Digital Difficulties

What makes digital television reception of KFDM so difficult?

Richard Kihn, KFDM

(1) The Digital cliff

Back in the days of analog broadcasting, when you had a weak TV signal, your television would still display a picture.  It was probably full of noise and "snow", but there was a picture.  This allowed you to rotate the antenna until the picture cleared up.  This is not true with digital TV.

The major problem with digital television reception manifests itself with a phenomenon known as "the digital cliff".  A digital picture is either perfect or it is not there at all.  There is no "snowy" picture to let you know that the signal level is low. If a digital signal is too weak, your TV set or converter box will not display a picture.  Instead, it displays the message "weak or no signal", if it displays anything at all.

This becomes a real problem when you connect your digital television (or converter box) for the first time.  If your antenna is not pointed in the correct direction the first time you "scan for channels", you may not pick up our signal.  KBTV, KITU, and KBMT may all show up, but there is no KFDM.  Our signal might be there, but your antenna is not quite pointed correctly to obtain a signal from our transmitter.  The reason for this signal level difference is discussed in item (3).

Now that the "scan for channels" is complete, you attempt to find us.  You punch the "channel up" button on the remote and it skips from 4.1 to 12.1.  There is no channel 6.1!  You scratch your head and try again; still no channel 6.1!  So now you type in "6 dot 1" (6.1) or 6 dash 1 (6-1) on your remote control (the "dash" or the "dot" depends upon your particular remote control; some have a dot, some have a dash).

Still no channel 6.1!  So now you move the antenna around and continue to punch in channel 6.1.  It still does not work.  Now you are getting mad at your set and channel 6. 

The reason punching in "6 dot/dash 1" does not work is due to the fact that my digital signal is not on channel 6; it's actually on channel 21.  Normally, during a "scan for channels", your TV or converter box looks at every TV channel.  When it finds an active channel (21 in the case of KFDM), it reads a little bit of the digital data and then tells you a lie (that you are watching channel 6.1).  This is called "virtual channel numbers", and is explained in item (2). 

 

(2) Virtual channel numbers

When local digital broadcasting began in 2002, every station was assigned a new TV channel to use for their digital signal.  This was done because it is not possible to broadcast an analog and a digital signal on the same channel at the same time.
Channel 6 (KFDM) was given channel 21, channel 4 (KBTV) got channel 40, channel 12 (KBMT) got channel 50, and channel 34 (KITU) got channel 33 for their digital station.  This means that although your television set tells you that you are watching channel 6, you are actually tuned to TV channel 21.  This swapping of channel numbers is called "virtual channels". 

Virtual channel numbering was instituted by the Federal Communications Commission (FCC) and was supposed to make your life easier.  Instead of having to start calling ourselves channel 21, we would retain our channel 6 name.  This kept viewers from having to remember a new set of TV station numbers.  And since the converter box (or digital TV set) would scan for the channels and call them by their "traditional name", you did not need to know that I was actually on channel 21 instead of channel 6.  This is a great idea, except for two things:

1. People did not know that they needed a UHF antenna in order to pick up my signal.
2. When the converter box/TV set failed to pick us up, no one knew to punch in "21 dot/dash 1" to find my signal.  Nor did anyone know that punching in "6 dot/dash 1" was a waste of time.

 

Many people have VHF antennas because that is all anyone needed to pick up channels 4, 6, and 12. But now that most digital stations are on UHF channels, you really need a UHF/VHF antenna in order to pick up all the stations. 
All full power analog TV transmitters were turned off on June 12, 2009.  Now that analog TV is gone, KBMT has changed from UHF channel 50 back to VHF channel 12 for their digital broadcasts.  The other 3 local stations stayed on their assigned UHF channels for digital TV.    

(3) Low Transmitter Power

KFDM is broadcasting 170,000 watts.  KBTV is broadcasting 1,000,000 watts and KITU is broadcasting 500,000 watts.  This means that KBTV and KITU are much easier to pick up than is KFDM.  KBMT is back on channel 12 for their digital signal.  This is a VHF channel, and the power levels of VHF and UHF stations are not easily compared.  Currently, KBMT is transmitting 18,200 Watts.  All this really means is that a VHF station does not need to broadcast as much power as a UHF station in order to cover the same area.  So we will ignore KBMT for the rest of this discussion. 

Your next question is probably "why is KFDM broadcasting at such a low power level"?  Well, the Federal Communications Commission limits our output power in order to protect KLTL in Lake Charles.  KLTL is actually on channel 20, although their "virtual channel" number is 18.  My antenna must also broadcast less power to the East than in all other directions to protect KLTL.  KLTL is also restricted on how much power they can broadcast in order to protect KFDM.
The fact that there is a channel 20 and a channel 21 in adjacent markets is due to a "minor" error back when the digital channels were first assigned.  Neither KLTL nor KFDM is happy about the situation.  But we can not change the past; we have to live with it. 

