The "TOAD", which I assume you're talking about the one at 1350 AM, is required to reduce power and change its transmitter pattern by FCC rules. The general rule is the change occurs at local sunset which as summer progresses and the sun sets at a later hour would mean that it would change/reduce later in the day and then as sunset slowly heads back the other direction, would be earlier. The power reduction/signal change is a requirement to keep them from interfering with other stations on the same frequency in other cities. AM stations travel farther at night due to the ionosphere. Some stations are required to make the change, others such as KFI which are licensed on what is called a "clear channel" do not. Hope this helps.
