Cat5 degraded video

[Sally2000]

I bought some ready made shotgun cables but chucked them out because I wasn't convinced of the quality or the likely voltage drop on the flimsy power cable.
I used RG59 for the signal and flat twin 3amp flex for the power. Both very cheap and simple to fit the plugs. Also with ready made cables and plugs fitted both ends, you need bigger holes to pull them through than with just the cut ends of cable. I fitted the PVR and power plugs after pulling the cables through into the loft.

Water cooling or soffit vents - sound too much trouble!
I used a 5 inch PC fan resting on a couple of pieces of wood, facing down a couple of inches above the DVR board and it's extremely effective. Powered directly from the DVR in place of the internal fan, and no permanent modification to the DVR. It's the volume of air flow that's important not its absolute temperature. If you can't find a redundant PC fan they are less than a fiver from Maplin. Job done.

 

[zuki79]

yallo, the cable i have used is

JSL 100% copper utp cat5e 24awg 100% bare solid copper conductor (well thats what it says on the spool)

i will try with the ready made cables, if they are pants, will get some rg59

cheers

 

[bernardgreen]

It's the volume of air flow that's important not its absolute temperature.

The absolute temperature is important. If the air is at 30°C then no matter how much air is blown onto the heatsink(s) they will never go below 30°C

The temperature difference between heat sink(s) and air determines how much heat can be dissipated.

 

[Sally2000]

Yes Bernard but we are not trying to cool the heatsink to 30 degrees. We are trying to extract the maximum amount of heat from the heatsink, to stop it going above a safe working temperature of say 60 or 70.

The amount of heat that any given heatsink can transfer depends directly upon the temperature difference between its surface and the surrounding air. This is a constant for any given heatsink.

Consider a heatsink that is designed to maintain a temperature difference of 30 degrees above ambient for a given power input.

If the air around the heatsink is static or only moving slowly, it will be heated up by the heatsink to something approaching the heatsink's own temperature. The ambient air might be 30 but the heatsink will be seeing surrounding air at 50 or 60, allowing the heatsink to get to 80 or 90.

By hitting the heatsink with a continuous flow of 30 degree air, it will always be seeing a surrounding 30 and will therefore stabilise at 60 degrees.

Think about the standard air cooling arrangement on a computer CPU. The cooling fins alone are not sufficient - it needs a fan to take its heated air away and keep its little microclimate down to a safe level.

 

[bernardgreen]

Sally. What you say is correct.

But also the cooler the heat sink the cooler the innards of the integrated circuits. Cooler integrated circuits last longer and can be ( over ) clocked at higher rates.

The die(s) inside the processor will be much hotter than the heat sink. How much hotter will depend on the thermal resistances between the die(s) and the heat sink.

die = the substrate on and in which the transistors and other components of the processor are created.

So using the coolest possible air to cool the heat sink is worth while and will probably significantly extend the life span of the devices.

 

[Sally2000]

But also the cooler the heat sink the cooler the innards of the integrated circuits.

Of course. That's why the heatsink is there!!!