Remotely Tuned Magnetic Loops & Remote Tuning the Alexloop – A Brief Review

Three years ago I considered acquiring an Alexloop PH1AHD as a travel antenna, but before placing an order I wanted to convince myself that such a device would work. Hence, I built my own small magnetic loop prototype with a Hoola-Hoop, a piece of braided grounding strap, a variable capacitor from eBay and some PVC pipe material. Here it is (click on the image for further pics):

Photo0011

This crude “VA3PCJ Hoola-Loop” would tune 15m to 80m (although for 80m its efficiency was dismal). However, the first time I used it in 15m I made an SSB QRP contact Ottawa to Greece. This and further testing convinced me that the principle worked, and I wrote to Alex PY1AHD to place an order for a travel Walkman PY1AHD Alexloop.

Since then, this antenna has served me well as a travel companion, allowing me to operate from several continents both indoors and outdoors, from summits, islands or parks and even from my small sailboat. Also, in the past, during the winter months, I did not mind operating outdoors in the cold. However, as I grow older, I tend to prefer operating outdoors “car-portable”: with portable equipment but from inside the car – my faithful (and heated…) Jeep Liberty RGB. Hence, it would be nice if I could minimize any exposure to the cold air outside the vehicle. In other words: I hate to have to get outside or open the car window every time I need to tune the loop. The solution would be a remotely tuned magnetic loop.

Many possible solutions have been proposed for remotely tuning different magnetic loops. Some are manual and some automatic; some require a cord and some are wireless. However, I decided to start by surveying what would be readily made and commercially available. Here is the list I came up with for currently commercially available remotely tuned HF magnetic loops:

Name: MFJ-1782
Maker: MFJ Enterprises
Country: US
Bands: 10m – 30m
Price: US $410
Reference: http://www.mfjenterprises.com/Product.php?productid=MFJ-1782

Name: MFJ-1786
Maker: MFJ Enterprises
Country: US
Bands: 10m – 30m
Price: US $450
Reference: http://www.mfjenterprises.com/Product.php?productid=MFJ-1786

Name: MFJ-1788
Maker: MFJ Enterprises
Country: US
Bands: 15m – 40m
Price: US $500
Reference: http://www.mfjenterprises.com/Product.php?productid=MFJ-1788

Name: MLAT-T
Maker: B PLUS TV a. s
Country: Czech Republic
Bands: 40m – 160m
Price: € 700
Reference: http://www.wimo.com/download/MLA-T_Manual_eng.pdf

Name: AH-521
Maker: INAC
Country: Spain
Bands: 15m – 40m
Price: € 390 (w/LAC1) or € 515 (w/LAC2)
Reference: http://www.wimo.com/download/Manual%20AH-521.pdf

Name: AH-1430
Maker: INAC
Country: Spain
Bands: 10m – 20m
Price: € 365 (w/LAC1) or € 490 (w/LAC2)
Reference: http://www.wimo.com/download/Manual%20AH-1430.pdf

Name: AX-330
Maker: INAC
Country: Spain
Bands: 10m – 80m
Price: € 980 (w/LAC1) or € 1100 (w/LAC2)
Reference: http://www.wimo.com/download/Manual%20AX-330.pdf

Name: Baby Loop
Maker: Ciro Mazzoni
Country: Italy
Bands: 10m – 40m
Price: € 1189
Reference:
http://www.ciromazzoni.com/#!loop-baby/c1fl3
http://media.wix.com/ugd/1aa222_ba54b9bbe4554cb08cb7596a916586f8.pdf
http://www.wimo.com/download/loop-manual.pdf

Name: Midi Loop
Maker: Ciro Mazzoni
Country: Italy
Bands: 20m – 80m
Price: € 1375
Reference:
http://www.ciromazzoni.com/#!loop-midi/c1ewt
http://media.wix.com/ugd/1aa222_d8a228bf1c764f4292a8dd3aeda44fda.pdf
http://www.wimo.com/download/loop-manual.pdf

Name: ML40HP MKII
Maker: G4TPH
Country: England
Bands: 15m – 40m (w/10 rails) 10m – 12m (w/7 rails)
Price:£ 365
Reference: https://create-cdn.net/sitefiles/20/6/8/206884/remotely_tuned_G4TPH_Magloop_Instructions_landscape_V.3.pdf

Unfortunately, with the exception of the G4TPH “ML40HP MKII” and the Czech MLAT-T all others cannot be considered as “portable”, and the MLAT-T does not operate in the high-bands (its smaller version, the BTV MLA-M V.5, which with the aid of jumpers is listed as able to tune 10m – 80m, can only be manually tuned.

I was hoping to also be able to consider the DK5CZ AMA remotely tuned magnetic loops (Jean Devoldere ON4UN, the “guru” of low band DXing, had one in his garden!). However, Chris Käferlein DK5CZ has been SK since 2005 and his antennas are no longer in production.

=================

Since I already own an Alexloop it would be great if I could just add a motor operated device specially designed for the Alexloop, that could be attached to its variable capacitor and allow it to be tuned from a remote location. In fact, Alex PY1AHD himself and his coworkers have been working on several possible solutions:

https://www.youtube.com/watch?v=ZKfOUCcYrz8
https://www.youtube.com/watch?v=PbnP8gIDb78
https://www.youtube.com/watch?v=OQJIm0kvKZ8
https://www.youtube.com/watch?v=ODbV7RKf2R8
https://www.youtube.com/watch?v=ctvgVuSEiTw
https://www.youtube.com/watch?v=ZIRorj6Alg8
https://www.youtube.com/watch?v=3YwfMmeBy4E
https://www.youtube.com/watch?v=X4jFzsXio58

And others have devised similar approaches, also for the Alexloop:

K2MVR: https://www.youtube.com/watch?v=cWZrClbHg5Y
VA2SS: https://www.youtube.com/watch?v=qFb-H4-Bsko

For the use I intend, the approach by K2MVR seems to be the simplest and easiest to implement. I also find his use of an ad-hoc “felt-clutch” to be very ingenious. Otherwise, the G4TPH ML40HP may be an alternative, unless… I succeed in convincing Alex to let me try one of his remote-control prototypes…

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