SKCC 5123T----- FISTS 14979----- Flying Pigs 2331----- NAQCC 3610-----QRP ARCI 14176-----Polar Bear 257

Sunday, June 30, 2013

The AlexLoop Antenna and RaDAR

The AlexLoop Walkham is a magnetic loop antenna designed and sold by Alexandre Grimberg PY3AHD from Brazil. See on the web. There are many experimenters building their own mag loops but the Alexloop is one of only a very few commercially available mag loops. The AlexLoop implements a mag loop for the 40 through 10 meter bands. It packs into a small bag that comes with the purchase. I am able to pack mine into a backpack with my KX3 and external battery. This is perfect for Rapid Deployment Amateur Radio (RaDAR).

AlexLoop and KX3 at St. Andrews State Park during RaDAR event

The AlexLoop is commonly supported by a camera tripod about three feet off the ground. I also use a four foot pole with a spike. It is necessary to be near the loop to retune it manually when there is a frequency change. The AlexLoop is rated for 10 watts on CW and 20 watts on SSB.

A backyard setup on family visit

The AlexLoop is about three feet in diameter. The loop itself is coax. The coax loop hooks into a capacitor box at the bottom using PL-259 type connectors. The vertical support for the loop are three plastic tubes that join together. The coax is unhooked and coiled and the tubes are broken down to yield the small pack up size.

The AlexLoop in my LowePro Flipside 300 Backpack

The backpack ready for RaDAR ops.

The AlexLoop can be purchased directly from Brazil. It is also sold by US vendors. I bought mine from W4RT and I see it now on the GigaParts web site. The price is around $350 which can cause a pause. However, you must consider that you are getting a ready to use product that is the result of many years of experimenting. It is not too different in price from the popular Buddipole products.

Now with the preliminaries out of the way, lets highlight what makes the AlexLoop a great choice for portable operations.

Size: The deployed loop is small compared to full size half wave or quarter wave antennas. It is also smaller than the typical shortened dipole or vertical. Note, there is no counterpoise required.

Height: It is recommended to be deployed at three feet as a vertical loop. I have used mine on a coffee table with the tripod legs shortened. So forget about masts or trees for support. It also could be deployed horizontally from a balcony.

Multiband: The loop operates 7 through 30 MHz. That is pretty good. Changing bands is fast as it just requires adjusting the tuning capacitor.

Bandwidth: Narrow! This is the price you pay. It does require retuning when moving up and down the band or changing bands.

Tuner: Not required and I advise against it. You will need an SWR indicating device.

Efficiency: I am not the technical expert on loops. I have seen figures of 90% on 10 meters down to 5% on 40 meters. In any case don't think that the efficiency will keep you from making contacts even on 40 meters.

Performance: I find it impossible to compare directly any two antennas for performance. Likewise, making contacts has a lot to do with conditions and opportunity that someone wants to QSO with you. Given all that, I have success on almost every portable outing. I have had the full range of operating outcomes. I have answered CQs with no luck, I call a station and get and get a weak report but QSO for 30 minutes and then call another station and get a strong report. This can be all in the same outing. I have also called CQ with no luck and also called CQ and get an immediate reply. I have also held a frequency down for an hour. This includes CW and SSB.

My web site documents many outings with the Alexloop. One outing yielded eighteen contacts on 20 meters and eight on 15 meters. This included F6HKA in France and V31JP in Belize on 15 meters. At lunch one day I worked South Africa on 10 meters. Of course, any indoor contact is satisfying and 40 meter contacts are awesome. Just envision that 40 meter dipole you did not put up.

I surprised my relatives by setting up on the coffee table 

The bottom line is that you are going to be able to operate in almost any portable situation. This includes indoors. I have operated from hotel rooms, hotel balconies, and also my relatives living room off their coffee table. I have a camera backpack that holds the KX3, AlexLoop, external battery and tripod strapped to the back of the pack.

I have to warn you that this antenna is not for everyone and your mileage may vary. A beginner may be frustrated with unsuccessful outings. There is luck involved and also experience to be gained in finding QSO opportunities. I think State QSO Party weekends are a good time to get broke in. Likewise, it is natural to have a mindset that you can't do so much with so little. Give the Alexloop a chance and you will be surprised.

AlexLoop Tuning:

STOP you do NOT need a tuner or analyzer.

First, Simply adjust the knob for the capacitor for maximum noise at the desired operating frequency. I find with the KX3 you may have to turn on the preamp to hear noise. For the KX3 take advantage of the S meter and tweak for a peak on the meter. You may be rewarded with being close enough. To complete the tuning produce a carrier (XMIT button on the KX3) and carefully adjust the knob for min SWR. You can get as low as 1.1 or 1.2. However if you get 1.5 to 1 a few KHz over it will be 1.1 to 1. On 10 meters the SWR does not get as low.

I don't have any financial interest in Alexloop, Other than I am a satisfied customer. I have really gotten my money's worth over and over. I really have to wonder why I should break out a larger antenna for portable ops. Also, Alex the ham is friendly and responsive. He participates in the KX3 and Mag Loop forums on Yahoo groups. Thanks Alex for a great product. Your efforts are appreciated.

KX3 and AlexLoop demo at the 2013 Orlando Hamcation

The Rapid Deployment Amateur radio (RaDAR) program is a good way to exercise your portable operating skills and equipment. The Alexloop is perfect for RaDAR. In RaDAR you might make a contact walk 1 kilometer and make another. This Alexloop fits that bill. See this link for the RaDAR Program rules. In addition, there is a Google+ Community for sharing your RaDAR operations at this link You don't have to join the community to participate in RaDAR. The RaDAR program is administered by Markus KD0JKM. The RaDAR concept was originated by Eddie ZS6BNE.