For those who live in Campbell, California and would like to use an Off The Air aka OTA antenna to directly receive broadcast television signals from San Francisco Bay Area regional television transmitter sites, the following chart provides information on receiving area signals. This information is oriented for people with modest antennas, especially indoor antennas as most apartment residents use and not for those with expensive outdoor antenna arrays high above the ground. The information is reformatted from information on links at bottom of image. The location used for the chart was approximately downtown Campbell, California. See links to obtain information for other locations. Although the below information is location specific, there is useful general information about antennas and broadcast signals. To copy the chart as a jpg image, Mouse right button click image then Save Picture As to download.
The TV Channel column is the familiar television channel displayed on HDTV tuners when switching through channels. Notice it reflects Station call signs ie. KNTV channel numbers with a dot one. Unlike former analog broadcast channels, today's digital channels are not actually transmitted in a sequence of lower to higher frequencies per channel numbers but rather old channels were re-allocated to higher 6 megahertz bandwidth frequencies where they could be fit in. The old lower analog frequency bands are now used for other purposes like cell phone transmissions. Note Channel 11 KNTV and Channel 7 KGO still transmit on re-allocated lower frequency bands. During analog television years, the length a rabbit ears antenna was extended to bore a relation to how well an antenna could pick up OTA broadcasts. For instance channel 2 with a lowest band frequency required a longer length while channel 13 a shorter length. In this era channel 2 is broadcast high in the UHF bands so the old antenna adjustments will receive signals poorly.
Reception of OTA signals is sensitive to antenna dipole length. The RF Channel column shows the re-allocated frequency bands. Notice KRON Channel 4 is RF Channel 38. Its center frequency is 623 mhz. Notice KNTC Channel 42 is RF Channel 14 with a 473 mhz center frequency. That is the lowest frequency of the new bands with KQEH Channel 54 at RF Channel 50 near the high end which is RF Channel 52. When an HDTV tuner scans for frequencies, it is the RF Channel numbers that are displayed. The next column 1/4 dipole inches shows the optimal antenna element length for receiving signals. Notice how the dipole length between the lowest and highest bands is 4.24 inches versus 6.29 inches or not very much. That is a reason a small UHF antenna of that size will receive all transmissions in the UHF band fairly well without having to make individual antenna length adjustments as in years past. Notice the long lengths however for noted Channel 7 and 11.
With a small indoor UHF antenna, an important issue is its placement in a room. Broadcast signals propagate with what is termed line of sight. If there are objects between a transmitting antenna and a receiving antenna, signals become attenuated. Accordingly station transmitting antennas are placed on towers on highest local mountains. Thus if one's residence is behind a taller building or trees in the direction of a transmitting antenna, reception will be affected. Accordingly antennas placed higher above the ground will receive better. If one lives in a two-story residence with a tv on floor one, it is better to buy a longer connecting 75 ohm coaxial cable placing the antenna on the second floor at a window versus using the antenna with a short connection to one's tv. It is also better to place an antenna next to a window versus in the middle of a room. Any metal objects near the antenna will steal the signal leaving little for an antenna thus a window with a metal screen will not work. And placing a little UHF antenna just outside a window will be even better.
Additionally antennas are directional meaning they need to be pointed towards incoming signal directions. On the chart the transmitter location and trans angle columns indicate the direction an antenna ought be oriented. Notice many of the stations in our area use the same transmitter sites that is good because most channels can be received well with a common receiving antenna orientation. The difference between Mt. Sutro in the city of San Francisco and San Bruno Mtn in South San Francisco is minor from Campbell. Due north is zero degrees, 270 degrees is due west, and 215 degrees is midway very close to 316/319. So one needs to understand how their residence is oriented to north and west which is easily noted by looking at any map. With a small UHF loop antenna, the hole the loops makes broadside is what needs to be oriented towards a transmitter. It does not matter if rotated 180 degrees from so.
Two other issues are distance between transmitting antenna and receiving antenna and transmitting signal strength. The Mt. Sutro and Mt. San Bruno sites are 42 miles and 38 miles distant. A little UHF antenna can easily pick up an unblocked solid signal from that distance. Although many antenna products proclaim the superiority of antennas with amplifiers to boost signals, usually that is a waste of money because they don't change the signal to noise levels which is more important. In other words boosting a weak noisy signal will usually not result in better reception free of annoying digital signal breakup. Better to leave that to much more sophisticated RF input circuitry within a tuner. Many indoor antennas have VHF rabbit ears plus a UHF loop. If rabbit ears are removed so all is received with the UHF loop the result is likely to be better including Channel 7 and 11. The kilowatts column shows the signal strength. Notice how Channel 7, 11, have relatively weak transmitting power. That is to limit interference transmissions to same channels just outside our region and because big network stations make less money when people cut the cord from cable corporations and instead receive OTA broadcasts for free. Accordingly they just meet FCC requirements with ironically both channels more difficult to receive than most of the small stations. Of note, both Channel 7 and Channel 2 have additional small power transmissions on a different RF Channel for those who live in Santa Clara County. Usually the Mt. Sutro transmissions will work however during cloudy stormy weather that can affect signal strength, one might re-orient towards Milpitas where the transmitting antennas are located on ridge line above.
On a personal note, I have not received cable television for years and before that for decades received only Basic Cable for about $15 per month that had just a short list of channels. Those with an interest in receiving OTA signals may of course also subscribe to cable television and simply switch modes on their tuner to receive either. It is not because I haven't been able to afford cable and that it is too expensive. And not because there is much any person in this modern era could not find much of interest and entertainment from. But rather much like the habit of reading daily newspapers, such will consume too much of my leisure time. Each of we m-f 8-5 working people have limited leisure time that I would rather spend time over my life in other more active ways than watching others or watching whatever. In other words on balance I would rather be out interacting and doing rather than watching others do so. That is not to say I never watch or enjoy movies, sports, and other visual media, or play video games, but rather prefer a more balanced life.