Recommended Website

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Wow, I really love this site by Julian W. OH8STN, and I wonder why I haven't heard about this site before. It's packed with information, innovative ideas, and inspirational videos for the off-grid, outdoor, and QRP radio operator. Go check it out:  HAM RADIO & OFF-GRID POWER - OH8STN.org



 

Homebrew SDR Tuning Knob Unit

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This is my latest little homebrew project; a tuning knob unit for my SDRPlay RSP1A software defined radio receiver. The project was inspired by the article "Wireless Tuning Knob" in the April 2018 issue of the excellent Practical Wireless magazine.

To make an easy to use tuning knob for your SDR receiver, the PW article suggests using the inners of a cheap wireless computer mouse, removing the mouse wheel, and connecting a rotary encoder instead. Then a tuning knob can be attached to the rotary encoder's shaft, and voila!

And that's exactly what I did, except I did use a wired USB mouse, not a wireless one, as I didn't want the hassle of having to change batteries all the time. The result is shown in the photos below. It works like a charm!

ADS-B

Last edited: 27.01.2018

This is my latest high tech creation, hi. It's a little 4-leg "spider" antenna for 1090 MHz (1.090 GHz) constructed around a nice old Amphenol SO-239 chassis connector that I had lying around. Its 4 legs and top element are made from copper wire and are about 68 mm in length.

Beside being a ham radio operator, I've always been a radio hobbyist in general, and every once in a while I like to explore radio related stuff outside of the ham bands. The little spider antenna is used to receive the ADS-B signals broadcasted from aircraft on 1090 MHz. ADS-B stands for Automatic Dependent Surveillance - Broadcast. ADS-B signals are periodically (twice every second according to the YouTube movie below) broadcasted by aircraft and contain among other things the aircraft's unique ICAO identifier, the aircraft's callsign, and data provided by the GPS navigation system of the aircraft, like GPS location, altitude, heading, speed, etc. ADS-B signals enable an aircraft to be tracked in real-time by for instance air traffic control stations. Since other aircraft can also receive the ADS-B signals from ADS-B equipped aircraft surrounding them, it also provides pilots with improved situational awareness.

I use my RSP1A SDR receiver (see my last blog entry) connected to the spider antenna to receive the ADS-B signals. Special software extracts the data from the signals. This data is sent to another computer program called Virtual Radar Server (VRS) which then plots the received aircraft on a map. With the aircraft identifiers received on 1090 MHz, VRS is able to retrieve additional information for the aircraft from various online databases, including the aircraft registration or "tail number" and the current route (destination and departure airport). When you select an aircraft, VRS also shows the aircraft type and model, operator, country of registration, and when available (most of the time) even photos of the aircraft (not just a random photo of the type and model, but the actual aircraft with the registration of the selected aircraft).

It's really fun to see in real-time what's up in the airspace above you. Of course you can also use some online service like www.flightradar24.com for this, but for the radio hobbyist it's a thrill to know that the aircraft that are plotted on the map are plotted there because their ADS-B signals have been received with his own radio equipment directly over the air.
With the antenna inside the house, depending on the height I place the antenna at (ground level or attic), I've been receiving aircraft up to distances of 100 to 200 km. You can even do some DXing, trying to catch aircraft from as far away as possible and trying to beat your personal record.

The ADS-B data extracted from the signals received on 1090 MHz

The aircraft plotted in Virtual Radar Server. For the selected aircraft (the one in yellow) additional information is displayed, including route, operator, country of registration, tail number, aircraft type and model, and any available photos of the aircraft.

Below some YouTube movies explaining how to set up ADS-B with your SDRPlay RSPA1/1A/2 receiver and explaining how ADS-B works.

See also:

https://en.wikipedia.org/wiki/Automatic_dependent_surveillance_%E2%80%93_broadcast
https://discussions.flightaware.com/t/three-easy-diy-antennas-for-beginners/16348/3
http://lucsmall.com/2017/02/06/making-antennas-for-1090mhz-ads-b-aircraft-tracking/
https://en.wikipedia.org/wiki/Aircraft_registration
https://en.wikipedia.org/wiki/Aviation_call_signs
https://en.wikipedia.org/wiki/List_of_airline_codes
https://en.wikipedia.org/wiki/Aviation_transponder_interrogation_modes#ICAO_24-bit_address
https://en.wikipedia.org/wiki/List_of_airports_by_ICAO_code:_A
https://junzis.com/adb/
https://www.flightradar24.com/
https://www.sdrplay.com/docs/SDRplay_ADS-B_User_Guide.pdf

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 http://radio-signals.com.

