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tophats and such on top of antennas

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Old 01-11-2010, 02:43 PM
BOOTY MONSTER
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Default tophats and such on top of antennas


theres varying claims on tophats and ball tops and stuff on top of cb antennas and and how effective they are . i was wondering what yalls experiences are with them ? from what i can tell most cb antenna builders claims about them lowering TOA and such are , guestionable , because theyre just too small to have the effect they claim on their antennas . i have read that they can be helpful to make an antenna less attractive for a lightning stike because they spread the elevated attracting charge out over a larger surface area so its not a such a little hot spot up there .

anyhow , whats your experiences , thoughts and knowledge on them on or around 27 MHz. ?


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Old 01-11-2010, 02:57 PM
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a cap hat can be useful on the LOW bands (not 27 Mhz). they give the antenna more bandwidth.

the claims by the manuf's you repeated above are pretty far fetched

Antenna Cap Hats

the little ball on the tip of an antenna is somewhat effective is reducing static noise

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Old 01-11-2010, 03:08 PM
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Quote:
Originally Posted by BOOTY MONSTER View Post
theres varying claims on tophats and ball tops and stuff on top of cb antennas and and how effective they are . i was wondering what yalls experiences are with them ? from what i can tell most cb antenna builders claims about them lowering TOA and such are , guestionable , because theyre just too small to have the effect they claim on their antennas . i have read that they can be helpful to make an antenna less attractive for a lightning stike because they spread the elevated attracting charge out over a larger surface area so its not a such a little hot spot up there .

anyhow , whats your experiences , thoughts and knowledge on them on or around 27 MHz. ?

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Old 01-11-2010, 06:41 PM
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Quote:
Originally Posted by hookedon6 View Post
a cap hat can be useful on the LOW bands (not 27 Mhz). they give the antenna more bandwidth.

the claims by the manuf's you repeated above are pretty far fetched

Antenna Cap Hats

the little ball on the tip of an antenna is somewhat effective is reducing static noise
Hookedon6, I might agree with you that the use of a top hat can increase the bandwidth in cases where its structure is a modest to significant portion of the elements wavelength. I don't make any claims about the info in the link you provided us, however both quotes below can be read to disagree with your claim---unless I misunderstand your words about "LOW BANDS."

Quote:
Originally Posted by K0BG
Adding a lot of insult, is the typical low Q of the loading coils, and short lengths. Fact is, few amateurs really understand just how inefficient an HF mobile antenna system is. In the worst of cases, efficiencies are less than 1% (80 meters), and in the best of cases, about 80% (10 meters).

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Originally Posted by K0BG
The measured receive signal strength difference between the cap hat configuration versus the whip, varied between ≈3 dB (80 meters), and ≈6 dB (20 and 17 meters). About 25 different measurements were made, over a 7 week period (early Summer 2009). I believe this is proof-positive that the cap hat design herein, does indeed increase efficiency significantly enough, to offset the mechanical aspects of the design, let alone the reduction in antenna tip height above ground.
I also agree with Booty Monsters comment about the use of top hats and balls on the top of vertical radiators being useful in helping to reduce the chances of lightning strikes.

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Old 01-11-2010, 07:30 PM
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"Adding a lot of insult, is the typical low Q of the loading coils, and short lengths. Fact is, few amateurs really understand just how inefficient an HF mobile antenna system is. In the worst of cases, efficiencies are less than 1% (80 meters), and in the best of cases, about 80% (10 meters)."


how fortunate for us chicken banders that our little peice of the sky is right nextdoor to 10 meters .

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Old 01-12-2010, 06:14 AM
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[QUOTE=BOOTY MONSTER;171796
how fortunate for us chicken banders that our little peice of the sky is right nextdoor to 10 meters .[/QUOTE]

there is a lot of truth in that statement, a 102" whip is a lot closer to a full wl on 11 meters than on the lower bands.

this may be the paragraph that some of you kinda missed:

It is also important to reduce the other resistive losses, primarily coil losses due to low Q. Installing a cap hat on a short, stubby antenna will improve its performance, but not to any great extent. Remember, ground losses dominate in any HF mobile antenna installation, but if the coil Q is low enough (less than 100 say), the coil's resistive losses could be more than the ground losses! In other words, adding a cap hat to an overly-lossy antenna is counter productive

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Old 01-12-2010, 06:59 AM
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Top gizmos are 98% gimmick on chickenbander base station sticks.

Mo-bile ants benefit anytime a loading coil's resistive loss can be reduced. Top loading does this by lowering the inductance necessary for resonance.

You have arrived when your 75 meter mobile stick is resonant and you can't get it to work at 50 ohms without some type of network at the feedpoint.

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Old 01-12-2010, 09:40 AM
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Years ago I helped a friend rebuild a Penetrator. It came with mostly unusable top hat radials due to being bent or broken.

Instead of making new ones he asked if they weren't just ornamental because he had a SigmaII a decade earlier and remembered it having nothing on top, and at that time we were running identical radios and lived only blocks apart (I was using a Penetrator) and we were always neck-n-neck.

So I told him that I thought we could get away without them but the radiator would require increased length.

We simply lengthened it and it worked perfectly.

A year later I decided to remove mine just to see if it would make any difference at all.

Static did not increase, signal remained the same except for maybe a needle width of increased receive from having 10" more height / vertical capture area.

Now I rebuild them w/o the top hat, just like the SigmaIV, SigmaII, Old Vector 4000, LW-150, etc...

Last edited by CDX-007; 01-12-2010 at 10:48 AM. Reason: correction

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