SOMETIMES CONGRESS does things that, by themselves, make absolutely no sense. The trick, as we old Washington hands long ago learned, is to put them together. I'm not saying that the sum will be any less loony than the parts, but at least you'll get a rough idea of what's going on.

Take my hand, and come with me to Cuba, a country whose capacity to unhinge minds in the U.S. government can never be estimated. In the dog days, when Congress starts contemplating Castro, you have to send for the butterfly nets.

First of all, the Senate voted to go to war with him last Wednesday. Yes, they passed, by a vote of 68 to 28, a resolution that said that we would use "whatever means may be necessary including the use of arms" to stop him. Later, it is true, they watered it down somewhat -- there are fainthearts in every crowd -- but reading the record you can hear the drums and the trumpets of the truly manly chaps in the upper chamber.

Might the senators themselves lead the charge? Would we have the first war in history fought by old men instead of young men?

There is reason to hope. I offer, by way of evidence, another Senate vote, that of Tuesday, in favor of a third Senate gym. Some of us, when the 100 voted themselves a second gym a while back, speculated that they were going to field a team in the Olympics.

We were wrong. Now I see that the third gym is a cover. The whole sports complex will be used as a training ground for the invasion of Cuba. There could be no other reason, I submit, that any group, mostly men over 50, would need such extensive body-building facilities. Can you think of one?

Sometimes, when they get low, our senators whimper that they have only one swimming pool. Some inner cities don't even have that, but please think in national security terms. Would the ghetto-splashers be strengthening their muscles with a view to bringing Fidel Castro to his knees?

The Senate swimmers would not be doing laps or floating on their backs trying to think of ways they could explain to their constituents why they voted $736,400 for a third gym at a time they are telling the lame, the halt and the blind back home to pull up their socks. No. I venture to say they will be under the command of Sen. Steve Symms, (R- Idaho). (I presume, as the author of the "whatever means is necessary" resolution, he would be supreme commander of the expeditionary force.) And they will be practicing wading ashore at some Cuban strand. Why not the Bay of Pigs? It has high name recognition.

Symms has other qualifications besides his fiery resolve to put Casto in his place. He is a famous gun collector. He could arm the Senate warriors from his own private arsenal, thereby cutting costs probably in the range of the cost of the third gym.

If you are still with me, I invite you to the House of Representatives, lest you think that Castro's ability to make men mad is limited to the world's greatest deliberative body.

Last Tuesday, the House gave a big push to Radio Marti, Ronald Reagan's odd scheme for telling the Cubans about Cuba from a tower built in Florida.

Thinking about Radio Marti for more than two minutes reduces the mind to mush. What is Radio Marti for? Do we need to spend approximately $10 million to win hearts and minds in Havana?

Doesn't anybody in Congress remember what happened in 1980? Thousands of Cubans flung themself on anything that floated to get themselves to our shores. We wish to create more refugees for Florida, more applicants for their welfare rolls?

Radio Marti's chief House backer, a Democrat, it should be noted, is Dante Fascell of Florida. He says the Cubans don't know enough about what Castro is up to. Now, mind you, Radio Marti would have no correspondents in Cuba -- at least until the senators land. Jesse Helms, one of Symms' hawks, was a longtime broadcaster, and once the Big Three (for the Third Gym) Division hits the beach, he could go live from the Bay of Pigs.

Radio Marti is a big part of the Big Picture because Fidel Castro has threatened to jam it.

And that -- hang on tight here -- takes us back to Des Moines and Ronald Reagan's old radio station, WHO, over whose airwaves, as "Dutch" Reagan, he was a happy sportcaster from 1933 to 1936.

His alma mater station could be the first casualty of the radio cold war. It has the same frequency as Radio Marti, which means that WHO will be restricted to a range of 45 miles. That means that the farmers in 5 surrounding states who tune in at 5 a.m. for the latest grain and livestock prices will be out of luck.

But it means much more than involuntary sacrifices in rural and business America.

Jamming will be considered an act of war. A Defense Department official, one James Duncan, told WHO executives that "If Castro jammed Radio Marti, it would warrant a surgical strike."

In other words, folks, I hate to tell you, what you've been hearing this week are the guns of August.