Coax cable - 90db or 110db?

Barack Obama

I've a choice between double shielded cable which is 90db or triple shielded cable with is 110db. Which to get to run from my dish to Dreambox?

I thought the lower the db the better but what the hell do I know!!

Thanks

Barack Obama

Stumbled across an answer here - http://www.satshop.tv/Edision-Coax-Cable-120-dB-100-Meter

watty

makes little difference if it's proper foil + screen sat cable.

Bigger number in this case is better. My test gear only does about 80dB accurately. 90dB is fine if it's proper cable.

For any outdoor runs you want copper core + copper foil + copper braid. Aluminium foils etc are cheap rubbish.

That edison cable is a gimmick as it's not even proper foil but coated plastic film

Tony

Using db which is a relational measurement can be very confusing and I curse the day when someone decided to use it on consumer products. In terms of cable shielding the higher the better usually but it does not say what the reference point is so as a guide to the quality of the cable its little or no value. LNB's on the other hand give a noise figure so the lower the db figure the better although most are below .2 db now so quality usually comes in the form of well made construction.

Take a look at the approved cable list from the CAI, this is the best bench mark I know of.

watty

In fact the 0.2dB NF is mythical. Professional LNBs only quote about 0.7dB to 1dB which is fine. In olden days a 2dB or 3dB NF was an issue. What the consumer LNB maker doesn't say is if that is total NF, average NF for a transponder, worst or best NF for a transponder, The noise varies with frequency. Also in areas with weak and strong signal (Spain on 28E) the dynamic range and flatness is more important than absolute NF in dB. For about the last 4 or 5 years you can ignore the LNB NF. Other parameters are more important now. At the end of the day the next size up dish, not a choice of LNB is important for Rain margin.

All Marketing likes to sieze on a single important figure (which may only once have been important) such as amount of RAM, CPU clock, but avoid mentioning battery Life or screen resolution, both which can be worse than a good laptop 5 or even 8 years ago!

There are really rubbish coax with single cobweb braid that does less than 20dB screening, so makers love to quote huge values for screening but neglect to mention loss per metre at 2GHz, or crush resistance, or UV/Water resistance outdoors.

Any reputable satellite cable with decent braid and foil has no screening issue. More important is minimum bend, crush/kink resistance, durability on outdoor part of run to LNB and such.