QRP Portable Operation

A Portable QRP Solution – Or having fun with Ham Radio when Travelling

Before you stop reading and dismiss this a another one of those articles that needs a suitcase full of equipment that then uses a wire antenna hanging from the balcony of the hotel or looped over a nearby tree- hear me out!

Working The World on 5Watts

This article has been written to tell you of some of the fun I have had with a QRP HF Station while traveling around the world. Normally I wouldn’t bother writing an article about what I have been doing however a number of my friends have been urging me to tell the story – so here goes!

If you have read this far then I am sure you have or want to take Ham-radio Portable. If you are like me and don’t want to reinvent the wheel you will have gone on to the internet and searched for possible ways to achieve this magical state of QRP Portable and found that most of the articles just don’t meet your needs?

Well that is exactly what happened to me and after quite a period of searching with little reward I began thinking “How hard can it be”?
What was so special about what I wanted to do? Was it so different from all those that had gone before me? Could it just be that I was not able to grasp the merits of the solutions that I was reading about?

In most of the solutions presented much of the discussions centered on the assembly of equipment and how to power the QRP station and then as almost like an afterthought the antenna solution became a loaded whip requiring a counterpoise or a long wire thrown over a balcony or a near by tree (assuming one existed).

What I wanted to do was to have a QRP Station that would be able to be carried onto an Aircraft without the need to have a separate suitcase full of equipment. I wanted to have an antenna that was efficient and not requiring a tree or a balcony and lastly I didn’t want a large battery to have to be carried around. On the surface that all seems rather reasonable to me and so the project began!

Initially I was drawn into the age old debate why not use a computer based solution such as “Echo Link” then all I would need is a computer? But this solution assumes that there will always be an internet connection where ever I was traveling and of cause this is far from the case. Secondly this solution while a great innovation that provides the ability to talk other Ham Radio operators around the world still does not give you the facility to use HF as most of the stations are using keyboard to keyboard or via a 2m or 70cm repeater contacts.

I have in the past taken a Dual Band Hand Held Transceiver which certainly works for calling into one of the local repeaters on 2m or 70cm if there is one but in 9 out of 10 locations there is no activity if there is a repeater and in many cases there has not been one in the location I was visiting.

FT817ND and Auto-Tuner

What then is the solution? It turned out to be staring me in the face. I have been using YAESU FT817 Transceivers for my Microwave Transverters with great success and have found these little units to perform very well. In addition they fit the QRP requirements very well with a maximum of 5watts output and in addition they are Multi-Mode and have an internal battery. In addition these units cover all of the HF Bands as well as 6m 2m and 70cm so if I did want to try one of the local repeaters then I would be able to!

In addition to the features outlined they have the ability to be interfaced to a laptop running software like Ham Radio Delux making it easy to keep a computer log of all my contacts.

The first part of the solution was at hand and now what was going to be the antenna? I am sure many of you have read at some time articles in Amateur Radio magazines discussing “Magnetic Loops” an how effective and efficient they can be for Ham Radio applications. In the 1980’s and 1990’s a number of manufactures produced a range of these antennas and while popular in some areas of the world at the time there seems to be little interest shown in this decade.

Searching the internet produced a number of designs all of which seemed to need a lot of setting up and critical placement of the feed point. I decided to try and produce a loop that I could take portable that was not critical to set up with robust elements that were almost self supporting. During the test phase I tried all manner of shapes and sizes. While most of them worked, the difficulty of support always seemed to be an issue along with how to make it small enough to take on board an Aircraft.

Squid Pole Mount

Finally I settled on a loop that was easy to assemble and dismantle, there were no critical components and it could be scaled to cover 40m to 6m and it has now been with me on a number of trips without any disasters.

The Loop Tuner

The accompanying photographs show the final solution. The antenna is made from 12 x 30cm lengths of aluminum 10mm wide by 2mm thick with a 3/16″ hole in each end. The pieces are held together with zinc plated 3/16″ bolts, spring washers, star washers and wing nuts. When assembling the antenna a star washers is placed between the aluminum bars to allow it to hold its shape with the spring washer ensuring when the wing nut is tightened the assembly remains secure. The loop is tuned using a 2 gang double spaced tuning capacitor (third gang obvious in the photographs was not used) mounted in a rectangular plastic electrical junction box with a switch to add or subtract the second gang depending on the tuning range required. A knob is fitted to the Tuning Capacitor to indicate tuning position and also to prevent RF burns (yes even at 5watts it will burn you).

