Wimo HF mini dipole for 20m

During my autumn holidays, I didn’t have time to play with the IC-7000 but did some experimenting with my two portable dipoles that I once bought but never used. The first one I tested, was a Wimo HF mini dipole. A pair of 1/4 wave radiators cost about €50 up to €70 and the R1 straight dipole center puts you back another €15. I ordered the 20m versie and paid around €65 for a single band dipole. Not very expensive, especially when you look at Buddipole prcies, but also not a bargain. Here’s link to the “Wimo portable HF antennes”, search on this page for “HF mini dipoles”:
http://www.wimo.com/cgi-bin/verteiler.pl?url=portable-hf-antennas_e.html

 

The dipole elements are made of 12mm aluminium tubing, the normal type you buy at your local hardware store. At 1m, there’s a black nylon tube where the end rod (10mm aluminium tubing) is inserted and it’s length can be adjusted. The elements are “base loaded” meaning there’s a big coil (around 5 uH) near the feading point. The coil is wound on a carton (…) insulator with 3/8″ thread and the 12mm tubing. To be honest; it doesn’t look very professional, more like a good homebrew project.

One of the elements has a yellow marker, the (brief) manual explains this yellow marker needs to be screwed in the hot (+) end of the dipole insulator. While base loaded dipoles tend to have a low impedance, I reckon both coils are not the same, but e.g. on has 4 uH and one has 6 uH in order to find a higher impedance (closer to 50 Ohms).

Does it work? I can be short here: No, it doesn’t! Even though there is resonance and a slight dip in SWR, the impedance is way to low on my 5m portable aluminium pole. MMANA calculates almost 4 dB loss compared to a full dipole and about 12 Ohms impedance. With the knowledge that I have right now (I bought these some years ago), even if you’re limited in space, I would not consider buying this system. It might work better on a roof and it’s not a dummy on a stick but there’s just so many better alternatives probably for less many that I would not recommend this sytem.

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