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cwm1276

join:2004-01-16
Stillman Valley, IL
reply to cwm1276

Re: [DTA] DTA pixelation?

So why would this just start in the last month, heat is the only thing that has changed.

What everyone said before that is the same old stuff that is always said and it worked for years prior. So I can't believe the root of the problem is a splitter. Plus if it is the outside line, why would the DTA with the shortest run in the house have the problem and not ones further away?

A low signal I can believe and I did not know signal could be affected by heat.

So what happens if the tech comes out when it is cooler, and the threshold has not been crossed?

I am trying understand why this could occur as I won't be able to be home when the tech is out.


gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
splitters, chewed cable, long stinger shorting out, braid on center conductor, voltage on the coax, water in the cable, corrosion, mandrel of a barrel spread too wide, dta is bad, etc....list goes on and on....and those are just isolated outlet issues...

signal is affect by heat due to metal being affect by heat.....optimum cable temperature is 68*F, once you get over that you start introducing thermal noise onto the line.
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I'm better than you!


THZNDUP
Deorum Offensa Diis Curae
Premium
join:2003-09-18
Lard
kudos:2
reply to cwm1276
Here is a simple(? ) explanation of temp effect on coaxial cable attenuation.

Coax cable attenuation/loss will change 0.1% per degree F. change.

The attenuation is usually spec'd by the vendors at 68deg F. So a cable having a 1.43db loss/100ft @500mhz at 68deg F will have a loss of 1.47db/100ft @500mhz at 99deg F.

This is just at air temp. A more realistic upper temp would be 120-150 deg F since the OH cable is in the direct sunlight. Using 128deg F, that same 100ft piece of cable now has 1.51db loss @500mhz.

Still not so much of a change right? Remember there are probably many miles of cable between you and the source. Using 2 miles, the total cable loss from the source to you goes from 151db @500mhz up to 159db @500mhz. That is an 8db decrease in available signal. Could definitely be enough to affect marginal levels.

The above is real simplistic just to show what the temp can do. Actual plant will have many more variables.

As far as only the shortest outlet having a problem when fed from a particular port on the splitter? [shrug] Cables and splitters/ports do go 'bad'. Let an onsite tech with a meter figure out what to do.

BTW, would someone double check the math......
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one should not increase, beyond what is necessary, the number of entities required to explain anything

cwm1276

join:2004-01-16
Stillman Valley, IL
Thanks THZNDUP. That is what I wanted to know. You were able to explain it clearly. It is the hottest summer in a few years.

I never said I was not going to call for a tech, but I don't want to call and have them tell me nothing is wrong, just because it is working while they are here.


THZNDUP
Deorum Offensa Diis Curae
Premium
join:2003-09-18
Lard
kudos:2
Request a later appointment window when it should be happening. Check the weather forecast for that day/time as well.........
--
one should not increase, beyond what is necessary, the number of entities required to explain anything