Review: EAntenna 13 element 2m & 70cm beam with free 6m!
As seen at the Burnham Beeches Radio Club show & tell evening, the EA270ZB is a neighbour-friendly dual-band 2m/70cm beam antenna that gives you two, if not three, bands. Although it has two sets of directors and reflectors there is only one driven element, so only one coax. (Some other designs have two feeders which would be a pain with my rigs.) The antenna design, by DK7ZB, is freely published online and can be constructed by anyone using parts also available online or completely homebrew of course. A couple of manufacturers also make commercial versions. I already had an EAntenna HF balun, which seems a very well-constructed bit of kit, so I thought I’d give their version of this antenna a try.
The antenna comes as a self-assembly kit (ie although the parts are pre-drilled, nothing is pre-assembled other than the driven elements being bolted to the boom clamp) and the components seem to be of high quality. There were a few spare nuts & bolts too, which may be handy if I haven’t done anything up properly. In reality this is unlikely to be a problem as shakeproof washers were supplied for almost every nut.
Assembly took half an evening, with a simlar amount of time spent on a few mods & cable termination. A few things to note:
- There is no balun but, as can be seen on DK7ZB’s website, 5 turns of RG58 on a 20mm former are all that is needed if you want one (I did).
- The coax terminates directly on the driven element via ring terminals and no housing or waterproofing materials are supplied (I used liquid tape, which seems to work ok)
- There are no assembly instructions but there is a diagram of the finished antenna, which is all that is needed really. Although this shows the elements spaced incorrectly compared to the placing of the pre-drilled holes in the square-section boom, it is not really a problem as the elements are shown in the correct order and length (I checked DK7ZB’s design which matches the boom drilling, not the diagram).
- Although nominally a Yagi, the 70cm elements don’t all step down in size as you move towards the front of the antenna due to interaction with the 2m elements, so check carefully when assembling
- Two elements are within 1mm of the same length – compare side by side to be certain you are fitting the right ones!
- I had one mechanical problem with mine – one of the two U-shaped boom clamps was too wide to fit through the mounting plate. Solved with a squeeze in a big vice!
Looking at advice online it seems that it is best practice to use non-conductive masts with UHF beams, particularly short ones. Many thanks go to Greg, G4EBY, who kindly donated a spare fibreglass pole. Now camouflaged with non-conducting silver paint it is above the rotator in the photo below.
The antenna seem to work pretty well. The QTH is quite poor for VHF/UHF (a bungalow 35m ASL with no chimneys) and I was quite pleased to see that the ON4VHF beacon is audible virtually all of the time with PI7HVN usually audible too. GB3VHF is around five S points higher than with my previous vertical which theoretically had 4 dB less gain. Even allowing for the polarisation difference that is still a big improvement. I haven’t had much opportunity to try 70cm but I think I’m getting better results on 2m than 70cm. My feeder is a bit long though, which may be having an impact.
You may be able to see my TV aerial on the same pole, which proved to be a bit of a problem. Originally I had a 2″ pole but the rotator only takes 1 1/2″ so I had to buy a new pole. Consequently I’m now on my third TV aerial! The wind loading of my original tri-boom TV antenna was making the 1 1/2″ pole visibly flex even on a day that was simply breezy, so had to go. Next I bought a low-windload log-periodic aerial but this proved to be a) slightly too low in gain and b) prone to TVI when located so close to the TX antenna. The reflector on the back of the original TV antenna was clearly helping to shield the active element from RF. The final antenna came from Maplin and seems much better in all respects. I did still have a TVI problem with one TV when the beam was pointed East. That seemed to be due to the use of an unscreened splitter in the loft rather than pickup by the TV aerial, as other TVs were OK. A TVI filter cured the problem but a screened splitter awaits installation.
Thanks to a bit of experimentation with his VNA, Colin G8RLZ found my antenna provides a 1.4:1 SWR match at 6m, although goodness knows how. The gain appears to be very low but a) it is metal and b) it is permanently in the air. I have the impression it works like a dipole as there isn’t a clearly defined peak as I rotate it but there are some fairly deep nulls. It is difficult to identify a main lobe but a mild peak in gain appears at 70 degrees off axis. The Amersham 6m repeater is S9++ on it here in Slough, which I think is much better than I was getting with my homebrew Buddipole @ 5m AGL. I heard a number of far-flung stations during the 50MHz Trophy contest but didn’t manage to work any of them. Within a couple of days of use though I’d managed to work Slovenia and Italy using my favoured data mode, JT65. Not bad for a small 2m/70cm beam!
Update July 2017
I have been taking part in RSGB UKAC contests, in part to see how far I can work using SSB. None of the contests have coincided with noticeable lifts and I have regularly worked into Normandy (257 Km) on both 2m and 70cm. This is easier on 2m but I’m also running 50w on 2m compared to 10W on 70cm. My best DX to date on 2m is 274km, although I have heard the odd station from further afield.