These cabling issues need to be uncovered

It did not, however, cover a particular aspect of the solid/stranded conductor business, an issue that needs to be laid to rest.

Other concerns also need to be covered. RG59 is very common in the security industry. It is a cable whose centre conductor is copper coated steel. There is a little demand for solid copper conductor from people who assume that this will give them better results with less loss – an assumption which is absolute nonsense.

The fact is that only the surface of the conductor carries the signal and this is known as the ‘skin effect’. There is, therefore, no difference between solid copper and copper-clad steel in terms of conductivity. If an advantage needs to be identified then it would be the DC loop resistance which is calculated by taking the sum of resistance between the inner and the outer conductor, the outer being the screen.

The percentage coverage or density of the screen is important in CCTV and by examination it is soon evident that there is a massive variation between RG59 options. This is due to the incredibly high price of copper which can be reduced by economy in the screen/braid density.

If you care to compare the attenuation between RG59 – which usually has a conductor diameter of 0.80mm – with a quality 1.00mm conductor TV distribution coaxial, you will find that RG59 is only half as good as the latter, but the coaxial is not twice as expensive. This is food for thought particularly when you consider the usual twin screening of the TV coaxial, which should be an approved type. Apart from performance, new legislation comes into effect in July 2005 which is known as the RoHS directive (EU2002/05/EG). This stands for ‘Reduction of hazardous substances’ and aims to ban impure PVC compounds which could contain lead, cadmium, mercury etc. Installers should seek evidence now from their suppliers of any PVC sheathed cables that the compound used in manufacture is pure.

LSF compound is another anomaly. You can ask for it – but do you get what you ordered? How do you know? Do you ask for certification? Your duty of care obligations suggest that you should. This also applies to LSOH compound.

Another thing that disgusts me is the fire tests done on cables. Ok, so your cables pass the tests and you receive a certificate which has no date of expiry on it. Therefore your cable can be sold as a qualified product indefinitely. This is dangerous. At least annual random re-checks should be done, called from batches that manufacturers must record and hold a few drums of in stock.

Quite frankly, controls throughout the cable industry are not brilliant and honest, reassuring information is obviously lacking. Surely the longevity and performance of a system is more important than saving a few pence by cutting corners on cable quality. Make sure you use proprietory cables and don’t shop on price alone.

Brian Taylor, MD, Qing Cables, Malmesbury Road, Kingsditch Ind Est, Cheltenham GL51 9PL