End Fed 1/2 wave antenna

[HomerBB]

Well that certainly makes more sense, Marconi.
It's just that part in front of it that threw me off.

"At my age, I probably don't have long, and then you'll all be happy, that I'm no longer looking over your shoulder."
It just goes to show how a person can mean a certain thing, but another can take it completely wrong . . .
I guess I'm just feeling my own mortality more than I used to.

I put some GP on the 1/2 wave and just put it in the air. They are 12 of them 36" long. I don't know whether I'll be able to tell any difference or not. Getting dark and can't play until maybe tomorrow.

 

[Marconi]

Well that certainly makes more sense, Marconi.
It's just that part in front of it that threw me off.

"At my age, I probably don't have long, and then you'll all be happy, that I'm no longer looking over your shoulder."
It just goes to show how a person can mean a certain thing, but another can take it completely wrong . . .
I guess I'm just feeling my own mortality more than I used to.

I put some GP on the 1/2 wave and just put it in the air. They are 12 of them 36" long. I don't know whether I'll be able to tell any difference or not. Getting dark and can't play until maybe tomorrow.

Homer, I may not have the specs exactly right with the models, but they are based on the same models I posted a while back, as an idea for your EFHW with and without radials. I called that project "Homer's 1/2 wave Ideas."

Here I include the top model with 4 x 99.6" radials on a 48' foot non-isolated mast.

The next is the same without radials and is not (ISO) isolated.

Next is this model that is ISO 1' foot at the antenna, with 12 x 36" radials.

Next is an overlay for all three of these models for comparison.

I also recapped these results at the bottom of my notebook, to try and make it easier to compare the data.

I see very little difference in gain, but the angle for the model with no radials shows maximum gain 1* degree lower at 7" degs that the other two models. So based on this, I predict you might not see much difference in you real world comparisons.

However, regarding the match, I do see some difference using 12 radials, and that might show up on your analyzer report. That might mean my prediction for radials making little to no difference might be off when using a better ground plane than the 4 near resonant radials I modeled earlier.

So Homer, if Bob and Nav's spiderplane design was able to improve the ground plane affect, for their EFHW over the models I made, then maybe I was wrong.

But, I propose to hold off with any judgment on this new information for me, until we see your reports.

View attachment Homer's EF .50 wave ideas.pdf

View attachment Recap of Homer's stuff..pdf

 

[joanne koffton]

iv been reading this thread with interest and i can definitely say that after i made a 4 turn 4" coil out of my coax, it stopped all my interference that i was getting.

lots of love.
jo.

 

[Marconi]

iv been reading this thread with interest and i can definitely say that after i made a 4 turn 4" coil out of my coax, it stopped all my interference that i was getting.

lots of love.
jo.

Jo, for my part of this discussion, the subject is more than just about TVI, but I think common mode currents (CMC) do tend to create a situation where they can cause electronic interference.

I also think that antennas that are installed relatively low can also create TVI with direct RF from the antenna, and a choke won't likely fix that. If the problem is CMC, the a suitable choke should mitigate such currents.

This is the distinction I was trying to make with Bob and his friend, but I didn't get to first base I'm afraid.

Thanks for checking in, and I welcome you to the forum.

 

[joanne koffton]

like i said... the cmc has all stopped after the coil was introduced

that my findings anyway.

jo

 

[Marconi]

like i said... the cmc has all stopped after the coil was introduced

that my findings anyway.

jo

I think I understood your remarks, but sorry I didn't make myself clear.

 

[HomerBB]

Interesting results.
I am at 36', and that may have differences.
With the weather like it is, and a commitment to my wife to help her with some school work (she's a non-traditional student in college), Iam afraid I'l have to wait a day or two before I can get back to the antenna.

I will be remeasuring the radials on and off aspects of the antenna with the MFJ-259b so as to have data more current than before. I have redone the matching system slightly, and the very wet weather lately may impact results with differences in the soil conditions here.

Removing the radials and putting them on is a matter of minutes.

 

[HomerBB]

Another photo:

 

[HomerBB]

While down on the ground the EFHW went through a couple of modifications.

