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LF / MF Antenna Planning
27 April 2017 | by  |
| courtesy: Chuck Roblin |
For U.S. amateurs, the 2200 and 630m bands will soon be a reality and I have no doubt that there will be an accompanying surge in interest among large numbers of homebrewers and low band diehards.
It should be an exciting time as new stations gradually start to populate the band from coast to coast.
High on the 'to do' list will be the planning and building (or modifying) of a suitable antenna system for the band(s) of choice. For most, this will be new territory, but the reality is that there has been a long tradition of operation in the LF and MF bands in the U.S. for many years ... all under the Part 15 'Lowfer' and 'Medfer' service.
Although activity in this category has fallen off over the years due to the availability of the much less-restrictive Part 5 experimental licences, there is still a great legacy of literature and information left behind that is every bit as useful today as it was back in the golden years of Lowfer operations.
Here is one such document from Stephen McGreevy's Natural ELF-VLF Radio website that many newcomers to these bands may find very helpful as it covers a wide variety of LF antenna-related basics in a down-to-earth manner.
An even more detailed treatise on virtually all aspects of LF and MF antenna topics is that found on Rik, ON7YD's website. His antenna pages can be found here. Although originally developed for the 2200m band, the principles are equally applicable to 630m as well.
Hopefully both of these sources will help you decide how to get a working antenna system up and running on the new bands. And as always, much help is available via the Internet on the Lowfer Reflector, the RSGB LF reflector or on the 600MRG Reflector.
2 Responses to “LF / MF Antenna Planning”
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….also, a new work by Rudy Severns, N6LF on LF and MF antennas. Rudy has 6 chapters of info that he recently posted at
http://rudys.typepad.com/ Then scroll down to “LF MF ANTENNA NOTES”. It is an awesome resource.
I built a 160 meter magnetic loop antenna using a 2″ wide strip of flashing aluminum that was 100′ long. The two pieces of flashing aluminum were connected by first sanding both to bare aluminum, then using 20 pop rivets the pieces were connected, then aluminum brasing rods from harbor freight were used to braise the heads and base of each rivet to the aluminum. The loop was errected using one fiberglass pole and two corner stakes to errect a delta shaped mag loop. The feed was a gamma match formed by grounding the coax at the apex of the loop and running a unshielded wire 20 feet down the side of the loop where it was grounded to the loop. The loop was bolted to the vac variable cap and tuned. In tests a 20 mile contact was made with s9 reports using 5 watts ssb. A 250′ long aluminum strip mag loop would have 25% efficency at 600 meters and would be relatively easy to errect as a rectangle.