Tuner and Couplers

The antenna is fed at the opposite side of the loop to the tuning box. The coupling is effected by the use of a toroid with 5 turns of hookup wire connected to a BNC socket one end of the loop has 0.1ufd capacitor in series to earth. As seen in the photographs the loop element passes through the Toroid forming an RF transformer connection to the antenna. As shown the Toroid assembly is placed an an electrical junction box to prevent damage. I have used 2 of these pickup units, one with 5turns (80, 40,30&20m) and one with 3turns to cover the remaining bands.

The Antenna is connected to the YAESU FT817 using a length of RG58 cu with BNC connectors on each end.

The Coupling Transformers

By now some of you will be saying but what do you hang the antenna on? My answer a “Squid Pole” as shown in the accompanying pictures. When collapsed it is permitted as cabin luggage. I have also supported the antenna from a curtain rod in a hotel room with good success.

The tune up process is simple: assemble the antenna, Attach to whatever support you decide to use however if you use the squid pole outside as is shown in the pictures it is best located with the bottom of the loop a maximum of 300mm above the ground. In the case of using it in a hotel room its shape can be changed to suit the window size available.
Once built turn on the transceiver, select the frequency to be used and tune the antenna for maximum received signal.

Packed Up and Ready to Travel

Call CQ and have fun – I certainly have !

Post script:
I invested in a LDG Z-817 battery powered tuner on one of my trips – best thing I could have done. The beauty of this device is that once the Antenna is initially tuned on a particular band the tuner allows frequency changing within any given band without the need to retune the Antenna and because it is battery powered from its own dry cells is fully automatic without draining the Transceiver battery. Push the “Black” button and it tunes!

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4 Responses to QRP Portable Operation

  1. goodnewmusic says:

    Thanks for the QRP Portable operation blog, been reading your posts since u gave me the url at the microwave day at Redcliffe radio club recently.

    A few questions. In the last photo there is an L-shaped (looks like PVC) item. What is it used for? You mentioned the coupler for the low bands (80m to 20m) but the photos are unclear as to the range of the other coupler. It looks like 14Mhz to 50 Mhz. Is that correct? if so then there is some overlap. is the yellow foam in the couplers there to hold the toroid in place? What is the diameter of the tubing in the couplers? A tight fit at 10mm or looser at 11mm or 12mm.

    Like the idea of the battery powered tuner. Will look up the specs and cost.

    Thanks again,
    Gordon

    • vk4zq says:

      Hello Gordon,
      I am glad that you found something of interest on my Blog.
      The PVC angle pipe that you asked about is used to support the tuning unit at the top of the squid pole! I could have used a variety of fixings to support the tuning unit but it seemed to be adequate and in reality this method allows the tuning unit to be connected, using the PVC saddle, with a rope if a squid pole is not available. I have thrown a rope over a tree branch and hauled the whole assembly into the air while operating in the field with great success!
      In regard to the size of the PVC pipe in the pickup; it can be any size but remember it has to fit through the toroid and allow the aluminum element to have a snug fit inside it. Any movement will effect tuning!
      As you have suggested, the foam is to keep the toroid stable within the PVC box.
      Experience has shown that the two pickup units do overlap and my prototype used just one with a number of taps on the winding but by having two units the size/weight is reduced and has proved adequate for all my needs.
      The battery operated tuner is worth it’s weight in gold an performs flawlessly! However remember, it should only be used to provide frequency agility. The loop should be set to resonance in the centre of the frequency range being used before using the battery operated tuner. The function of the tuner should only be used if you QSY away from the resonant frequency of the loop.
      If it is used in this way maximum efficiency of the system will be achieved.
      I trust this answers your questions and I hope that if you build a Magnetic Loop that you find as much enjoyment from it as I have.
      Thanks again for visiting my Blog.
      73 Roy VK4ZQ.

  2. normd says:

    This is a great article. I am very interested in building one of these. I found that when I tried to click on many of the images, they are not found. Could you check the links for them?
    From what I can see, the loop is not an open loop. Could you clarify how the tuner is connected to the loop?
    Thanks
    Norm W9IFW

    • vk4zq says:

      Hello Norm, I am sorry for the broken links but it appears WordPress has been updated and I can’t seem to re-establish the links.
      As far as the loop is concerned, it is tuned by the ganged tuning capacitor at the centre top. The capacitor needs to have a good set of insulators as the voltage across the plates, even with 5 watts from the FT-817nd , is significant. As I mentioned in the text, I use a toggle switch to add an extra gang for the lower frequencies. Make sure the insulation of the box used is also of good quality.
      I have found this little unit to work very well. I hope you meet with the same success.
      Regards Roy VK4ZQ.

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