Not sure...
I think you are simulating the presence of a gamma match in your models. If so, can you leave it out and instead put a capacitance hat on the tip of the vertical like the Astroplane has.
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Base New Vector 4K radiator at 0.75 - 0.82 - 0.875 wavelength.
- Thread starter Marconi
- Start date
I think you are simulating the presence of a gamma match in your models. If so, can you leave it out and instead put a capacitance hat on the tip of the vertical like the Astroplane has.
Eddie all vectors & lw150's have 4 radials,
for the upgraded version sirio extended the radials from a little over 89" to 107" using the same size hoop and shorter radiator with wire ball tip,
sirio part swapping again, new vector looks like its made from the old gpe 5/8,
most of their antennas use common parts,
i will be using a hoop a bit larger than 30" with the longer radials so i don't have to move the spreaders up onto the upper tubes.
for the upgraded version sirio extended the radials from a little over 89" to 107" using the same size hoop and shorter radiator with wire ball tip,
sirio part swapping again, new vector looks like its made from the old gpe 5/8,
most of their antennas use common parts,
i will be using a hoop a bit larger than 30" with the longer radials so i don't have to move the spreaders up onto the upper tubes.
Bob, in this thread Homer posted an old link for his S4/NV4k antennas experiences. I think Homer told us he made his first V4K after making a successful S4 that worked fine and had no radial offset. His description of this V4K sounded to me like he just modified his S4 model by adding another radial. I also think he told us...for some reason that antenna did not work right.
Again, he said he was making a Vector and I was a little amazed to find out he did not make the radials 107" long.
Bob. I think Homer answered me saying he did not want to change several things at once in his new Vector...and that makes sense.
It is not a big deal folks, I was just trying to piece together a bit more of Homer's history with this style antenna.
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Homer I have lots of models.
Did you see a specific model you have in mind?
Maybe you can give me some help with the name of a model or give me a link to a post where you saw such a model...as you have in mind. This way maybe I can better explain your idea above.
I can model a top hat about <>24" long on each side of the radiator, and shorten the radiator to resonance, no problem. If you don't want a gamma in the model where do you figure the feed point should be...at the base of the radial bracket, similar to the real antenna?
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A brief summary of my S4/V4k journey:
S4
3 cone radials with 96" hoop (30" diameter)
No radial offset.
Spec sized gamma dimensions.
Spec length vertical.
Set tune with good SWR using SWR meter (did not own analyzer, yet).
#1 Nv4k
Added one more radial.
Used same hoop as S4 had.
Did not extend radials.
Did not offset radials mount points.
Extended vertical to 7/8^.
Used same gamma as on S4.
Could not obtain tune using MFJ-259B.
Modified Nv4k
Shortened vertical to 3/4^.
Added offset to radials mount point.
Lengthened radials to 106.5".
Kept same hoop.
Lengthened dog bone to 6".
Built bigger gamma (see previous post).
Obtained good tune using MFJ-259B.
Traded away this antenna.
2nd Modified NV4k (QuasiNv4k/QNv4k)
All the same as above modified version except :
I inserted an inner tube within the lower vertical tubes for 6' to increase the strength of the antenna.
Used 1/2" tubing for radials with adjustable tips.
This produced a slightly heavier, but more robust antenna.
Tuned out beautifully with MFJ-259B.
S4
3 cone radials with 96" hoop (30" diameter)
No radial offset.
Spec sized gamma dimensions.
Spec length vertical.
Set tune with good SWR using SWR meter (did not own analyzer, yet).
#1 Nv4k
Added one more radial.
Used same hoop as S4 had.
Did not extend radials.
Did not offset radials mount points.
Extended vertical to 7/8^.
Used same gamma as on S4.
Could not obtain tune using MFJ-259B.
Modified Nv4k
Shortened vertical to 3/4^.
Added offset to radials mount point.
Lengthened radials to 106.5".
Kept same hoop.
Lengthened dog bone to 6".
Built bigger gamma (see previous post).
Obtained good tune using MFJ-259B.
Traded away this antenna.
2nd Modified NV4k (QuasiNv4k/QNv4k)
All the same as above modified version except :
I inserted an inner tube within the lower vertical tubes for 6' to increase the strength of the antenna.
Used 1/2" tubing for radials with adjustable tips.
This produced a slightly heavier, but more robust antenna.
Tuned out beautifully with MFJ-259B.
I was referring to the last model you just made comparing gamma vs endfed V4k antennas.
The model without the gamma you endfed showed less bandwidth.
I wished to see the one without a gamma with a capacitance hat as a replacement for a gamma. Length of vertical and cap wire to be determined by the model's success.
Curious about its match and bandwidth, and if it would work at all...
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Homer, below is a Free Space model showing the Average Gain is = 0.990 close to 1 which is perfect. I did this model with 3 x 24" x 1/8" inch as a top hat. I made the radiator shorter. I made the radials 107" inches long. I also end-fed the model per your request. I did nothing more to the models, so I refer to them as "No Tune."
