Archive for June, 2013

ARRL Field Day 2013

Posted: June 24, 2013 in Amateur Radio, Engineering, News
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This past weekend was the 2013 ARRL Field Day. Field Day encourages amateur radio operators worldwide to get on the air using alternate power or different locations to test emergency preparedness. Both me and my brother Tony were on the air with our local clubs. The Gator Amateur Radio Club (GARC) teamed up with the Gainesville Amateur Radio Society (GARS) for Field Day here in Florida. Tony worked Field Day from Ohio. In addition to using the club radios and antennas, I also tested out my MagLoop and Icom 706MKII. I worked 2 contacts on digital with just 40 watts. Considering I was hoping to use it with QRP power levels (less than 10 watts), I was quite pleased to get 40 watts out of it. It could probably go higher, but I do not want to arch across my capacitor. Below are a few pics from our setup in Florida and of the loop in action. Enjoy!

Photo Credit: Sam K4ZVD

Photo Credit: Sam K4ZVD

The loop was easy to tune with the help of the MFJ antenna analyzer. I need to improve my ability to tune based on sound, although it is pretty to get it close. It was just outside the tent (you can kind of see some of the copper in the picture).

Photo Credit: Sam K4ZVD

Photo Credit: Sam K4ZVD

We were all impressed with the low noise and excellent performance of the loop antenna. It got quite a bit of attention from both club members and the general public.

Photo Credit: Sam K4ZVD

Photo Credit: Sam K4ZVD

The American and Gator flags flying high above our beam! Go Gators!

Photo Credit: Sam K4ZVD

Photo Credit: Sam K4ZVD

The members of the Gator Amateur Radio Club at Field Day: (from left to right) Ronnie, Andy, Jeff, and Sam (taking the picture).

The next few are from my phone. It took really nice pictures, even at night. (I have a Nokia Lumia 928.)

Gator Tower and LoopW4DFU Tower and my loop in the foreground.

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Florida State EDICS Trailer and Tower in the background.

Gator Tower at night

At night, the towers were up lit and looked really cool!

LEGO Gearbox for MagLoop

Posted: June 21, 2013 in Amateur Radio, Engineering, LEGO
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So the Magloop I posted about earlier was hard to tune. The problem? I cannot turn the dial in small enough increments. After some discussion on the MagLoop email chain, it was suggested I gear it down by about 50. Now Field Day is less than 24 hours from now and I am short on supplies. However, as many of my readers know, I do a lot with LEGO, from Robots to large scale models. I had a few gears on hand and made a 48:1 gearbox.

To get started I attached an axle (along with a gear for stability) to the shaft of the air variable capacitor. I did this simply with 5 minute epoxy. I added some more after it dried so it would be stronger.

WP_20130621_001The next step was to mount the gearbox. I removed the 48 tooth gear. To keep it flexible, I only attached one of the frames (the top one in the picture below) to the air variable capacitor. The rest of the gearbox is held together the same way as any other LEGO Technic model.

WP_20130621_003I took off the bottom part of the gearbox and slipped on the 48 tooth gear. Note that the handle seen in the picture below is attached to a worm gear. The picture below shows the completed gearbox assembly. It does add some overall length to the assembly, but I was able to tune up just fine. There is some slip in the gear-train, but the steps are so small that it doesn’t appear to be an issue.

WP_20130621_005Below is a close up of the gearbox. It turned out really well and I can’t wait to be on the air tomorrow with my new, functional, easy-to-use MagLoop! This very well might be the first time LEGO products have ventured into amateur radio. Following Field Day, I am going to expand the system to include an EV3. This would allow for even better accuracy using the encoded motors, attached to the gearbox.

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HF Magnetic Loop Antenna

Posted: June 20, 2013 in Amateur Radio, Engineering
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Been a while since I lasted posted, but I have been super busy! My latest project is a magnetic loop antenna. This past fall I got my amateur radio license. My callsign is KK4LWR and I am an Amateur Extra Class operator. I run an Icom 706MKII.

Anyways, back to the loop. I live in an apartment and space is limited. To counter this I have been looking at magnetic loop antennas (magloop). A Magloop is an electrically small loop antenna. The loop is feed by a smaller loop connected to the coax and the large loop has a capacitor to tune it for various frequencies.

I found an air variable cap on ebay for $18 and it has a range between 15 and 260 pF.

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Once I got the cap I went to Lowes and picked up some copper tubing. I bent it into a circle and then soldered and crimped some wires on the end to attach to cap.

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I had some scrap material that I used to mount the loop and cap to. Using zip ties I was able to mount the loop and cap.

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For the coupling loop, I used some 8 gauge wire my grandfather game me and connected it to an SO239 connector as seen below.

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Once all the parts were constructed, I attached it to a PVC pipe and placed it in a mount. The mount is a steel pipe in cement. I am planning to use this on my Cushcraft R7 that I am working on getting up and running again. As you can see below, the loop is quite small and I am able to tune it to a SWR of 1.1:1 or better on 20, 30, and 40 meters. I plan to take it out for field day this weekend. Only thing left to do is add some gearing to the cap so it is easier to tune. Right now it is very hard to get it right on a signal. I will post more as I get it on the air.WP_20130620_002