I have designed an elaborate DC Protection and Distribution unit for the 70MHz SSB transceiver project, the purpose of this module is to provide two stage reverse polarity protection, power on/off switching, filter and a switched DC bus for transmit and receive. I have designed the 70MHz linear power amplifier (yet to be finished) to provide… Read More »
Well, having taken a pause on the build of the big rig, the HF642 I am taking a slight diversion for a few months and designing a single band, 70MHz SSB transceiver. Keep checking back for progress info on both projects, I am easily distracted so hopefully this will not turn into two expensive half-baked… Read More »
Impedance matching transformer calculator Please feel free to download this software and use it to aid designing toroidal and multi-aperture core transformers for matching Crystal Filters and interstage coupling transformers. The software is provided as-is with no warranty, please feel free to distribute the software to others however please make sure you give me credit… Read More »
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 »