what about the length of the top hat? It may have been discussed already but generally is not about 60% of the top hat length considered as electrical length.
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BBT Delivered Hy-Gain Penetrator 500 Today
- Thread starter Eastside
- Start date
i know you can make an antenna any length you want then build a matching circuit to get 50 ohms and no reactance but i think an antenna is really what it measures. thats why there called a 1/4 or 1/2 or 5/8 wave. when you measure the old penetrater and find its 6 or 7 inches longer then the new one it makes me think its a .64 especially when thats what it measures
i read the velocity facter of air is .9979 so only about 1/2 inch in 23 feet
NB, without some supporting evidence, your claim is just like mine, an opinion. It's just such opinions that I've heard for years, which got me started trying to better understand the various vertical CB antennas we discuss here on WWRF. Opinions are great, they gives us something to talk about and consider.
My ideas, in this regard, are based on my real world experience, and it has always been...I didn't see nearly as much difference in performance as most other's talked about. Now with my modeling, I think I see some support for my experiences and opinions...and it is more-often-than-not.
Here is what my Eznec5 models show.
There is little to no differences, when I modeled an A99 vs. Imax at different lengths and diameters at 40' over Real Earth. I started with the A99, at 17.5' long with a wire diameter of .125". I then increased the wire diameter in steps from .125", .50", 1.0". Then I set the radiator length to 18.5' feet, and did the same thing as above with the wire diameter. Finally I set the radiator to 19.5', and again the same for the wire diameter. I did this just to see what happened as I made the antenna longer and thicker. This is not all that happens to these models, but the images here show what I was interested in, the antenna view with current, pattern, gain, and maximum angle.
I did a similar setup using an Imax starting at 22.5' with a wire diameter of .125". I took fewer step on this antenna by leaving out the middle test for both length and wire diameter.
In my opinion, these models below likely simulate the nature of these two antennas, at 40' feet over Eznec5's feature for real Earth...using an Average Ground setting.
View attachment NB's ideas .625 vs. .64.pdf
yeah marconi that makes me think theres problems with your program because ive seen differences when swiching antennas for me or a friend that were alot more then your models show but then you dont see diferences so i guess its fine and every person just has to find the best antenna for his own station.
i dont think you can make a antenna 18 feet long and call it a 5/8 or 3/4 just because you can match it. i think its what it maesures and then you build the match that works. i dont consider the macov58 a 5/8 because its to short so its not 5/8. its not a 1/2 wave iether because its to long so i dont know what you call it, maybe a 5/9 wave but its not a 22 1/2 foot so i dont call it a 5/8. if a antenna measures 64 of a wave legnth then it is 64 and will have the match it needs. it just seems like in some of my reading i have read where some think you change the antenna length number acording to matching system but i dont. i still hope you can try 64 with the i10k to see if it works differently then your model says
i dont think you can make a antenna 18 feet long and call it a 5/8 or 3/4 just because you can match it. i think its what it maesures and then you build the match that works. i dont consider the macov58 a 5/8 because its to short so its not 5/8. its not a 1/2 wave iether because its to long so i dont know what you call it, maybe a 5/9 wave but its not a 22 1/2 foot so i dont call it a 5/8. if a antenna measures 64 of a wave legnth then it is 64 and will have the match it needs. it just seems like in some of my reading i have read where some think you change the antenna length number acording to matching system but i dont. i still hope you can try 64 with the i10k to see if it works differently then your model says
Yep NB, you may be right for several reasons. Modeling is not necessarly meant to set into stone...antenna design or performance. Anyone using modeling for their design work, probably should do real world testing, and compare the trends modeling might produce.
Eznec is widely reported to have limitations, and data entry and understanding are very important to its successful use. I believe it when you say you've seen the kind of results you claim, so have I occasionally. I do a lot of signal report comparisons, so I can average out the unusual reports, both good and bad that show up at times. I also take my time, trying to mitigate changes in conditions...by my use of averaging many contacts at different locations. So, if you're just depending on one or two very good reports then your conclusions could be just as skewed as my modeling. That said, there are probably areas around that will consistently show more or less difference in antenna signal comparisons and responses, so all I ask is to consider my idea and what I see. I post my models in order to show the bases of my thinking. If they don't agree, then I would say so. I just think more contacts at different locations and more testing, compared to your report from a buddy, is always better.
I should not have started this part of the discussion, because it is a bit petty to make so much of such a patently simple, but arguable issue. Getting such measurements down to the nitty-gritty in discussion...is dependent on many real world factors, and is generally not productive IMO. I try to avoid being categorical in my claims.
I understand your point, and I don't disagree with your math or your terms. I just disagree that there is a big difference between these two...based on my experience and the way I understand the theory. In real world testing, every location can be different, and it might even be different from hour to hour...depending on conditions and surface surroundings at both ends of a two way contact.
I just hope if I ever get around to doing the comparison testing you asked about, that I'm able to convince you of my results, or that I'll have to change my mind and agree with you...that there is a big difference between the responses from a .625 vs. a .64 wavelength vertical antenna.
