As Soviets plan countermissiles, East Europe is visibly glum

East Germany and Czechoslovakia are waiting apprehensively for the first installment of the Soviet Union's threatened response to new NATO missiles. The rest of Eastern Europe is keeping its head down, still hoping the United States and the Soviet Union will go on negotiating before the tit-for-tat missile deployment is taken any further.

Such hopes carry little optimism. The popular mood is visibly increasingly glum; and leaders concerned either with economic reform or, at least, preserving meaningful economic relations with the West are frankly pessimistic about prospects if the arms race goes on.

From East Germany recently and elsewhere in the Communist bloc - even from the Soviet Union itself - it is being reported that ordinary people have begun to talk in quietly nervous terms of a danger of war, something which has not been heard for many years.

''If deployment goes ahead,'' said one Communist bloc journalist, ''without doubt the Russians will break off or withdraw from the Geneva negotiations. Countermeasures, you may be sure, will follow.''

The NATO deployment, the same commentator said, would be for the Soviets ''a final proof'' that negotiations with the Reagan administration were ''without point'' and Moscow would have no option but respond in kind.

Deployment remains NATO's order of the day. And the first of the Soviet Union's countermeasures was announced Oct. 24 in a Soviet agreement with the East German and Czech governments to prepare installations for short-range ''operational and tactical (battlefield) weapons complexes'' in both countries.

These are predictable choices. They are the two economically strongest, most ''conformist'' Soviet allies. They are the two Warsaw Pact countries bordering on NATO area - specifically, West Germany, which is to get most of the cruise and all of the Pershing II missiles.

The other East Europeans are not involved (not now, at least). Poland, still under internal crisis is a questionable spot for new Soviet missiles. Nor are Hungary, Bulgaria, and Romania (which, under present circumstances, would reject deployment) directly concerned.

But, whether ultimately they might be involved or not, all these countries know they would be seriously affected if tensions between the superpowers - and between East and West generally - hardened, and deployment and counteraction supplant negotiations.

Both Bulgaria and Romania can expect economic stress from escalation of East-West tension. Bulgaria, which is market-minding its economy and ''liberalizing'' its agriculture, has growing ties with the West and Japan. Romania is more dependent on US and West European economic goodwill and support than ever.

Pioneering Hungary stands to lose most of all, with its ''new economic mechanism'' a going concern, a number of profitable joint ventures with the West and, above all, plans - and the need - to carry its ''open'' market to both East and West still further.