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

http://forum.solar-electric.com/discussion/18083/voc-vmp-imp-isc-explained/
http://www.kg4cyx.net/solar-panel-specifications-explained/

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

http://www.g4ilo.com/wonder-loop.html
https://rsars.files.wordpress.com/2013/01/simple-rg213-hf-loop-30m-15m-g8ode-iss-1-31.pdf
https://sites.google.com/site/g7aqkhamradio/home/my-qrss-beacon
https://americanhoplite.wordpress.com/2016/07/01/my-experience-so-far-with-the-mfj-9232-loop-tuner/
https://www.nonstopsystems.com/radio/frank_radio_antenna_magloop-small.htm

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)

http://www.uksmg.org/content/magnet.htm
http://www.britastro.org/aurora/jamjar.htm
http://blog.stevemarple.co.uk/search/label/Magnetometer
https://fear-of-lightning.wonderhowto.com/how-to/measure-geomagnetic-storms-with-diy-magnetometer-0132960/
http://www.eaas.co.uk/cms/index.php%3Foption%3Dcom_content%26view%3Darticle%26id%3D74:how-to-make-a-very-sensitive-jam-jar-magnetometer-by-robert-cobain%26catid%3D10:equipment-reviews%26Itemid%3D16
http://www.swpc.noaa.gov/sites/default/files/images/u33/Activity_7.pdf
http://gw7eri.com/homebrew/magnetometer/magtalk.pdf

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.

https://www.nonstopsystems.com/radio/frank_radio_antenna_80m-dipole.htm

PH9HB/AM

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Here on www.dxcoffee.com, you can find an interesting interview with Jerry van der Goot, PH9HB. Beside being a passionate ham operator, Dutchman Jerry also is a Boeing 737NG captain for a carrier based at Amsterdam-Schiphol. During flights, when duties permit, he often can be found on the HF ham bands operating from the cockpit as PH9HB/AM using the aircraft's HF radio. "AM" stands for "Aeronautical Mobile" and is added to the radio amateur callsign when the operator is aboard an aircraft in flight. Just as "MM", or "Maritime Mobile", is added to the callsign when aboard a ship at sea.

It's always a thrill to work an /AM station. I've done it only once, with ON/GM7DIE/AM on 20m back in January 2014. I also managed to pick up Jerry's signals, but so far I've never had the pleasure and luck of making a 2-way contact with him. Jerry's /AM activities always attract a lot of attention, and getting through the pile-up isn't easy.

Jerry PH9HB (source)

PH9HB/AM take off (source)

As Jerry explains in the interview, the antenna used on the Boeing 737NG airplane is a so-called Shunt antenna. More information on this antenna type can be found here.


See also:

https://www.google.com/patents/US7511674
https://www.qrz.com/db/PH9HB

High Altitude Balloon (HAB) carrying WSPR payload

Last edited: 25.07.2017

Around the world, regularly experimental High Altitude Balloons (or HABs) are released into the earth's atmosphere carrying amateur radio payloads. These payloads often include an APRS or WSPR (or other mode) tracker transmitting position reports, enabling ham operators to track the balloons on their voyage. Often travelling at a height of more than 10km, and depending on the mission's goal sometimes even entering the atmosphere's "near space" region, some of these balloons (the so called "floaters", long-distance travellers designed to reach a certain altitude and then float with the prevailing winds) even manage to circumnavigate the globe before finally coming down to earth again.

Dave VE3KCL from Canada launched several floater HABs carrying a WSPR payload based on the Ultimate3S kit of QRP Labs. QRP Labs is well known to the radio amateur for developing and selling WSPR transmitter kits which work as stand alone devices not needing any PC to generate the WSPR signals.

At the time of writing this, VE3KCL's HAB flight S-18, released on October 17th, and after completing a circumnavigation on October 27th, is still aloft and transmitting WSPR signals on the 30 and 20m HF bands. It's currently over the Atlantic Ocean west of Africa. The tracker's battery is charged by solar panels, and after sundown it will quickly be depleted and no position reports will be sent. I didn't learn about the S-18 flight until yesterday, and so far due to QRL I haven't been able to monitor for the mission's signals during the balloon's daytime. I'm planning on listening for it coming Sunday though, provided the balloon is still in the air by then.

More information on the S-18 can be found on the website of QRP Labs here. Might we miss this one, the list of QRP Labs powered WSPR balloons shows another VE3KCL balloon flight planned for the future, and hopefully more missions will follow.

Track of the S-18 flight on November 3, 2016. The red parts of the track are based on actual received position reports.

If you want to learn more about amateur radio HABs, take a look at the website of ARHAB Amateur Radio High Altitude Ballooning - The Poor Man's Space Program at www.arhab.org.

A list of all the missions that managed to circumnavigate the globe can be found here.

By the way, I'm planning on buying a QRP Labs WSPR Ultimate3S kit for use at my home QTH. I'd like to start simple, with just one band, and I think the 40m band is the one I prefer at the moment. Stay tuned!

Addendum 06.11.2016
It seemed balloon flight S-18 already had descended down into the Atlantic Ocean by November 2nd, as is now reported on the balloon's web page. Now let's keep an eye on the flight list and wait for the launch of S-20.


See also:

https://en.wikipedia.org/wiki/High-altitude_balloon
http://www.arhab.org/ 
https://tracker.habhub.org
http://www.qrp-labs.com/
http://www.popsci.com/technology/article/2011-12/amateur-radio-balloon-makes-record-transcontinental-transatlantic-flight
http://makezine.com/projects/near-space-balloon-cam-with-arduino-and-aprs-radio/ 

The HF Voyager Project

Last edited: 29.09.2016

Interesting project here by the Jupiter Research Foundation Amateur Radio Club (JRFARC) on Hawaii: an autonomous ocean-going Wave Glider roaming the oceans, and carrying a HF ham radio payload which can be contacted in PSK31 by amateur radio operators! Would be nice to see a similar project in Europe someday. Read more here: http://www.jrfarc.org/hf-voyager/. While you're there, also check out the other fascinating projects of JRFARC and the Jupiter Research Foundation (listen live via the Internet to humpback whales singing for instance!)