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REVIEW DECEMBER 2011 ♦ RADCOMSTEVE NICHOLS, G0KYA ♦ E-MAIL: INFOTECHCOMMS@GOOGLEMAIL.COM

NEW COMPANY. Vortex is a new UK antennacompany that produces a range of Yagi, DeltaLoop and Moxon beams for HF and 6m, bothin monoband and multiband variants. It alsooffers a range of dipoles, vertical J-poles andantenna accessories.

The company, launched in December 2010and based in Peterborough, is run by SteveLawman, G0UIH/VK2IAY/3D2FI and Stevesays that the company prides itself in onlyusing premium quality hardware andcomponents. Steve is a seasoned DXpeditionerwith a passion for IOTA and island chasing,having activated many Pacific island groupsas a solo operator. He has also built many ofhis own antenna systems and has enjoyedexperimenting and building systems since 1979.He is supported in the business by wife Gail.

When Steve offered a Whirlwind four-elementDelta Loop for 50MHz (6m) for review wejumped at the chance. It was soon on its way to G0DWV's antenna farm in Norfolk for appraisal.

MANUFACTURE. The beam reviewed wasthe company's heavy duty model. The rangehas specifically been built with strength inmind, which is reflected in both the gauge of aluminium used and the quality of theassociated brackets.

Vortex uses 6086-T6 industrial structuralgrade aluminium alloy (310mpa), which isconsiderately stronger than general purpose6060-T6 or 6063-T6 variants. This has beenspecially manufactured for Vortex in the UKand is available in six diameters ranging from

38.1mm down to 12mm – all of which telescopeneatly into its counterpart. They also stock a 6082-T6 variant from UK manufacturerAalco. This alloy is even stronger at 340mpaand Vortex supply this at no extra cost whenin stock. The boom was made from squaresection tubing, which looked both sturdy and long-lasting.

The black polyamide antenna clamps are by Stauff, manufactured to DIN3015 inGermany and designed primarily for the oiland gas industries apparently. They offersuperior ultraviolet resistance and in theheavy-duty range are backed by M10stainless steel hardware.

The overall impression is one of sturdinessand quality – you are unlikely to get hardwarefailures. The build is reminiscent of aircraft-quality engineering.

The four-element beam uses aluminiumtubing to form the ‘V’ and then a hefty lengthof 4mm Flexweave cable connects the two endsto complete the delta loop. The elements aremade from 16mm tubes that 12mm tubeslide in to for adjustment purposes. All theelements are insulated from the boom – ashort Flexweave wire tie is used at the bottomof the V to connect the two elements.

The driven element uses a gamma match,created by a shorted aluminium tube that fits into another piece of tubing with a PTFEinsert as a capacitor dielectric. This is simpleand robust. Vortex supplies a section of mil-specglue-lined heatshrink that then seals the gammamatch from the external elements.

ADJUSTMENT. Vortex supplies the initialvalues for the length of the shorting bar, but you may have to adjust yours to get thelowest SWR. This is in fact what we found,but it only took a few minutes adjustment to get a 1:1 SWR at about 50.200MHz.

Any adjustments must be made with theantenna away from any metallic objects toavoid interactions.

We built the antenna without any hitches.The only suggestion I would make to Vortexwould be to consider spacing the SO239 feed point socket a little further away from the boom to make it easier to wrap it with self-amalgamating tape. It is perfectlypossible to wrap the tape around the plug, but you end up cutting off strips as there isn't enough room to pass the whole reelthrough the gap.

UNDER TEST. Chris, G0DWV and I mountedthe antenna above his five-element 6m Yagifor comparison purposes. The whole lot wasthen cranked up to about 40ft on a Versatowerand fed with about 60ft of RG213 coax.

Steve had told us that the antenna gainwould be just over 11.00dBi (8.87dBd),which has been optimised using EZNEC+.The gain of the five element Yagi would be less, at around 10.35dBi. The boomlength of each antenna is the same, ataround 5m, so this makes for a goodcomparison – especially when the loop has one element less. We actually found the loop to be slightly better than Chris' Yagi.

We also noticed though that noise levelswere about 1 S-point worse on the Vortex.This had us scratching our heads a little, but we decided that this could be due to thefact that the Vortex elements are insulatedfrom the boom, whereas Chris' Yagi hasgrounded elements.

In practice this made little overall differenceto the performance, but is something thatVortex might look at.

Conditions on 6m were poor at the time of the test. We heard the GB3BUX (Buxton),GB3BAA (Tring) and ON0SIX (Belgium) 6m

The Vortex Whirlwind 6M4Longboom four-element delta loop for 6m

The Vortex beam mounted above the test Yagi.

Chris, G0DWV tightens up the fittings. The substantial Stauff element clamps.

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beacons in Norfolk with no difference in signalstrength between the two antennas.Other signals were thin on the ground

– there were slight snatches of some beaconsfrom around Europe, but little Es propagationto speak off (in late August).We did work IZ5ILX in Italy who said that the

Vortex was 4 S-points stronger than Chris' five-element Yagi. F5MAG in France said that theDelta Loop was 1 S-point stronger. On groundwave, G3MWV in Cromer (about 18 miles)saw a slight difference in favour of the Vortexand G4DCJ (about 40 miles away) said wewere 2 S-points stronger on the delta.Chris, G0DWV says his Yagi is a 0.2 spaced

NBS design from an ARRL handbook – notthe most up to date design, but it works OK.One surprising observation (found by

accident): the Vortex is actually a pretty goodreceive antenna for 20m as well!The technical data provided by Steve from

EZNEC+ seems to suggest the loop has a lowerangle of radiation compared with the Yagi. Ata height of 15m the main angle of radiation of the loop was only 5°. The Yagi would bearound 7°, so the Delta would make a goodlong haul DX antenna.

CONCLUSION. Overall, the Vortex is a verywell-made antenna and looks like it would easily

outlast its buyer! The quality of construction isfirst class, as is the performance (the antennasare extensively modelled in EZNEC+ v5.0 tooptimise their designs). If you are looking for a sturdy beam with good performancecharacteristics they are well worth a look.Vortex also offers the home constructor a

comprehensive array of bespoke 6082-T6

tubing and antenna parts for their ownprojects and designs.The 6M4 costs £359.99 — £393.99,

depending on whether you want a boom tomast mounting plate. Our thanks go to Vortexfor supplying the review antenna. Vortex canbe found at www.vortexantennas.co.uk or call 07943 871 893.

REVIEWRADCOM ♦ DECEMBER 2011

EZNEC+ plots for the antenna.

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