NICE AND EASY: What if you use the wrong impedance cable?

Look we have all been there. You need a cable quickly and you have the wrong one. Or, you’re trying to put up something new, and you didn’t realize the entire building was wired with the wrong kind of cable. As installers we try to think of every possible scenario but sometimes things happen.

The most common scenario is that you are trying to reuse old 75 ohm cable with a 50 ohm system. You’ll see this a lot in commercial cell booster installation. Another common issue is getting sent the wrong antenna. (Other web sites do this, at Solid Signal we try very hard not to.)

So what’s the harm if you just try it anyway?

The good news

The good news is that you’re not going to cause an electrical fire or anything really serious like that. You won’t cause the equipment to short out. That’s about the limit of the good news.

The bad news

The amount of bad news here depends on what you do. If you use a 50 ohm antenna on a 75 ohm cable (or vice versa) chances are it will work and you’ll just see 3-6dB loss compared to using the right antenna. That might not make enough of a difference when you’re looking at rewiring an entire building. It can also be a temporary fix while you’re getting the right antenna.

On the other hand, using the wrong cable between two devices can really be an issue. The signal flow through the cable can get unpredictable as the signal bounces around in unexpected ways. This can mean a lot of loss or issues that are hard to diagnose. You’ll especially see this in the higher frequencies that satellite TV and some cell boosters use.

There are adapters that can transform from 50 to 75 or from 75 to 50 but there’s often a large about of loss here as well. Not as much as you’ll get if you use no adapter but it’s still better to eliminate that option and use the right antenna or the right cable.

Make the right choice

The best way to avoid this sort of issue is to do a good site survey first. If you’re planning to use existing cable, be sure what’s there and know if you really want to use it. If you are buying all new cable and equipment, give yourself a day or two leeway so that in case the wrong thing is shipped you’ll have time to get the right thing. And of course, the smartest thing you can do is to call Solid Signal at 877.312.4547 or order at SolidSignal.com.