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Different Look At 102" Whip Discussion

But I've seen a lot of recommendations in other threads to use a steel whip for a vertical and 102" wires for the radials in a homemade 1/4 wave GP. And no mention was ever made about using a spring with the whip. Hence my confusion.
 
That length thingy deals with resonance, not SWR, or impedance matching. Especially with a typical groundplane antenna, varying the angle those radials 'droop' can make a big difference in SWR/impedance matching/input impedance. The formulas for length are always an approximation, never exact. They can certainly get you in the 'ball-park' with resonance though. Those are two different thingys altogether, resonance and SWR, they are not related.
- 'Doc
 
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Need some help. Am really confused.

According to the antenna calculators I find online, 1/4 wave on 11 meters is around 103 inches at the middle of the band (27.2). But I am understanding most of you to be saying it is closer to 106 inches (or more).

What am I doing wrong?

Thanks!
Jim

Jim, I think you're not reading what the calculator link in the beginning of this thread is showing dimensions for. The explanation for its purpose is right there in the words at the top of the page.

If you are considering a mobile installation this calculator will not be of much help IMO. Who really knows how the antenna sees the car body as the ground plane in a mobile install? Some setups work and some don't in such cases.

The calculator is giving you the dimensions for a base type antenna install using a vertical 1/4 wave radiator, and 3 or more horizontal radials. But, assuming you want resonance and the impedance match to look really good on your meter you will need to slant the radials down 45* degrees or more.

Setting the radials horizontal will also work just about as good, but the match will be off at resonance.
 
Thanks, 'Doc. I keep forgetting they are two different things.

Thanks, Marconi. I'll learn this stuff someday. By the way, it's good to have you back. I think you went missing about the time I came aboard a few months ago. Glad you've returned.
 
Thanks, 'Doc. I keep forgetting they are two different things.

Thanks, Marconi. I'll learn this stuff someday. By the way, it's good to have you back. I think you went missing about the time I came aboard a few months ago. Glad you've returned.

If you go back in this thread and read my post #11, you will read that I was pretty much saying the same things to Wire Weasel back then too.
 
If you go back in this thread and read my post #11, you will read that I was pretty much saying the same things to Wire Weasel back then too.

Yes sir. Got it.
I don't have room for 7 (or even 4 full-length radials) because of my roof. How will it perform with only 2?
 
Yes sir. Got it.
I don't have room for 7 (or even 4 full-length radials) because of my roof. How will it perform with only 2?

Just kidding! Been there, done that with 4' Firestiks. Worked pretty well and while steel whips would be better, I'm guessing it wouldn't be THAT much better.

Are you sure none of you need a MINT Royce 619? I have it listed in the CB Swap forum for $125 (you can see pics there) but would let any of you have it for $100 as you've all been very helpful to me in many forum threads. Free shipping. The cover has never been off of it (has not been meddled with).

Thanks,
Jim
 
Velocity factor of a 1/4 wave steel whip in air which is the dielectric (the main determining factor of propagation velocity, but type of conductor has effects too) ,lies between .95 and .99 of a wavelength. i ain't getting into that debate.

so here goes

at 100% velocity factor, 1 wavelength at 27.205 mhz = :

299792.458 (exact speed of light) / 27205.000 (exact frequency, unless your using a cb,where it will be as close as dammit) = 11.02m or 11.02 x 3.28 (converts from metres to feet, if you want metres from feet divide by 3.28) = 36.14feet
(or for you hardcore imperial guys 36 feet 1 3/4 inches approx.)

.95vf = 299792.458 / 27.205.000 = 11.02m or 36' 1 3/4" x .95 = 10.47m or 34 feet 4 inches approx. divide that by 4 for a 1/4 wave and you get 2.62m or 8 feet 7 inches give or take a few thou. x12 to give inches = 103.01inches, or 103 inches and a thou or 2.

