bands along with design characteristics, sensitivity analysis, construction details, and test results ... [Antenna parameters | Radiation pattern].
Advanced Rugged LDMOS Transistors
Although GaN transistors have been all the rage in recent years for broad-band and high-frequemcy applications, LDMOS is still the leading technology for high-power amplifier designs from HF to UHF. Predominantly, rugged LDMOS can be used up to 500 MHz, and with the correct thermal design, rugged devices will withstand high levels os SWR up to 65:1 ... [Design limitations | New LDMOS].
Lunar Noise at 80 GHz
The expecyed EME activity in the amateur 4mm (76-80 GHz) band motivates to pay attention to the Moon's radiation itself, because the lunar noise is an important natural factor limiting the receiver system temperature and therefore the real sensisivity of EME receiving systems. We measured the lunar radio noise at various times during the Moon's apparent orbit ... [The radiometer at UA3AVR | Analysing the measured data | Atmospheric attenuation | Noise floor in EME communications | Math annex].
Echo Mode in WSJT-X 2.6.0
Most amateur Earth-Moon-Earth (EME) enthusiasts use echo testing as a tool for optimizing station performance. For the past twenty years the software package WSJT-X and its predecessor, WSJT, have included a basic Echo mode to facilitate such tests. This capability was developed and tested mainly on the VHF and lower UHF bands ... [Operation | Echo mode setup | Measuring SNR].
A selective no-tune 432 MHz Transverter for SDR
A selective no-tune 70cm transverter with modern parts is decribed that is well suited for use with and SDR ... [Preamplifier | PIN diode attenuator | Mixer | TX amplifier | Local oscillator | PCB Layout].
Low-impedance Antennas with extreme high F/R ratios
It is well-known that for 50-ohm antennas the reflector has to be mounted rather far away from the driven element, leading to negative effects on the F/R ratio. However, if we reduce the impedance at the feed poin, simple feeds can be realized which enables non only excellent F/R ratios but also high antenna gains ... [12.5-ohm antennas | below 10-ohm | Simulations].
Microwave Europe.
Microwave North America.
Microwave Japan.
Tropo Reports.
October 2022 Solar Cycle 25 Report.
Aurora Reports.
News & Comments
Expeditions, Beacons update, Comments.

DUBUS 3-2022 Vol-51

Editorial.
A Life for Amateur Radio - a look back
DL2AM in the 83rd year of life ... For many years, I organised the field day for shortwave for the DARC P16 local branch, which took place on Mt Hohenrucken. In the course of time, the radio frequencies became higher and higher and therefore experimentation increased. My first attempts were on 2 m and 70 cm. By reading a lot of technical leterature ... [122 and 241 GHz QSO story | Photo album].
Updated 122/134 GHz Transceiver
Adapting a mmWave transceiver module intended for distance measurement over 10-20 metres to one that can communicate over fifty or more kilometres has many challenges. Like all projects, the process of experimentation continues to the point where the collective improvement makes the original design obsolete. With newer 120 GHz modules now released, it was also time to upgrade the base project. This article details the upgraded V4.0 main PCB and new RF PCBs ... [122 GHz PCB and circuit diagram | PLL & control PCB and circuit diagram | 40 MHz VCTCXO and circuit diagram | Part list].
Waveguide Matching Plates. Connecting different size waveguides
For most amateur microwave bands, there are two or three standard waveguide sizes that will work. However, the components we might have for a given band are typically not all the same size waveguide, so we are left to find a way to fit them together. Since waveguide characteristic impedance is a function of wavelenght in each size guide, the impedance of each size guide is different ... [Sketch of waveguide matching plate | 10/24/47 GHz plates | Measurement | Reference].
Compact Low-Noise Reflector Antenna System for Satellite Communication
We discuss our use of the new radio amateur satellite-based transponder, QO 100, installed on the Es'hail 2 geostationary satellite, confirming that the modest-size earth station antennas recommended by the satellite producer can be successfully used for either uplink or downlink communication ... [G/Ts ratio and antenna size considerations | Feed design | System design | LNB test | Reference].
Direct Upconverting Beacon Drive Source - as used on GB3SCS
The Bell Hill family of microwave beacons, GB3SC#, operating on the 2.3 to 24 GHz amateur bands have been gradually developed and enhanced over a period of more that 25 years ... Over the years these beacons progressed through frequency locking to a master reference locked to GPS and then adding multi-frequency WSJT modes to the keying sequence. At each upgrade, to make use of existing hardware as much as possible, the 3.4 to 24 GHz beacons all adopted the "reverse DDS" locking technique ... [Quadrature upconverter | Baseband DDS].
First ever QSOs DL-PA on 122, 134 & 241 GHz.
Aurora Reports.
August 2022 Solar Cycle 25 Report.
Microwave Europe.
Microwave Spain & Portugal.
Microwave VK & ZL.
Microwave North America.
Microwave Japan.
Tropo Reports.
8, 6 and 4m News.
News & Comments
Expeditions, Beacons update, Comments.

DUBUS 2-2022 Vol-51

Editorial.
A Very Low Noise Voltage Regulator
With oscillators, noise from the power supply is easily propagated to the output signal. The same is true for very low noise amplifiers where PSSR must sometimes be sacrificed for other features ... [Low noise regulator circuit diagram | Layout | Noise density plot].
Building your own Waveguide Calibration Kit
For the serious weak signal microwave operator a waveguide system is almost mandatory, at least on the receiving side. There is a need to measure the various items used. It also is sometimes necessary to measure phase, hence the need to use a vector network analyzer and its associated calibration kit ... [OSL and OSLT calibration | Waveguide calibration kit | The Ham calibration kit imperfections file].
Checking the Dish
This report describes two pratical ways to verify te illumination and physical curvature of a parabolic dish ... [RF probe | Test set | Optical verification of the mechanical curvature of the dish].
Is it possible to predict Sporadic-E? G3YLA tries every day!
British radio amateurs and TV viewers are familiar with him: meteorologist Jim Bacon, G3YLA, presented the weather forecast on BBC TV for many Years. Viewers' letters and his own obervations of disturbed TV images during enhanced propagation then aroused his special interest, first in tropospheric propagation and later in Sporadic E ....
Sporadic-E Summary 2021 - 144 MHz
39 maps and comments for Europe, North America, Australia and New Zealand Es openings.
Q65 3cm Beacon
Having jumped on the digital band wagon several years ago, 6 meter FT8 to Europe every summer, it was readily apparent that digital modes were made for beacons ... [10 GHz beacon block diagram | Beacon requirements and operation | Project photos | Circuit design].
10 GHz Terrestrial Tests from Hawaii to California in Summer 2022
The basis of this exercice is to use EME capable 10 GHz portable equipment in conjunction with digital modes to attempt to extend the 10 GHz terrestrial World Record of 2793 km to around 4000 km ... [General plan | Equipments | Detailed objectives | Appendix: propagation on 5.7 GHz on the Hawaii to California path].
Aurora Reports.
April 2022 Solar Cycle 25 Report.
Microwave Europe.
Microwave North America.
Microwave Japan.
8, 6 and 4m News.
News & Comments
Expeditions, Operations, Beacons update, Software, Days with good EME conditions.