domenica 1 aprile 2012

Coaxial stub half-wave end-fed antenna for 10m band

I'm a true fan of end-fed antennas, and I've built one for 10 meters band.
The antenna itself is 5 meters long, and matching is obtained using lambda/4 coaxial stub. The matching method is the same used in J-Pole antennas: a lambda/4 * VF (velocity factor) transmission line shorted at the end.

I've used RG58 cable for matching line and 1mm PVC-covered copper wire.
The sketch below shows the building detalis:

The left side of coax is shorted; the right side is connected (only central conductor) to half wave wire (braid is not connected). At feeding point I've used a BNC T adapter to connect all together.

I use the antenna mounted vertical on a fishing pole and attached directly on the rear connector of my FT-817 (no cpunterpoise, no choke, no balun, no antenna tuner on 10m). SWR is acceptable (1.5 - 1.8 between 28.400 and 28.600).

Today in the morning I've got some nice QSOs. The most remarkable is Japan (Yeah!!!!)JA1NVF with 5W SSB! Not bad anyway, eh?

This antenna, tuned with my Elecraft T-1, is useful also on 12 and 15m. Build one for your preferred band, is an "instant" antenna, very cheap and simple to build. Of course, if you've a few meters of twinlead for build matching line, the performance may be better (modify lenghts....).

07-08-2014 UPDATE: Using this antenna I've many QSO with DX locations (Brazil, Argentina, Japan), and I won the 2013 CVA DX Award, see here.

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