It was during the Xmas holidays in 2008 when ZLs were reporting good Es openings into VK and A35, that I decided to make a 6M antenna using bits from old lowband VHF TV aerials and a tribander stored in the basement.
I researched Google and came up with a few ideas and asked my mate Bill (W0WOI) who sent me a link to Pop Ljubisa’s YU7EF Antennas website. Pop has helped immensely with questions I’ve had and can re-calculate for different freqs and changes of aluminium size.
I wanted an aerial shorter than the Steppir so as not to incur the wrath of the neighbours so settled on a 5 element 4.5m boom model (EF0605A).
The aerial was built to Pop’s specifications and I’d recommend his designs to any keen constructors.
The 25mm boom was made out of 3 old lowband TV antennas which were joined with an internal sleeve and two rivets either side as well as top and bottom. I also filled all the old holes in the boom and the elements with silicon sealer to prevent moisture ingressing and whistling.
The element clamps were mid-boom mounting as was the insulated boom clamp for the driven element. All the bolts were smeared with grease to prevent rust and allow for eaiser assembly/disassembly.
A standard TV Vee block assembly off one of the TV antennas was used.
I didn’t have sufficient aluminium for one-piece construction of 3 of the elements so some tips were sleeve-joined with rivets
As per Pop’s separately e-mailed instructions, the design included a coax choke consisting on 10 turns of RG213 on a 100mm former and the coax was connected directly across the dipole. The design parameters where to provide a 50 Ohm impedance so no matching devices are required!
The driven element insulators were formed from two folded dipole insulators back-to-back. The rectangular gap between them was routed and filed out to suit the boom.
The coax choke is held onto the boom with cable ties which are in turn wrapped in insulation tape.
Lugs are crimped and soldered onto the coax and bolted onto the driven elements and all the hardware is coated in aluminium bonding paste, then wrapped in self amalgamating tape. The tails of the coax and similarly wrapped.
The finished article below the SteppIR antenna.
And how well does it work? SWR flat as a pancake and first log was A35RK 3116km within 30 minutes of going to air!
Copied below is Pop’s response to a question I has about feeding the antenna, and some photo examples.
“Since all my designs are with intrinsic 50 Ohm feed impedance and with almost none reactance, all antennas can be fed directly with coax cable and should work well without any additional adjustments However, in order to prevent CMC (common mode current) flow over coax shield resulting in RF being radiated by coax as well as noise being collected buy coax, it is definitely better to use either some good quality 1:1 current balun with ferrite or made from coax (see attached drawing) or an RFC made from feed line coax as you can see on attached pictures. This will isolate RF from your antenna and prevent the cable being part of the antenna. Since you are using RG213 it is a good way to use 80 – 100 mm PVC water pipe as a form and make coil consisting of some 10 close wound turns. No need to cut your cable or install connector unless you want it for some reason. From attached pictures you can see how this can be done in various ways and all of them work excellent. Using this as starting point you may come up with even some other solution – it is not that critical for antenna functionality”
NB: This antenna was replaced by another YU7EF design, 7-el 8m boo, operational since March 2014 and responsible for finally working W and XE!