80m Inverted L Antenna (updated for 60m)

What to do when the XYL is watching crap TV and the nighttime has stolen the higher bands away?

Yes folks!  It's time to go 80m!  [Update: and now, 60m!]

I first decided to try 20m of equipment wire (read: much cheaper than 'proper' antenna wire, whatever that is!), at the end of an end-fed matchbox made by the Hawaii Emergency Radio Group.  This is a very handy multiband box I bought a long time ago, but really only an adequate arrangement that gets you on the air in some form.

I ran this up to the tower at 10m, then down again to near the ground in a bent end-fed arrangement.  It worked, but the signals, though reaching where everyone else's were getting to, weren't very strong and matching it wasn't as easy as it needed to be.

Down it came!

Following night, after browsing some other clever people's inverted Ls, I decided to fix 10m of wire from the tower to a 10m fishing pole (at 9m high), whereupon the remaining 10m of wire hangs down to the ground where I initially used a 4:1 balun, a single elevated, 20m-long counterpoise and a short copper ground rod (I have exceptional ground) are connected to it.  At just 10m long, this is an 80m antenna that can fit in a fairly small garden without performance compromise.

[UPDATE:I tried two elevated radials, but found the second one made no difference at all as reported by WSPR receiving stations.  So you can certainly spare yourself the space and expense of an additional 20m of wire!  I found through very careful WSPR work during exceptionally stable conditions (13/12/13), that the best radial system is one elevated radial under the top wire, and as many buried radials of about 0.1 lambda or a bit longer as you can accommodate.  The buried radials added a consistent 3dB to the received signal]

My inverted L.  Feed is at bottom left.

Results?  Very good indeed - for DX!  Being predominantly vertical radiation, it's not an antenna for talking to your mates up the road.  In fact, you're unlikely to hear them at all on 80m, but is very good for NVIS at 60m.  Easily up there with the best of the 80m DX WSPRing crowd and, during early December 2013, I was the first and, for a fairly long period during the earlier evening, the only station getting across to the US and VK on 80m.  On 19/12/2013, I was the only one hitting VK7DIK from anywhere in the world on WSPR.

And if you want evidence, here it is, showing VK7BO's receptions of WSPR signals over the 24 hours spanning 17/18 January 2014.  Mine was one of only two being heard from any 80m station in the world:

World-leading 80m performance - from a piece of equipment wire!

So, a definite success.  What's more, both the internal and external transmatch match up the antenna very easily.  Native SWR (at the design band of 80m) is very good indeed - see plot on Update 2. Remember that, even at high SWR, losses with even cheap coax at the lower end of HF are just small fractions of a dB, so no need to worry or install expensive feedlines!

This is how MMANA-GAL thinks the radiation goes out when fed with an exact model of the above-pictured antenna (radial supported 1.3m off the ground - plants or fence posts in the garden achieve this!)  Real-world RF measurements support the pattern:

Not a bad pattern for such a simple antenna.  Red is vertically polarised; blue horizontal.  Gain figures are for my ground, which is exceptionally good and sloping.

So there you go.  Dirt cheap wire off E-bay, and I'm doing the business on 80m!  Now it's your go.  Two 10m fishing poles supported by fence posts are just as good - you do not need a tower!  Or just use one pole and slope the horizontal section; it only has a very small effect on overall gain.  Wind tolerance is about 45mph with my arrangement.  Not an issue if you have trees or a tall house, of course!


Here's the schematic.  Measurements are not critical, as the nature of the antenna necessitates the use of an ATU.  The 20m 'counterpoise' is raised in that fashion to allow a person to pass under the wire.  If you don't need to do this, the wire ought to be roughly 1.5m above ground.  About 90% of the return current is picked up well within 0.1 lambda of the vertical section, which is why the buried return path wires can be this short.

Update:

Having had an unused Notice of Variation for 60m for a couple of years, and with the onset of autumn, I set up the same inverted L and matched it up - which it does easily - for this relatively new band.

I had good results on WSPR, but the real surprise came when I came across 59+15dB signals from all across the UK in the SSB sections of the 60m band.  There's also surprisingly little noise on most nights, making QSOs at short range stable and comfortable.  I made several SSB QSOs using the above antenna, but by now, the horizontal wire slopes to just 6m off the ground at the 'far' end, because of my 12m Yagi's tower usually being deployed at that height.  This makes little difference to the performance.

The 80m inverted L, operating at 60m.  A very useful pattern for this great band.

Modelling the new antenna, I can see why this inverted-L does so well on short skip, and clearly will do well on DX too - a very 'bread loaf' pattern, highly reminiscent of a corner-fed delta loop's pattern.  In short, this is perhaps an antenna perfectly suited to 60m.  Thanks to all on the band who made me so welcome, too!

UPDATE 2 - March 2016.

Having my own SARK-110 analyser now, this is what the inverted-L looks like without an ATU fitted.  That's an extremely good match at 80m!

The SARK-110 plot of the inverted-L at 80m.

A full-HF plot showing the multi-band possibilities of this antenna.  Even though it doesn't look so promising at 60m, the antenna does, in fact, work very well, with easy ATU matching.  An auto-ATU at the antenna base will clearly reduce losses considerably at 60m.