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  #21 (permalink)  
Old 08-16-2017, 7:12 PM
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You've not been using the right spring then. Not all springs are designed to handle a 102" whip--you need a beefy one designed specifically for the purpose, not one designed for a Firestik less than half the length.

If you hit something with the tip of the whip, yes it will flex. But if you hit something within a foot or two of the base of the antenna, that's another story. Something is going to get bent permanently, or break.

And I didn't say SWR was off...
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Old 08-16-2017, 8:05 PM
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First used the 102" whip back in the mid to late '60s WITH a spring and never had the whip "...only thing a spring does is allow the antenna to sail around, beat everything around within five feet of it,.." doing that.
I've used the spring for all the 102" whips.
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Old 08-18-2017, 2:56 PM
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Default size might matter

as opposed to what someone posted, the 102 whip IS used with a 6" spring to bring it to 108".
that is the quarter wave for CB. yes it helps with being hit with something.
only very short antennas don't bend but also don't perform well.
ok 1/4 wave is calculated to be 103.282, so a little bending is ok.

i used to work in suffern new york and had two cars parked next to me, both had a k40 antenna.
both their radio's were silent and mine had a trucker asking for upper or lower level on the george washington bridge. over 20 miles away and daytime. they both agreed, my antenna was the way to go.
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Old 08-18-2017, 3:14 PM
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Quote:
Originally Posted by wtp View Post
as opposed to what someone posted, the 102 whip IS used with a 6" spring to bring it to 108".
Making the antenna slightly longer than the calculated 1/4-wavelength is standard because the ground plane on a typical vehicle is not ideal. You'd need a clear section of roof >18 feet in diameter to be ideal, which is obviously impossible with any standard vehicle. The extra length changes the antenna impedance, which partially compensates for the imperfect ground plane, and usually results in lowest SWR.
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Old 08-18-2017, 5:14 PM
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Quote:
Originally Posted by wtp View Post
as opposed to what someone posted, the 102 whip IS used with a 6" spring to bring it to 108".
that is the quarter wave for CB. yes it helps with being hit with something.
only very short antennas don't bend but also don't perform well.
ok 1/4 wave is calculated to be 103.282, so a little bending is ok.

i used to work in suffern new york and had two cars parked next to me, both had a k40 antenna.
both their radio's were silent and mine had a trucker asking for upper or lower level on the george washington bridge. over 20 miles away and daytime. they both agreed, my antenna was the way to go.
Just for my edification, How long have you been involved in the CB Hobby?
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Old 08-18-2017, 6:06 PM
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Default quite a while

from about 1980.
i did like station wagons .
so i had a great ground plane.
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Old 08-19-2017, 1:03 PM
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Quote:
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from about 1980.
i did like station wagons .
so i had a great ground plane.
What is the significance of the number 2808?

Ball mount dead center roof of a 78 Suburban with a 96" whip and 6" spring. Pain in the posterior at the bank drive through or gas stations. Can't tell you how many florescent light bulbs it claimed.

SWR is not the be all, tell all. The above setup was patterned and tuned with a field strength meter. Pattern was strongest off the nose and tail. It would talk ground wave from Lawton to Oklahoma City with a box stock
Royce 1-639.

The second best set up I had was a 1972 Vega Hatchback with co-phased Hustler center loaded antennas 2/3 way up the hatch. Pattern was strongest straight off the nose.


Ahhh, the good ole days.
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Old 08-19-2017, 1:28 PM
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I'll bet that 96" whip was fiberglass. Antennas will be a bit shorter when covered with insulation or fiberglass, so an equivalent 102" whip using a copper wire embedded in fiberglass is usually 96". Add a 6" spring and your resonant on 27MHz in most cases.
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What is the significance of the number 2808?

Ball mount dead center roof of a 78 Suburban with a 96" whip and 6" spring. Pain in the posterior at the bank drive through or gas stations. Can't tell you how many florescent light bulbs it claimed.

SWR is not the be all, tell all. The above setup was patterned and tuned with a field strength meter. Pattern was strongest off the nose and tail. It would talk ground wave from Lawton to Oklahoma City with a box stock
Royce 1-639.

The second best set up I had was a 1972 Vega Hatchback with co-phased Hustler center loaded antennas 2/3 way up the hatch. Pattern was strongest straight off the nose.


