End Fed 1/2 wave antenna

[kt4ye]

End Fed Resource

This month's issue of antenneX, the on-line antenna magazine, has an interesting article on end-feeding 1/2 wave antennas.

The author developed a technique for feeding the 1/2 wave antenna using a tuned transformer. One side of the secondary is the 1/2 wave "monopole." the other side goes to a VERY short "counterpoise." He claims that this configuration is stable and provides a good match with good common mode rejection.

He's a hands-on kind of guy, so all the info is from measurements, not NEC models.

No info on bandwidth nor takeoff angle.

The site is antennex.com. It is a subscription site, but many of the site's features are free. Don't know if this article is a freebie or not.

All the best,

Bill

 

[HomerBB]

Thanks, Bill.
I have the free sub, so I'll take a look.

 

[Marconi]

Hey Bill, is the article you note by Steve Yates, AA5TB?

If so, here is a link that is free for sure: AA5TB - The End Fed Half Wave Antenna

 

[The DB]

Interesting article. Good information there.

I also like how he puts the term "counterpoise" in quotes every time it's used...


The DB

 

[W5LZ]

!!
I noticed that. And I think it's a good idea. It's quite common to use the wrong name for a particular object and those quotation marks 'point' to that fact. I think a better generic 'name' would be the "TOH", 'The Other Half' of an antenna. It would describe what's being discussed adequately without being too specific.

- 'Doc

 

[HomerBB]

I tend to agree with you, Doc. The confusion around and mis-application of the term "counterpoise" is rampant. There would be some benefit to accuracy if another term came into common use.

 

[HomerBB]

I am wanting to hear from some of you regarding a phenomenon I have experienced recently, and was posted about within the thread A vertical is best for working DX?.

I put this antenna, an EFHW together taking great pains to make sure the length was resonant at my chosen frequency - 27.405. I then tuned it to a very good SWR. I mounted it where my vertical dipole was, but the EFHW was higher due to it being end fed and the dipole being center fed. The EFHW was noisy, an occurrence not experienced with the antenna in this thread. The dipole by comparison was very quiet in spite of being vertical. I replaced the EFHW with the dipole, and once again it is quiet with better receive.

Thoughts?

I do make note of the fact that the EFHW in discusion in this thread had a set of radials - TOH (Doc), and this latest one does not. The EFHW is made from parts laying around the garage/shack.

 

[Marconi]

Homer, you might try and lower the EFHW about 8-9 feet and see if the noise changes. I have felt the noise on my verticals sometimes was notable in different layers above ground while testing at different heights. I was probably checking for changes in match and noticed same while making my SWR bandwidth scans.

The difference you note is about a 1/4 wave and that may have been in the range of change I was seeing.

Some antenna guru's note that noise is associated with excessive common mode currents. Do you note any TVI with this EFHW compared to the dipole?

 

[2RT307]

My EFHW is very quiet, Homer. Mounted horizontally though... I may try it vertically very soon. Weather is nice this weekend. Here's a vid showing off the shack, and you can listen to the dx and noise level. NR was set to "2" in the menu, so it's on a very low setting. Sorry for all the moving around, I was trying to get the sun off the 718's display so you could see the meter.

End fed half wave reception - YouTube



73,
RT307

 

[HomerBB]

Marconi, although the photo shows the dipole up at 36 feet to center, they are both, in fact, being compared at four feet above the roof ridge, which is 22' from the ground. This EFHW was showing the same symptoms at 10' above the ground.

I wish less to clean up the receive of this antenna than I would like to discover what properties of the antennas make one noisier than the other.

Brett, to your point I have not had such noise in an end fed as I do in this one since I quit using an A99.

It could be CMC. I did not have a choke on the EFHW at 10', but I did at 22'. No change. I did not have a choke on the dipole at 36', but I do at 22'. No change. I have also used the dipole at 22' with no choke, and it was the same - quieter than the EFHW.

 

[HomerBB]

My EFHW is very quiet, Homer. Mounted horizontally though... I may try it vertically very soon. Weather is nice this weekend. Here's a vid showing off the shack, and you can listen to the dx and noise level. NR was set to "2" in the menu, so it's on a very low setting. Sorry for all the moving around, I was trying to get the sun off the 718's display so you could see the meter.

End fed half wave reception - YouTube



73,
RT307

That wire is certainly quieter than the one I am showing to be so noisy, and apparently doing a good job for you.
Is it still 10' off the ground? Is it the only antenna you are running now?

 

[kt4ye]

Hey Bill, is the article you note by Steve Yates, AA5TB?

If so, here is a link that is free for sure: AA5TB - The End Fed Half Wave Antenna

Yes... It sure looks the same.

And yes, there is good info there.

Bill

 

[2RT307]

That wire is certainly quieter than the one I am showing to be so noisy, and apparently doing a good job for you.
Is it still 10' off the ground? Is it the only antenna you are running now?

Homer, yes it's the only antenna I am running. I do have a double extended zepp that I am planning on hooking up horizontally once I try the end fed half wave vertically. Will let you know how it receives once I do, but lots of honey do's around here this weekend!

73,
Brett

 

[Marconi]

Marconi, although the photo shows the dipole up at 36 feet to center, they are both, in fact, being compared at four feet above the roof ridge, which is 22' from the ground. This EFHW was showing the same symptoms at 10' above the ground.

I wish less to clean up the receive of this antenna than I would like to discover what properties of the antennas make one noisier than the other.

Brett, to your point I have not had such noise in an end fed as I do in this one since I quit using an A99.

It could be CMC. I did not have a choke on the EFHW at 10', but I did at 22'. No change. I did not have a choke on the dipole at 36', but I do at 22'. No change. I have also used the dipole at 22' with no choke, and it was the same - quieter than the EFHW.

Homer, I wasn't looking at pictures, I was referring to your post where you claimed your diople was mounted lower than your new EFHW. Are you now claiming these two were mounted at the same height?

I also asked if you saw any symptoms of TVI with the EFHW.

 

[HomerBB]

Homer, I wasn't looking at pictures, I was referring to your post where you claimed your diople was mounted lower than your new EFHW. Are you now claiming these two were mounted at the same height?

I also asked if you saw any symptoms of TVI with the EFHW.

The dipole feed point is at the center of the dipole which is mounted vertically. The end fed halfwave is fed on the end and is also mounted vertically. The result is that the bottom of the EFHW is 9' higher than the bottom of the dipole although they are both about the same length and have their feed points at the same elevation.

No, I saw no evidence of CMC nor TVI, but the only thing in the house that shows that symptom is an old cathode ray tube in the bedroom. It is too far from me to either hear or see and the wife wasn't home watching it when I keyed up and modulated the radio. The computer speakers I have near the radio have not shown any feed back, TVI nor evidence of CMC in a long time regardless of whether I have a choke in line or not.

My wife complained about TVI on that old TV with the non-choked dipole before, but she hasn't been using it since I put this one up there last evening. The mount they are on is directly above the master bedroom. Out on the mast in the yard she never complains of TVI.