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Regarding Cable Loss - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


 Post subject: Regarding Cable Loss
Posted: Thu Jun 16, 2005 11:40 pm 
Hi all,

I had a question regarding measuring cable loss, How to connect the equipments to calculate the cable loss from one end of the cable to another if you have a Signal Generator, Spectrum Analyser and Power meter. How should I connect the cable to and what are the parameters Should I change to know the cable loss.

Thanks in Advance!

Dreamer


 
  
 
 Post subject:
Posted: Fri Jun 24, 2005 11:15 am 
 
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Joined: Sun Aug 03, 2003 2:02 pm
Posts: 653
Location: Erie, PA
Greetings Dreamer:

If all you need to measure is the loss of the cable, then all you need is the spectrum analyzer (SA)* and, if both ends of the cable cannot reach the SA from the same place, a signal generator (SG).

* If the SA has a generator output built in.

If both ends of the cable can reach the SA and it has a built-in generator, then simply calibrate the SA and place the two cable ends between the In/Out ports and measure directly.

Otherwise, measure the output of the signal generator and either se tthe S/A to give a relative measurement from there, or note the power level to do the math yourself. Then, connect one end of the cable to the SA input and the other to the SG.

A good thing to do is place an attenuator (at least 3 dB, preferably 10 dB) at the output of the SG both when taking a reference reading and when connection the SG to the cable. Doing so helps minimize any error that might be caused due to impedance mismatch between the SG and the cable. When measuring down to tenths of a dB, it can make a noticeable difference in the measurement.

In both cases, be sure that the SG is injecting enough power that the SA can measure easily after passing through the attenuator and cable loss.


- Kirt Blattenberger :smt024




Posted  11/12/2012
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