Building end-fed antennas

[ka3jjz]

Viking1 wrote on 6/13:
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Speaking of antennas, if anyone is interested I build end fed antennas that can be used for SWL and transmitting on HF (80-6m) up to 150W (with a tuner) They're sealed from the elements, tough as nails, multi-band, and contain the correct hand wound transformer to match the longwire to the 50ohm impedance of the radio. The units I build also can be RF grounded off of the transformer as well making it a quieter RX antenna (and more efficient when transmitting)
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Moved to the receive antennas forum from the LW thread - please don't hijack threads. Amateur antennas also have their own forum

Thanks for your future compliance...Mike

 

[prcguy]

Here is a link to an easy to build end fed antenna: http://www.earchi.org/92011endfedfiles/Endfed6_40.pdf This will work fine for a SW receive antenna as described in the article and I for that purpose I would use a longer wire like 50 to 100ft.

For transmitting its best to use a half wavelength of wire and if you use 66ft for a half wave on 40m it works fine on harmonically related bands like 20 and 10m. I use a similar antenna (PAR EF10/20/40 with 66' of wire) with an Elecraft KX3 QRP rig and am amazed at the contacts it can make.

Since an end fed half wave is around a couple of thousand ohms and this balun transformer is a 9:1 it matches 50ohms to about 450ohms which is not quite enough but with a tuner it works fine. I would not try to use it on 80 through 6m with a random wire of 22 to 30' as the article says because the antenna will not be very efficient on any band with that method, use a half wave or multiples of a half wave.

There will be some RF on the feedline and adding a common mode choke at the feedpoint will help isolate the antenna from the feedline better than just the 9:1 balun alone.
prcguy



prcguy