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Base Open Sleeve EFD
- Thread starter Marconi
- Start date
Homer, my models have shown more or less the same for the NV4K for some time now. I went back to the days in my Eznec antenna index file when I was modeling these antennas using taper on the elements. Not much has changed if I just tweak those older models a little bit...I can see similar results today.
Improved information on the dimensions have help with some models I don't own too.
I just wish more folks with these type antennas could give us some real-world comparison report. It is rare to see much reporting on these antennas anymore. If it wasn't for Bob, you, and a few others...one might wonder if they sell. Also, it is impossible for me to forget about the huge traffic we use to have on the CB band.
I guess a few on this forum today...don't even have a clue what that was like back then.
I am so busy anymore I hardly have time for fun. Nevertheless, I want to make a 2m sized version to play with. Hopefully soon.
I think you need somebody that lives where the terrain is flat for miles so the extra height of the longer antennas only gives it an advantage in height of current maxima above ground to reflect models over real earth,
you can gain an extra advantage unrelated to gain on the same mast that will never be seen in models,
the extra height above obstructions such as buildings trees or a terrain that is not flat.
the idea is depicted in over blown form in the astroplane adverting.
you can gain an extra advantage unrelated to gain on the same mast that will never be seen in models,
the extra height above obstructions such as buildings trees or a terrain that is not flat.
the idea is depicted in over blown form in the astroplane adverting.
@bob85 i am currently visiting 3 hours NNW of my home. I would expect to be at a higher elevation than where I live. However, according to my GPS, I am 792 feet above sea level here. At home, the base of my antenna mast is 1363 feet above sea level. I would expect my radio results here to differ to some degree from what they are where I live.
Citation needed.
Strangely, this statement was made in response to a modeler looking for someone who has done/could do a "real world" comparison of said antennas to confirm his modeling results. Isn't someone trying to get a "real world" confirmation of modeling results a good thing?
The DB
RS, among other things, when we're working our radios and depending on our senses, understanding, and imagination for what is going on...I figure at this level, real world radio/antenna performance is pretty much a "guesstimate" too.
I've commented, I'm about as sceptical as anybody aught to be Bob, but I'm not near as picky. If somebody popped up here citing a radio/antenna report just like you described above...I bet you would be the 1st. to question some detail you saw overlooked or possibly the whole idea.
Regarding radio and antennas in particular...I think many realize there is a lot more going on than we mortals can see or measure at our level being a hobby. However, over time I thank you for helping us see some of these ideas.
Can you demonstrate to us, maybe using EzBob images, what the real situation is...going on in the Avanti ad you refer too?
I've commented, I'm about as sceptical as anybody aught to be Bob, but I'm not near as picky. If somebody popped up here citing a radio/antenna report just like you described above...I bet you would be the 1st. to question some detail you saw overlooked or possibly the whole idea.
Regarding radio and antennas in particular...I think many realize there is a lot more going on than we mortals can see or measure at our level being a hobby. However, over time I thank you for helping us see some of these ideas.
Can you demonstrate to us, maybe using EzBob images, what the real situation is...going on in the Avanti ad you refer too?
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Regarding guesstimates, at Home Depot a customer comes in with his total square feet of flooring space wanting carpet. Based on those square feet a tentative cost for his flooring and installation is calculated. However it is stressed that these preliminary numbers are not binding. Not until an on premises measure and inspection of the actual floor plan can a real cost be nailed down. Too many variables are at work. The way the floor is shaped, multi-levels, stairways, trim, transistions, etc. The customer is told he is looking at a guesstimate.
Personally, I think good modeling goes beyond a tentative guess with only one (sq ft of total floor) known variable. For me, if the modeler is proficient with his craft the model guides me toward a given expectation.
Installing an antenna and then reporting a wildly exaggerated result operationally leads me to doubt the report. Too many fluctuations in conditions alone can be misleading, and the same antenna at the very same qth will not always yield the same outcome day by day.
Only once have I talked into South Africa from my mobile. Frustratingly, I struggle in the same mobile to QSO in the US under current conditions.
For me, models are not a guess, but a baseline for antenna performance expectations.
Personally, I think good modeling goes beyond a tentative guess with only one (sq ft of total floor) known variable. For me, if the modeler is proficient with his craft the model guides me toward a given expectation.
Installing an antenna and then reporting a wildly exaggerated result operationally leads me to doubt the report. Too many fluctuations in conditions alone can be misleading, and the same antenna at the very same qth will not always yield the same outcome day by day.
Only once have I talked into South Africa from my mobile. Frustratingly, I struggle in the same mobile to QSO in the US under current conditions.
For me, models are not a guess, but a baseline for antenna performance expectations.
