The Switch to Digital TV

emc c:

There should be a category for outstanding answers. it was a delight to read your reply post.

best regards

The Mast antenna is a 300 Ohm and I already have the 300 -75 Ohm converter on it.

Why would I suddenly need a preamp for the Mast antenna since I did not need one before I hooked up the DTV converter. Does the converter require that much of a stronger signal.

The Rabbit ears I used have both a VHF and a UHF antenna. I said Pointed But I guess I should have said turned just the right way.The small rabbit ears by the way did not pick up a signal when I tried to use them before so I put up the masted antenna. No power plug on the rabbit ears. Though I did try that type too before I put up the mast. I still have that one stored around the house someplace. I could dig it out and play with it too.

As far as the orientation of both antennas I'll have to look. I didn't really think about this until you brought it up. I know the Mast antenna is pointed to the North East. Because I remember that's the direction I needed it pointed to get the most stations. I could have bought a motor to rotate it to get all of them but I'm mostly interested in local news reports. Otherwise I don't watch TV. The kids hate the fact that I don't have cable or satellite but I can't see paying that much for them to sit on their butts turning into TV zombies.

Will any of this change when the official switch happens? I believe the stations I watch now have been switched over for years. Are they sending both types of signals until the official switch or just the New Improved" signal.

"The Mast antenna is a 300 Ohm and I already have the 300 -75 Ohm converter on it."

This might be your problem right here. If the equipment doing this conversion has a comb filter that use to remove the unused inter-channel frequencies to reduce interference. Well this is where DTV signals reside. Some older antennas cleverly used a parasitically powered preamplifier with a comb filter to boost sensitivity and drive a 75 ohm cable.

As far as why the rabbit ears need to be oriented to the mast and not the station is because the mast is reflecting energy from the station down to your rabbit ears.

But this will be a permanent switch. The DTV frequencies being used now will be the DTV frequencies used in the future.

First of all, thanks to those who gave GAs to my original post.

Here are some answers to scotch drinker's further questions, based on extra information from some of the other responders.

My original response was predicated on the assumption that the broadcast frequencies hadn't changed, just the signal coding (digital vs. analog). Other posters have since indicated the frequency of the transmission may have changed as well. If a channel you used to receive in the vhf band is now coming in uhf, then you will suffer signal loss relative to the original frequency. This assumes you using the same masthead antenna, and the broadcaster maintaining the same ERP (equivalent radiated power) at your location. Even if your masthead antenna has the same gain at vhf and uhf, you will get less signal at uhf. Signal reception is given by

Pr = Pd*G*(wavelength)^2/4 pi

where,

Pr is the power out of the antenna into your 300 Ohm twinax,

Pd is the power density illuminating your antenna,

G is antenna gain, and

wavelength (meters) is 300/frequency (MHz).

You can see that for the same gain, you get less signal at higher frequencies. Here is a place you can go to check the frequencies of the channels you are receiving:

http://www.csgnetwork.com/tvfreqtable.html.

If you find there has been a shift to uhf, that would explain the loss of signal, and again the preamp should help you get that back.

Perhaps I am wrong in my general understanding of DTV and converter boxes as I am an unstudied novice but doesn't the DTV system use UHF to transmit the signal? The poster may have issues with his multi pole Yagi antenna being tuned for VHF and shunting the UHF band and the rabbit ears may do a better job at passing the UHF band. He is simply getting a signal reflection from the mast to the rabbit ears.

I have tried both rabbit ears and the antenna I built. Rabbit ears (vhf) picks up analog signals much better than the antenna I built. It will not pick up any digital stations. The antenna I built does not pick up analog signals very well (at least not the ones I can receive at my location) but will pick up 2 digital stations (uhf) perfectly and occasionally 2 more when they are broadcasting (once I got 4 PBS stations but they have disappeared for now). I expect things to change after February 17th. I am hoping that I will be able to get more stations. Whether the antenna I built will pick them up if they are being broadcast on vhf frequencies is yet to be determined. All I know is, all I can get right now is uhf digital. It would be nice if I could get enough stations in HD to get rid of my satellite dish but I doubt I will be able to do that.

As a side note. Because the digital signal will reach the same coverage area with less power I believe that the stations will be reducing power. I think this might even be a requirement (correct me if I'm wrong). Therefore, if you live in a fringe area you will be receiving a weak signal still. This is not good. A weak signal with analog will allow you to still watch a program if you choose and you don't mind a little snow or occasional interferrence. A digital will either work stunningly, become very pixellated or not work at all ("no signal"). Usually it becomes pixellated then stops working for me. I have had instances where a plane flying overhead has caused my tv to go to the blue screen of death (so to speak) right in the middle of a program. This technology is great for city dwellers that are fairly close to the broadcast towers. It is also great for the government agency that can sell the unused frequency after February 17, 2009. It is lacking (big time) for rural people in fringe areas. These are the very same people that normally want to receive their television signals from antennas if they can't afford or have objections to satellite programming. In my opinion, this government mandate is discriminating against poor people and those who have moral objections to satellite programming for the sake of profit. One other thing is that if you live in an area that needs a repeater (in a valley on the other side of a mountain) those repeater stations will be allowed to continue to broadcast in analog or NTSC. You should check to see if your signal is from a repeater station (low power) or the original station.

Multipath distortion (such as when signals bounce off buildings and take a slightly longer path to reach your antenna, arriving a fraction of a microsecond later) will also severely limit the ability for digital tuners to decode the signal. Not all converter boxes are equal and price is not always a good guide to quality either.

http://blogs.chron.com/consumerwatch/2009/01/higherprice_dtv_converter_box.html

I've just started looking into DTV/HDTV antenna requirements. Found a couple of good reources:

Antenna Research & Development
http://www.digitalhome.ca/forum/forumdisplay.php?f=186

Getting Started with HDTV and DTV
http://www.hdtvmagazine.com/forum/viewforum.php?f=37

How to Make a TV Antenna for HDTV
http://www.tvantennaplans.com/

According to the information being dished out by the government, if you receive over the air analog signals with your antenna you should be able to receive digital with the use of a converter box. However, the type of antenna you have does make a difference. If your antenna is designed for vhf you will have trouble receiving a strong enough signal for digital reception because of the uhf frequencies used to transmit digital signals. Also, from what I can tell, the antenna must be positioned precisely in weak signal areas to obtain enough signal strength to allow for conversion from digital to analog to work well. Some stations are not transmitting digitally full time yet as they are testing their capabilities and options so you won't be able to receive their signal sometimes. In my opinion, your existing antenna has little to do with your ability to receive the digital stations you are currently receiveing with your rabbit ears. More likely is that the uhf portion of your rabbit ears is able to receive just enough signal to give you reception even though you live in a fringe area. It has to be positioned precisely though or the signal goes away. I built an antenna using coat hangers, a one by four piece of wood, some fender washers and screws, and some #14 wire, and a 300 ohm to 75 ohm adapter. Here is a link to some very good instructions: http://www.youtube.com/watch?v=EWQhlmJTMzw

This antenna works very well for me even though I am a good 45 to 50 miles away from my nearest transmission tower. Mounting this antenna in an attic if one is available also works well because it is not very pretty to look at.

By the way, here is a picture of the one I built.

Regards,

Keywalker

Hey, a little paint, and you could tell people it's a sculpture inspired by Picasso!

This antenna is actuall in an area I call my computer room and is very cluttered with all kinds of electronics. It fits in quite nicely!

I'm a pragmatist - whatever works is what's right!

Yeah! me too! (I had to look it up first though)