Category: Transmitters and receivers

This category lists all posts related to homebrewing your own transmitters and receivers.

Neophyte receiver for 60 meter

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The receiver is ready, except the RX gain potmeter which is still in backorder…

The Neophyte receiver is an easy-to-build receiver, already built by lots of people. Many radio clubs used it as a project for starting builders. It was developed by John WA3RNC and first published in QST, February 1988. The circuit can be used to create either a 80m or a 40m receiver, depending on a few capacitors. The 60m band is just in between, therefore I decided to find out the correct caps for this new amateur radio band (well… at least new in the Netherlands, from December 2015).

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Receiving SAQ and other VLF stations

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The huge VLF antenna of SAQ near Grimeton, Sweden (credits).

This article is about receiving radio stations operating in the VLF band (3-30 kHz). Due to the very low frequency, receiving such stations requires some special equipment, since most radios don’t support these low frequencies. One of the interesting stations in this band is SAQ, which occasionally transmits at 17.2 kHz. Other stations include submarine communications and time services. — more →

Tiny Tornado for 80m

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The closed box.

Many years ago I built a prototype of the famous “Pixie 2”, one of the simplest and smallest CW transceivers ever designed. The main issue is that the TX and RX  frequency is the same, so the opposite station needs to shift which he probably doesn’t know, so it takes quite some patience to get a successful QSO. Once published, lots of improved designs appeared in magazines and on the internet, one of them being the “Tiny Tornado”. Since I had some mint tins left, I decided to build this little wonder. — more →

First experiences with my 30m QRP transceiver

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Final shot of the rig, including labels, key and headphones.

This year I built a very nice 30m QRP transceiver, based on a design by Onno PA2OHH. Meanwhile I have used this rig a couple of times, and did some measurements too. This article tells some of my experiences with this great little box. — more →

30m QRP transceiver – Part 4

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Inside view of the radio, including all modules built so far.

Since I finished all modules for the receiver part (power, LF, VFO and RX-board), it was getting time to put everything together and place it in a nice case. Onno PA2OHH (designer of this radio) managed to put the complete transceiver in a single Teko 4B case, so I ordered that same box. Actually I already bought it at the beginning of the project, to help me dimensioning the modules. With such limited space, planning the physical layout of the radio (both the front panel and the inside) is very important. — more →

Kenwood interface for visually impaired radio amateurs

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The interface, ready to be mounted to the radio.

This article describes an add-on for modern Kenwood transceivers to allow visually impaired operators to use these radios with a VS-3 or VGS-1 voice synthesizer. I built this interface for Adrian PA0RDA (using a TS-2000), but I’m almost sure that more visual impaired radio amateurs will be interested. The add-on is easy to build, most of the work is mechanical while the electronics are easy. — more →

30m QRP transceiver – Part 2

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The finished VFO, just before closing the lid.

Building a stable VFO is challenging. Oscillators tend to drift away due to (very small) temperature fluctuation, or due to small capacitive changes in the direct environment (e.g. the frequency changes when you move your hand towards the oscillator). The VFO used in my 30m QRP transceiver is not different from others, so I had to deal with the same issues. — more →

ATV transmitter for 23cm

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Front view of my fully assembled 23cm ATV transmitter.

Although I was already able to receive the local ATV repeater PI6ATV, it has been a wish for about 8 years to be able to uplink too. So I once bought a couple of modules from PE1ACB that would allow me to do so. However, due to lack of time and other priorities the modules lost my attention and ended up on some shelf. Since I started my new job I have more spare time, which I spend (among other things) on this fantastic hamradio hobby. So then I remembered those modules. I designed a front panel and bought a case, switches and connectors. — more →

30m QRP transceiver – Part 1

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The first modules of my 30m QRP transceiver.

This summer I want to go walking in the beautiful highlands of Scotland, together with my wife. The mobile phone coverage in this desolate area is none or poor, but hey… I’m a radio amateur! For a daily “sign of life” I need a lightweight transceiver, and 30m (10.100 – 10.150 MHz) seems to be a perfect band for this purpose.

After browsing the web for designs, I stumbled on the website of Onno PA2OHH. Besides lots of other interesting QRP projects, I found his NiceRig 40-30 QRP Transceiver. I immediately fell in love with this design and decided to build this thing.