The truth is what matters to me.
Don't give up on me yet.
to late. ive completely given up on you marconi
but really i dont need you to see any earth shattering diference just want to see it you see any at all. i cant expect theres much diference in 6 inches of antenna but if there basically the same then id opt for the longer one anyway just to have the most metal in the air that i could before it starts going down in performance. i might try a vecter next because its so tall. maybe that will have better ears at least but i just dont know if i like a gama matcher
but really i dont need you to see any earth shattering diference just want to see it you see any at all. i cant expect theres much diference in 6 inches of antenna but if there basically the same then id opt for the longer one anyway just to have the most metal in the air that i could before it starts going down in performance. i might try a vecter next because its so tall. maybe that will have better ears at least but i just dont know if i like a gama matcher
i think the old one was 40 inches folded in half and went up about 18 inches 1 inch wide and 1 inch away from the tubing. the ground side was 14 1/2 inches. it took me a few minutes to search but heres the measurments i found from a couple years ago but i think this old one measured 64 long not 5/8 like the new one so the match might be different to
A Subaru Outback oil filter also works well for getting the curve bent correctly.
For the Beta match the overall length of 12g copper you'll need is 41".
That includes enough for the loop you'll need to make on each end.
Since you have a Penetrator to measure by, simply attach one end to the very bottom connection coming through the insulator cup, and bring it up and over the radials with the Outback oil filter curve, plus another 3", then bend it across at a 90* for a 1" spacing, then back down to the connection at the base of the radiator.
If you bent & curved it right you should have just enough left to make the loop to reach the hole at the bottom of the radiator.
You might want to get 20' of 12ga just in case you need to practice 2-3 times.
The shunt is most likely what took the brunt of the energy and I'll bet it's toast, so, cut another piece of 12ga copper, 16" long, which will include the 5/8" or so required for the loop on each end.
The length measures 10 5/8", bend to bend.
The top extension is 1 3/8" from the bend to the center of the loop.
The bottom extension is 2 3/4" bend to center of loop.
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Just finished building my new Penetrator, and It's giving me weird readings on my MFJ-259. R=72, X=15 and VSWR is of course, 1.5. Can't get it lower than 72 ohms. This occurred at 27.4, 28.4 and at 28.8; no difference. Anyone have any ideas?
Noticed that the dimensions are different in the matching system, between the old and the new. I will measure both, and report my findings.
I have to take apart my old antenna, and drill out the rivets holding the base to the bracket. Then, repair the internal wire going from the SO239 to the feed point on the base. Probably will use a piece of braid, or 1/4" copper flashing. Then put it all back together. Might replace the new one with it, and put the new one back in my antenna stock.
Noticed that the dimensions are different in the matching system, between the old and the new. I will measure both, and report my findings.
I have to take apart my old antenna, and drill out the rivets holding the base to the bracket. Then, repair the internal wire going from the SO239 to the feed point on the base. Probably will use a piece of braid, or 1/4" copper flashing. Then put it all back together. Might replace the new one with it, and put the new one back in my antenna stock.
Well NB, I'm not sure the old and new are the same like some have claimed, but your idea doesn't agree with a picture I have with a tape rule beside it. Of course pictures can fool you with perspective. But, I'm only interested in the New SP 500, just in case they are different.
Here it shows the ground side of the matcher wire about 14" and the feed side wire looks about 13.25", with the ground wire itself about 10.5", but I think this is an old Penetrator. I would like the specific measurements for the new SP 500.
I have a bracket from another old HyGain that is only 11.5" long. So, if these brackets are the same length, then the ground wire couldn't be 14" and still fit inside the flanges.
I think Eastside is still waiting to put his new antenna up, so maybe he can help with some good accurate measurement for these two wires.
Thanks anyway.
i think those were his measurments before you bend the curve into it. didnt they have even two different old versions for before and after 40 channels came out? i wonder if there matchers were a little different to
I don't know NB. I never owned one. I asked guys over the years about any changes they saw, but to no avail. They said, we just put em up and talk.
I did try to study and understand these CB antennas, and put my hands on the manuals when I could, but the details didn't really matter to me either, until I tried to model them with Eznec...and then the smallest details are important.
Here is my first attempt at doing the matcher. It is very complicated to model due to the way Eznec lets you do things. I don't have good measurements yet and the matcher is not working well at this point.
View attachment SP 500 matcher.pdf
your tape measure picture looked like 15 1/4 and 15 3/4 inches in length plus about one inch for the shorter angle diagonall bend and maybe 1 1/2 inches for the longer one at the other end. it looks like about a 3 1/2 inch long curve but its more than half a circle so i figured the curve as 70% a 3 1/2 inch circlke and got 11 inches times 70% and got 8 inches minus the 3 1/2 inches it measures strait across which is already counted in the 15 1/4inches. then i added 1inch for the 90 degree fold at the top plus 3/4 inch on each end for the circles for connecting and when you add it all up i get 41 inches but the circles are only maybe 1/2 inch so thats why i thought 40 inches total looks about right to me and oo7 sounded like he had one right there to measure