|Subject:||Re: [TowerTalk] Vertcal Dipole|
|From:||Bill Tippett <email@example.com>|
|Date:||Sun, 17 Oct 2004 21:27:52 -0400|
> Par Electronics offers the following series of
> End-Fed 1/2 wave antennas which require NO radial
> and NO tuner. I've been using the EF-20/40 which
> works very well with direct feed from my QRP rig.
> With the EF-20/40 plus KD1JV's AT Sprint 2, I have a
> complete 20/40 station including transceiver, battery,
> earphones, paddle and antenna (no tuner needed) that
> weighs ~1 lb total.
>We shouldn't mistake that for a good system. The only reason you get away with it is you are running QRP, or have a lucky feedline length.
Only the dual band 20/40 which I have is rated at less (25 watts continuous). It is purely resistive at resonance measured with an MFJ-259B. I'm not sure what Dale W4OP is doing inside his matching network but whatever it is seems to work very well.
>It is impossible to end-feed a half wave antenna without having equal current entering the feed cable as common point as the current entering the antenna end. That's what makes these antennas unpredictable.
Perhaps there is some capacitive coupling to the coax shield, but it seems to work equally well with either short runs (a few feet) or longer runs (~30') in my experience.
Just 2 weeks ago I used the EF-20/40 while on a camping trip and it worked very well on both 20 and 40 in the Spartan Sprint (a QRP to QRP contest). I was also amazed to even work several EU stations running 2 Watts on the low end of 40, but that was surely due to their antenna rather than mine! If anyone is looking for a very simple yet effective portable antenna, I highly recommend the Par End Fedz. FWIW they also have some very nice recommendations on eHam:
http://www.eham.net/reviews/detail/3632 (100W mono banders) http://www.eham.net/reviews/detail/3717 (25W dual bander)
I never heard of this company until I got involved with QRP, but the End Fedz monobanders would certainly make a nice system for anyone operating portable with 100 Watts. Of course you could do the same with an LC network but would need a 1/4 wavelength counterpoise.
73, Bill W4ZV
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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