(4) The antenna

The receiving antenna is the cause of most reception problems.   Regardless of how good your TV set or converter box is, it can not make a picture unless the antenna provides it with a reliable signal.  With very few exceptions, if you can not pick up my signal, the antenna system is the most likely cause of the problem.  This is true even if you can pick up the other digital stations. This is still true even though you were picking up all the analog stations with your old antenna. But this does not mean that the antenna is bad and needs replacement, maybe it just needs adjusting.

Bear in mind that the converter box or TV set could be bad, but it is unlikely.  I know of only 3 people where the converter box was actually bad.  This is less than one percent of all the reception problems I have dealt with.
Digital signals are simply more difficult to pick up than was analog TV.  Digital TV should be just as easy, but it is not.  The bottom line is that what worked for analog may not work for digital.

Types, groups, and classes:

There are three types of TV antennas, UHF, VHF, and the UHF/VHF "combo" antenna.  VHF antennas are designed to pick up only channels 2 through 13.  UHF antennas are designed to pick up any TV channel above 14.  A UHF/VHF "combo" antenna will pick up all TV channels.

There are two major groups of antennas: indoor and outdoor.  Indoor and outdoor antennas are available in all the antenna types: UHF, VHF, and UHF/VHF.  Indoor antennas are available in two classes: amplified and non-amplified.  I will attempt to make the last two paragraphs make more sense in the remainder of this article.

Indoor Antennas:

Normally, an indoor antenna should work if you are less than 20 miles from the TV station tower.  But this is based upon the TV station broadcasting at "full power" (which in this case would be 1,000,000 Watts).  Since I am only broadcasting 170,000 watts, this 20-mile range is reduced to about 10 miles. If you live to the East of Vidor, this 10-mile range will be reduced even lower than normal since my signal to the East is lower than in all other directions in order to protect KLTL.  I would expect an indoor antenna to work no more than 4 miles from my transmitter if you live to the East of Vidor.  If you live in a mobile home or have metal siding or a metal roof on your home, an indoor antenna may not pick up my signal due to the metal blocking my signal from getting to your antenna. 

"Rabbit ear" antennas that consist of only two telescoping rods are VHF antennas.  If your TV set have a built-in antenna, which consists of one or two telescoping rods, it is a VHF antenna, and will not work well for UHF digital signals. In most cases, a VHF only antenna will need to be replaced with a UHF/VHF antenna.

If you live very close to Vidor, you may be able to pick up our UHF signals with a "rabbit ear" VHF antenna.  But as the distance between your home and our transmitter increases, the likelihood of this happening decreases.  KBTV (UHF channel 40) with its 1,000,000 watts can be picked up with an indoor VHF antenna ("rabbit ears") for a much greater distance than the signal from KFDM.

One of the best indoor antennas is the "Silver Sensor" by Zenith.  This is the antenna I have been using for my signal level tests throughout the area.

Amplified Indoor Antennas:

The purpose of an amplified indoor antenna is to increase (amplify) the signal level obtained from the antenna. This type of antenna will work for greater distances than the 10-mile range that I mentioned earlier.  If you live less than 15 miles from Vidor, an amplified indoor antenna may allow you to pick up our signal.

An amplified version of the Silver Sensor antenna made by Terk is available at Radio Shack and Best Buy.

Indoor antenna tips:

If all you have are "rabbit ears" and you live very close to Vidor, you might get a signal if you push the two rods to their shortest length.  This will not harm reception of KBTV as they have so much more power than KFDM.  This might reduce the signal from KBMT, but probably not enough to lose their picture.  In most cases, it is better to have the rods of the rabbit ear antenna lying flat, not straight up and down or at an angle.  But feel free to try any angle; if it works, don't argue with it.

If you live more than 10 miles from Vidor, you should replace the rabbit ears with a UHF/VHF antenna.  You might want to try an amplified indoor antenna if you live within 15 miles of Vidor.  Save the box and your receipts in case you need to return it.  But you should try the following tips before you spend any money on a new antenna; you just might get lucky.

In general, you should place the antenna as high as you can.  If possible, do not put the antenna on top of the TV set, as the TV set can actually interfere with the antenna's performance.  If you live on the second or higher floor of an apartment building, higher may not always be better (the antenna is already high because your home is high).  In this case, putting the antenna on the floor may work.

