Capacitance Hat's Don't add Audio

[Moleculo]

I'm just not categorical minded enough to make the claim that you and Moleculo made earlier, "...that the design of the Merlin, Golden Rod 50, or the mobile shown here on the truck are bad designs." I could be convinced otherwise, but I have a different idea at this point.

What in that article did you read that made you believe that placing a cap hat directly on top of a coil is a good idea?

A coil adds inductive reactance. A capacitance hat adds capacitive reactance. What happens when inductive reactance and capacitive reactance are the same? They cancel each other out. When you place the capacitance hat directly on top of the coil, what capacitance that was introduced is going to directly interact with that coil, shunting the inductor. There is no way around it, and whatever you're trying to accomplishing is going to get screwed up. Maybe someone else can explain it better or more accurately than I am able to.

On that Immortal, if he's trying to make a very short antenna that performs better than others with the same overall height, he should just get rid of the coil at the top, leave the hat. He would probably have to adjust the length between the coil and hat or change the number of turns in the loading coil.

 

[HomerBB]

I think Moleculo said it well enough to express why I think stacking the cap hat on the coil is bad design, but I'll look for more.

Homer, who made these quotes, and in this article it discusses two viewpoints for how a coil works.

The author (Yuri Blanarovich, K3BU, VE3BMV, VE1BY) of the article is quoting his rival (W8JI ) in the debate. He is using W8JI's own words to disarm him of his stubborn refusal to accept the truth over disproved data. K3BU appears to show that W8JI has accepted the authority of no less than the then current edition of the ARRL Antenna Handbook whose writer of that section had drawn material from previous writers whose work was subsequently shown not to be true. K3BU seemed to feel that saying the words, but not living them, was dishonest.

 

[BDOG-T7]

Information's

A lot of good infomation here! But stealing images from a web site without permission and copy other's information is not cool. Dogging a guys product without trying it, well that was not fair. Once again BRAVO!

 

[Moleculo]

No pictures were stolen and no copyrights violated. A better understanding of the rules of the internet are necessary.

Dogging a guys product without trying it, well that was not fair.

Drug dealers use that same line. Snake-oil salesmen use that line that to get you to buy what they're selling, too. How do you know that snake oil won't cure what's ailin' you without at least trying it? I'm not telling anyone what to spend their hard earned cash on. However, I can try to help people understand what they are and aren't getting for that cash. After that they're free to make their own decision.

 

[pro151]

The farther this thread goes, the more confused I get.

 

[Marconi]

What in that article did you read that made you believe that placing a cap hat directly on top of a coil is a good idea?

A coil adds inductive reactance. A capacitance hat adds capacitive reactance. What happens when inductive reactance and capacitive reactance are the same? They cancel each other out. When you place the capacitance hat directly on top of the coil, what capacitance that was introduced is going to directly interact with that coil, shunting the inductor. There is no way around it, and whatever you're trying to accomplishing is going to get screwed up. Maybe someone else can explain it better or more accurately than I am able to.

On that Immortal, if he's trying to make a very short antenna that performs better than others with the same overall height, he should just get rid of the coil at the top, leave the hat. He would probably have to adjust the length between the coil and hat or change the number of turns in the loading coil.

Moleculo, I haven't read anything that suggested placing a top hat right on top of a coil is a good idea. On the contrary I've heard or read the same thing you're telling us here.

My opinion and my question differs with this response based on my working with both the Golden Rod 45 and 50 made by Signal Engineering. Since I was very impressed with both antennas compared to a 1/4 wave whip, I just wondered why someone would make such a claim...that placing a top hat directly over an inductive coil is a no-no.

The idea you present sounds to be very destructive to any good results. Can you describe precisely what happens with the antenna response when setup this way? Your saying that capacitance is canceled by inductance does not describe for me...destruction or getting things screwed up for an RF device. As I understand working with a resonant antenna that is precisely what we want...cancellation of reactance.

My father and I reasoned together that such a setup raised the current distribution higher up the stinger than the continiously loaded whip and that top loading the short stinger should return the affect back to or near full length. This is why I question this claim.