Building this rig takes quite some time, so I publish this project in different posts, showing you the progress of this project. — more →

Spijkerradio

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Introduction

“Spijker” is a dutch word for nail, which you would normally use to hang something on the wall, or to construct wooden stuff. However, (brass) nails can also be used as as solder pad. PA0KLS used this idea to construct a receiver, called the “Spijkerradio” (nail radio). It is a nice project for starters to build their own radio.

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The receiver is based on the good old 0V1. This was a very simple receiver with only one tube. PA0KLS redesigned the schema to replace the tube by transistors. He also added a small audio amplifier to allow usage of modern (low impedance) headphones or a small speaker. — more →

Automatic antenna tuner using an Arduino

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Introduction

OLYMPUS DIGITAL CAMERAThe Arduino board is a fantastic tool for rapid prototyping, and can help radio amateurs in lots of homebrew projects. I wanted to demonstrate that it is very easy to build an automatic antenna tuner with the Arduino. I connected an old SWR meter to one of my Arduino boards. Furthermore I build a simple L-tuner with a fixed coil and a rotating capacitor (400pF). The capacitor is driven by a servo, also connected to the Arduino. By doing a full sweep with the capacitor, the Arduino tries to find the position with the lowest SWR. After the sweep it turns the capacitor to that position. You can view the video below to see the tuner in action. Mind the SWR meter (right needle) in the back while the capacitor is rotating. — more →

CW keyer for foxes and beacons

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Introduction

Beacons and foxes have to identify themselves. Although I could sit along all day with my morse key, transmitting my call, I wanted to have some automatic keyer. Since I recently bought a PIC development kit (Velleman K8048), I thought that it would be a nice idea to create my first PIC application by building a CW keyer.

I never wrote PIC source code yet, but I have done some assembly for 68000 and x86 in the past. So it shouldn’t be to difficult to write a simple program, keying one of the outputs of a PIC. On the CD of my PIC development kit I found some sample programs, including one for a flashing LED (this appears to be the “Hello, World!” application for microcontrollers). I modified the source code and finally build the bunch of code which you can find on the bottom of this page. I’m sure that this code is not the best PIC program of the world, but it works and at least I understand how it actually works. If you have any suggestions, please feel free to send them to me! — more →

Fox transmitter for 80m

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Introduction

Fox hunting is one of the many aspects of ham radio. It’s some kind of game, where the “fox” is a little transmitter, and competitors have to locate it using a directional antenna and receiver. I already built a special receiver for fox hunting, and my wife (PD2W) built one too. So having 2 receivers it would be a nice idea to add a fox to these, to get a complete mini-fox-hunt-kit. One of the members at the club pointed me at the so-called “OXO transmitter”. I looked it up at the internet, and immediately liked its simplicity. So I started to build it.

Schematic

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Pixie2 QRP transceiver for 80m

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Introduction

The smallest QRP transceiver for 80 meters, called “Pixie 2”, is a very nice project to start building your own equipment. Minimum components, maximum fun. The spec’s are poor, but what else might you expect for just a few dollars?

The G QRP Club compiled a nice booklet called The Pixie File, which includes the history of this little transceiver and some variants. — more →

Your first transmitter

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my1sttxWith just a few components, you can make your own morse code transmitter. The output is only a few miliwatts, but this is enough to receive on any radio in your home.

In fact, it is only a simple Clapp Oscillator with the output directly driven into a few meters of wire. The transmitting frequency depends on the used crystal. This may be any crystal between 1 and 15 MHz, higher frequencies may perhaps work also, therefore you may lower the 2 capacitors a little bit.

The transmitting frequency is not only the one shown on the crystal, but also “harmonics”: If you have for example a crystal of 3.56 MHz, then it transmits (of course) on 3.56 MHz, but also a bit at 7.12 MHz (2 * 3.56), 10.68 MHz (3 * 3.56), 14.24 MHz (4 * 3.56), etc.

The operating voltage is not critical, a 9 volt battery will do the job.

Components:

  • C1 – 100 picofarad
  • C2 – 100 picofarad
  • R1 – 10 kilo-ohm
  • R2 – 1 kilo-ohm
  • S1 – Morse key or switch
  • T1 – BC547 or any other universal NPN transistor
  • X1 – Any crystal you like between 1-15 MHz