The double extended (two 5/8 wave elements) zepp is one of my all time favorite
wire multi band antennas. I just picked up two of this exact antenna from open
wire guru, W7FG, earlier this week This antenna has gain over a standard 1/2
wave dipole (almost 1.8 dB on 80 and more on the higher bands). It should be
fed with open wire the whole way (no coax, no baluns, no magic boxes) to a high
performance antenna tuner that is balanced line capable. In my
opinion the best tuner for this application is the Johnson Matchbox. I have
also had good success with the Heath 2060 and 2060A. Sure you have to adjust
the tuner when you QSY, but the performance of the antenna is super! There is
no free lunch!
Thomas Rieff wrote:
> I recently built a 80 double extended zepp using the HamCalc configuration.I
> cut the lengths for 3.555 MHz. Hoping for a broader multiband performance
> with a tuner. The lengths are as follows...168.4 ft for each top leg and 38
> ft of 450 ohm ladder line for the matching section and then into a 1:1
> current balun.
> My question is should the swr be 1:1 for the design frequency, is it
> attainable, or are double extended zepps inherently a high swr antenna. It
> currently runs about 5:1 without the tuner and goes higher on the other
> bands.I have not done any trimming or adding to the antenna lenghs. The
> information says to trim the ladder line matching section for lowering the
> swr. Another source I found said that the ladder line matching section should
> be cut at 30 ft.
> I see a couple of options; scrap the balun and coax and run ladder line
> directly to the tuner, start trimming the ladder line (what is a reasonable
> amount per test?), scrap the antenna entirely and put up something else. I
> recently built a 40 meter loop with 72 ohm matching section and it worked
> perfectly 1:1, at its design frequency. I have a fair amount of room to put
> up wire.
> Your thoughts are appreciated.
> Tom KC0PYK
> Thomas Rieff
> 2059 Sundance Lane
> North Mankato, MN 56003
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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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