End Fed antenna question

[W5BRM]

Hi. Been thinking a lot lately about trying an end fed antenna. Something like the EARCHI end fed with the 9:1 balun. I understand the basic theory behind how the antenna works.

Question I have is about the coax. Most of the material I have read on the net about this type of antenna says the coax is used as the counterpoise but none discuss the coax length. If using coax in this manner, does the coax need to be a tuned length or will any length work?

I am thinking that if a wire counterpoise is used, then coax length shouldnt matter but if no other counterpoise is used, then it seems that the coax length should be a tuned length. Am I wrong in thinking this? I know a tuner is required to use this antenna. If the counterpoise isnt tuned, will it take a sturdier tuner to be able to tune the antenna?

Question 2. If a wire counterpoise is used instead of using the coax, does it need to be elevated or just toss it on the ground?

My plans are to get 100ft of coax and the MFJ949 tuner. I plan on buying the coax with pl259s already attached. will this length be too long and create too much of an imbalance for the 949 to tune it? I'm also going to try to build the 9:1 balun using the plans on the EARCHI website PDF

[PA5COR]

http://www.earchi.org/92011endfedfiles/Endfed6_40.pdf this one I suppose?
As the PDF describes the length of the wire should be 24 to 60 feet, the PDF also states the coax ( used as counterpoise) should be 16 feet minimum.

I rather not use the coax as counterpoise, for obvious reasons getting RF in the shack and on the equipment that can get some weird results.
On the 1:9 torroid is a ground connection, use an wire or several if you can and just put them on the ground minimum length the same as the coax should be long, or longer.
Then use another torroid or several clamp on ferrites directly on the coax after the torroid so that the coax really now is RF free.
It also prevents the coax from picking up RF noise on the outer shield and feed it into the receiver.

Additionally also use a few ferrite clamps near the transceiver on the coax.
This setup with 1:9 balun works, but the efficiency on some bands/frequencies might suffer, don't put too much power in the torroid and check if the SWR changes or the torroid gets warm.
If you run 100 watts into it, an efficiency of 10% means 10 watt on the wire, just 10dB down, still enabling you to make fine contacts though.
Some bands/frequencies you will have good efficiency others less, depending on your length of wire used and grounding system.
Using the T 130-2 torroid and 3 x 9 windings the XL would be 357 Ohm at 7.1 MHz, 710 Ohm at 14.1 MHz and 1461 Ohm at 29 MHz.
Personally I think it is a bit low, an end fed antenna fed at an voltage point will have 2500 - 3000 Ohms.
That is the reason you need to pick the length of the wire carefully, making sure you won't hit the voltage point on any of the bands you want to use.
Personally I use the FT 240-43, larger torroid and then make a 5 band end fed half wave antenna with a few coils in it, but that is a different antenna set up.


My Inverted L is fed at the base with an legal limit autotuner coax with ferrite running to my transceiver and even there ferrite on the coax.
Used from 160 - 10 meters.

[W5BRM]

OK thanks. Yes thats the one EARCHI I am thinking about. The thing about RF getting back into the shack by the coax as counterpoise was running around in the back of my mind as well. I wasn't sure if that would have been an issue as the coax i plan on using will be 100ft.

As to using the wires on the ground, if I use 100ft coax, the wires should be 100ft+? I was thinking maybe 33ft as I don't plan on going below 40m.

Also, what type of ferrite should I use? i know they should be clamps but what mix do I use? Never have used ferrites before on coax.

thanks

[NQ6U]

A type 43 mix works well at HF.

[PA5COR]

Use one long radial or use more shorter ones.
Several of 33 feet spread out will work just as fine as 100 feet coax, and not give the coax the RF on it, if you use the ferrite on the coax.( mix type 43)
So on the ground connection of the 1:9 come the radials, then directly after the plug on the coax on the 1:9 come the ferrites forcing the RF to the radials and keep the coax free of RF.

To understand how this antenna works:
http://www.w8ji.com/long_wire_antenna.htm

The ground system with radials is specially important where your wire is about 1/4 wave long and fed in current.
Where the antenna is fed as 1/2 wave the ground is much less important, and fed in voltage.
Since you will use an length that will not be resonant it is the best as I wrote before, use several ( shorter) and longer ground radial wires and decouple the coax with clamp on ferites or use a torroid to wind the coax several times through.

An air coil won't have the full range of frequencies you want to use the antenna for to decouple the coax effectively, most air wound coax coils are nice for one or mostly 2 bands close to eachother but not more.
I even used discarded ferrite bars from old AM radio's and wound the coac around these ( RG 58) that will be quite effective as well.
For thicker coax just tape 3 or 4 old AM ferrite bars together to get a larger diameter to wind the thicker coax around.

Just for laughs, a more effective antenna needing a bit more work:
http://pa3hho.nl/wp/?page_id=471

[W5BRM]

OK got it. So other then mine wont be a true vertical, the radials and radiating element operates like a vertical antenna? 1 radiator and several radials. simple enough. I just may make it into a vertical as I THINK I have room under my tree. My rope system is about 35ft to the bottom of the branch it's strung over. Sounds easy enough to install and take down when I head off to work then. Thanks guys

[K7SGJ]

OK got it. So other then mine wont be a true vertical, the radials and radiating element operates like a vertical antenna? 1 radiator and several radials. simple enough. I just may make it into a vertical as I THINK I have room under my tree. My rope system is about 35ft to the bottom of the branch it's strung over. Sounds easy enough to install and take down when I head off to work then. Thanks guys

The branch or the antenna?

[W5BRM]

The end of the rope and tie off are a few inches below the branch. The branch is at about 35 ft. The rope goes over the branch. In installing my dipole antennas, I just pulled the rope over the branch to pull the dipole up. I know I should use a pulley system of some other support mechanism but I don't have a ladder high enough to go up and install a permanent pulley and the branch is too thin to support anyone who would be crazy enough to climb out where the rope is anyway...

[PA5COR]

Vertical will give good DX low angle radiation.
For more "local" qso's you might opt for a nvis low hanging dipole with tuner.

[W5BRM]

Side question: Is a 40m inverted V fed with coax easily used on 30-10m with a tuner? I could put up a 40 inv V but the ends would be a bit low to the ground. Cant put up a horizontal dipole as I only have my 1 tree I can use.