A drip torch is used to light fire. The fuel in it consists of mostly diesel with some gasoline added to make it a little more volatile. It is used for burnout operations where fuels next to a fireline are burned in advance of a fires arrival. They are used to light prescribed fire. They are used to light slash piles, which consist of thinning debris and other fuel on the forest floor. They are also used to light backfires, a very complex operation involving the ignition of fuels ahead of the head of a fire, which is drawn into the head of the fire the air it is drawing in to burn. With fuel removed ahead of the main fire's head, the advance is stopped. Ignition of backfires is very tricky, with wind direction, fuels, location and timing factors in the tactic's success.
If you enjoy watching fire behavior, understand fire ecology and the stages of forest succession lighting fire is quite fascinating. Unlike arsonists, fire management personnel are using fire to return fire to fire dependent ecosystems, removed by the arrival of European man, resulting in unnatural conditions in forests. Fire managers understand the factors affecting fire behavior and how to use it to imitate the natural role of fire.
The six repeaters on the KNP are not simulcast, at least as of last year. They are used one at a time depending on the location of the person using a handheld.
You may be in a location where you are only able to receive the transmission of the input frequency from the remote base station on Parkridge Peak or Mountain. You are likely out of the range of the repeaters located some distance from Parkridge. You can't hear the output of the six repeaters or the handheld's input frequency so you will only hear dispatch transmitting on the input. The remote base station on Parkridge has a receiver that due to its location, is able to hear the output transmissions of each repeater. The dispatch center at Ash Mountain is linked to the remote base at Parkridge using a phone line, a 400 MHz link or by microwave.
The situation you describe of hearing only what the dispatcher transmits on the repeater input frequency is a situation encountered in many other locations where the remote base is the only mountain top site within range of a scanner. Given what you have told us, I think there is a 80-100% chance that my answer is correct. I've encountered the situation you describe many times in my radio hobby years. The way to verify the answer to what you are hearing is to drive and walk if necessary, to the location of the remote base. Keep the input frequency in manual on one scanner and the output frequency on another. You will notice a very strong signal on the input frequency and a weak one from the distant repeaters your scanner can hear, with only a handheld antenna, while at the remote base station's location. I have no idea how to access Parkridge, but if I was you that is what I would do to verify my suggested description of what is causing you to only hear the input frequency.
Hoffman Peak is not likely providing any coverage for the north end of KNP. The Clark Range on the southern boundary of YNP and Kaiser Ridge north of Huntington Lake are in the way. The repeater in Evolution Valley, north of Muir Pass was put in to provide coverage of the upper South Fork of the San Joaquin River on the north end of the park.
Knowing your location, fuzzhead, would be helpful in determining if what I suggest as the situation you have encountered is correct. I would guess you are in northern Tulare or southern Fresno County, fairly close to the foothills. Maybe in the east or east of Visalia, Exeter, Dinuba or Sanger. If you drive west to almost Interstate 5 I would guess you will pick up the output of a couple of the repeaters. You may be in the shadow of Parkridge where hearing the repeaters, all located east of that location, is blocked by the ridge itself.
This is all conjecture on my part based on what I know of the topography in and around KNP. I could be way off too. I would be most interested in where your scanner is located.