1. It grew a set of 3' x 12 GP radials.

2. It was also outfitted with a slightly smaller matching network.

The Following is a photo of the matching network currently employed, and a series of analyzer readings with the MFJ-259b on the current antenna with radials at 37' (measured today) from the earth. It is isolated from the mast, and utilizes a coax choke at the feedpoint.

 

[Needle Bender]

OK, but how well does it perform compared to the 5/8 at that height?

 

[HomerBB]

We'll see, NB.
Right now conditions are pretty good, so DX is really unreliable as a measurement. I am tearing it up on AM and sideband, but that isn't the way to really judge this thing . . . . It is when and if I can catch some more local and distant local traffic that I'll be able to tell more.
It has shown some promise. One of the problems I've had with my 5/8 antennas locally is that they seem to disfavor local contacts out to 20 -30 miles or so.

 

[Needle Bender]

We'll see, NB.
Right now conditions are pretty good, so DX is really unreliable as a measurement. I am tearing it up on AM and sideband, but that isn't the way to really judge this thing . . . . It is when and if I can catch some more local and distant local traffic that I'll be able to tell more.
It has shown some promise. One of the problems I've had with my 5/8 antennas locally is that they seem to disfavor local contacts out to 20 -30 miles or so.

So are you finding that there's a ring of null area out about 20-30 miles when using a 5/8 which you tend not to have from using other designs?

 

[HomerBB]

So it seems. There are two or three local stations from 15 to 20 miles or so that are like digging out from the dirt on a 5/8 antenna. I have to listen for them to get on the air to make a comparison. Encouragingly, today Rhett_RT307 was out locally in a rental car and I had a great copy from him on the 1/2 wave antenna. There seemed to be better response from it to the area he was in than I tylocally get from my GP mounted 5/8 wave. Again, further observations of contacts wili tell more.

 

[Marconi]

While down on the ground the EFHW went through a couple of modifications.

1. It grew a set of 3' x 12 GP radials.

2. It was also outfitted with a slightly smaller matching network.

The Following is a photo of the matching network currently employed, and a series of analyzer readings with the MFJ-259b on the current antenna with radials at 37' (measured today) from the earth. It is isolated from the mast, and utilizes a coax choke at the feedpoint.

Homer, the 1/2 wave still looks to show little difference in the match with/without radials. Maybe this matcher shows a little less band width, and the range of frequencies seems to have tended down a bit, but the numbers are still in about the same range with little differences vs. earlier reports.

Concerning the reactance, I see the capacitor appearing to have very good control over a wide range of resonance in order for the meter to show X=0 over such a broad range. Do you think these static type caps are better (more broadbanded), than the variable cap you used earlier?

Is that the way you read these results?

Do you think maybe Bob's idea for the spiderplane might be the issue that made the difference they reported?

I have considered that maybe checking the radials, looking for any match difference is not the way to go. It might be typical for a Bob report, but the guys never said anything about match that I recall. They just suggested the addition of that GPK idea made a nice difference in gain.

I still have to believe that adding radials has to make a difference in the match, if we are to expect them to make a big difference in the performance, but with antennas we just never know.

How say you?

 

[HomerBB]

Until I have a solid way of measuring/observing the differences between known stations it will be hard to answer all your questions.
I did not use the variable cap very long, and when I did I had it static. Rotating it away from fully open resulted in a severe mismatch.
Unless I come up with a smaller variable than I have, make one/buy one I won't rightly know.
What we see on the analyzer is still open for interpretation it seems.
To get the match down from around 1:3 to one to 1.0:1 on 27.405 I had to shorten the antenna 1-1/2". The new matching network and the radials may have contributed to this difference. What I'd have to do is remove the GP and see where the tune landed afterward compared to now.
The comparison to the antenna with the previous matching network has too many dissimilarities to be a reliable reference, IMNotSoHO.
I had a match previous to the GP with this network, however I didn't record it.
I have not read whether anyone retuned their antennas after the addition of the spiderplane, either so we have no point of reference to the effects of the spiderplane on the match. As for creating the swastika thing I could always hang a picture of Adolf Hitler in the shack and see if that will help. Just kidding. I could add wires to the ends of the radials at 90 degrees.