Ham Radio Coaxial Cable Power Handling and Loss Specifications - Velocity Factors of Feedlines

7/28/2019 Ham Radio Coaxial Cable Power Handling and Loss Specifications - Velocity Factors of Feedlines

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Coaxial Cable Characteristics and DataUsed in Amateur Radio Stations

It is of importance when making decisions about getting the right coax for your Ham Station

to understand that there are trade-offs that have to be considered between transmitter

power, antenna gain, coax loss, erp, and your total Ham Station system performance.

Your bank account may also enter into the equation like most Hams.

The db differences in gains or losses on transmit and receive between the choices

available to you are the important issue.

A difference of 3 db either way will not be apparent to the stations that you are

communicating with on the other end; around the block or around the world. They won't

hear or see (on the S meter) any difference if you run your transmitter at 50 watts instead

of its maximum 100 watt output power as an example.

This is a difference of about 3db! The same ratio holds true comparing 500 watts with

1000 watts!

Now take this same analogy and apply it to coax.

Here is an example:

Your present coax is 100 feet long and has a loss of 3db per 100 feet.You change it to the

same length, 100 feet, using a more expensive coax that has only about .1db loss per 100

feet.(Very Expensive Stuff!)
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This is about a 3db increase in signal strength to the antenna that you were loosing in the

old coax.

The station on the other end usually won't know the difference, and usually, neither will

your receiver!

A difference of 3 db or less between two antennas, two types of coax, or two station

configurations is usually not sufficient to justify the higher costs of the more expensive,

lower loss, coaxial cable unless you are a perfectionist with lots of money.

However, a difference of 6 db may well justify the more expensive approach with the

higher quality coax or antenna setup.

Remember, if you can't increase your transmit or receive signal by at least 5 or 6 db or

more, if may not be worth the effort and expense.

The tables below should help you decide what if any coax changes you need to make.

Color Key:

Green shade 50 - 52 ohm

Coax dB Loss per 100 Feet using common coax types:

dB Loss / 100 feet

Frequency Mhz

Cable Type

1.0 10 50 100 200 400 900 1000 3000 5000

6A, 212 .26 .83 1.9 2.7 4.1 5.9 6.5 9.8 23.0 32.0

8 MINI, 8X 1.1 2.5 3.8 5.4 7.9 8.8 13.0 26.0

LMR -240 .24 .76 1.7 2.4 3.4 4.9 7.5 7.9 14.2 18.7

8, 8A, 10A, 213 (RG8/8A hard to find

).15 .55 1.3 1.9 2.7 4.1 7.5 8.0 16.0 27.0

9913, 9086, 9096 0.9 1.4 1.8 2.6 4.2 4.5 13.0

4XL8IIA, FLEXI 4XL 0.9 1.4 1.8 2.6 4.2 4.5 13.0

LMR-400 .9 1.2 2.5 4.1 4.3
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LMR-500 .7 1.0 2.0 3.2 3.4

LMR-600 .6 .8 1.4 2.5 2.7

8214 .60 1.2 1.7 2.7 4.2 7.8 14.2 22.0

9095 1.0 1.8 2.6 3.8 6.0 7.5

9, 9A, 9B, 214 .21 .66 1.5 2.3 3.3 5.0 7.8 8.8 18.0 27.0

11,11A,12,12A,13,13A, 216 .19 .66 1.6 2.3 3.3 4.8 7.8 16.5 26.5

14, 14A, 217 .12 .41 1.0 1.4 2.0 3.1 5.5 12.4 19.0

17,17A,18,18A, 218, 219 .06 .24 .62 .95 1.5 2.4 4.4 9.5 15.3

55B, 223 .30 1.2 3.2 4.8 7.0 10.0 14.3 16.5 30.5 46.0

58 .33 1.2 3.1 4.6 6.9 10.5 14.5 17.5 37.5 60.0

58A, 58C .44 1.4 3.3 4.9 7.4 12.0 20.0 24.0 54.0 83.0

59, 59B .33 1.1 2.4 3.4 4.9 7.0 11.0 12.0 26.5 42.0

62, 62A, 71A, 71B .25 .85 1.9 2.7 3.8 5.3 8.3 8.7 18.5 30.0

62B .31 .90 2.0 2.9 4.2 6.2 11.0 24.0 38.0

141,141A, 400, 142, 142A .30 .90 2.1 3.3 4.7 6.9 13.0 26.0 40.0

174 2.3 3.9 6.6 8.9 12.0 17.5 28.2 30.0 64.0 99.0

178B,196A 2.6 5.6 10.5 14.0 19.0 28.0 46.0 85.0 100

188A, 316 3.1 6.0 9.6 11.4 14.2 16.7 31.0 60.0 82.0

179B 3.0 5.3 8.5 10.0 12.5 16.0 24.0 44.0 64.0393, 235 .6 1.4 2.1 3.1 4.5 7.5 14.0 21.0

402 1.2 2.7 3.9 5.5 8.0 13.0 26.0 26.0

405 22.0

LDF4-50A .06 .21 .47 .68 .98 1.4 2.2 2.3 4.3 5.9

LDF5-50A .03 .11 .25 .36 .53 .78 1.2 1.4 2.5 3.5

Note: These tables are typical specifications for comparison only.Values may not be exactly as quoted by a specific mfg.


