SA2CLC radio stuff

 I wanted full QSK in the big amplifier. QSK, also known as full break-in, allows the transmit/receive switching system to operate fast enough that you can hear between the dits and dahs while sending CW. Once you get used to it, it is difficult to go back to conventional semi break-in operation. Achieving full QSK requires very fast relays and, in many cases, a sequencer to ensure that all relays have settled before RF is applied. To find out what would work, I measured a large number of relays that I had available and compared their switching times. The goal was to determine which relays were fast enough for reliable QSK service. Below is the result. One thing worth noting is that relay speed can often be improved by driving the relay coil with a higher voltage than its nominal rating. This is a commonly accepted practice, provided that a suitable current-limiting resistor is placed in series with the coil. Relays tested. Interesting was that Omron G2-RL relays was very fast with...

 The Swedish 30K1, exciter part 2. The exciter had it's transformer missing. I got a lead on a suitable transformer from a ham in the south of Sweden, and an agreement was set. He would bring it to Eskilstuna hamfest, where Erik, SM2CLY, would pick it up and bring it north, to me. Eskilstuna hamfest takes place in May on a saturday. Erik called me on sunday a, and told me he was in Umeå. I then drove out to meet up with him, and I got my transformer. Unfortunately, it was about 3/8" too large to fit the space available. I contemplated rewinding another transformer, or possibly ordering a new, custom transformer. I also considered cutting out the back panel of the ecxiter, having the transformer protrude out the back. But all of a sudden, I figured, why not mill the transformer to fit? Being cheap, I decided to go with the last option. Said and done, a visit was paid to Mike, SJ2W. The transformer was rigged in his mill, and successfully hogged down 8mm. It now fits. Tight, but...

  PCBway – Part 2: Useful, simple things you’ll actually use Here is part 2 of the PCBway board order. As stated in the previous post, I made several boards. Simple does not mean stupid. I realized that I sometimes spend a lot of time building the same things over and over when building or restoring old electronics, so I when Emily at PCBway got in touch with me, I made a few boards that could ease my future repairs and restorations. Universal rectifier boards Universal rectifier boards and the components they replaced First up: rectifier boards. I build and repair a lot of equipment, both high voltage stuff, and lower <24 V. A lot of older gear contains selenium rectifiers, which I like to replace with silicon. So instead of hacking together diode bridges in mid-air every time, I designed two universal rectifier PCB's. The larger is stackable, or rather possible to series connect to increase voltage handling, up to 1800V for two boards. The smaller board is just a full wave rec...

 I needed to knock down the second harmonic from my amplifier as I was getting spotted on 20 when conditions were good, when calling CQ on 40 using my multiband vertical. At first I was thinking about some sort of low impedance, series resonant circuit on 20, installed between vertical feedpoint and ground, but then I shifted to coax stubs, but I had no SO239 tee's. I wanted to it done right away so I figured I'd install panel mount SO239's on an aluminum box, and make the stub connection on the inside, when I read about W2VJN's hybrid lowpass filter. It's a three pole lowpass, but instead of capacitors, it uses coaxial cables with their ends open. Since they need to be left open, they are cut to 1/4 wave on the frequency that we want to supress. For 20M, this works out to be approx 3,4M.  The series coil is about 1uH to resonate with the coax capacitance. I built this because it was an easy design, and no more work than to drill 4 holes in a 1590B box. I used, afte...

A Small Utility: F-Key Router for keyer programs When operating CW, function keys quickly become muscle memory. Most logging software maps F1–F12 to macros — CQ messages, exchanges, TU, QRZ and so on. The problem appears when the logging program does not have focus . You might be typing in another window, checking cluster spots, or adjusting some other software. Pressing an F-key then does nothing for the cw keyer, because the keystroke goes to the active window instead. To solve this I wrote a small Windows utility: F-Key Router . The program listens for function key presses and forwards them to a selected application window , regardless of which program currently has focus. What the Program Does The program is intentionally minimal. It does only three things: Select the target window (for example Log4OM , N1MM , or another logging program) Start listening for F-keys Forward the keypress to that window This means you can press: F1 for CQ F2 for exchange ...

Handling negative voltages and getting boards sponsored by PCBWay PCBWay supplied the PCBs for this project as part of a collaboration — my write-up here is focused on the technical aspects of the design and build. The problem  In the amplifier project, I need to measure currents and voltages. Plate voltage (Ua), plate current (Ia), screen voltage (Ug2), screen current (Ig2), control grid current (Ig1) and also control grid voltage (Ug1). My first approach failed due to me not thinking properly. The current measuring relies on shunt resistors, which is a proven and reliable way to measure dc current. A resistor is placed in a branch of the power supply and by measuring the voltage drop across the resistor we can calculate the current, using ohms law, I=U/R.  Upon testing the amplifier I realised that the arduino would not measure any current. Voltage measurment (Ua, Ug2) uses voltage dividers, and that worked as planned.  Eventually it dawned upon me that I was trying to ...