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).
“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.
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 →
Thanks to a interesting article about the so called Half Extended Double Zepp (HEDZ) by W5DXP we managed to get our EDZ working om both 80m and 160m. The antenna is working fine now on 80m. I couldn’t test in on 160m yet, because my own rig (IC-730) doesn’t work on that band, but the measurements with the MiniVNA show a acceptable SWR between 1800 and 2000 kHz. When breaking up we will do some physical measurements to see what the exact size of the dipole and feeder is. The (H)EDZ is also a little bit lifted now, the center is 12 meters above the ground, the endpoints 8 meters.
We also erected the remaining antennas: the 1/4 wave vertical for 40m, and the HyGain AV-12AVQ for 10/15/20m. In the upcoming weeks we will extend the number of radials for the 40m vertical.
Setting up antennas on a corn field is not really easy. Ok, there’s no corn in the winter, but the field is very wet and muddy. When the temperature drops below zero, the field becomes icy, and above zero the amount of mud under your (wooden) shoes grows with every step.
In 2009 we built an extended double zepp (EDZ) for 80m, which also performed really nice on 160m. Although the antenna performed well in the past contests, it was always a big trouble to match it. After lots of experiments and measurements, we finally found an unexpected relation between the length of the feeder and the “resonance” frequency. Ok, this antenna is not resonant on the desired working frequency, it only provides a workable impedance and very well radiation at some point. I always thought that this point was merely depending on the length of the dipole, and that the length of the transmission line merely influenced the impedance. Well, not for the EDZ! It is a non-resonant antenna, and all sizes do matter! So this makes the antenna a bit more complex, compared to a simple halfwave dipole.
We found some websites stating that the length of the feeder line should be about 48 degrees, so 48/360 wavelength. We want to have a 80m EDZ, center frequency at 3700kHz (= 81.08 meters), so the length of the feeder line will be 81.08 x 48 / 360 = 10.81 meters. This is not a practical length, since the shack is not right beneath the antenna. So we add 1/2 wavelength feedline, resulting in a total length of 10.81 + (81.08 / 2) = 51.35 meters.
Setting up the EDZ took quite some time. We had to options: the weekend of 4/5 December, or the weekend of 11/12 December. The first weekend would be freezing cold, the second weekend really wet. Since the cornfield is almost inaccessible when really wet, we decided to go for the first weekend. With the snow hitting in our face, ice hidden below the fresh snow, and a really cold wind, we managed to set up the EDZ. But due to the bad weather and ground surface conditions it took us lots of time, so we did not manage to get the feeder in the correct length. Two weeks later, the dipole came down due to the large amount of ice. So there is still some work to do on the EDZ…..
The zeppelin antenna (or simply “zepp”) is a popular end-fed wire antenna for shortwave bands and has lots of simularities with the J-pole antenna. It consists of a long wire (half wave length), connected to one of the wires of a balanced feedline (quarter wave length). The idea is that the end of the wire has a high impedance, and the quarter wave transmission line transforms this to a low impedance, at least low enough to get to 50 ohms using a balanced tuner. A Double Zepp is a normal zepp, but the other (unconnected) wire of the feeder is also connected to a second wire. The Extended Double Zepp (EDZ, sometimes also known as Double Extended Zepp or DEZ) is the same, but the wires are now 5/8 wavelength instead of 1/2. The tricky part of this antenna is now the length of the feeder. Paul N8ITF gives you the measures for all versions of the EDZ. — more →
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.
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?
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.
- 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