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Guest Message by DevFuse

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Loosing satillite signal at night HELP


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24 replies to this topic

#21 OFFLINE   P Smith

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Posted 19 November 2012 - 09:55 AM

most likely, it's bad solder/solder crack
either case - extensive long testing plus expensive repair or easy replacement

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#22 OFFLINE   AntAltMike

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Posted 19 November 2012 - 10:15 AM

One of the "funkier" temperature related LNB problems was back when the Phase 3 LNBs were first introduced, and some of them, when the temperature got down to near zero degrees, would leak through their 22KHz tone signals such that, if any one receiver called for a Sat B or Sat C transponder, all four ports would be toggled to Satellite B/C.

#23 OFFLINE   P Smith

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Posted 19 November 2012 - 11:30 AM

very funky behavior ... that's bad if China plants doesn't have environmental cameras to test LNBs at such cold temp

#24 OFFLINE   TomCat

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Posted 19 November 2012 - 08:25 PM

... I have had spools of RG-6 in which, on short cut jumper wires with lengths or one foot long or so, I can easily push the center conductor in with my fingertip.

The good stuff will never do that. Throw the cheap stuff away.

Actually, the effect of the shrinkage differential that takes place due to temperature cycles is common enough and significant enough to have its own term, "suck outs". One commercial antenna company I briefly worked for called them "creepers" It was easy to find contemporary use of the term "suck outs" using google, but "creeper" didn't come up on the first twenty results, so I don't know if other installers ever embraced that term or not.
...

In my extensive professional experience "suck-out" refers to two things, but neither of them have to do with a differential between both ends of a section of cable, or relative migration of a CC in one direction but not back in the other direction over time.

When it refers to the center-conductor "sucking out" of where it belongs, that is a differential not between one end and the other, but between the CC and the shield. The shield is typically crunched down into a connector at both ends, and when temps drop, the entire length of cable may become shorter, meaning that the CC becomes shorter along with and in concert with the shield.

But since the shield is crunched down, it still makes contact with the housing on both ends. Under tension, but still connected. The CC is not connected to anything on either end for RG-6, so while it contracts in concert with the shield, it can pull out of the location it needs to be, breaking contact. But there is really nothing that could cause it to suck out of one end and not the other unless it was cut shorter on one end, and when temps return the CC expands to the same postion it had originally.

If this other theory of yours did hold any credence, the farther away from the center of the span, the more the CC would move relative to the shield, but in opposite directions depending upon which side of the center of the span we are talking about. There would also be no relative movement at all in the physical center of the span. And there is no reason it would not "creep" back to where it crept from either; there is no magical longitudinal force operating in just one direction along the length of the CC that is not also operating equally upon the dielctric, shield, and jacket as well.

For hard-line cable this can happen at one end only because one end of the CC is mistakenly not always crunched down while the other correctly is (typically it mates using a set-screw rather than floating against spring fingers like RG-6), which is why there are expansion loops in every span. And hard-line cable CCs are indeed bound to the foam dielectic to prevent this, which is why you might see more issues with air dielectric or with dilectric spacers than with full foam dielectric. This problem accounts for a lot of the cable outages that happen when temps drop to 20 below (and coincidentally exactly when you want to stay in and watch TV), and is why full foam is better in cold or harsh climates.

But just like with RG-6, when temps go back up, the CC goes right back to its original position relative to the shield. Nothing would make the shield migrate relatively north over time while the CC migrates relatively south; that's completely ludicrous and against all known laws of physics, as well as takes into account all possible forces.

The other "suck out" refers to a notched out part of a frequency band. But none of these could account for the CC migrating independently to one end, unless maybe you are using magic cheap cable procured off the back of a truck from the Russian mafia. The "gravity" argument seems to not really hold any water either, and even if it did would not apply to a typical home DBS installation.
It's usually safe to talk honestly and openly with people because they typically are not really listening anyway.

#25 OFFLINE   P Smith

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Posted 19 November 2012 - 10:03 PM

If you are an engineer, you would easy calculate shrinking of plastic , shield and insulating and center copper conductor between say 0 F and 140 F. For max length 120'.




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