DUBUS 2025

DUBUS 4-2025 Vol-54

Editorial.
A 200W+ GaN PA for 1296 MHz
by Charlie Suckling, DL3WDG
GaN devices are becoming more widely adopted by amateurs for high power PAs in the microwave bands. Compared to Si and GaAs devices, GaN offers higher gain, operating frequencies and efficiency, due to the wider band-gap, higher electron mobility and lower thermal resistance of the substrate materials used in the fabrication of the devices. The author first got the opportunity to work with GaN about 15 years ago and initally developed a number of amplifiers for 3.4 and 5.7 GHz ... [Amplifier development | Construction details | Testing and Performance | On-air tests].
Almost 30 Years of VE7BQH Antenna Tables
by Hartmut Kluver, DG7YBN
Whar is it about? Tge Gain-to-Temperature Ratio of an Antenna (G/Ta) is a function of Gain in boresight direction divided by the Antenna Temperature. Antenna Temperature is the sum of any noise picked up by the antenna. Noise from the sky (Tsky) is contributed by cosmic background radiation ... [First ever widely published G/T table | Basic theory | Antenna performance].
Image Rejection Improvement and LO Nulling on IQ Mixers
by Luis Cupido , CT1DMK
Recent advances in the microwave and millimeter-wave devices, namely in MMIC designs, lead to the availability of single chip up-converters and down-converters using image rejection techniques so that TX and RX chain depend less on the image filtering and also to enable zero IF telecommunication systems. Radio-ham designs soon adopted these devices ... [Mixer concept | Forcing amplitude and phase balance | Approach for an existing design | The LO leakage].
TinyPLL - locks without a PLL chip
by Daniel Uppstrom, SM6VFZ
A crystal oscillator is not always stable enough. Operation on UHF and above demands much more than on HF for basic frequency accuracy and stability. And the popularity of digital modes has highlighted the need for an accurate, non-drifting signal also on lower frequencies. To solve this problem ... [Principe of operation | Test board | Circuit diagram].
A 47 GHz EME Setup
by Ivan de Cesaris, IZ0JNY
Sergei RW3BP and Manfred DL7YC have shown pioneering groundbreaking efforts at the 47 GHz band. This year, they achieved remarkable milestones by successfully completing a series of EME QSOs utilizing both the Q65 mode ... [The transverter | The feedhorns | The LNA | Control board schematic | Software].
10 GHz Booster for IC-905, Project Follow-Up
by Mauro Ottaviani, IZ1OTT
Following the successful assembly and deployment of several units now operating with high user satisfaction accross EU and the USA, I'd like to share an update on my 10 GHz Booster for the IC-905/CX10G ... [Updated design overview | PTT and SEND signal clarification].
Bragg effect: Look left and right!
by Nils Schiffhauer, DK8OK
The Bragg effect occurs when radio waves encounter moving sea waves. Certain Doppler traces can then be detected in the reflected signal. Nils Schiffhauer, DK8OK, has investigated this fascinating connection between radio waves and the sea waves in theory and practice. Anyone with an SDR can do the same ... [Spectrogram demo | Simulated Doppler spectrum | WERA and CODAR observation].
REF / DUBUS European EME Contest 2025 Results.
The next REF / DUBUS European EME Contest 2026.
Tropo Reports.
Microwave North America.
Microwave Japan.
Microwave France.
Microwave UK.
Microwave Spain.
Microwave Italy.
News & Comments
Contest, Expeditions, Beacons update, Comments, Classified Ads.