Moving the antenna a few inches could make a big difference.  Turning the antenna a little bit might also help. But try only one change at a time.  Remember to leave the antenna in its new position for at least 5 seconds to give your converter box or TV set time to notice the new position.

The best place for an indoor antenna is near a window that faces towards Vidor.  The walls of your home will reduce the signal available to the antenna, while a window does not.

If you live in a mobile home or if you have metal siding or a metal roof, an indoor antenna will not work very well.  About the only thing that will help in this case is to put the antenna in a window.  Mobile homes and those with metal siding or metal roofs may require an outdoor antenna.  The higher power of KBTV may allow its signal to make it through the metal although my signal will not.

 

Outdoor Antennas:

Outdoor antennas are pretty much required if you live more than 20 miles from Vidor.  Outdoor antennas are rated in mileage; meaning that they should pick up a usable signal up to the distance rating of the antenna.

There are many different antennas available with different mileage ratings.  You should pick an antenna that has at least half again the distance your home is from Vidor (40 miles from Vidor should have an antenna rated for 60 miles).  Again, this is due to my low power.

I live in Anahuac, Texas and I can pick up our signal with no problems.  I have a UHF/VHF antenna (rated for 60 miles) mounted about 12' above the ground.  This is not the suggested 1-1/2 times the distance between Anahuac and Vidor, but it is as close as I could get.

As stated earlier, VHF only antennas were the cause for some of the reception problems I have dealt with. In general, if you are far enough away that you need an outdoor antenna, a VHF only antenna will not pick up my low power UHF signal.  KBTV's 1,000,000 watt UHF signal can be picked up on a VHF antenna.  But this is not true for my low power signal.  Since KBMT is a VHF station, you should be able to pick them up with an outdoor VHF antenna.  But since you are reading this article, I will assume that you are trying to pick up my signal, and that you are probably already picking up the other stations.  You need a UHF/VHF antenna to pick up my signal.

In cases where the antenna is indeed a UHF/VHF model, my low power level is probably not the cause of your reception problems.  The problem could be as simple as the antenna pointing in the wrong direction.  Due to my low power, you need to aim the antenna at my transmitter in Vidor.  The higher power from the other stations will allow their signal to be picked up although your antenna is not pointing directly at them. 

An outdoor antenna can be mounted in an attic if you have the room.  However, be aware that mounting the antenna in your attic will reduce its reception range by about half (an antenna rated at 50 miles will be reduced to a 25 mile range).  The roof reduces the signal level as it goes through the shingles, felt, wood, and the nails.  You should not mount the antenna in your attic if you have a metal roof, as the signal level will be too low by the time it passes through the metal.

For places within 30 miles of Vidor, I usually recommend the Radio Shack model U-75R UHF antenna ($35) or the model HBU22 UHF/VHF ($40) for an outdoor antenna.  For areas beyond 50 miles, I like the Winegard model HD8200U ($160) available at Ralph's Electronics in Beaumont at 1293 Broadway (833-9443).  Similar antennas are available at Radio Shack.  I have not seen any outdoor antennas at Sears, Best Buy, or at Wal-Mart.  I have heard that Lowes has outdoor antennas, but I have not been there to check.
When you install your antenna, pay close attention to which end of the antenna is the front.  This is the end that needs to point towards Vidor.  In general, the longest rods on an outdoor antenna are located on the back end of the antenna.

Outdoor Antenna Tips:

(1) Higher is almost always better.  If you live in areas such as Jasper that have hills, lower may be better since the hill has already raised the antenna for you.  This is not very likely, but it has happened.

(2) Trees always reduce the signal level available to the antenna.  Unless you can raise the antenna above the trees, just get the antenna as high as you can.  If high does not work, you may also want to try and put the antenna below the lowest limbs of the tallest trees.

(3) I have found that cedar trees will block my signal.  A nearby oak tree did not reduce the signal very much, but the cedar tree totally killed the signal.  Avoid cedar trees.

(4) Use coax cable.  Twinlead antenna wire (a flat cable with two wires) will pick up interference to which coax cable is immune when properly installed.  Make sure all connections are tight.

(5) The center wire of a coax cable should be clean and shiny.  It should also be slightly longer than the connector.  If it is not, replace the connector or the cable.

(6) If all else fails, try moving the antenna to a different area.  Moving the antenna location a few feet has been known to find a signal where none was present in the previous location.

(7) Any metal near an antenna (indoor as well as outdoor) can cause distortion of the received signal, which may interfere with reception.  Large metal objects close to the antenna can also block the signal.  Avoid placing your antenna above a metal carport, for example.  If you or your neighbor has a metal building, place the antenna as far away as possible from these buildings.