What I saw when testing these two, I thought were positive responses in responding well to both DX and local horizontal signals, without seeming to be ill-affected with known vertical responses. The gain and bandwidth was just as good as the 1/4 wave whip compared, and the match was better. We didn't see any marked difference in local signals, so this shorter antenna worked just as good as the longer one did mounted on my Pop's 1 ton truck in the coastal cotton fields of Souteast Texas.

BTW, I don't think for a minute that Terry would put his seal of approval on anything that was just plane "Snake Oil."



This thread has gone to hell in a handbasket.

Bulldog? Man you are looking real bad.

 

[HomerBB]

I would like to clear the air on this one point. I do not recall ever posting a photo of something on a public forum that was not either a personal photo I owned, a photo of a product that was previously posted for sale by the vendor, or already posted on a forum for public perusal, none of which is underhanded.
As for quotations of any written materials, I have always cited the original location on the www, with a link to the article for due credit to the source. Additionally, any materials I have posted, graphs, and text, from the ARRL Antenna Handbook were taken directly from my personal copy of that volume on my personal computer and uploaded for the sole purpose of the discussion at hand.
I have never been guilty of dogging anyone for the product they sell.
Every single line I have posted in this thread, and similar, have been in the obvious context of trying to understand the issues that have been forwarded as relevant to antenna theory, and the right and wrong of it. I am trying to learn, and with everything I've written I have exposed myself to as much criticism as anyone else by being forthright in how I feel about a point of theory. I have made mistakes, misunderstood, had to reconsider, and admit error. If anything I've posted seems to be, or is in conflict with anything else posted or practiced it is because that is the nature of debate. Pardon me for the Biblical reference, but the only true Know-It-All said,

"Iron sharpeneth iron; so a man sharpeneth the countenance of his friend"
Proverbs 27:17 (King James Version)

I regret any tendency within the thread to degeneration, or any seeming veering away from the sole purpose of education that has occurred, however I feel I've no reason to be thought of as being less than a gentleman, or an honest inquirer who invites an examination of my ideas, and a clarification of any other's ideas whom I challenge in my honest pursuit. To that end I invite absolutely everyone to enter his arena and help me.
Respectfully,
Homer/Charles

 

[loosecannon]

saying that someone needs to buy a product to know how it really works is the oldest sidestep in the CB marketing game.

go take a look at the Copper electronics forum archives and see how many times that exact opinion is expressed.

like i said in the beginning, if he has come up with something that no one else has figured out yet, he should get a patent on it.
if he does not want to do that, there is only one reason.
it is not new.

as for the coil below a cap hat thing, it seems to me that its just two different approaches to electrically lengthening an antenna.

if the goal is an antenna of a particular length that matches at 27mhz, then these techniques can accomplish that.

i would rather use just the cap hat so as not to introduce the resistance that the coil brings with it.
maybe i can make an antenna for 27mhz that is only 38.5" long by using a cap hat and maybe i cant, if the horizontal radials of the cap hat stick out past the edges of my vehicle, maybe i dont want that, so i add a loading coil below the cap hat so that the horizontal radials stick out only as far as i want them.
if my main goal was to be able to fit into a particular garage at the end of the day, then this would be one way to accomplish that.

the only difference i see between using a cap hat and a loading coil besides the resistance of the coil, is the difference in Q factor that might yield different bandwidths.

this all goes back to our discussions on the astroplane patent sheet where Herbert Blease talks about replacing the 4 foot vertical member up top that has the cap hat on it with a full sized 1/4 wave vertical radiator.
as far as i remember, the difference was in the bandwidth.
LC

 

[Moleculo]

Marconi,

Try this article at Antenna Cap Hats on Cap Hats to see if it answers some of your questions about the placement of them in relation to the coil.

Here is an excerpt:

Tech Talk: Whatever capacitance any given cap hat adds, is the same no matter where it is placed. However, whether or not a cap hat increases the effective length and/or increases the radiation resistance and/or increases overall losses, depends on where (how high above the coil) the cap hat is placed. For example, when placed too close to the loading coil, the capacitance can have a detrimental affect on the coil's Q, and will indeed produce an increase in the measured input impedance. For example, the left photo depicts a cap hat incorrectly installed. The input impedance and bandwidth will indeed increase in this example, however the changes are due to increased coil losses, and not by an increase in radiation resistance (Rr).
​

Also:

In fact, the bandwidth of an antenna with incorrectly mounted cap hat (directly atop the coil), will be greater than a correctly mounted one, and with far less efficiency as well.

