November 22, 2017

So many projects, so little time...

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So many projects, so little time... Most of you hams out there reading this probably know exactly what I mean. I currently have so many amateur radio related plans, ideas, and projects in mind, that I just don't know where to begin. Trying to give it all some structure, and to have an easy way to link to related webpages, I've made a list here of all the projects that are in the PA7MDJ "pipeline". I know myself, and probably not all projects will be finished or realized, but some of them definitely will! Suggestions, hints, and tips are very welcome of course. The information on this blog will be constantly edited, links and other information is continuously being added.

Launching a High Altitude Balloon with a HF WSPR tracker payload
This is my main project at the moment. I'm awaiting the special QRP Labs U3B balloon WSPR tracker to become available. QRP Labs currently still has the U3B in its test and development stage. At present the exact date of the U3B becoming available is unknown. Another blog post that I wrote earlier about the U3B, can be found here.
I've already acquired the needed 36" foil balloons (I'm planning on flying the lightweight payload on a single balloon), 0.1 and 0.2 mm enameled copper wire for the dipole antenna, and 52x19 mm and 39x19 mm solar cells, 100 of each. The solar cells are rated average 0.5 V / 300 mA / 160 mW and 0.5 V / 240 mA / 120 mW respectively. It will take about 6 cells to power the U3B.

Some things still to do: buy a bottle of helium, buy 0.8 mm enameled copper wire, buy a precision electronic weighing scale accurate to 0.01 gramms

An interesting forum with lots of info on WSPR balloons is

Powering up my U3S transmitter with solar cells
While awaiting the U3B, and since I got plenty of them, to get more experience and more knowledge of the little solar cells described above, I've taken up the plan to try powering up my U3S transmitter here down on earth using these same little solar cells. The U3S has to be powered with 5 V and draws about 110 mA at idle and 220 mA when transmitting, so it will require some more cells than the U3B. Soldering to the cells, I've been told, is not easy. I'm awaiting the arrival of a package with special tinned wire strip and a flux pen. Once arrived I can start soldering to the solar cells. The soldering experience I will gain during this project will be invaluable for the U3B balloon project.
I have several circuit designs in mind including the following components, either individually or a combination of them: 5.5 V 1 F supercapacitor, a 5 V LDO regulator, a DC-DC boost regulator, a 3.7 V 100 mAh LIPO battery.
I'm still learning about solar cell specific things like Isc,Voc, Imp, Vmp, and the solar cell I-V curve (see links below).

Some things still to do: buy schottky diodes

Building a Pixie CW QRP transmitter and an electronic keyer based on Arduino
I already bought the Pixie kit back in the summer at HAM RADIO 2017 in Friedrichshafen. An earlier blog post I wrote about it can be found here. There you can also read about the Arduino based electronic keyer I want to build so that I can use the Pixie with a dual paddle.

I recently made a 40m CW contact with my SOTA friend Roger F5LKW on SOTA F/AM-680. During this SOTA activation Roger used a Pixie transmitter. The CW signal sounded very clear, and if I didn't know better, I would have thought it was coming from one of the more expensive rigs usually used on SOTA activations. This definitely sparked the urge for me to finally start assembling the Pixie kit.

PA7MDJ in the log of F5LKW/P SOTA F/AM-680.
Building a simple QRP magnetic loop antenna and participating in the QRSS beacon annual New Year's Eve Operation Celebration
I would like to build a big (5 to 6 m circumference) QRP magnetic loop antenna of RG213 coaxial cable to use with my QRP Labs U3S transmitter. I hope the mag loop will have enough efficiency to put out decent enough signals on 40m. I secretly hope it still has enough efficiency on 80m as well, and I will experiment on that band as well.

I will use a variable tuning capacitor taken from a never finished antenna tuner project that I bought from a fellow ham at the local club some time ago. The air gaps between the capacitor's vanes is probably big enough for the antenna to handle up to 5 - 10 Watts. So maybe beside using it with my U3S, I can also use it in the field with my FT-817.

If finished in time, I would like to try sending QRSS beacons with my U3S on 30 or 40m with it during the recently announced annual New Year's Eve Operation Celebration.

Some things still to do: buying two 2 metre long planks to build a cross support frame

Building a magnetometer
I've always wanted to build a magnetometer to experiment with taking my own measurements of the activity of the geomagnetic field at my own QTH.
You can build one easily with a jam jar and a light or laser pointed at a mirror on a suspended bar magnet, but I prefer another similar design by GJ4ICD which uses a Hall effect sensor instead of the mirror/light like presented at the UKSMG site here and linked to below. Unfortunately the Hall effect sensor 634SS2 is not available anymore, and I have no clue about what replacement part I can use.

DIY Magnetometer design by GJ4ICD (source)

Building an 80m loaded dipole
In my small garden I can only fit a wire antenna of about 10 to 12 metres in length max. A full size dipole for 80m will be about 40 m in length. With a loading coil in each element the length can be reduced. I'm not expecting much of a 12 metre long loaded 80m dipole, but I still want to see what it can do with my 200 mW U3S WSPR transmitter, and maybe even try to make my first ever 80m 2-way contact, in CW, SSB, or some digi mode. Again, I'm not expecting super DX from it though. If working ok, I'll also want to try making one for 160m. Making coils with the right inductance value is the challenge in this project. I don't have an LC meter. I've been looking at those cheap ones available at the various Chinese selling sites, but the reviews for these are varying from the device being inaccurate garbage to ok for the price.


  1. Ja ik ken dat, heb ook zoveel dingen die ik nog wil doen. Denk dat 1 leven gewoon te kort is voor deze hobby. Prachtige projecten die je nog gaat doen. Wat betreft de magnetische loop, dat is echt een aanrader. Maar ik heb RG213 gebruikt en was er niet kapot van, je hebt echt iets nodig dat steviger is. Zelf gebruik ik bamboe9 coax maar dat kan je niet even in een winkel kopen. LMR400 is vergelijkbaar of aircom+. Iets met een dikke vaste kern. succes met de experimenten! 73, Bas

    1. Hallo Bas,
      Bedankt voor je reactie! Ik heb inmiddels de magloop gebouwd. Hij werkt prima en ik ben zeer tevreden over de resultaten dus wat dat betreft voldoet de RG213 prima. Om de cirkelvorm van de loop enigszins te behouden zijn naast een kruis nog wat extra supports nodig (zie foto verderop op mijn blog) en wat stuggere, stevigere coax zou denk ik inderdaad in dat opzicht betere resultaten geven.