Tuesday, June 29, 2010

Happy Chladni Day - June 29

Amazing how fast the year goes by, and now our favorite holiday to commemorate Ernst Chladni observed in Massachusetts, Maine and Puerto Rico,

Here is a link to all about Chladni!

Tuesday, June 15, 2010

Return Loss, SWR, and Antennas

A lot of people talk about antennas in terms of "SWR" or Standing Wave Ratio. Hams do it primarily, and so do CBers and others.  SWR is sacred to hams, who have developed a belief or myth that if their SWR is low, everything is fine.  Well, that's partly true to their transmitters that have automatic high SWR foldback circuits, and to their feedlines that can arc over if the voltages get out of hand, which they can in a high SWR condition.

But a more modern term for describing how efficiently power is transferred to an antenna or other device is referred to as Return Loss.

Return Loss does not tell you how well an antenna receives signals!  There are plenty of other characteristics that are important, but Return Loss does give you a very good idea of the impedance mismatch of the line into the antenna when power is applied.

Here is a link to a paper on Return Loss, more than you probably want to know. But we will be referring to it in the future because Return Loss is one measurement of antenna quality that is starting to show up in spec sheets, and you know how that goes: Some people buy on the specs, others buy for a variety of reasons and not necessarily the published specs. In the microphone world, we found ample evidence, which we have no intention of providing, of "spec inflation". I will let you figure out what that means. We also used a term to describe people who only considered the specs in microphones to be "curvemeisters". Pretty funny, unless you are one of them.

In antennas it's different.   In case you want to read a good basic paper on Return Loss, below is a link to one.  There are a lot of websites that get it wrong, but I think this one is right, so I'm going with it.  I'm getting this minutiae done early, so we don't have to repeat it later. Yes I know this is a boring topic, but Return Loss  measurement is one of the more important measurements, right up there with gain. All you will need to know about our products is that they work, but we won't make you take it at face value - we'll actually measure them like we did with microphones, and report actual results when they mean something.

Here is the link.

Nice Picture of Cubby and KSM313

Link to an article in PSW about the use of this mic here.