DUBUS 3-2025 Vol-54

Editorial.
Finding your Antenna's Position by the Milky Way
by Joachim Koppen, DF3GJ
The Milky Way may come handy, if the positioning system of an antenna on 1420 MHz (or nearby) does not work, is unstable or not calibrated, and we need to know the actual position in the sky where the antenna points to, but cannot make use of the Sun. Recording the noise at 1420.4 MHz during the entire 24 hours picks up the Milky Way's emission in the line of atomic hydrogen. During this time the galactic equator will pass twice through the antenna beam ... [The Method | How to proceed | Analysis].
GaAsFET LNA Bias - Simple, Cheap, and Fool-resistant
by Paul Wade, W1GHZ
Last year I read an article about negative bias for GaAsFET and newer low-noise devices using an optoisolator to generate the negative voltage ... The article suggested that connecting the LED in the optoisolator in series with the FET current could ensure that the FET would never operate without bias ... [Circuit | How does it work? | Design Procedure].
RG-213 Coaxial Chokes for Yagis: HF Utility vs VHF Constraints
by Justin Johnson, G0KSC
For the technically-minded radio amateur, particularly those employing Yagi-Uda arrays, achieving the theoretical performance of their antenna system hinges on meticulous attention to detail, especially concerning the feedline ... [The InnovAntennas Choke Calculator | Air-Wound Choke Mechanics | The VHF Challenge | Effective VHF Choking Techiques].
RA3AQ's Rectangular to Circular Waveguide Transitions for 47/76 GHz
by Matej Petrzilka, OK1TEH
The vast majority of contemporary equipment for tropo operation in the 47 ant 76 GHz bands is built on the principle of a simple sub-harmonic mixer, where the output power is around 0.5 mW or in the case of a reversible amplifier usable for both RX and TX, a maximum of 30 mW ... [Waveguide Transitions | Dimensions].
100 years ago: The discovery of the ionosphere
by Nils Schiffhauer, DK8OK
On 11 Dec. 2024, it was 100 years ago that the newly appointed physics professor Edward Victor Appleton, together with his first assistant Miles Barnet, proved the existence of the ionosphere in an epoch-making experiment ... [Research | Cooperation with the BBC | Fading pattern | Today].
Moonbounce Communications in the 47 GHz band
by Miguel Pelicano, CT1BYMbr>It has been almost three years since my first tests receiving signals reflected off the Moon. On July 4, 2022, I successfully decoded a signal transmitted by Manfred (DL7YC) using only a 90 cm offset parabolic antenna ... [System development | First 47 GHz EME QSO].
Earth-Moon-Earth in the mm-wave range - a historical perspective in the 21st century
by Manfred Plotz, DL7YC
The appeal of Earth-Moon-Earth (EME) communication has always been the tech nical challenge of reflecting radio waves off the moon. While EME has been operating on traditional bands such as 2m or 70cm for decades, the mm-wave range long representing a seemingly insurmountable barrier. Nevertheless, in the early 2000s ... [How it begun | Experiments | What do you need for a successful QSO].
Experiments on 47 GHz Moonbounce
by Hans van Alphen, DC1EHG / PA0EHG
Since 2010 I became interested in moonbounce on 47 GHz. After my previous successes with small power on 24 GHz EME the next step would be 47 GHz ... [The story | Tests].
A 24 GHz System for EME Activity
by Ivan de Cesaris, IZ0JNY
In this article, I describe the implementation and design choices behind the construction of my 24 GHz system for EME communications ... [The full assembly | The main unit | Operating sequence].
Tropo Reports.
Holiday Activity Report SV8/OE2UKL in KM08HT.
DK0NA, Report from a Contest Winner.
Microwave Italy.
Microwave Spain and Portugal.
Microwave France.
Microwave North America.
Microwave Japan.
News & Comments
Contest, Expeditions, Beacons update, Comments, Classified Ads.

DUBUS 2-2025 Vol-54

Editorial.
Dish Antenna Diagnostics at 30 THz
by Barry Chambers, G8AGN
Following on from a successful 523m 30THz test carried out in the autumn of 2024 by G8AGN and G4APV, an attempt was made over a longer path of 610m but this was unsuccessful. The reasons for this are not yet clear but it led to an investigation into the radiating properties of the 30THz transmitter's spiral heater feed and its associated dish antenna ... [InfiRay P2 Pro infra-red camera | Telescope configuration | Test signal].
Measuring the Atmospheric Attenuation at 47 (and 24) GHz
by Oachim Koppen, DF3GJ
For frequencies above about 20 GHz the attenuation of signals by the Earth atmosphere becomes important. ITU's Recommendation P.676 predicts for any radio frequency the average attenuation at the zenith based on local weather data. The actual attenuation we can determine by measuring the noise from the empty sky at various elevations. We did this on 47 and 24 GHz for various sky situation ... [How to Measure Sky Attenuation | Sky profile measurement | Measure attenuation of the solar signal | The Moon on 47 GHz | The Sun at 24 GHz].
2m TEP Update Spring 2025
by Joachim Kraft, DL8HCZ
In spring and fall of 2024, TEP paths between southern Europe and South Africa were bridged on 2m for the first time in decades ... [2m TEP paths 2024/2025].
Sporadic-E Summary 2024 – 144 MHz
by Joachim Kraft, DL8HCZ
55 hotspot maps ... [Europe | North America | Australia and New zealand | Asia and Far East].
75 years ago: The World's very first 2m-Es-QSO
by Joachim Kraft, DL8HCZ
On June 24, 1950 W5VY worked W8WXV on 144 MHz for the world's first known 2-meter contact via sporadic-E, which also set a new distance record for that band ... [The historical 2m Es path].
60 years ago: Europe`s first big 2m Es Opening
by Joachim Kraft, DL8HCZ
60 years ago, on July 4, 1965 from 0820-1126 UTC, the very first big 2m Es opening was observed in Central Europe ... [The historical 2m Es path and log].
3 GHz Bridge Reflectometer. Reflection Measurements at high Frequencies
by Aljaz Blatnik
For radio hams, a bridge reflectometer is a real lifesaver when you dont have access to a fancy network analyzer ... [The principle of using a bridge | Construction plan of a bridge | Directivity comparison | Required materials].
Non-Line-of-Sight DX Propagation at 730 nm (Near Infrared)
by Rex Moncur, VK7MO, Dr Andrew Klekociuk and Merv Millward, VK7EKA
VK7MO and VK7EKA, have been conducting tests on 730 nm, 410 THz, (near infrared) over a 206 km non-line-of-sight (non LOS) path over mountains in central Tasmania. The transmitter uses a 90-light emitting diode (LED) array ... [Background | Humidity limits for cloud formation | Summary of results | Determining cloud formation | Transmitter and receiver].
A High Efficiency Solid State kW Amplifier for the 2m Band with Planar Baluns, Part 2
by Sylvain Klingebiel, F6CIS and Michel Bourdon, F6DZK
The aim of this article is twofold: To characterize several thermal pad references in order to facilitate supply in the event of obsolescence. To simplify the mechanics of the copper base plate and validate this new structure with different thermal pads ... [Characterization of thermal pads | Milling of copper baseplate | Mounting the LDMOS | Measurements].
Microwave Japan.
Microwave Europe.
Microwave Italy.
Microwave Spain and Portugal.
Microwave North America.
Microwave Australia.
Aurora News.
News & Comments
Contest, Expeditions, Beacons update, Comments, Classified Ads.