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Power Handling Characteristics of Coax

Power Handling Vs Mhz

Coax type1.0 10 50 100 200 400 900 1000

55, 6A, 212 4000 1500 800 550 360 250 150

8 MINI, 8X 4000 1500 800 550 360 250 150

8, 8A,10A, 213 11000 3500 1500 975 685 450 230

9913, 9086, 9096 3500 1500 975 685 450 230

4XL8IIA, FLEXI 4XL 3500 1500 975 685 450 230

9095 11000 3500 1500 975 685 450 230

9, 9A, 9B, 214 9000 2700 1120 780 550 360 200

11,11A,12,12A,13,13A, 216

8000 2500 1000 690 490 340 200

14,14A, 217 20000 6000 2400 1600 1000 680 380

17,17A,18,18A,

218, 21950000 14000 5400 3600 2300 1400 780

55B, 223 5600 1700 700 480 320 215 120

58 3500 1000 450 300 200 135 80

58A, 58C 3200 1000 425 290 190 105 60

59, 59B 3900 1200 540 270 270 185 110

62, 62A, 71A, 71B 4500 1400 630 440 320 230 140

62B 3800 1350 600 410 285 195 110

141,141A, 400

142,142A19000 9000 3500 2400 1600 1100 650

174 1000 350 160 80 80 60 35178B,196A 1300 640 330 240 180 120 75


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188A, 316 1500 770 480 400 325 275 150

179B 3000 1400 750 480 420 320 190

393, 235 25000 9500 6300 4300 2800 1700

402 9000 3500 2400 1600 1100 650

405 130LDF4-50A 19000 6100 2600 1880 1310 906 563 551

LDF5-50A 44000 7700 7740 5380 3720 2550 1620 1520

LMR-400 Power handling = 2100 watts


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14 2512

15 3162

16 3981

17 5112

18 6310

19 794320 10,000

Note that these numbers above assume no loss in feedline or antenna and used the CSG Calculator)

You will alw ays have some bit of loss in your feedline but this calculator is considering only power and antenna

gain.

Example: Coax loss

Using 100 watts output from transmitter and assuming your old coax had 3db loss, with no

changes to antenna system except replacing your old coax and also assuming the new

coax has 0db loss, the ERP of the antenna system would increase by 3db and would be

199 watts.This is a 3db gain achieved by the new coax.

Example: Antenna Gain

You use an antenna that has 6dbd gain vs the old one that had 0dbd gain.

What effect does this have on your erp?

By using the chart above, you will see that with 100 watts at the antenna feedpoint, your

effective radiated power would be 398 watts!

Remember, you have to achieve about 6db gain or loss to to make much difference on the

air to the other station on receive.

Using this table, you should see that with every 3db increase or decrease, your effectively doubling the ERP orcutting it in half.Your feedline will always have some loss so in calculating your total antenna system loss, always subtract the totalloss of your feedline from your antenna gain.

Example:

Your antenna gain is 6dbd.
http://www.csgnetwork.com/antennaecalc.html


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Your coax loss is 2 db per 100 feet as stated by the mfg. You use 50 feet.

Your total system gain or loss would be:

Antenna gain 6dbd - loss of 1db(50 feet) = total gain (or loss) = 6 - 1 = 5 db

Another example:

You add 100 feet of coax with 3 db loss at your operating frequency to an antenna with 0 dbd gain.

So 0db - 3db = -3db loss in signal strength...you just cut your signal in half.

Velocity Factor of Propagation Through Coaxial Cable

The velocity factor is the speed at which an RF signal travels through a material compared

to the speed the same signal travels through a vacuum. The velocity of propagation is

inversely proportional to the dielectric constant.Lowering the constant increases the velocity.

Generally, the higher the velocity factor, the lower the loss through a coaxial cable.

"Typical" Velocity Factor of Coaxial Cable by type

VF% Transmission line type

95 ladder line

82 twin-lead79 coaxial cable / foam dielectric

75 RG-6 and RG-8 coax (thick)

66 RG-58 and RG-59 coax (thin)

General Rules for Coaxial Cable

D = diameter of insulation under the shield


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d = diameter of inner conductor.

Velocity Factor, Velocity of Propagation, Vp

The higher the velocity factor, the lower the loss through the cable.

Raising the D/d has no effect on Vp

Raising the dielectric constant lowers Vp

Capacitance

Raising the D/d ratio lowers capacitance

Raising the dielectric constant raises capacitance

Impedance Raising the D/d radio raises impedance

Raising the dielectric constant lowers impedance

Attenuation or Loss

Raising the D/d ratio lowers attenuation

Raising the dielectric constant raises attenuation

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Ham Radio Coaxial Cable Power Handling and Loss Specifications - Velocity Factors of Feedlines

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