There are two issues with wire length. Voltage drop and noise pickup. Of these two voltage drop is probably the most significant. When using high power settings, I am not just referring to Philips extenders, but to any driver of IR emitters, the primary question is what voltage are they running at. Xantech uses 12 volts which gives them lots of voltage headroom, i.e can tolerate significant drops. Many drivers use 5 volts (TTL) and some are now starting to use 3.3 volts (CMOS). The lower the driver voltage the less tolerance to voltage drop over the cable.
I have never seen a noise problem. If you had to reverse an IR emitter it had nothing to do with line length it was just backwards. I have run several hundreds of feet with 12 volt drivers with no issues over 22-24 gauge wire. I have run about 50 feet with a 3.3 volt driver, and I am sure a 5 volt driver is somewhere in the middle, closer to the 3.3 volt experience.
You can generally increase the power at the driver. This is normally done by increasing the current in the line by lowering the series current limiting resistor built into the driver circuitry. Power loss is by the square of the current times the resistance. Voltage drop over a given length of wire is current x resistance per foot of wire x length of wire.
The bottom line is I always try and use a xantech amplified connecting block which uses 12 volts as the driving voltage and supplies more than enough power for runs that will exceed anything in a home.
In all cases where I was getting poor results it was things like, emitter not over receiver, emitter too powerful and swamped receiver (Receiver AGC could not handle the load), Too much interfering light in the IR spectrum; a mismatch on the wired input of some component. a bad or marginal IR pattern. If the pattern is proper it's duration should not be a determinant over longer wires
IR is not magic. It is at times frustrating, but when all is said is done it just has to be understood for what it is and how it works.
Last edited by Barry Gordon
on January 14, 2009 00:40.