# Question about a dual end fed antenna - possible?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W4LLZ, Aug 5, 2020.

1. ### W4LLZHam MemberQRZ Page

I have currently an EndFed wire antenna that has a 9:1 UNUN for HF running north to south. Is it possible, reasonable, practical, to connect another wire of same length to the same 9:1 UNUN and have it radiate East and West as well as North and South to get signals in all 4 directions.
Thanks

2. ### AB6RFHam MemberQRZ Page

Nope, unfortunately that would not work.

When more than one antennas are connected in parallel, the antenna radiation patterns don't simply get superimposed on top of each other.
The combined radiation pattern will depend on the phasing of the radiated signals, and if done randomly would most likely create an ugly pattern with peaks and nulls at all kinds of random directions.

A much better approach would be to put an antenna relay up to the point where the two antennas come together, and feed only one antenna at a time depending on which one gives you the better signal to a given particular direction.
Each antenna would probably need its own unun, otherwise the relay would need to handle all kinds of high voltages and/or high currents.
(if the relay is between the unun and the two antennas)

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3. ### AK5BHam MemberQRZ Page

Take your two antenna halves, connect them to a center insulator, attach a feedline, and voila! You have just constructed a Hertz (dipole) antenna.

Use the formula 468 dived by the frequency in MHz to get into the ballpark for length depending on the band of choice (or use OWL and a transmatch for operation on more than one band otherwise.

73,

Jeff

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4. ### WA7ARKHam MemberQRZ Page

How high is it?
How long is it?
What are you doing for a ground-plane/counterpoise?
How long is the coax?

5. ### AI3VHam MemberQRZ Page

What makes you think your half antenna (the other half being every wire in your house) is directional ?

These kluge attempts at antennas are always a completly random crapshoot.

Rege

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6. ### AI3VHam MemberQRZ Page

Oh yeah, he's got a counterpoise alright.

Rege

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7. ### KB7WGHam MemberQRZ Page

A vertical will give you compass coverage.

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8. ### W4LLZHam MemberQRZ Page

Ground Plane: Its an End Fed, the braid in the Coax is the counterpoise; however i have 2 60 wires connected to the UNUN as well as a counterpoise as well to dissipate the reflective power.
Coax is 100'.
Wire is 145'.

All good - apparently its a "kluge" idea.

The radiation pattern of a 1wl center fed dipole is narrower than a 1/2wl center fed wire. The impedance will be 10,000 Ohms --- calculated using the proportional physical effects of a center fed 1/2wl wires. It can be driven with a link coupled anti resonant tank using a capacitor and inductor with 5000 Ohms reactance; these are a pair of end fed 1/2wl wires which are mutual counterpoises. This makes a formidable antenna needing no other help.

Regards Jim K9AXN

10. ### W9XMTHam MemberQRZ Page

Below is a NEC4.2 calculation for a typical installation of a 1WL, center-fed, h-pol dipole at 1/2WL AGL.

The feedpoint impedance for these conditions is outlined there with a red rectangle.