.96vf = 299792.458 / 27.205.000 = 11.02m or 36' 1 3/4" x.96 = 10.57m or 34 feet 7 inches (approx) /4 = 2.64m or 8' 8"(roughly) x 12 = 104 inches.

.97vf = 299792.458 / 27.205.000 = 11.02m or 36' 1 3/4" x .97 = 10.68m or 35 feet 1/2" give or take a thou or two, /4 = 2.67m or 8' 9" x 12 = 105 inches or so.

.98vf 299792.458 / 27.205.000 = 11.02m or 36' 1 3/4" x .98 = 10.79m or 35 feet 3 3/4 inches or so. /4 = 2.69m = 8 ft 10" x 12 = 106 1/4 inches

so there you have it, no fancy antenna calculators, just a calculator as found on any windows pc and a bit of knowledge and you can instantly see that no matter what people agree the velocity factor of steel is in air, its not going to resonate on 27.205 Mhz if its only 102" Long

i ain't getting involved in vf of steel conductors in air, but my personal opinion is it lies around .97-.98 .


If i recall correctly US steel whips were originally 108",and this 102 inch whip notion came from the fact an antenna that has a fibreglasss coating as the dielectric and not bare, too the air, is where 102 inch whips originally came from.Which would indeed shorten the antenna for resonance, as fibreglass will have a different vf constant to air.

i may be wrong here but i believe 102 inch steel whips were originally designed for uk market which has a higher centre frequency than fcc frequency, and 96 inch whips came from coating uk designed antennas in fibreglass.

it may be sheer coincidence, but i doubt it, that fibreglass coated whips for uk market are 6 inches shorter than the steel ones, and by sheer coincidence 102 inch fibreglass whips are 6 inches shorter than the US steel ones, that used to be sold at 108" , is that sheer coincidence?

Draw your own conclusions.
Old thread, and some inaccurate information. Fiberglass whips are shorter than a 102 due to a lowered velocity factor caused by the fiberglass over the wire.
 
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I have six 102" whips and they're all close to 102.5" long to the bottom of the base, not including the threads.

Here is my Marconi 3x with 3 x 102" radials, and 1 x 102" radiator on a GPK hub from an A99, using a mirror mount L bracket, at 31' feet to the hub. There is an image of this setup in my profile image above.

View attachment 10350

The black circles are reports noted from my Autek VA1 thru the feed line noted in the report details. The squares are reports from my SWR meter in line at the radio. Take note of the nice control over the complex (Z) values accross the very nice bandwidth <2.0:1. The SWR bandwidth also reflects a nice flat match as well.
Are you the same Marconi I used to talk from Houston?
 
You use a 6-8 inch long aluminum bar that add's length and moves the antenna horizontally away from the vehicle. Assuming it is being mounted to a metal bumber on a truck this keeps it out of the way of the tail gate, gives you the extra length and keeps the SWR flat from 26-28 and still really good from 29 to 32Mhz . I think I was using 18 feet of LMR 240 or 400. This was used from 1991 to 1998 on 1986 Toyota 4Runner. It is hard to find a spring that is worth a darn most of them have cheap wire, cheap still and cheap other bits that rust.
 
Somebody throw me the GOLDEN SHOVEL!
Yes this is an old thread but, I am using a very heavy duty barrel spring my Dad bought back in 1967 and it still works perfectly. And, it is very strong. He ran it for yrs and yrs on his 1967 Chevrolet pickup truck and that spring and whip took a beating! As a matter of fact, I'm using his old 102 in whip also.
They talk just as good as the day he bought them.
 
It's a good idea to look at the braid inside the spring, most cheaper chrome plated springs have a low quality braid inside that connects the top and bottom.
Even the Hustler Stainless Steel spring uses a copper braid that overtime will deteriorate.
Especially if you live in a area were the are exposed to salt.
I chased a intermittent SWR problem one time and learned that lesson.

73
Jeff
 

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