 

How to position the antenna correctly:

I have talked to a lot of people with reception problems since June 12th.  A majority of these people were able to pick us up by adjusting or replacing their antenna.  For this discussion, we will assume that your converter box or TV set is working properly.  I will also assume that you have a UHF/VHF antenna (if not, get one).  When I use the term "box", I am referring to your converter box, or digital set.  When I state that you should enter "21 dot 1" (21.1), you may need to enter "21 dash 1" (21-1), depending upon which character (a dash or a dot) your remote control has.  See note 1

Case 1: The "other" stations come in fine but your box skips from 4.1 to 12.1

First, go to channel 4.1 on your box.  Now punch in 21.1 on your remote control.  This forces your box to tune to my digital signal on channel 21.  If your box stayed on channel 4.1, you will need to stay on this channel for the remainder of this procedure.  See note 2.

The reason that I suggest channel 4.1 if your box will not go to channel 21.1 is that channel 4's transmitter is about 1 mile west of my transmitter. 
Assuming that your box went to channel 21.1, you may have my picture already.  If so, congratulate yourself, but continue with this procedure.  See note 3.

Find the signal strength meter on your box (while tuned to channel 4.1 or 21.1).  Some boxes have a button on the remote control labeled "signal", but most do not.  In this case, you will need to enter the setup menu and find the signal meter the hard way.  In some cases, this signal meter was located somewhere in the "antenna" option on the main menu.  See note 4.

Now that you have either 4.1 or 21.1 selected, rotate your antenna until you get the highest reading on the signal meter.  If you were able to use channel 21.1, you should be watching our station after the signal level gets close to half of the maximum reading available.
If you get a signal level on 21.1, but never get a picture, this means that the antenna is not picking up enough of our signal.  Try moving the antenna if you are using an indoor antenna.  If you are using an outdoor antenna, an antenna amplifier may be all you need.  In extreme cases where an amplifier does not allow for reliable TV reception, you will need a larger antenna (one with a higher mileage rating).

If you had to use channel 4.1 for this procedure, you should now perform a "scan for channels".  With any luck, channel 6.1 will show up.  If channel 6.1 does not show up, rotate the antenna a few degrees, and scan for channels again.  Although you peaked on 4.1, there is no guarantee that the antenna is positioned correctly for receiving our signal.  This is due to the high power signal for channel 4.1, which can be picked up on the VHF section of your antenna.  Although this procedure should have maximized the UHF section of your antenna, the signal from the VHF portion may still cause the antenna to be pointing in the wrong direction.  Try other positions, and perform a rescan every time you move the antenna.

 

Case 2: Channel 6.1 is in the channel listing, but there is no picture

This means that your box saw our signal at one time, but lost it.  It could be caused by the memory in the box being scrambled.  Converter boxes and digital TV sets are a lot like computers; their memory needs clearing out every so often.  This can be accomplished by one of two methods:

1. If you can find the "restore factory default settings" on your box, this will clear out the memory.  Your box will now show no channels since the box thinks it has never been used before and it will start the initial setup procedure which includes a "scan for channels".  This should restore all stations including channel 6.1.
2. If you can not find the factory default setting option in your menu, or you don't want to waste time looking for it, perform the following procedure.  Disconnect the antenna from the box.  Scan for channels (it should find none).  Unplug the power from the box for about 10 seconds.  Reconnect the power and antenna to the converter box.  Scan for channels again.  This procedure is called a "double rescan" and should restore all stations including channel 6.1.

If you have access to the Internet, you can go to www.dtv.gov/maps to help in positioning your outdoor antenna.  Another good site is www.antennaweb.org to obtain a list of every station you should be able to pick up and where to point your antenna for each station.  You may be surprised at the number of stations available to you.

If you do not have access to the internet, you can go to your local library and use one of their computers.

 

And finally; some good news:

KFDM is fully aware of the fact that many people can no longer watch our station (why else would I be writing this article?).
We are investigating several different options, but the leading solutions are expensive, time consuming and require FCC actions. 
Hang in there!  We will get you a signal.  And hopefully, one that is much easier to pick up.

Notes:

1. Some TV sets force you to choose the TV station you want to watch using a menu. If your set is of this type, select channel 4.1 since channel 6.1 is not yet shown on the menu. 

2. This means that your box will not accept direct channel number entry, use channel 4.1.

3. Your box got confused during the initial "scan for channels" and forgot to add us to the channel list.  Forcing the box to our real RF channel (21) caused it to find us again.

4. I could not purchase one of every type of box or digital TV set available.  Therefore, I don't know where the signal strength meter is on every box or digital TV set.

Last update: September, 2009

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