While not parabolic, the reception equipment used for of Off The Air (OTA) channels is an important component of any Earth Station. Some folks utilize the highly compressed Local-Into-Local (LIL) of the LSD companies. I prefer to watch for free. The cost of the antennae and supporting equipment is easily recouped when amortized against the monthly cost of satellite or cable delivery of these channels. More importantly, the quality of NTSC is substantially better when directly received (though not nearly as good as satellite reception).
Now, my configuration is a bit more elaborate than many (what's new). However, that is partially due to our proximity between several major markets. The first OTA installation consisted of two Radio Shack 192" UHF/VHF combination antennae, combiners, an FM-only antenna, rotor, and two 10' tripod mounts. RG6 was used for all connections and the entire configuration is bonded to the grounding web described in Sinking Feeling The antennae are mounted at opposite ends of the roof. One for Lansing. One for Detroit. The Detroit antenna (pictured left) is on a rotor for fine tuning and tuning other markets..
The trick is in the combining of these signals. From Lansing, I obtain WKAR (PBS/23) and WLNS (CBS/6). I obtained two Join-tennas and a UHF/VHF combiner from Stark Electronics. A Join-tenna is an indoor/outdoor device with having an input on which only a specific frequency (channel) is passed, and another on which the entire UHF/VHF spectrum is passed except for the specified channel. The result is a combined output that appears as though the "notched" channel exists in the same direction as do all other channels. The Lansing downlead is sent to the Detroit tower where it is attached backwards to the UHF/VHF combiner resulting in separated UHF and VHF cables. The UHF output is then combined with the Detroit UHF/VHF downlead using a Join-tenna for channel 23. This output is then fed to a channel 6 Join-tenna and combined with the VHF lead from the Lansing tower. The entire combined downlead is then input to a Winegard Spartan 29db pre-amp and sent down to the Wild Wire Web and then into the house.
The result of this is that I have the basis for the MannyVision cable system utilizing the OTA broadcast signals in my area. To this potpourri of channels, I inject additional channels using NetMedia Triple Channel Digital Modulators. Each channel carries one of several video devices (e.g., satellite receivers, VCR, etc.). Each injected channel requires a guard channel on each side, so it can be difficult (not impossible) to find combinations that do not interfere with one another. I inject a total of six channels for now, but have more that I could utilize.
Despite this favorable configuration, I managed to have difficulty when we added digital OTA reception. This, from an antenna that I had once used to watch Cleveland VHF broadcasts (some 150 miles away)! I'm sure that I had just timed it right and got a good Tropoduct, but still it was pretty cool and a testament to my gear (and geekiness :-). The problem was that I wasn't obtaining enough signal from the Detroit area digital broadcasters. Part of this was due to less than optimal transmission levels, potentially the first generation decoder in my Unity Motion HDTV receiver, and the requirement that at least half of the gained signal be shared with the rest of the house (lest I find myself in hot water).
Anyway, I managed to acquire a Channel Master 4248 antenna and a Channel Master 7775 pre-amp (on top of the Lansing tower to the left). Both devices are UHF-only since all digital broadcasters in our area are UHF. I used RG6 Quad for the downlead which, after passing the WWW, goes directly into the Unity Motion. With the exception of FOX (which IMO has little of value beyond NFL and NASCAR), I get very good reception characteristics. I do, depending upon atmospheric conditions, occasionally have to utilize the 4248's dedicated rotor.