Wind, wind, wind

December was a very windy month. Most antennas did held, however the fibreglass pole of the 20m vertical broke. We contacted the supplier (DX-Wire, Germany) and luckely spare tubes were available for a few euro’s. So we ordered a replacement tube, and also ordered 2 more masts for future use.

We were not able to do lots of testing on the antennas, since work lasted too much time. So that has to wait for the next month.

Perfect weather to erect all antennas

November starts with 2 weeks of mild weather, with lots of sunshine and no rain. This means that the corn field is rather dry now and easy to walk on. In the first weekend I put lots of tonkin poles in the ground to mark all antennas. I also rolled out the HEDZ (100m) and the beverages (2x 80m). The beverage is nearly ready already, including matchbox and feeder. Wytske helped me to erect the 15m center pole of the HEDZ. Within a couple of hours a kestrel already liked the pole and is now regularly seen sitting on the top.

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Automatic antenna tuner using an Arduino

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 →

First preparations for the PACC 2012

We had some nice weather in the last weekend of October, so I went into the corn field to do some long walks: setting up the new beverages (length: 80m each) and the HEDZ. We bought some new, higher poles this summer for the HEDZ, the center pole will be almost 15m tall now. The poles are not erected yet, but I was on my own that weekend while I need 2 or 3 people to get the poles up.

What are the plans for PACC 2012? Well, we will set up all antennas of 2011 and add some new ones. We built 2 beverages during the REC fielddays, which will be used in the contest now. And we will build a small array of verticals for 10m, since it will be likely to have some propagation on that band during the contest.

Squalo antenna for 6m

Introduction

squalo-6m-1Adri PA0RDA, a friend of me, is trying to do some DX on 6m for a while now. His antenna position is very poor: he lives in the bottom flat of a 5-floor building. He has a balcony on the rear (south) side, but high buildings are very close, he has no direct sight in any direction. At the balcony he has a Diamond V2000 vertical antenna for 6/2/70, and an MFJ loop antenna for 15-40m. The 6m band is his most popular one, since he get best results on this band. However, since most DX on 6m is horizontally polarized, he needed a horizontal antenna. I remembered an all-direction horizontal antenna made by Jan PA3EGH (one of the members of the local radio club). So I contacted him, and he pointed me at his website. It was the “Squalo” antenna, or square halo. In fact, it’s just a square folded dipole. It radiates in all directions, with -4dB gain on the sides (compared to the front and back side).

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Contest after heavy winds

Looking a bit tired at the contest final...

Looking a bit tired at the contest final…

The first weekend of February was really windy. The rough wind ruined the just finished HEDZ, and nearly nocked down the other antennas. And there was nothing I could do, since I was suffering from influenza. I recovered during the next days, and on Friday (just one day before the start of the contest) Adri PA0RDA helped me to fix the antennas. The main pole of the HEDZ was broken, but luckely it was easy to repair. We checked all pins and guys, measured all the antennas, resoldered an inductor in the 40m matchbox, etc. In the afternoon the antennas were in top condition again, so we could start rebuilding the shack.

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Finalizing the antennas

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.

Optimizing the EDZ

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…..

Goodbye corn, hello antenna’s!

Our 5/8 vertical for 20m, during a windy day.

Our 5/8 vertical for 20m, during a windy day.

Thanks to a local farmer we are allowed to use the corn field during the winter season. So during autumn it’s always a nice moment when the corn is being harvested. First we get some view to the east again, since the wall of corn next to the house is gone. But more interesting is the fact that this is the beginning of setting up the antenna’s for the yearly PACC contest.

Preparing the antennas

To prepare for the 2011 PACC, we did quite some work on our antennas. During the fielddays of our local radio club we focussed on the extended double zepp, which was hard to tune. so we played arround with the length of the feedline and performed measurements using the MiniVNA. We concluded that the antenna was too long, we will shorten it when setting it up for the PACC.

