17m + 15m Magnetic Loop

Loops are always under test in one form or another up in the old shack.  Winter is a great time to build small antennas, because it can be done comfortably, indoors!

In cutting up an old design that resonated too low for what I needed, I recycled some copper tube, including recycling the expensive bend fittings, into a 17m loop.

A very hastily cobbled together test loop for 17m and above.  Just 0.55m a side!

The initial experiment was two loops in a figure of eight fashion, each loop being just 0.55m  on a side.  The antenna worked fine, but I found that it behaved much like a single loop of the same total perimeter.  So, that being the case, it was more of a 20m and below loop.  Handy, because it's more portable than a single 4 or 5m perimeter loop, but not what I was after that day.

So, chop off one loop, use just the other.  At 0.55m a side, the loop is at the lower limit of an ideal size for a 17m loop; this was a product of making the loop such that it would work well on higher bands, too.

The capacitor is a wide-spaced, roughly 10-250pF air spaced type, manually tuned.  The loop being borderline size, it's a little fiddly at 17m to tune, but much easier on 15m.  However, the old 'by ear' tuning system works easily enough!

The very simple Flexweave primary loop, just 0.44m long.  Matching is easier with a primary that overlaps the secondary.

Result?

It's working indoors, so a clear-site, outdoor test will have to wait.  But, it was picking up a JH station nicely on the grey line at 17m this morning, and is putting out a very strong signal across the EU.  It's certainly working properly.  As I write this, R0AU had picked up my 5 Watts at 3534 miles, at -27dB.  Weak, but it's early yet...

Remember that we're not trying to out-do SteppIR beam twiddlers here.  But we are offering a cheap, very simple to build loop for 17m that gives those living in apartments, HOA and other antenna-hostile locations a chance to go live and work the world, albeit more likely on low power digital and CW modes, on a band that otherwise needs a fairly extensive piece of wire.

Oh, and ignore those folks - and models - that say loops are not efficient.  They are.

The next step will be to revisit the multi-loop development, closely following the fine work of G3JKF, who has the most efficient magnetic loops I have ever seen.