Capacitance Hat's Don't add Audio

[Radio75]

No, that is a Merlin 55 base antenna. It's a 1/4 wave ground plane antenna that has been butchered. Even sites that sell it don't know WTF it is, though. Check out this quote:



Merlin-Antenna

LMAO.
[/COLOR][/FONT]

$299 for what is basically a Starduster clone???!!!!!!!!!!!!!
I am in the wrong business.

 

[Moleculo]

Moleculo, I'm just curious, but in general what does this coil do for the antenna, and would the coils location affect the antenna in a similar way (noted to be a bad idea when right below a top hat) if there was a straight stinger installed above the coil rather than the top hat?

It's doing nothing for the antenna except causing the radiating element to be shorter than the full length 1/4 wave that it should have been. If he had made the cap hat large enough, he could have found the exact size to cancel out the effect of the coil completely and then the radiating element would have been full length again!

If there was a stinger above the coil instead of the cap hat, it would be no different than any mobile antenna with a loading coil in the middle. You would have to adjust the length of the stinger until you found the correct length. There is no good reason for doing this on an 11 meter base antenna unless you have some serious height restrictions. What is really funny is that the guys buying and promoting this nonsense are typically running them at very high power levels and putting them up pretty high.

 

[Moleculo]

I just stumbled up the NEW title holder for snake-oil...this frankentenna called the Immortal by 55:

It just keeps getting better and better....LMAO

 

[Radio75]

But this one is only $140 and the combo top hat/coil makes the radiation pattern more of an egg shape than omni directional doncha know!

 

[kor b]

I think you guys are trying to flush coolbreeze out of hideing.

 

[BOOTY MONSTER]

I just stumbled up the NEW title holder for snake-oil...this frankentenna called the Immortal by 55:

It just keeps getting better and better....LMAO

notice it has one coil at the top and one at the bottom .
the merlin is a VERY SHORT 1/4wgp .

BTW . the immortal was designed with big rigs in mind using a mirror mount . the lower coil is supposed to help with ... cough cough ... compensating for the poor ground plane that mount can have . once again we have someone (who is supposed to know WTF goes on with antennas) claiming pieces and parts on the hot/vertical element contribute to a better ground plane .

 

[Moleculo]

BTW . the immortal was designed with big rigs in mind using a mirror mount . the lower coil is supposed to help with ... cough cough ... compensating for the poor ground plane that mount can have . once again we have someone (who is supposed to know WTF goes on with antennas) claiming pieces and parts on the hot/vertical element contribute to a better ground plane

There is a way to do what you're describing but what is shown in the pic is not it. One way to do it is to make what is basically a dipole with the bottom section replaced with a coil. If you really needed to shorten the top 1/4 wave section, you could do that too. Keep in mind that this is real compromise for an antenna.

 

[BOOTY MONSTER]

for truckers with fiberglass cabs or that just cant get a good ground-plane , would a big coil below the mount (say.... 12 inch diameter with 3 or so loops about 12-18 inches tall) help them

 

[Moleculo]

for truckers with fiberglass cabs or that just cant get a good ground-plane , would a big coil below the mount (say.... 12 inch diameter with 3 or so loops about 12-18 inches tall) help them

I don't know many turns you would need with a coil of that diameter..you would have to figure it out. Have you ever seen those mirror mount dipoles where someone puts a helical wound coil antenna (like a firestick) on the downward pointing side? That's basically the same idea.

 

[BOOTY MONSTER]

MFJ Enterprises Inc.

 

[HomerBB]

I found these quotations interesting:

"By using a flawed and seriously over-simplified model, the results are totally misleading when applied to conventional antennas. Repeating misleading information in article after article does NOT make it correct. It certainly does not make our community more skilled or better informed about how things work."

and

"While I appreciate all your (K0BG) efforts, it is important that readers and writers fully understand why and how something works before reaching conclusions. Otherwise this all just wastes bandwidth, and people learn incorrect information. The goal of E-Ham and Internet should be to INCREASE technical skills through mass peer review and learning, not to repeat misinformation. "

In fact, the entire article can be found here, and for me was very enlightening.
Current distribution in the Antenna Loading Coils.

 

[Marconi]

I found these quotations interesting:


In fact, the entire article can be found here, and for me was very enlightening.
Current distribution in the Antenna Loading Coils.

Homer, who made these quotes, and in this article it discusses two viewpoints for how a coil works. Question is which do you believe?

I have some opinions even though I don't have any good understanding about the electrical circuit or this part of RF for that matter. But, when I read I do still try to form some conclusions that I hope to remember and with conversation...maybe one day understand even more. 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 do you see in this article that speaks to the design that makes folks claim a Top Hat close and above a coil will not work good or at all, and thus is bad design? In other words, what convinced you that you are right?

I'm trying to learn.

 

[Radio75]

Marconi, towards the end of the article look at figure 9-40 representing the actual measured results of load verticals with and without cap hats.
You can see that adding a cap hat increases the amount of current distribution towards the top of the antenna.
W8JI claimed that he measured not only the same amount of current in the top of the coil as the bottom, but actually more current at the top than the bottom. How a coil increases current is a mystery to me.

 

[Marconi]

Marconi, towards the end of the article look at figure 9-40 representing the actual measured results of load verticals with and without cap hats.
You can see that adding a cap hat increases the amount of current distribution towards the top of the antenna.
W8JI claimed that he measured not only the same amount of current in the top of the coil as the bottom, but actually more current at the top than the bottom. How a coil increases current is a mystery to me.

75, I tend to agree with you, I don't see how it is possible for the current to ever increase in its travel toward the top of a coil. That just doesn't make sense to me. Maybe it can remain the same, depending on many factors like being in tune, resonant, or harmonic, but I figure the current amperage is destine to drop a bit in such a situation.

I thought he was saying, until changing his mind, that the current across the coil was the same, top and bottom. I think the gist of the article was about the current values in the coil decreasing a bit from bottom to top.

Personally, I don't know what all this means, but I always consider that the big thing a coil does is more or less raise the current higher up the radiator, and not the magnitude, than it would be for a continuously loaded radiator. I also believe this small change can and does affect performance increases by a detectable amount, but I stand to be corrected.

 

[HomerBB]

Marconi,
I personally subscribe to the idea that the current diminishes as it travels from the bottom of the coil to the top, that it's less at the top than the bottom as proven in the article cited.
As for the belief that the cap hat right against the coil being inferior design, I will have to wait until I get home from work to give further information, but some of the material is included in this article:

Antenna Cap Hats