The Homebase10 is a simple to make wire halo antenna for 10m (28MHz) built using parts available from the local DIY store.The resulting antenna is very effective on 10m despite its small size and light weight. Also shown is a dual-band version for 10m and 6m.
A copy of the original Practical Wireless (PW) article is attached (see bottom of the page).
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What follows is an antenna option combining a very small footprint, near omni-directionality, low cost, easy sourcing of parts, easy assembly and easy adjustment. If mounted in the clear, it is capable of very useful performance just a few dBs down in gain when compared with a large HF beam. Full details appeared in September 2008 Practical Wireless, so this is just an overview.
T The remainder of each dipole leg is 105cms long added to the ends of the folded dipole section. The folded dipole is made by paralleling up two pieces of the PVC cover multi-strand wire and holding these close together with cable ties. A choke consisting of 6 turns of the coax cable about 5cms diameter close to the feed point helps to keep RF from the outer of the coax. Firstly, assemble the support strut woodwork by taking four pieces of 21 x 12 mm wood 1m long (with the 21mm side vertical) and drill two holes close to one end to line up with metal corner brace holes. The four 50mm corner braces and the drilled aluminium plate are screwed together and to the wooden struts. When screwed together, the four wooden pieces form a cross with the aluminium plate trapped between two of the corner braces and the wooden struts. Coat the wood, the assembled brackets and the nuts & bolts with three layers of outdoor yacht varnish to protect them from the elements. A better alternative may have been to use nylon rods but the rectangular wooden struts allowed a simpler mechanical arrangement.Next assemble the wire dipole. Note how the feedpoint attaches to the centre of the folded dipole section. Initially “tack” the wire onto the corners of the cross. The feed point is attached at one end of one of the cross members. This helps to provide support as this is the heaviest part because of the added weight of the coiled coaxial choke. Bring the coaxial feeder away from the feedpoint back towards the middle of the antenna along the wooden support strut. The free ends of the wires are pulled together via a thin piece of insulating nylon or polypropylene cord. Make small loops in the end of each wire to attach the cord. The losses of the material used to connect the wire ends together may be checked by putting a length of it in a powered microwave oven for 60 seconds to see how hot it gets: if it remains cool, the chosen material should be OK.
Connect the 28MHz rig via an SWR bridge to the antenna. Position the antenna in the air clear of other wires and metalwork. This is best done in the garden as some adjustment of the wire length may be needed. Check the SWR at the bottom, middle and top of the 28MHz band. If all is well, the match should be <1.5:1 over about 600kHz of the band. If adjustment is needed, lengthen or shorten the free ends of the wire until the lowest SWR is centred where you want to operate within the band. My version was adjusted to give a low SWR between 28-28.6MHz where most of the SSB, CW and data DX activity is found. Try to position the antenna in the clear when checking resonance each time. Adjustment should not be too critical.
Once adjustments have been completed attach the
antenna wire to the corners of the cross in a more permanent fashion ensuring
the soldered connections joining the folded dipole section to the end wires and
the feed point junction to the coax are suitably waterproofed. Joints should be
covered in heat-shrink sleeving or waterproof tape. Use nylon cable ties to
secure the folded dipole wires to each other, the coax choke and the coax
feeder. In my version I added a small extra piece of wood joining the tops of
the wooden strut supporting the feed coax and its opposite part to give this
Contacts so far suggest the antenna is working as planned with a near omni-directional radiation pattern. Despite running only 5 or 10W on SSB and CW, reports have been excellent. I've even had 4 QSOs with 599 reports into Europe when running just 50mW. Best DX has included VK, PY, LU, D4 and W. The antenna does not need any matching when used over its intended part of the band, but an auto-ATU such as that in the IC703 helps to optimise the match in other parts of the band.
Unexpectedly, the antenna performs pretty well on other higher HF bands too. Indeed I had contacts on 12m and 20m, matching the antenna successfully with the IC703 auto-ATU, before the 10m band opened up to allow any QSOs on 10m. Of course, if you strap the coax cable inner and outer together at the base of the feed then the coax feed works as a vertical with the halo being a top capacity hat. This way, bands from 500kHz upwards can be used using an ATU.
Although only tested at 5-10W - the most I can run, HI - this antenna should work with full legal power as long as the losses in the support cord joining the free antenna ends are low.
Wire (PVC insulated multi-strand) 10m total approx (including some for prototyping)
All parts except the coaxial cable may be obtained from DIY stores. Coax is available from many sources including Maplin.
An improved version of the design would replace the wooden struts with PVC or nylon rods for reduced weight and increased durability.
The photo shows the arrangement used. Some small adjustment of the 6m lengths may be needed but mine was almost spot on first time.Being able to cover the SSB/CW/DATA parts of 6m and 10m on a simple but effective antenna is extremely useful.