The Dipole vs Indoor Magnetic Loop Antenna

May 12, 2017 Julian OH8STN Ham Radio 0

These days it seems like everyone and their mother is attacking the very popular, small, lightweight, and extremely portable,  magnetic loop antenna.  As annoying as it is, it doesn’t look like it’s going to stop anytime soon.

Lately there’s been a few forum threads, blog posts, and video comments, reportedly comparing the performance differences between a magnetic loop antenna and dipole antenna in various deployment scenarios. For the most part, these comparisons are absolutely valid and well meaning. Unfortunately, there are those instances, when comparisons present a very one sided view, leaving much to be desired. Often the “comparisons”only focus on the 40 meter amateur radio band. Small portable loops are at a distinct disadvantage on 40, 60, & 80 meters, in comparison to a full size antenna. Everyone knows this, but none of the tests or comparisons will ever show you 30, 20, 17, 15, 12 or 10 meters because the test results, would no longer be as “clear”. 

Loop performance (efficiency) increases as we head higher up the band. So much so, that a dipole and magloop could be indistinguishable on higher band results. In fact, it actually becomes an outright fair fight! Focusing solely on the 40 meter band is not a lie, it’s just doesn’t tell us the whole truth.

We also need to point out, these comparisons usually ignore the larger diameter magnetic loops as add-ons, multi-turn loops, and larger “less portable” loops, since doing so would completely debunk the results as presented in these tests. So their focus is usually the less efficient but very much smaller, more portable, lightweight and easy to deploy little Brothers. For example, magloops like the Chameleon P-Loop, F-Loop in their default configuration, the Alexloop and so on. So let’s point out for the record operators don’t usually build or buy small portable magnetic loops for their excellent performance on 40 meters. They use these systems because of their portability and very small deployment footprint. In a way, these compsrisons are as ridiculous as saying “lets test a dipole versus a small magnetic loop in my kitchen”.

The test configuration

  • Band: I set up the test on the 30 meter band. Results will be viewed and compared using www.dxplorer.net. The plan is to run the test for a few days, periodically updating this post with new data. The day of posting is day 1. 
  • Dipole OF8STN: On one side, we have the Broadband terminated dipole. One leg is South by Southwest the other leg is west-northwest oriented. The center portion is at 12 meters height from the tower stand-off. Driving the Broadband terminated dipole is a Yaesu ft-817 at 500mw, controlled by wsjt-x on Ubuntu Linux.  The dipole has the upper hand, with greater output power, a clear view to horizon,  and is more efficient. It should easily outperform the loop.
  • The magnetic loop OH8STN: On the other side we have the Chameleon P-Loop 2.0.  It’s tripod-mounted with its capacitor at 2 meters height. It’s being powered by the SOTABeams WSPRLite at 200mw. The loop is mounted indoors under the rafters of the attic in my garage. Loop oriented Southwest/Northeast. So not only is it purposely underpowered, it’s also indoors (not to worry). The loop should definitely fail, right?

    As I mentioned, the dipole has the clear advantage in every way, so we expect an overwhelming difference in performance. Why then aren’t the spots maps much worse for the magnetic loop? I used the ft-817nd because I only have 1 WSPRLite. I’ll order a second WSPRLite in the coming week.

    First few hours

    OF8STN is the BBTD. OH8STN is the loop.  in regards to range, the loop is definitely down an average of 400km under the dipole.  This should not be surprising as we’re using half the power, with an indoor Loop. With the exception of EA8BFK, the range of stations isn’t really that different than the dipole. This is just an observation. 

    Map Spots from both stations

    here are a few example spots from receiving stations which have heard both the dipole and the loop. Pay close attention to the signal-to-noise ratios. The question I have to answer is why the magnetic loop, underpowered, mounted indoors, isn’t performing worse in comparison to the dipole!? The dipole is “the winner”, but what about at 200mw with an additional WSPRLite? What results could we expect then? We shall see!

    Don’t forget to check out SOTABeams WSPRLite at www.sotabeams.co.uk who sent the wsprlite to 65°N for testing and review. 

    I’ll continue this test when I have the second WSPRLite!

    That’s all for today

    de oh8stn


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