Quote:
Originally Posted by rohit
http://www.choisser.com/channels.html shows that KGO 7 is transmitting with the lowest power among all the Sutro tower broadcast tenants - and they have an application for a 2 kW station on monument peak under consideration so things may improve.
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Watch out when comparing transmitter power. Low frequency signals propagate more easily than high frequency signals so it takes less power to cover the same amount of distance.
Low frequencies are also better at diffraction (bending over mountain tops), so they tend to do a better job of "filling in" areas that are behind terrain blockages.
As an example, take a look at the following two coverage maps.
Here is
KABC's coverage map.
Here is
KXLA's coverage map.
Both of these transmitters are on Mount Wilson overlooking the Los Angeles area. KABC is on channel 7 with 25 kW while KXLA is on channel 51 with 1000 kW. If you compare the two coverage maps, you will see that they both do an excellent job of covering everyone in the Los Angeles basin despite the 40-times difference in broadcast power.
KABC actually does a better job of reaching people in the high desert north of LA in places like Lancaster and Palmdale due to the better diffraction effects on channel 7.
Even though KGO's 23.8 kW *sounds* low, it is actually plenty of power for that channel. All of your Sutro channels are reaching your location with Noise Margins of about 50-60 dB, and KGO is in the middle of the pack at around 54 dB.
It all boils down to having the right antenna for the job. Your DB4 is probably getting around +10 dBd of gain on your UHF channels, but it's channel 7 performance is probably somewhere around -18 dBd (that's about a 28 dB difference compared to your UHF channels). You might want to take a look at this page,
http://www.hdtvprimer.com/ANTENNAS/comparing.html, and scroll down to the section labeled "Using a UHF antenna for VHF". Adding a VHF antenna to your setup will probably get you back to around +7 dBd of gain on your VHF stations (a 25 dB improvement from where you are now).