A Look At The AL-705 Alpha Antenna Magnetic Loop. Tuning The ICOM IC705 Made Easy.

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[@DaDitDa]

If you intend to use this loop for 40m QRP, you'll be disappointed. Assuming the loop is about 8 foot circumference and the loop's conductor about 0.5 inch diameter, with zero antenna system resistive losses. Applying an idealistic mathematical model for calculating loop efficiency: on 40m it's about 5% efficient. On 30m it's about 15% efficient. On 20m it's about 35% efficient. On 17m it's about 55% efficient. The shorter wavelengths (12m and 10m) are about 80% efficient. Obviously, in reality, the antenna system has greater than zero resistive loss; and if the loop is less than 8 foot circumference and/or 0.5 inch conductor diameter, then its true efficiency is less than the idealistic model. On the other hand, if you intend to use the loop for receive-only, then transmit power efficiency is moot; i.e., it'll perform well on all bands as a receiver-only antenna. And, given the above approximate efficiencies, it should perform relatively well as a transmit antenna on 20m and higher. My experience with small loop antennas is limited to 10 foot and 15 foot circumference QRP loops, with loop conductors varying from 0.5 to 0.75 inch diameter. Generally, the 10 foot loop seems to perform well at and above 20m, and the 15 foot at and above 30m -- on 40m it's poor to marginal. Ken WA8FCI

[@jason2e1hko59]

Thanks Ken, that’s very interesting. When I get out in the field I’ll bare that in mind. Take Care 73

[@FFdo.]

antenna is better than no antenna. a loop is the only thing that gets me out in 80m from the middle of city. QRP. go figure.