We also completely revised the Hy-Gain 12AVQ (originally built in 1970!), which was our only antenna for 10, 15 and 20m so far. All plastic parts were replaced, dirt was removed, new stainless steel bolts, nuts, washers and clamps, new tuned radials (the shorther ones extended with ropes to get the right corner), etc. We retuned the antenna using my MiniVNA. The antenna is now ready to be used again for many years.

During autumn we built a 5/8 wave vertical for 20m. More activity on the higher bands is to be expected due to more geomagnetic activity of the sun. Therefore we need more antenna’s on 10/15/20m, also because we want to start using a multiplier station this time. Being on the air with 2 transceivers also requires proper filtering, so we started building RF filters (design K1TTT).

TNC-X

Introduction

All you need to use email, without having a local internet connection: laptop with Winlink installed, TRX (with antenna) and TNC-X.

All you need to use email, without having a local internet connection: laptop with Winlink installed, TRX (with antenna) and TNC-X.

The Dutch Amateur Radio Emergency Service (DARES) is currently setting up a messaging system for emergency communications. Email is sent over radio using the good old AX.25 protocol. Part of this project is the TNC-X, a simple packet radio modem with a USB interface. I am trying to get rid of those RS-232 boxes, so having a TNC with a USB interface is one more step in that direction. Hans PA3GJM managed to get lots of radio amateurs together to buy 100 TNC-X modems. I was one of them.

More info on the TNC-X can be found on this website: www.tnc-x.com. — more →

HEDZ antenna for 80 and 160m

Introduction

The HEDZ for 80m and 160m requires 3 poles A, B and C. Pole B is 15m tall, A and C are 9m. The distance from A to C is over 100m.

The HEDZ for 80m and 160m requires 3 poles A, B and C. Pole B is 15m tall, A and C are 9m. The distance from A to C is over 100m.

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 →

DK7ZB yagi for 144MHz

Introduction

The result.

My DK7ZB yagi for 144MHz

After the somewhat disapointing results of the DJ9BV antenna, I decided to try another model. This time I selected a 9 element DK7ZB for my test. I already bought some square alu bars, each 250cm tall. Since the 9 element DK7ZB is 5 meters tall, this should fit perfectly.

Click here to visit DK7ZB’s homepage, including all his antenna designs and lots of references. — more →

CW keyer for foxes and beacons

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

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

fox_80m_transmitter_schematic
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DJ9BV yagi for 144MHz

Introduction

I just started building a new yagi antenna for 144MHz. I used to work with short yagi’s, based on DL6WU, with 6 elements. These antenna’s were about 2m long. I stacked them, tested them both vertically and vertically polarized/stacked, etc. I did lots of DX using these antenna’s. After a long period without radio activity I finally decided to start again with the hobby and try another antenna design. — more →

6-Element yagi for 144 MHz

Introduction

My homebrewn VHF yagi antenna's in Elst, stacked, about 12m above the ground.

My homebrewn VHF yagi antenna’s in Elst, stacked, about 12m above the ground.

I designed this antenna in 1995. I wanted a horizontal antenna which has nice characteristics for contest usage. The side lobs are minimized, the beam width is quite large while it has a reasonable gain and front/rear ratio. — more →

HF 1:4 balun

Introduction

hf-balun-case2Some years ago a friend offered me an HF radio: an Icom IC-730. I decided to buy it, since I didn’t have a HF rig yet. I gave it a nice place on my shelf, connected some meters of wire on the antenna plug, and from that moment I sometimes listen to all kind of chirps and beeps. I recovered my Hamcomm modem to see some wxfax images and SSTV, I tried to follow CW QSO’s again, listened to some conversations in SSB, etc.

Although this is not bad at all, I wanted to participate again. Since I moved to Utrecht, my radio activity was very low. I didn’t have any antennas on the roof, which made it difficult to pick up this nice and interesting hobby again. But… after participating in the 2002 jamboree on the air I decided to revive my radio hobby. And since I moved back to the country late 2005, I had all opportunities to set up antenna’s.

The first HF antenna I wanted to build was a Windom Antenna. This antenna required a 1:4 balun, so I made one. — more →

Pixie2 QRP transceiver for 80m

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

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