Starting to look like a radio… The front panel assembly has started, next stage is to wire all of the controls, meter and display. The black bezel was formed by using a piece of clear perspex sheet with the meter and display windows masked off then spray painted using car bumper spray paint on the… Read More »
Here is a short video showing the modified W7ZOI s-meter driver in operation.
Little bit of playing around with the IF stage today, finished the C++ code for the IF Shift feature – here is a short video listening to a QSO on 40 meters. A second video listening to Volmet on 5.450 and 5.505MHz, no BPF or preamp just random wire straight into first mixer.
Having noticed some serious performance issues with the first and second mixer filter stages, I identified the problem to be poor design choices and a lack of gain in the first IF stage. I have split the first IF mixer and filter and added a dual gate mosfet variable gain amplifier on the output side… Read More »
Recently I was drawn in the direction of a simulation software package called LT Spice, Pete Juliano N6QW uses it in several of his articles so I gave it a shot and not having used it before it was surprisingly easy to use. I modelled my original IF amplifier based on the Hybrid Cascode design… Read More »
Some progress for the end of a Bank Holiday weekend – ran out of parts, BF245 FET was probably not the best choice when I have a stack of MPF102 devices, unfortunately the pinout is not compatible with the PCB track layout 🙁 Beer time!
I initially set out to use the AD9959 DDS and invested a great deal of time writing the code to make it function as a VFO, BFO and local oscillator for other stages of the transceiver, however I have ran in to several issues with it in terms of reliability, spectral purity and overall complexity.… Read More »
Having spent the weekend debugging several of the transceiver modules I have managed to breath some life in to the receiver section, firstly a few notes on design and construction snags that have caught me out along the way. When using a design somebody else has published as a base for your own, make sure… Read More »
I bought a pair of AD831 pre-assembled modules from China, $10 each – not bad considering the price of the individual AD831 chip, the board comes ready to use “plug and play” with all ports terminated in to 50 ohms with SMA connectors – neat. Testing the mixer saw excellent results and the added bonus… Read More »
Having re-evaluated the receiver mixer and filter stages I have re-designed the front-end to accommodate the first and second mixers with both the roofing filter and SSB filter daughter PCB’s on one single module, this allowed easy assembly and modular testing of the filter stages. Each filter PCB has the impedance matching networks along with… Read More »