Ahhh, the good ole days.
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Old 08-19-2017, 4:21 PM
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Quote:
Originally Posted by prcguy View Post
I'll bet that 96" whip was fiberglass. Antennas will be a bit shorter when covered with insulation or fiberglass, so an equivalent 102" whip using a copper wire embedded in fiberglass is usually 96". Add a 6" spring and your resonant on 27MHz in most cases.
prcguy
Nope, the places I go a fiberglass whip has a life span measured in seconds. It is bad enough that a SS whip ends up looking like a pretzel after banging it into tree branches.

The 102" either whip or 96" whip plus 6" spring puts the frequency to high and above channel 40. But (there is always a but)(and this is the part that everyone always forgets) the ball becomes part of the radiating element and adds length to it. So depending on the particular ball mount you use between 1 and 2 inches are added to the length of the antenna putting it at a total of between 103 and 104 inches or right where the formula says it should be for channel 19, the exact middle of the band, 2808/27.185=103.292".
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Old 08-21-2017, 9:01 AM
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Let me understand the mount. I have a light bar behind my cab - plates at top for my lights and antennas - to get better use out of my whip - shall I add some flat stock to my existing mount, to get the whip more to the center of my cab roof ?

Thanks
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Old 08-29-2017, 12:38 AM
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I have found that a 108” whip very much out performs a 102” whip with a 6” spring. I have attached a picture of my car with a 108” whip on it. Due to not needing a spring the 108” whip is less expensive than a 102” whip with a spring.
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Old 08-29-2017, 1:29 AM
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Quote:
Originally Posted by Hydrogen18
I believe having it centered above the cab would be the best for the radiation pattern.
I have always wondered about these huge antennas...

Wouldnt they also work as a good base antenna also?? (I reckon they would)
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Old 08-29-2017, 8:05 AM
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So if a whip needs a 1/4 wave length centered around the antenna ! Would the whip work well centered on a 24' x 30' metal barn ?
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Old 08-29-2017, 8:40 AM
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You set on top of the mountain, using the whip distance is not much of a problem. Height is very important.
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Old 09-16-2017, 7:31 PM
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Using a cheap rad shack simple 40 channel CB with a 102 inch whip on a 6 inch spring mounted on a ball mound drivers side of bed of truck I could sit in a little valley while working at night and chat with folks 25 to 30 miles away no problem. I could monitor farther out as well. no need for mounting it on the roof or what ever ball mount on drivers side of bed in rear and if you can get a clip for it bend it down when passing thru overhead places like banks and Mc Ds and such [or your own garage].
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Old 09-16-2017, 7:33 PM
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Yes.
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Originally Posted by arkieguide View Post
So if a whip needs a 1/4 wave length centered around the antenna ! Would the whip work well centered on a 24' x 30' metal barn ?
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Old 09-17-2017, 9:32 AM
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hank you guys for your help.
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Old 10-07-2017, 12:12 PM
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Seems like a lot of confusion on, and about, 11 meter band radio . Just remember full eave 11 meters = 433.07 inch's. 1/2 wave = 216.535 inch's. 1/4 wave = 108.2675 inch's. so a 102 inch antenna needs another 6.2675 inch's, to = 1/4 wave. I think many people get 11 meters mixed up with 11 yards are 11 feet.
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Old 10-07-2017, 12:16 PM
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i might add - the spring added to the 102" whip, makes it close to 1/4 wave at 108.2675 inch's.
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Old 10-07-2017, 12:27 PM
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You are forgetting to compensate for velocity factor.


I'm putting connectors on the cable for the quarter wave on the new truck. Let you know what it ends up at after tuning.


It is done. Ended up with a 1.2 to 1 at 27.2

whip and
spring
inches. / Frequency of lowest SWR
105.5 / 26.0
104.5 / 26.2
103.5. / 26.5
102.5. / 26.7
101.5 / 27.0
100.5 / 27.1
99.5 / 27.2

Velocity factor, proximity to body parts, composition of body, size of body, and location of antenna on the vehicle are some of the variables. Pick a starting point, measure, trim, repeat until reaching the desired result.
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Last edited by jhooten; 10-07-2017 at 1:29 PM.. Reason: coloums lost alignment.
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