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How to measure cable signal strength with test meter?

Regular Visitor

How to measure cable signal strength with test meter?

I have a new cable signal strength meter and I'm hoping to get some advice on its use, since the instructions are sparse and in Chenglish.  I have a complex structured video wiring arrangement in my home, and I'm having trouble getting the proper signal to some locations.  This new tester can test both digital and analog, and can test signal level by channel (both audio and video), carrier to noise ratio, and mains voltage.  It's clear enough on how to make the measurements, but I'm a reasonably technical homeowner rather than a cable tech, so I don't know what to measure.  The cable signal goes through several splitters, and amplifiers in some places, and my goal is to measure the signal at different points in order to insure that I'm delivering the proper signal levels at each node.

 

Is there anyone out there who could offer some tips on what to measure with this meter?  I would assume signal level is key, but what about the S/N ratio and mains voltage?  What does variation in those tell me?  I'd appreciate any help you could provide, thanks.

Jeff

Official Employee

Re: How to measure cable signal strength with test meter?


Jeffreypatton11 wrote:

I have a new cable signal strength meter and I'm hoping to get some advice on its use, since the instructions are sparse and in Chenglish.  I have a complex structured video wiring arrangement in my home, and I'm having trouble getting the proper signal to some locations.  This new tester can test both digital and analog, and can test signal level by channel (both audio and video), carrier to noise ratio, and mains voltage.  It's clear enough on how to make the measurements, but I'm a reasonably technical homeowner rather than a cable tech, so I don't know what to measure.  The cable signal goes through several splitters, and amplifiers in some places, and my goal is to measure the signal at different points in order to insure that I'm delivering the proper signal levels at each node.

 

Is there anyone out there who could offer some tips on what to measure with this meter?  I would assume signal level is key, but what about the S/N ratio and mains voltage?  What does variation in those tell me?  I'd appreciate any help you could provide, thanks.

Jeff


Without knowing what you are starting with outside your house, you won't know what to compare it to on the inside.  You would also need to know all the different frequencies of channels used in your market ( only techs in your market would know that), what channel(s) are   docsis channels etc. With multiple amps and splitters, there's nothing constant either and harder to account for any signal difference/gain or loss. Applaud you for trying but if you're having issues a tech visit with a tech and their meter would have probably been the better route.

 

Regular Visitor

Re: How to measure cable signal strength with test meter?

Thanks for your note.  Let me elaborate a little - My plan is to test the signal at the comcast junction box where the cable run to my home begins, then test the signal where the long cable run hits the grounding block and enters my house, and again at the distribution panel and after the amplifiers, etc., as well as at the room nodes where I'm either experiencing a signal, or not getting one.  I just need to learn which signals to test.

 

It would be great to have a Comcast tech out to do all that, but they don't have the time to troubleshoot my structured wiring setup, and I couldn't afford to pay them if they did.

 

So, could you give me some tips about which tests to perform that would be most diagnostic, in terms of signal strength and signal quality?  I understand that I would need to test several frequencies, but it's not necessary to test them all, is it, in order to determine that I'm getting decent signal strength and quality all the way through the wiring system to a room node?

 

Anyway, I'd appreciate any tips you or anyone could offer in helping me learn which tests to run.

Jeff

Silver Problem Solver

Re: How to measure cable signal strength with test meter?

I would be easier to just hook up a TV and look at the picture. Try many channels.

New Poster

Re: How to measure cable signal strength with test meter?

Cable is measured in decibels (db). You will not have access to the ped (pedistal) which supplies your home. The measurement coming to your home should be at least 14db higher side about 18db. Under 14db is low for the main feed and may want to involve Comcast tech as you may have an issue only they can fix. Think of cable signal as someone talking to you. If they are whispering (low db) its bad, normal talking (12-15db) is good, yelling (15-20db). !!! Keep all junctions as clean and simple as you can !!!

Now when it comes to splitters and amplifiers...

AMPLIFIER - Should be used on the main line in before any splitters (except a pass through splitter for any modems). You DO NOT want to amplify low signal or after several splitters. (Amplifying whispering is still hard to hear) You should aim to have 12-16db at every access point. This is all basic math and you shouldn't get virtually any loss of signal unless you are going over 100ft stretches (I believe it was .5db every 100ft). If you are getting signal loss, it is either a bad connector or bad line. Make sure you measure the signal going in and out of the splitter/amplifiers and use basic math skills to make sure your gains/losses are on point. If it falls outside of the proper range, replace the device.

SPLITTERS - Use these strategically to pad any over signal issues. Keep in mind, the more junctions (amplifiers, splitters, barrell connectors) used will make it harder for the signal to report back to comcast (lag in cable boxes, slower internet response, upload internet speed) Be careful of the splitter types you use. Once again, this is just pure math. If you are starting with 20db and you use a 2 way splitter, you will get a loss of 3.5db on each split so you should expect 16.5db coming out of the splitter.

These digital boxes are very finicky and should have a minimum of 12db, any less could cause service issues.

Try to get a clean line (unamplified) to any cable modems. Use a passthrough splitter which will have NO LOSS (to modem) on one split and extra loss on the other(s) While amplifiers are useful, they will also amplify noise back to comcast so DO NOT USE AMPLIFIER UNLESS YOU HAVE TO.

Hope this helps.

Former cable/internet technician with Comcast.
Official Employee

Re: How to measure cable signal strength with test meter?

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