OH2GAQ
Some Current and Past Projects
Projects
Microwave Transverter Controller
The Microwave Transverter Controller is the heart of OH2GAQ microwave band transverter system. It contains subsystems to provide the functionality needed for generating SSB or tone modulated signals (like JT65) and receiving them, provides a very stable 10 MHz reference signal to lock microwave transverter LO's, has a audio and control signal interface to a PC, and provides T/R sequencing and monitoring for up to 4 transverters. The block diagram is as shown below. An article describing the Controller in detail was published in QEX for July/August 2013 and is available here Microwave Transverter Controller. Updated versions of the MTC using SDR technology in the RX and TX parts rather than analog technology are available here Microwave Transverter Controller V2 and here Microwave Transverter Controller V2.1. A much improved design is now in use, the Version 3 controller. It supports up to 6 half-duplex transverters plus one full-duplex transverter, and is described here Microwave Transverter Controller V3
10 GHz Transverter
The present 10 GHz transverter used at OH2GAQ is described here 10_GHz_Transverter. An article describing the 10 GHz 3.5 watt power amplifier stage, which was published in the Finnish Radioamatööri Magazine for April, 2013, is available here 10_GHz_Power_Amplifier
5.7 GHz Transverter
The present 5.7 GHz transverter used at OH2GAQ is described here 5.7_GHz_Transverter An article describing the 5.7 GHz 5 watt power amplifier stage used at OH2GAQ, which was published in the Finnish Radioamatööri Magazine for April, 2014, is available here 5.7_GHz_Power_Amplifier
SAT COMM
An article describing a transverter intended for use with QO-100 geostationary satellite, which was originally published in the Finnish Radioamatööri Magazine for March, 2019, is available here. The version on this website contains some updates compared to the published article SATCOMM
FULL DUPLEX MTC
This is a preliminary set of documents describing a full duplex 144 MHz transverter and control system intended for use with equipment such as microwave transverters (e.g. the SATCOMM device above).The heart of the unit is the Hermeslite 2 Transceiver by Steve Haynal and others. The version on this website contains a general description, schematics, pcb layouts, Gerber files for some of the pcbs and SW for the Arduino controller. FULL DUPLEX MTC
RTL SDR
An article describing the use of a USB stick SDR and how to improve the shielding and noise performance, which was published in the Finnish Radioamatööri Magazine for Jamuary, 2014, is available here RTL_SDR
Multipurpose Sequencer
In almost all high power VHF, UHF and even low power microwave systems, a sequencer is required to ensure that key components in the system are protected during changeover from RX to TX and vice-versa. Also monitoring of the operation of the high power amplifier(s) and other conditions is often required. The sequencer is described here Multipurpose_Sequencer The sequencer schematic is here Multipurpose_Sequencer_Schematic. A user package, containing diagrams, high resolution photo., parts lists and SW source code is available here Multipurpose_Sequencer_User_Package
Phase Locked Xtal Oscillator
In almost all microwave systems, a large number of highly stable and low noise oscillators are needed for various applications. With narrow band techniques stretching up to at least 48 GHz now-a-days in ham projects, conventional or even oven temperature stabilized Xtal oscillators are at their limit. So the next step is to phase lock a lo-noise, stable Xtal oscillator to some better reference. Here is yet another module to do that task, in this case fairly compact and having low-power consumption. It is used in OH2GAQ projects in many applications. The oscillator is described here Xtal_PLL The oscillator schematic is here Xtal_PLL_Schematic The oscillator parts placement is described here Xtal_PLL_layout A small number of the final PCB's for this project are available, as is the parts list and the source code of the PIC SW, and a spreadsheet which "semi-automatically" calculates the various parameters that must be loaded into the PLL chip.
Microwave Printed Circuit Board Design
From time to time you will want to design Printed Circuit Boards for some Microwave application. The following article is from a lecture presented at the 2013 Nordic V/U/SHF conference in Ostersund in May/June 2013.PCB_Design
Tektronix 492 Spectrum Analyser Repair
Many of us have (or would like to have !) a useable spectrum analyser. Tektronix SA's are often available on e-Bay or other sources for quite reasonable cost, even including freight. As they are now generally over 20 years old, and have had considerable use or abuse, often repairs are needed. The attached article tells how a Tek. 492 Attenuator was replaced with a more readily available Agilent device, also how some faulty co-axial relays were replaced in the front-end. Tek_492