 

[HomerBB]

Moleculo, those were the exact excerpts I was trying to return to in order to reply to Marconi's question to me. Thanks.

I know it's not the exact same setup, but I think it can represent some part of the electrical principle at work in the setup described in your post.
I have a short fiberglass Francis whip. When I mount it on my SUV puck it exhibits a good match with no matching network whatsoever. When I mount one of my center loaded antennas I have to find the match with whip adjustment. The question is, How can this be?
From what I've read, apparently, the short antenna finds it match through excessive ground losses. It is a match based on inefficiency. The short antenna works, but clearly not as well as my taller, center loaded counterpart.

This personal example of antenna behaviors helped me to visualize what was potentially occurring when the mutual cancellation of a cap hat immediately over a coil renders both of them almost invisible on the antenna. Without them at play to their optimum, I have what is essentially a short inefficient antenna reliant on major losses for SWR match. I can not with any real confidence support what I'm saying unequivocally, but it has helped me to think this through somewhat...

I am learning that the mounting of a mobile antenna has unique challenges not presented in setting up of a static base antenna where heights of 1/2ƛ or more are possible. No matter where a mobile antenna is mounted on the vehicle there are ground losses to contend with due to the closeness of the earth over which the automobile drives. The one and only strategy available to maximize the efficiency of the mobile antenna is the highest location of the antenna's current maxima. The first thing to use to do this is physically mounting the antenna as high as possible. After that, wherever it's mounted, the trick is to use the longest antenna possible to the user. If that can not be a full 1/4ƛ whip, then the use of an optimally designed center (sorry bottom loaders) loaded coiled, or usually impractical top loaded, antenna can raise the current maxima higher up on the antenna. A further step would be to properly place at the right distance a well formed cap hat at the top of the antenna to limit over all height if necessary. Longer whips will negate the advantages of the cap hat, and affect the size and placement of the coil, as a full 1/4ƛ whip would eliminate both.

 

[loosecannon]

Homer, i agree with everything in your last paragraph, as thats how i see it also.

one thing to remember is that the cap hat over the coil (in the right place) allows you to use less inductance in your coil, which means less resistance from the coil itself.

about the ground losses, i think this depends greatly on frequency/wavelength.

we have to remember when reading the ARRL handbook, that while its good info, they tend to "cover their a$$es" so to speak by wording things in a way that covers all of the HF bands from 3-30 mhz.

this means that things like ground losses in a mobile installation can seem a bit overstated when applied to a radio service that only serves a .5mhz spread, at 27mhz.

i dont know how much of a consideration the ground losses at 27mhz are though, and would be grateful to anyone who wished to enlighten me on that.


and just so that no one in the future misunderstands what we're talking about; ALL of these things are compromises when compared with a full sized 1/4 wave vertical radiator.
LC

 

[Marconi]

I did not finish so I'll post later.

 

[1iwilly]

ok i have a set of fighting sticks that i bought from 55 he claim that it would increase my forward power by at least close to a 1/2 s unit but since i bought them i haven't use them beacause acourding to him i don't have them tune wright. but now i have a mfj meter. so this weekend if the weather is good i'll give it a try again. the problem i had was when i tune them for the lowest reflect on my bird meter 2 watts reflect with 800 forward people were telling me that my audio was kind of low.but when i put my coils on audio was loud but with these by the way they call them bowties. my audio was low hard to beleive but true i call 55 and all he could say was i don't have them tune wright.i have include 2 ticture of what they look like and since this post is about top hats i thought i would add my 2cents.

 

[pro151]

Got to say I have never seen an antenna quite like that before. Are you supposed to be able to run these while at highway speed?
Looks like the wind would just fold the "Bowties" right over.

 

[Moleculo]

he claim that it would increase my forward power by at least close to a 1/2 s unit

It's claims like this that are an example of the problem. A guy trying to peddle his nonsense by making BS claims is basically a thief. A full sized 5/8 wave ground plane antenna should have gain of about 3db, which is roughly what the gain of 1/2 S unit. So he's claiming that a very physically short, 1/4 wave antenna is going to have 3db gain over another physically short 1/4 wave antenna? It's impossible.