Disregard the error I made in naming this series of models. It is not an Open Sleeve design...it is a Skeleton Sleeve (SS) I''m modeling here. I'm not going to go back and change all the names.
Homer, thanks for your perspective here. It got me to thinking, why I had a feeling that this Skeleton Sleeve model surprised me at just about every turn. I'm not even sure my model is close to what was represented in the ARRL article at 2 meters, or if I figured right in the take-off for the dimensions I ended up with.
The model worked pretty good at 146 MHz, but after scaling I had to make adjustments on the radial lengths and spacing as well as test every move for the radiator length. This antenna does not look to me to be so easy as indicated in the article. At 2.48:1 ratio of radials to radiator...changing ratio was easy compared to doing this design in real life. I did not plan this ratio, it is what I ended up with after doing many iterations trying for a good match. I don't remember if I every checked the Average Gain on these models, but that would change the results if the AGT turns out to be out of a good range not = 1.
This is not an antenna for beginners nor will it be easy to build unless you have all the specific dimensions to start. You will be able to adjust the radiator and the radial length, but how will you adjust the spacing without building another hub plate? Maybe with 11 meters and 21/2 feet one could drill a series of holes for all the likely adjustments on the radial hub plate. IMO, adjusting is not going to happen, because the spacing, which is going to be fixed, is not likely to be set to adjust.
When I saw the first pattern for the antenna that was close to a match...I said this is no Sigma4.
The model in the book was predicting resonance at 146 MHz. So, I had a thought that scaling the model to 27 Mhz might present some problems with the size of parts. Tubing is one thing, but a large hub bracket at 2 meters will really be large at 11 meters. At 11 meters I have a hub that is 2.46' feet square, what to do?
I think Bob saw in this article an issue regarding ratios and asked is this similar to the way the S4 design works.
Do I keep the wire size and scale the length only? I may have to pull a trick out of the bag to do this. hehe!
Do I change the wire size to wire gauge so the scaling does not change in the process?
Or do I pay it no mind and let the cards fall where they may and just scale the whole thing?
1. The PDF file below shows an image of how large the big plate bracket is after scaling from 2 meters.
2. or overlays of the Skeleton Sleeve pattern vs. NV4K, vs. 1/2 wave J-Pole. Here we see how erratic the Skeleton Sleeve is on changing height.
We also see the J-Pole patterns at various heights and the NV4K look very similar...while the SS is off in the weeds and changes radically as the height is changed.
Also, the match for the NV4K and the J-Pole change very little as the antennas are raised higher, while the Skeleton Sleeve does change enough to be noticed as a difference.
This might help explain why Sirio referrers to their New Vector 4000 as a "coaxial J-Pole"...I see the patterns are similar...if that distinction means anything?
Do we still have any "Never a J-Pole" followers still with us?
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Eddie
The real situation with the astroplane advert showing a 5/8 groundplane been blocked by buildings is that 5/8waves don't radiate from down near the radials as depicted,
they radiate most 1/4wave from the tip if they have no hat, so the astroplane only has the 4ft or so advantage the hat gives it.
The real situation with the astroplane advert showing a 5/8 groundplane been blocked by buildings is that 5/8waves don't radiate from down near the radials as depicted,
they radiate most 1/4wave from the tip if they have no hat, so the astroplane only has the 4ft or so advantage the hat gives it.
Eddie
where did you get the 2.48 ratio from ?,
skeleton sleeve monopoles have 3:1 ratio of radial to radiator like the vector,
when built correctly i can't see what could make it different to the other two with regards to height above ground,
why do you think its notably more effected in your models ?.
where did you get the 2.48 ratio from ?,
skeleton sleeve monopoles have 3:1 ratio of radial to radiator like the vector,
when built correctly i can't see what could make it different to the other two with regards to height above ground,
why do you think its notably more effected in your models ?.
From the last .pdf set three quickly noticeable things...
1) the skeleton sleeved model exhibits the best overall gain over a broader range of radiation angles at 32',
2) the v4k and jpole exhibit similar radiation characteristics throughout the elevation shifts, and
3) the v4k still separates itself for some inexplicable reason from the jpole with more gain at same 18' elevation.
At 0.45 dbi difference might this be the edge one needs to drag a weak signal out of the mud into your receive?
1) the skeleton sleeved model exhibits the best overall gain over a broader range of radiation angles at 32',
2) the v4k and jpole exhibit similar radiation characteristics throughout the elevation shifts, and
3) the v4k still separates itself for some inexplicable reason from the jpole with more gain at same 18' elevation.
At 0.45 dbi difference might this be the edge one needs to drag a weak signal out of the mud into your receive?