- 30th October 2006, 22:45 #1

- Join Date
- Jul 2005
- Location
- Indonesia
- Posts
- 79
- Helped
- 0 / 0
- Points
- 1,791
- Level
- 9

## coaxial cable impedance

Hi all,

I need a coaxial cable with impedance 50 Ohm. After looking at my local electronic store there is only 75 Ohm Coaxial cable. Is there any way to converting 75 Ohm Coaxial Cable into 50 Coaxial Cable ?? perhaps by adding some circuit?? Please help me. Thanks

Regards,

Elits

- 30th October 2006, 23:38 #2

- Join Date
- Jul 2002
- Location
- Middle Earth
- Posts
- 4,632
- Helped
- 478 / 478
- Points
- 37,801
- Level
- 47

## 50 ohm to 75 ohm converter

A transformer, minimum loss attenuator, or LC network will work. If you do not know how to design these, you would be better off buying 50 ohm cable via the internet.

Your application might work with 75 ohm cable.

- 30th October 2006, 23:38

- 31st October 2006, 01:02 #3

- Join Date
- Oct 2004
- Location
- West Coast
- Posts
- 7,943
- Helped
- 2302 / 2302
- Points
- 160,151
- Level
- 95

## cable impedance

Code:Impedance matching network usign resistors The matching network shown below can be used to match two unequal impedances, provided that Z1 is grater than Z2. ____ ----|____|---+--------- R1 | | | Z1 | | R2 Z2 |_| | -------------+---------- The resistor for this circuit can be calxulated using the following equations: R1 = Z1 - Z2*R2 / (Z2+R2) R2 = Z2 * sqrt(Z1) / (Z1-Z2) The table below will show some precalculated values for some most common interfacing situations: Z1 Z2 R1 R2 Attenuation (ohm) (ohm) (ohm) (ohm) (dB) 75 50 42,3 82,5 5,7 150 50 121 61,9 9,9 300 50 274 51,1 13,4 150 75 110 110 7,6 300 75 243 82.5 11,4

IanP

- 31st October 2006, 01:02

- 31st October 2006, 04:23 #4

- Join Date
- Apr 2002
- Location
- USA
- Posts
- 3,944
- Helped
- 649 / 649
- Points
- 40,208
- Level
- 49

## 75 ohm to 50 ohm balun

A balun converts between balanced and unbalanced, hence it's name.

- 31st October 2006, 04:23

- 31st October 2006, 05:56 #5

- Join Date
- Jun 2006
- Location
- Phils
- Posts
- 69
- Helped
- 7 / 7
- Points
- 1,439
- Level
- 8

## impedance matching coax

yeah u r right...

- 15th May 2007, 08:31 #6
## 50 to 75 ohm converter

You can convert the 75 Ohm coaxial cable to 50 ohm coaxial cable or vice versa by adding a Balun (Balanced Unbalanced) having impedance =sqaureroot of(75*50)

Or in other way you can use a transformer or a parallel resistor circuit .

- 26th March 2009, 10:47 #7
## 75 ohm to 50 ohm converter

may i know what kind of adapter to used to convert coaxial cable impedance from 50ohm to 75 ohm

- 27th March 2009, 03:41 #8

- Join Date
- Nov 2004
- Location
- Tamilnadu
- Posts
- 657
- Helped
- 36 / 36
- Points
- 5,970
- Level
- 18

## 50 ohm to 75 ohm balun

balun trensfomer or quater wave tranformer transmission line can be used for impedance matching

- 28th March 2009, 00:01 #9

- Join Date
- Mar 2005
- Location
- USA
- Posts
- 1,323
- Helped
- 272 / 272
- Points
- 11,332
- Level
- 25

## 50 to 75 ohm balun

Elits,

As IanP stated, a simple Resistor network can be used. However, this method results in power loss. A matching transformer will provide an impedance match with (theoretically) no loss. The turns ratio will be the square root of the impedance ratio. In your case, Sqrt(75/50) = 1.224. Others have mentioned the use of a balun. This would work, but is overly complex. Since both coaxial cables are unbalanced, the balanced - unbalanced feature provides no useful function. You probably won't be able to find a commercially available balun for 75:50 conversion.

Regards,

Kral

- 13th April 2009, 09:59 #10

- Join Date
- Nov 2003
- Posts
- 16
- Helped
- 1 / 1
- Points
- 1,835
- Level
- 9

## convert 75 ohm to 50 ohm

See if you can find a 50 ohm to 75 ohm matching transformer (I think it's quite common and avaliable in hardware stores).

Regards

- 14th April 2009, 06:43 #11
## 75 to 50 ohm balun

I guess a quarter wave transformer will do the job....the impedance of the tansformer line would be sqrt(75*50)

- 29th July 2010, 22:03 #12

- Join Date
- May 2002
- Location
- España
- Posts
- 17
- Helped
- 2 / 2
- Points
- 2,490
- Level
- 11

## Re: How to Converting coaxial cable Impedance from 75 to 50

Hi:

In TEST equipment if the outputs are set to 50ohm just put a 25 Ohm resistor in series and calculate the insertion loss. (Method recommended by Marconi Instruments)

Regards

#### LinkBacks (?)

- 17th October 2011, 11:21