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FM and TV Propagation and Reception

Question: What conditions need to exist for SPRTV's DTV channels to be available in my home or business?

Technicians are presently on call to visit your neighborhood and investigate the availability of over-the-air digital television signals.

FM radio and television signal reception is highly variable dependent upon location and terrain. While a line of sight between a high VHF band television transmitter antenna and a television receiver antenna will assure the optimum signal strength this is not an absolute requirement. Reflection and diffraction play a role in electromagnetic space-wave propagation allowing reception to occur even when a line of sight does not exist. In regards to distance, when this is doubled the strength of the signal is reduced to one-quarter of its former value. In other words, the radiated power from an antenna is reduced as the square of the distance from its source. This is known as the inverse square law.

The lines represent the flux emanating from the source. The total number of flux lines depends on the strength of the source and is constant with increasing distance. A greater density of flux lines (lines per unit area) means a stronger field. The density of flux lines is inversely proportional to the square of the distance from the source because the surface area of a sphere increases with the square of the radius. Thus the strength of the field is inversely proportional to the square of the distance from the source. Source: http://en.wikipedia.org/wiki/Inverse-square_law .

Another factor that effects signal strength is antenna shielding. Simply stated, when an antenna is positioned indoors the surrounding structure forms a barrier that the FM or TV signal must penetrate. The degree of attenuation depends upon the structural material. (See Shielding Theory and Transfer Functions in EMC Shielding Design for additional words on this subject.)

While the performance of other television receive antennas in a general locality provide useful data, the best way to know what form of antenna will actually work is to visit the specific location and evaluate reception starting with a dipole reference antenna. While it may be found that an indoor antenna will work for people fairly close to the Breckenridge DTV translator (within 2.5 miles or so) SPRTV recommends an exterior-mounted directional high VHF band antenna. A combination high VHF band + UHF band antenna may prove useful if SPRTV adds a UHF TV translator or LPTV station in the future.

". . . Summit Public Radio proudly announces that we are now broadcasting Rocky Mountain PBS (KRMA) on DTV Channel 10.4. . . . You will need an outside TV antenna and a digital television to receive the RMPBS signal. . . ."

While it is possible that an indoors dipole antenna very close to Baldy may work, given the uncertainty of FM radio and TV signal propagation here in the mountains it is prudent for prospective TV translator users to adopt an outside antenna.

Regarding the quality of digital television transmissions in general, unlike analog TV signals that are usable even when very weak, DTV signals may seem like they are either there or they are not. Also, digital TV translators are not as powerful as the typical broadcast DTV station transmitter so an indoor antenna may not work properly. The power of the channel 10 DTV translator on Baldy is about 270 watts. The KCNC/CBS transmitter at Lookout Mountain is 1,200,000 watts and many of their viewers need an outside high-gain directional antenna to get that signal. It stands to reason that Summit County DTV translator users may require the same.

Question: What equipment is required to receive SPRTV's DTV signals?

The Summit Public Radio Channel 10 analog television translator has been switched over to the new digital format. What does this mean? In order to receive the Channel 10 television signal you now need a digital to analog TV set-top converter box or a digital television set. Also, you may have to upgrade your TV antenna to receive the new digital signal.

For DTV reception using a new digital television:

Make sure your rabbit-ears TV antenna has an internal antenna preamplifier. SPRTV's digital TV translator is not as powerful as a typical broadcast DTV station transmitter so an unamplified rabbit ears antenna positioned inside of your home may not work.
Connect the antenna to your television's analog TV input, tune your television to channel 8 or 12 and try to pick up one of these old analog TV signals still being transmitted. If you are successful you can use the received analog TV signal to "peak" your antenna. Move your TV antenna to different locations inside and outside of your home searching for the very best reception. (You'll have to use an older television for this step if your new television is DTV-only.)
If you are successful in picking up one of the analog TV translators then shift the antenna over to the DTV input on the back of your television and then scan for the block of new DTV channels.
If your scan locates the channel 10 DTV translator but the picture is broken up or pixilated you will need a better antenna before you can start enjoying the new era of over-the-air digital TV. You may wish to use the Summit Public Radio and Television Digital Television and FM Antenna Selection Guide.

If repeated scans find no DTV signals then SPRTV will send a technician out to your location to determine if over-the-air television reception is at all possible at your home

For DTV reception using an analog television plus a DTV converter box:

Make sure your rabbit-ears TV antenna has an internal antenna preamplifier. SPRTV's digital TV translator is not as powerful as a typical broadcast DTV station transmitter so an unamplified rabbit ears antenna positioned inside of your home may not work.
Connect the antenna to your analog television's RF antenna input, tune your television to channel 8 or 12 and try to pick up one of these old analog TV signals still being transmitted. If you are successful you can use the received analog TV signal to "peak" your antenna. Move your TV antenna to different locations inside and outside of your home searching for the very best reception.
If you are successful in picking up one of the analog TV translators then hook up your DTV converter box to your television, shifting the antenna over to the converter boxes RF antenna input, and then run a scan for the block of new over-the-air DTV channels.
If your scan locates the channel 10 DTV translator but the picture is broken up or pixilated you will need a better antenna before you can start enjoying the new era of over-the-air digital TV. You may wish to use the Summit Public Radio and Television Digital Television and FM Antenna Selection Guide.

Once again, if a DTV channel scan finds no stations a technician is available to look into the matter and see if the over-the-air digital television signal is available in your neighborhood. For assistance tuning in the new DTV translator call (970) 453-9293 and ask for Gary.

On FM and TV antennas in general, all of the following will usually result in better reception, listed roughly from most important to least important.

Point the antenna towards the translator (the importance of this depends on how directional the antenna is).

Move the antenna higher.
Use a bigger, higher gain antenna.
Use a more directional antenna.
Mount the antenna outside.
Use a single run of new RG-6 coaxial cable that's no longer than necessary.
Use an antenna preamplifier if you are very far from the translators.
Don't use a distribution amplifier unless your coaxial cable is longer than 100'. (If you use a distribution amplifier, make sure it's a high quality low noise type.)
It's not strictly necessary to do all of these things, but each one will help. For example, if you aren't able to mount the antenna outside it still helps to have a directional antenna and put it as high as you can, like in the attic.