Dave Richards (AA7EE) has written an article detailing his tunable passive HF preselector: When I built the VE7BPO DC Receiver Mainframe recently, it wasn’t intended to end up as a final finished project. The intention was more to have it as part of an experimental platform. The little box that contains the DBM, diplexer, and […]
Category Archives: RF
High efficiency 4V supply QRP amplifier
Low voltage, high efficiency QRP RF amplifier project @ circuitsalad.com This is an example of a high efficiency QRP transmitter designed to work at very low supply voltages (3v-5v). It can produce 2 watts a 4 volt supply @ 70% efficiency. It uses small, inexpensive switching mosfets. The primary requirement for these mosfets is low […]
FV-1 based mini SDR radio
FV-1 based mini SDR radio @ circuitsalad.com: I have really enjoyed my FV-1 based mini SDR radio but it has one problem…its too small! I made the thing so small; it’s hard to operate and assemble. So I decided to make it a little larger, allowing for all the controls to be larger and more […]
Yaesu FT-817 companion display
Andy (G7UHN) over at SWLing Post has written an article detailing the build of his genius companion control display for the Yaesu FT-817 transceiver: Like so many I love getting out portable with my FT-817 but I do seem to spend so much of my operating time fiddling through the soft-keys because my most used […]
M17 open source radio
Wojciech Kaczmarski (SP5WWP) and his team have been working on the M17 open source digital radio project: Open source handheld for a novel digital communication standard called M17. The goal here is to kick the proprietary protocols off the airwaves. To do that, it’s not just good enough to be open, it has to be […]
Build your own HF balun
Miguel, EA4EOZ, posted this great DIY tutorial on building your own balun: A balun is a MUST for dipoles or similar antennas when they are feed with coaxial cables. Many hams connect the center conductor of the coaxial cable to one side of the dipole, and the shield to the other. Wrong!From the RF point […]
How to make a very cheap VHF receiver
Sverre’s cheap VHF receiver: What is the cheapest receiver you can make for VHF? Here is a candidate where all you need to do to modify a small FM headphone receiver is to desolder one end of two capacitors, and connect a short cable with an antenna connector. See the full post on LA3ZA Radio […]
A different power source for field ham radio operating
Gwen, NG3P, has been working on a power source project for field ham radio operating: We’re coming up on a confluence of two things: Nice weather, and relaxing of the Covid-19 lockdowns in much of the United States. This means more hams leaving their home shacks and taking their operating to the field. For some, […]
Shirt-pocket SSB transceiver
Peter (DK7IH) blogged about his 14MHz shirt-pocket SSB transceiver.
An experimental HF 6-band SSB transceiver
Peter (DK7IH) has been working on HF 6-band SSB transceiver: Part 1: Project Basic Outline Presentation Part 2: The Oscillators (VFO, LO and Testtone Osc.) Part 3: The Microcontroller (ATMega128) Part 4: Bandswitching Logical Circuits Part 5: Measuring Transceiver Data Part 6: The Receiver Part 7: The Transmitter Part 8: Transmit/Receive Switch Unit Part 9: […]
FIREO – a low power SSB/CW tranceiver with its unique speech processing
Kang.K.P.S. writes: “FIREO” (Pronounced FIRE-O), is basically a bit of non-conventional QRP (low power) SSB/CW transceiver design in which speech compression is implemented using FM limiter circuit. This unique approach of speech processing increases the effective average transmitted power and thus it improves on the signal strength reports at the receiving end. Consequently this technique […]
Compact Si5351 based SDR
Ray Ring has written an article detailing the build of his mini SDR radio using FV-1 Audio processor and Si5351: This is a revised version of my FV-1 based SDR. I replaced the CS2100 clk generator with the Si5351 clk generator. The Si5351 has some advantages over the CS2100, namely you can generate quadrature clks […]
“Cigarette Pack”- 14MHz SSB QRP Micro-Transceiver
Peter Rachow (DK7IH) built a 14MHz SSB QRP Micro-transceiver into a cigarette packet size case: This article describes the “Cigarette Pack” SSB QRP transceiver” for 14MHz that I first had mentioned some months before. Recently, when taking it from the shelf, the transceiver dropped to the floor and was severely damaged. This lead to serious […]
Ham Radio HT turns CW (Morse) transceiver
Ham radio HT CW transceiver project from WhiskeyTangoHotel.com: Really not much explanation needed; just connect as shown above. This project uses an electronic keyer, but a simple straight key/oscillator combo could also be used. Oh… and you will also need to know Morse Code.
A transmit converter (and amplifier) for 630 and 2200 meters
KA7OEI has a great write-up on building a transmit converter for 630 and 2200 meters: As the name implies, a transmit converter takes another frequency – such as that produced by a conventional HF transceiver – and converts it to another frequency. In my case I use an FT-817 – a low-power (5 watt) all-mode, […]
WBR-Oscar regen receiver
A nice write-up on Sheldon’s (N6JJA) version of N1BYT’s WBR regenerative receiver: This article is broken into two parts. First comes the “Oscar” preselector/preamplifier. As I said, I intended it to be either part of the overall receiver or used as a standalone where desired. The second part deals with the WBR upgrades. Both designs […]
A simple 8-channel receiver voting controller for enhanced repeater coverage and usability
KA7OEI has written an article detailing a simple 8-channel receiver voting controller: To simplify things, this voting controller sits in “front” of an ordinary repeater controller, taking the audio and COS inputs from the various receivers and outputting a single audio and COS signal. If the repeater system in question uses subaudible tones, it is […]
N6QW Heathkit SSB transceiver
Pete Juliano, N6QW, has a nice build log on his newest version Heathkit 40M SSB Transceiver: What are you thinking — I am not trying to break any world record? My XYL asked me that question today — why are you building another rig? Followed up by a snide comment that I had so many […]
Automated channel switching with Motorola GM3x0
Florian Wolters wrote an article on automated channel switching for POCSAG/DAPNET transmissions on MMDVM system: With the integration of POCSAG/DAPNET features into the MMDVM/MMDVMHost I came to think about if it would be possible to combine an MMDVM repeater/HotSpot with a DAPNET tranmitter. The advantage in Germany is that there is a single coordinated frequency […]
A limited attenuation high-pass filter for the KiwiSDR
KA7OEI published a new build: One of the issues common with using a broad-band, direct-sampling SDR (software-defined radio) like the KiwiSDR is that of overload by strong, low-frequency signals, such as those on the AM (mediumwave) broadcast band – but there’s another problem that should be considered as well: The high generally-high signal levels at […]