Iowa Public Television

Tuesday, August 26, 2008

Are You Receiving Me?

I have been on the road a lot doing DTV information sessions across the state of Iowa. As part of the presentation I bring along my Philips Silver Sensor antenna and few different converter boxes and generally hook them up to an analog television so I can show the attendees how the boxes work. The reason I bring along the Silver Sensor is because it is small and easy to set up but I frequently have people ask me about it because a number of them have tried traditional rabbit ears and are not entirely satisfied with the results. Many folks marvel that the Silver Sensor is not amplified and yet it works in areas where their amplified rabbit ears don't. I am often asked where to acquire this antenna and if I recommend it and it is those questions that I would like to answer in this message.

First, a simple statement of fact. Indoor reception in inherently difficult and unreliable. The reason for this is that in order to just get to the antenna, the transmitted signal has to pass through walls and windows and all of the trees and anything else that is a ground level just to get to the antenna and all of these items degrade and disrupt the signal. In addition everything in the room with the antenna is a potential source of reflection which further degrades the receivability of the signal. On top of that add to the mix that anything in the room that moves, like the viewer, the kids, the dog or the cat will also dynamically disrupt the signal and further degrade received service and unlike analog television where the picture on the screen gives you a clear indication of how poor the incoming signal actually is, digital gives no indication until the decoder realizes it doesn't have enough information to make a picture and it either freezes, macro blocks (blockiness) or goes away. So I will never recommend indoor reception or an indoor antenna.

So why then does the Silver Sensor work when I am doing demonstrations? It is pretty simple really, the Silver Sensor is a directional antenna where as rabbit ears are omnidirectional. Plainly stated the Silver Sensor receives very well from one direction at a time so in a room where there may be signal coming from all directions, it ignores them and delivers a much less disrupted signal to the receiver than rabbit ears in the same location. Directional antennas also act a little like a satellite receive antenna (dish) in that they tend to gather more of the signal coming in from a specific direction and add it all together. This is referred to as the gain of the antenna and is specified in decibels (dB) which is a ratio. In the case of most antennas, the gain specified in dB is a comparison to the directional antenna and a dipole and guess what, rabbit ears are a dipole. In the case of the Silver Sensor, it has a gain of about 6 to 7 dB compared to a dipole but don't jump the gun, that doesn't mean it is 6 to 7 times better. The way the math and physics work out, the Silver Sensor probably collect about 2.5 times as much signal as a dipole (rabbit ears) and probably as important it ignores signals coming from other directions. That is why it works better than rabbit ears. I have had people say but my rabbit ears have a 10 dB amplifier built in so that should overcome the gain improvement of your Silver Sensor. This is not entirely true because remember that dB is a ratio so an amplifier with 10 dB of gain is taking the signal coming in to the amplifier and increasing the amount of signal by 10 dB. Okay but the amplifier is after the antenna so that the signal that is being amplified in the rabbit ears has already been degraded by all of the items I mentioned above and therefore all you are doing is increasing the size of the degraded signal but the receiver and decoder still can't figure out what the message is no more than yelling at someone who doesn't understand English makes them understand.

So I can't recommend an indoor antenna with any degree of certainty because the number of things that will disrupt the service using an indoor antenna are virtually unlimited and constantly changing. I will always tell people to look at outdoor antennas as their best option. I have had a number of people tell me that they are not permitted to put up an antenna because of local restrictions. I would suggest that you follow this web link ( and I believe you'll find that many of those restrictions are superseded by federal rules that in most cases will allow you to install an outdoor antenna, even in rental properties. So you might want to look at antenna reception again. Remember, rabbit ears work great on rabbits but not so well on television signals.


Sunday, August 3, 2008

Q&A and Screening of Iowa DTV Answers Thursday, August 7 at 6:30 p.m.

Iowa Public Television and the Science Center of Iowa are teaming up to give you answers about DTV!

With so much information out there about the universal switch to digital television, many of us are still left with basic questions: Will I need a new TV? Will I still get all the same channels? Why is this happening, and what do I need to do to be ready?

On Thursday, August 7 at 6:30 p.m., the Science Center of Iowa and Iowa Public Television will present an information session that answers these questions and more as you prepare for February 17, 2009 when analog TV becomes a thing of the past. The evening begins with Iowa DTV Answers, a 30-minute program that addresses many concerns about the transition. Then at 7 p.m., IPTV Director of Engineering Bill Hayes will answer your questions about digital television.

The event will be hosted in the John Deere Adventure Theater at the Science Center of Iowa and is ideally suited for anyone with questions about digital television. Doors for this event open at 6 p.m.

For driving directions and parking information about visiting the Science Center of Iowa, please visit and click the “Visiting SCI” link. For all other questions about the event, please contact Jennifer Konfrst at 515-242-3146.