J Pole Antenna question

[davidbroxson]

I'm new at building antenna's, so I decided to try and build a j pole for 145.49 a repeater I like to stay on. There's plenty of instruction on the internet to follow but I'm running into a problem. The measurements are in meters, so I convert that into inches( using an online converter), example 1.47 M = 57.87". How do I convert the .87 to a measurement I can read on a tape measure? I've looked on the internet for converts that will give me fractions (1/8,1/4,3/8,1/2..and so on) but can't find any. I don't know if the cuts in the cooper pipe have to be that accurate anyway, but I'd like to get it close as possible to the instructions. Any internet link or formula would be greatly appreciated. Thanks guys

 

[W6KRU]

9/10" should be plenty close.

 

[kny2xb]

7/8" = .875"

That's probably close enough to what you're looking for. I doubt that .005" off is going to give you a high SWR.

update: I just figured how to convert fractions and decimals on my TI calculator. It is 7/8"

 

[AlmostHandy]

For future reference, you can use this link.

 

[burner50]

A plumber's special?

I have built a few, they're great!!! The hardest part is attaching the feedline in the right point to get the best SWR.

I've also built an aluminum dual band j-pole... That thing is bulletproof. If toppled 40' when my mast came down and still works like a charm.

 

[zz0468]

Why not just get a tape measure that has a metric scale? It's phenomenally easy to understand.

 

[AK9R]

How do I convert the .87 to a measurement I can read on a tape measure?

At the risk of sounding like an old fart, what are they teaching you kids in school these days?

Your metric to inches conversion leaves you with 57.87 inches. Taking just the decimal portion of that number, multiply 0.87 times 16. The result is 13.92. Round that off to 14. OK, you now know that 0.87 inches is 14/16 inches, but that isn't a commonly-used fraction. If you divide both the numerator and denominator of that fraction by 2 and you get 7/8 inches. So, the measurement you'll look for on your tape measure is 57 and 7/8 inches.

Or, you can just work out a table of decimal equivalents for common fractions:

1/16 = 0.0625
1/8 = 0.1250
3/16 = 0.1875
1/4 = 0.2500
5/16 = 0.3125
3/8 = 0.3750
7/16 = 0.4375
1/2 = 0.5000
9/16 = 0.5625
5/8 = 0.6250
11/16 = 0.6875
3/4 = 0.7500
13/16 = 0.8125
7/8 = 0.8750
15/16 = 0.9375

 

[SCPD]

Plug and Play

I'm new at building antenna's, so I decided to try and build a j pole for 145.49 a repeater I like to stay on. There's plenty of instruction on the internet to follow but I'm running into a problem. The measurements are in meters, so I convert that into inches( using an online converter), example 1.47 M = 57.87". How do I convert the .87 to a measurement I can read on a tape measure? I've looked on the internet for converts that will give me fractions (1/8,1/4,3/8,1/2..and so on) but can't find any. I don't know if the cuts in the cooper pipe have to be that accurate anyway, but I'd like to get it close as possible to the instructions. Any internet link or formula would be greatly appreciated. Thanks guys

J POLE ANTENNA DESIGN CALCULATOR by K4ABT

 

[poltergeisty]

The keyword is of. Of what part? .87 of a particular unit of measure. In this case inches and in 1/16ths. So .87 x 16 gives you the result. As stated it's a uncommon fraction so you must divide each by 2 to split in half.

You do know that Google, being the MASSIVE search engine it is, is also a calculator and converter???

Just Google .87*16 and it will give the result. Try other equations and conversions etc...Like 32 degrees Celsius to F.

If you have a vernier caliper, on the back they usally have a cheat sheet for decimal to fraction equivalents.