DUBUS 1-2025 Vol-54

Editorial.
Building a Transverter Box for 10 GHz with 7W Output
by Ivan De Cesaris, IZ0JNY
In this article I document the project of a transverter box for 10 GHz, with a power output of 7W and feed integrated into the enclosure. I give all the technical information and the reference of each component ... [Project description | Dish feed | Coax relay | SSPA | Low-noise power supply| Enclosure | Assembly].
Large W2IMU Feedhorns for Improved G/T on Offset Dishes
by Paul Wade, W1GHZ
The W2IMU dual-mode feed has been popular for many years. It offers high performance and is relatively easy to make. The classic version, 1.31Lambda aperture diameter, offers best performance for a F/D around 0.5 to 0.6, which gives a pettern which is a bit wide for common offset dishes, leading to excess spillover which results in increased noise temperature. Still, it provides very good performance, particularly for terrestrial communications. In his original article, Dick Turrin, W2IMU, also described a large version, 1.86Lambda diameter. The large version is best for ... [Dual-mode feedhorn | Feed fabrication | G/T | Sun noise measurement | Comparison].
High Performance 1.9m Station for 23cm EME
by Bill Siino, KB2SA
Discussed here is a high performance 1.9m mesh wire dish station for 23cm EME. This paper helps quantify the extraordinary performance observed by some 23cm EME stations (e.g., KA1GT) and explores further enhancements to this performance. A key measure of performance is Antenna Gain divided by Antenna Noise Temperature (G/Ta). We wish to maximize this ratio for best ... [Why use a 1.9m dish | Loss budget | Simulation highlights | Feed design].
"WSPR Radar": Final Crash Landing of a windy Idea
by Nils Schiffhauer, DK8OK
In September 2021, Dr. Robert Westphal, former DARC chairman, presented his idea of using WSPR log data to locate aircraft. This found fervent and prominent advocates among his fellow club members as well as outspoken sceptics, first and fore most Nobel Prize winner Prof. Joe Taylor, K1JT, who was instrumental in developing WSPR. A long-announced study of the data on a statistical basis was finally published on January 1, 2025, and was supposed to give this "nonsense" a professorial blessing. But it was the last rites. DK8OK took a look around the crash site ... [Flight paths and path losses | SNR plots].
Versatile Programmable Microwave Source
by Goran Popovic, AD6IW
Frequency sources are fundamental building blocks for microwave and mm-wave frequencies. In the past they were based on low frequency ovened crystal oscillators and cascaded multipliers. Changing frequency was difficult, because it required another precision quarz crystal, and re-tuning of the multipliers. Phase noise and frequency stability were also issues. Digital and narrow band communications demand better stability and phase noise. Such improvements are possible with the new generation of fractional uW PLL synthesizers ... [ADF5356 data sheet | Circuit description | Construction].
10 GHz Booster for the IC-905
by Mauro Ottaviani, IZ1OTT
This article not only presents a project for the 10 GHz band but also aims to demostrate how the same concept can be effectively adaèted to develop similar systems across all microwave bands supported by the IC-905, including the forthcoming 24 GHz band, soon to be launched by Icom ... [Preamplifier | Power amplifier | Relay and cabling].
Tropo Reports.
Aurora News.
Microwave Italy.
Microwave Spain and Portugal.
Microwave Europe.
Microwave Japan.
Microwave North America.
News & Comments
Contest, Expeditions, Beacons update, Comments, Classified Ads.