I MUST CONFESS to the Mobil Oil Company that although I did watch "Death of a Princess" on PBS last Monday evening, I didn't see it very well.

You see, we in Washington get the Public Broadcasting programs on ultra-high frequency waves, as opposed to the four commercial stations in this town who bring up their shows on very-high frequency. There is quite a difference in the two. VHF programs come through loud and clear. But to get a UHF station you first have to sandpaper your fingertips like a safecracker, and then twirl the dial carefully.

Sometimes, if atmospheric conditions are right, we get to see only one McNeil and one Lehrer on the "McNeil-Lehrer Report" -- but on other evenings they appear as ghosts in a dust storm, and there is no way to distinguish between the two.

We're one of the few cities in the country that watched every episode of "Upstairs, Downstairs" through what looked like a blizzard, and Dick Cavett always comes into our living room as if he's being drenched in acid rain.

But it's a small price to pay for getting PBS programs, and one gets used to it.

Frankly, I had no intention of watching the docu-drama on the Saudi Arabian princess until there was such a fuss about the show. Had the Saudis kept quiet about it, I'm sure the program would have had its usual prime time PBS audience in Washington of about 140 families.

But after reading so much about the controversy, curiosity got the better of me, and I decided to tune in the program.

This precipitated an argument between my wife and myself. She felt I was being disloyal to the Mobil Oil Company.

"If they don't want us to watch the program, they must have a good reason," she said.

"Of course, they have a good reason," I told her. "They do a lot of business with Saudi Arabia, and they're just trying to suck up to the Royal Family."

"I'm sure that's not it," she said. "Mobil is a very public-service orientated company. If you read their paid advertisements, you will realize that they have only the best interests of the American people at heart."

"Maybe," I said. "But I don't think it's the role of an oil company to tell the American people what they should or should not watch on television."

"They give a lot of money to Public Television to bring us programs, and they know what's worth seeing. Mobil does so much for us and asks so little in return. I think the least we could do is respect their wishes when they ask us not to look at a program about a Saudi Arabian princess who committed adultery."

"Look, just because they're making a bundle of money selling gasoline doesn't give them the right to censor our TV viewing. We should be smart enough to decide what is good and what isn't."

"Don't talk so loud. Someone from the company might hear you."

"I don't care. Let them hear me. It's still a free country."

"It won't be if the Saudis cut off our oil for watching public television."

"Look, I've only got an hour to get the picture tuned in. You can go upstairs if you don't want to watch."

Unfortunately, it was a bad night for PBS reception; and instead of one princess, we watched three caught in an adulterous act.

"You see," my wife said. "Mobil told you the show would be distorted."

"It isn't the show. It's the set," I shouted.

"Well, as far as they're concerned, ti's the same thing."