EH Antenna

Well, just when you thought there were no more antenna experiments to conduct, I've come back to the EH antenna!

If you look up the EH online, you will find most rubbish the whole antenna concept, saying it simply doesn't work.  A few have gone to great lengths to measure, analyse and assess the antenna, concluding, similarly, that it's a dud.

Compare that with some operators who claim the complete opposite: that, whilst small and perhaps less capable than a full-sized conventional antenna, it does work, and significant numbers of QSOs, even DXCC awards, have been conducted with them.

Even a leading member of the UK ham community has built and tested an EH, finding he was "pleasantly surprised" with it, despite being placed in a non-ideal, roof space.

So, not ever being one to automatically believe others, I set off to the shops this morning to buy some cheap deodorant cans (with an awful, soap-like odour!) to cut up for the EH.  These proved to be steel, which is not ideal, but are fine for a quick test.

Made in a hurry, but comes in at 1:1.8 SWR before any adjusting.

The backbone of the EH is a PVC tube, but avoiding black ones, which are said to contain conductive carbon particles.  I happened to have some white, 42mm tube lying around, which happened to be about the right diameter for an EH to cover the 15m band.

Now, there is some wire to place inside the EH's tube.  Getting access to the inside of a long 40mm inside diameter tube is, well, impossible.  I figured that by cutting a long slot down most of the length of the tube, leaving a few short gaps to maintain strength and shape, I could then get my fingers and a pair of long-nose pliers in there to fix things together.  This proved to work well.

In fact, there is no need to use PVC to support the antenna components - they can just as well be screwed to a timber batten, which will make access and the whole construction a hell of a lot easier.  You only need the tube to wind the tuning coils.   Alternatively, you can still use the tubing, but arrange all but one of the wire connections externally, rather than internally; there is no reason other than cosmetic appearance to struggle with shoving it all inside a small tube!

So, it's simply a case of following one of the many, and not often the same kind of design found online, and hooking up.  I was short of time when building this thing, so was amazed to find that even when thrown together, the native SWR was only 1:1.8.  My ATU of course easily handled it down to 1:1, where I set it to work on 15m WSPR.
 
Sadly, there's been an awful lot of solar activity the past weeks, so 15m is all but dead.  What does seem clear is that the EH is hearing pretty well - it seems quite lively, akin to a 1/4 wave vertical.  Until the band clears up, I can't say much more than that.  When it's clear, I'll run the EH next to my vertical 15m delta loop, see how it shapes up.  A test has, as you might expect, already been done with WSPR, this one at 40m, which certainly doesn't indicate the EH is a dud.

As to feedline radiation, there doesn't seem to be a significant amount; it is there, but then I can find that on any transmission line, if I shove an RF detector at full sensitivity right next to it.    My RF meter indicates there is moderately strong omnidirectional radiation, with a pretty low peak of 10 degrees or less; I followed the 'DX' version in making this EH, so the radiation angle seems to support this description as correct.

Certainly an interesting antenna, and very easy and cheap to build.  What's more, even the strongest winds will have no effect on it - a very big plus at this QTH!

UPDATE: 

Whilst 15m remains almost dead, I have been able to conduct some more RF meter measurements on the antenna.  As many have noted, and some calculated theoretically in the scientific literature, this antenna seems only to 'work' by virtue of feedline radiation.  There appears to be almost no field strength from the cylindrical radiators, whilst there is strong radiation, even with the presence of a well-made balun, from the coax.  This feedline radiation only became clearly apparent when I raised the antenna to 2m above ground, allowing a decent length of vertical line to reveal this effect. The previous 'low angle' conclusion was merely my meter picking up less radiation from a much shorter vertical section of coax.

So, it does appear to be a complete dud, after all - so much so that I'm not spending any more time or even poicket money resources on a lower band version.