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102" ss whip. is it still the best


102 inch ss whip, best quality 6 inch spring,, quality and well built mount,,, that is the best antenna,,,

I agree 100%. A close second is a 96" fiber glass whip. I used to run a Francis "Amazer" glass whip, and it was the best mobile antenna I have ever run. It was on top the roll bar on my Toyota 4x4, so it didn't look too weird. No need for a spring. Lighter and didn't bend as much as a steel whip on the road. Since the Amazer is NLA, I use a Shakespeare 4208 8' Loran antenna now. Great performer and tough, Only available in white. I painted mine hot rod black. Shipping to Colombia was more than the cost of the antenna, but worth it.

- 399
 
A typical ball mount is about 4" tall, plus that 6" spring and an 8.5' whip and you have 9.2', or close to it. A 1/4 wave on 27.200Mhz id around 8.6' long. The resulting antenna is too long by almost a foot. Right? So if you tune that thing then I would have to agree that it's a pretty rugged and typical antenna.
Those numbers aren't exact, but they're certainly ball-park.
 
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Those numbers aren't exact, but they're certainly ball-park.

Ball-park is really about as good as you can get. If the ground plane is to small, you can compensate by making the antenna longer, and vice versa. What are the odds that the vehicle chassis is going to present the exact size needed for a ground plane to such an (or really any) antenna? Not good, actually, it will likely never happen.

Luckily these antennas are wide banded enough that close is good enough.


The DB
 
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"If the ground plane is to small, you can compensate by making the antenna longer, and vice versa. What are the odds that the vehicle chassis is going to present the exact size needed for a groundplane..."
The first part, compensating for a 'too small groundplane' is not true. It doesn't work that way, sorry.
As for the size of a vehicle providing an adequate groundplane, most vehicles will provide an adequate one. Keep in mind that the vehicle -plus- the dirt/concrete under it make up that groundplane, not just the metal of the vehicle.
It's easier to think of the 'groundplane' as the 'other half' of a 1/2 wave antenna. That means it should be at least as long. Most vehicles will provide more than enough metal for that 9' (ball park number) not to mention the dirt under the vehicle.
 
"If the ground plane is to small, you can compensate by making the antenna longer, and vice versa. What are the odds that the vehicle chassis is going to present the exact size needed for a groundplane..."
The first part, compensating for a 'too small groundplane' is not true. It doesn't work that way, sorry.

Actually it does. It works with the same principles of an off center fed dipole. As long as both sides add up to equal and electrical 1/2 wavelength, the antenna will function.

As for the size of a vehicle providing an adequate groundplane, most vehicles will provide an adequate one. Keep in mind that the vehicle -plus- the dirt/concrete under it make up that groundplane, not just the metal of the vehicle.

What I was talking about was the electrical length presented by said vehicle chassis. I've actually taken a 1/4 wavelength whip tuned for one place on one vehicle and on a different vehicle I had to retune it. I've seen some that you have to tune a little longer than the mathmatical resonant 1/4 wavelength, and others that you have to tune shorter, hence why I specifically honed in on your words, namely "ball park". I have seen this personally multiple times.

If you want to say that their is capacitive coupling between the chassis of a vehicle and the earth (or in most cases street) below, that is fine, I would agree with that, the chassis of the vehicle does act much like a "capacitive ground" system, which used to be used on old AM broadcast towers. This type of ground system is well studied and experimented with, and how well it works is directly related to the conductivity of the earth below the said capacitive ground system. The conductivity of street pavement is terrible to even worse. While their are currents that will flow on the earth below and around the vehicle (aka the street), they will be very minimal, especially compared to the currents flowing in the chassis of the vehicle itself.

Seriously, look at a ground mounted 1/4 wavelength vertical antenna. Why does it work better if you use actual radials on (or buried just below the) earth as opposed to a ground rod for an earth connection? The reason for this is the exact same as the reason I am saying the above currents flowing in the "street" will have no noticeable effect compared to the currents flowing in the chassis of the vehicle.

It's easier to think of the 'groundplane' as the 'other half' of a 1/2 wave antenna. That means it should be at least as long. Most vehicles will provide more than enough metal for that 9' (ball park number) not to mention the dirt under the vehicle.

As I said above, from experience, their isn't one length of whip that will tune to resonance on every vehicle. As the electrical length presented by a vehicle will changes from one vehicle to another, if you are tuning specifically for resonance you will have to make an adjustment to compensate, and the easiest place to do that is the length of the whip in question.

I wasn't disagreeing with what you said, in fact, I was simply restating what you said from a different point of view. What I said was, in fact, dependent on what you said being true.


The DB
 
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Not only the size of the vehicle but where you put the antenna on the vehicle effects what length the antenna tunes @ and what impedance it will present to the coax @ resonance,

Try tuning an antenna roof center on an eldorado size car then move it to a festiva size car,
hope you did not chop the whip down too much.
 
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"If the ground plane is to small, you can compensate by making the antenna longer, and vice versa."

You can't compensate, physics requires you to. If you don't you're not getting a 50 Ohm match.
 
the 108 inch whip might be technically electrically better .... but real world use differences ????? as other said , the ground side will make the bigger difference .
 

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