Then I added a 4" inch isolated mast and set the model over Real Earth. Again, I made no other changes to the model, but I did set it to resonance per your request adjusting the radiator length after setting the Top Hat elements to 24" inches like an A/P.
Even though the match is not so good...both models are resonant and the real Earth model shows very nice gain when compare to some of my other S4 models.
I did not leave any inductance in the radiator...the cap hat took all the inductance out, but the resistive part of the match is still too low. IMO this model does very well, but you will likely need to tune it a little.
While I had the model basically finished for your purpose, I decided to check along the length of the base of the radiator for a 50 ohm point, and it ended higher up on the radiator than specs call for...when using a gamma match. This happens in part because I average the overall radiator diameter since I did not use taper on the radiator. This lower part of the radiator is actually 1.50" inches in diameter and I use an average of 0.80" inches for the entire radiator. Then I undid the modifications and finished your model idea.
Sorry Homer, but I can't give you a good bandwidth on these two models...the match is over 2.00:1 SWR for both models. There is still a nice curve above 2 so you can get an idea that the BW will likely be narrow in any case and based on these models.
I can't explain why the Vector I did earlier that was end fed...matched better than this model...except of course the shortening due to the addition of the top hat.
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Homer, I removed the top hat from the 'No Tune" model above and extended the radiator back to resonance. Then the full length end-fed Vector model showed a little better match with 1.937 SWR vs. 2.317 SWR noted above with the top hat and a shortened radiator noted as "No Tune."
That said however, the Vector antenna that is end fed still needs to be matched somehow. So, in my opinion I think the Gamma match is the logical way to go.
To fix my model with a gamma, resulted in a little less gain, and this confirms what Henry reported in his comprehensive article on "The Avanti Sigma4." However, the amount of difference looks to be so small...as to question if the advantage really matters. Again, only real world testing can possibly tell.
Homer, I'm just guessing here, but I hope this link below answers your question. Both models are in Free Space and they show a close up of a Vector 4K, one with a gamma and one that is end fed. Look for the feed point (O) somewhere on the base area of the radiator inside the cone for both of these models.
Here are those models in my post #42, New Vector 4K radiator at 0.75 - 0.82 - 0.875 wavelength.
If I guessed wrong, then maybe you can post a link to the model you have in question?
My point in producing these models was because this subject in Henry's article "The Avanti Sigma4" came up in the thread.
I recalled Henry making the claim that with the Sigma4 design we can find a match at various points up and down the base section of the radiator...and thus we could possibly find a direct match at the base. He also suggested, doing so could be an advantage due to direct feeding and reducing losses. I was just checking what Eznec might predict regarding this idea.
Henry was right, my models show direct end-feeding makes for a little more gain.
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Thanks Homer, I also had a feeling we were not communicating well, but that happens sometimes. I should have left out the part of my comments you noted above.
I was probably thinking of my discussion with Bob...where we were talking about Henry's claim for end-feeding the S4. I must have assumed you were up to speed on the conversation.
I'm satisfied your post #51 got me up to speed understanding what you did developing your ideas and constructing you S4/NV4K antennas over time. I thank you for that.
I think you saw something and had a question, but I'm not sure exactly what your were meaning.
Sometimes, when I make assumptions reading the words of others...I guess wrong. As a result, after that, I was probably rambling on and for sure did not respond to the point you raised. See your post below.
The "No Tune" models, in my post #53, were posted just to show what the models look like with dimensions set to specs, and I leave the models with no correction for the Average Gain Test results. Both models are the same antenna, the 1st is in Free Space, and the 2nd model is set over Real Earth. I should have been more clear in my words on that post.
This is a classic example of why my post are often wordy...and I know being wordy is sometimes a problem as well. I emailed you guessing again, that trying to explain your question may be difficult for me to answer on the public side of the forum. That was probably confusing too.
Sorry Homer, I think this confusion started off wrong when I responded to your comments in your post #44.
I was probably thinking of my discussion with Bob...where we were talking about Henry's claim for end-feeding the S4. I must have assumed you were up to speed on the conversation.
I'm satisfied your post #51 got me up to speed understanding what you did developing your ideas and constructing you S4/NV4K antennas over time. I thank you for that.
I think you saw something and had a question, but I'm not sure exactly what your were meaning.
Sometimes, when I make assumptions reading the words of others...I guess wrong. As a result, after that, I was probably rambling on and for sure did not respond to the point you raised. See your post below.
The "No Tune" models, in my post #53, were posted just to show what the models look like with dimensions set to specs, and I leave the models with no correction for the Average Gain Test results. Both models are the same antenna, the 1st is in Free Space, and the 2nd model is set over Real Earth. I should have been more clear in my words on that post.
This is a classic example of why my post are often wordy...and I know being wordy is sometimes a problem as well. I emailed you guessing again, that trying to explain your question may be difficult for me to answer on the public side of the forum. That was probably confusing too.
Sorry Homer, I think this confusion started off wrong when I responded to your comments in your post #44.
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I think it's all sorted out.
The only odd thought I have is that I considered these antennas to be end fed by design.
The only odd thought I have is that I considered these antennas to be end fed by design.