Function Digital
Can my FTA satellite dish function as an antenna to receive digital broadcasts for the DTV transistion?
I want to use it with my digital tv converter box if possible.
I’m going to have to tend to agree with Classicsat. While a parabolic dish can be theoretically used at any frequency, it is often impractical for frequencies below 1 GHz because of the size of the dish required for effectiveness increases as the frequency decreases. Let’s take the highest DTV channel there is, 59. This equates to about 743 MHz. To judge gain (over isotropic) of a parabolic dish antenna, you take the quantity pi squared times the diameter (in feet) squared all divided by the square of the wavelength of the frequency being received. Wavelength (in feet) is 984 divided by frequency in MHz. Remember that 10 times is equal to 10 dB and double is equal to 3dB. Figure on a 3 foot dish as the average size of an FTA dish. This works out to be a little over 16dBi. Now this is a best case scenario figure, not even taking into account the spillover loss, the illumination loss, loss from the feed shadowing the path, etc. And remember this is the highest DTV frequency there is, so any channel lower the figure is even worse.
Now consider this. A yagi at this frequency the length of your arm will have a gain of about 12dBd or over 14dBi. So, which is more practical? A 3 foot diameter dish with a couple feet long feed arm that’s heavy and has a lot of wind loading or a 3 foot long 8 inch wide yagi that’s lightweight with hardly any wind loading? This doesn’t mean it won’t work, because it will with the proper feed, but remember the lower in frequency you go, the lower that gain is going to be. Let’s look at the lowest DTV channel, 2. 57MHz. Plug that into the equasion and see what you get. Nothing! In fact, you’re probably incurring a loss because the reflector is less than 1/4 wavelength away from the feed for all of the low VHF channels!
Your best bet is to get a good Channel Master antenna that covers where your DTV channels are in your area. For most people this is UHF, and for some it’s VHF high and UHF, and still some others all of VHF and UHF. A proper antenna will outperform a jury-rigged FTA dish any day. Don’t forget, the local channels on FTA will still work after the transition. There’s a good few on G10R.
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