Declare

The man was nodding rapidly, his bald head shiny with sweat now. “And you can’t go back to Oxford, our people in Europe approved your profile and specifically asked for you. A teacher! Damn it! WT was the main description for you, that’s wireless telegraphy. I’ll have to interrupt the transfer, send on an explanation and a—a recommendation, God help me! Either way is bad, but I think I’d be most remiss if I didn’t ask for a two-week postponement on delivery of you, so as to run you through the accelerated course at our hedge school in Norfolk. There’d be no facilities across the Channel.” He stared at the bewildered Hale as if at an armed lunatic. “I’ll have to drive you up to Norfolk tonight, on the unsupported assumption.” A drop of sweat had rolled down the man’s jowls, and it occurred to Hale, for the first time, that being a spy might be to live constantly in the shadow of people like the coldly jovial man he had met in the Haslemere railway station.
    Of course he never saw the little fat man again after being dropped off that afternoon at a pub off the A12 up in Norfolk, where two men bought Hale a pint and then walked him to an old farm-house up an unpaved track somewhere near Great Yarmouth; and for the next fourteen days Hale sat with a dozen other uncommunicative men in a sweltering barn and studied wireless as he had never studied anything before.
    He learned about the Heaviside Layer, an atmospheric blanket of ionized air molecules that would reflect radio waves and let them “skip” across great distances; the layer was only about sixty miles above the earth during the day, with the sun pressure forcing it down, but at night it sprang up to a height of two hundred miles and split into two layers, and though transmission was clearer and stronger at night, signals could sometimes get caught between the layers and bounce along for thousands of miles before finally escaping to earth. The skipping effect was necessary for long-distance transmission, but Hale’s instructors spoke of the Heaviside Layer with a sort of irritated respect, for its capricious billows and varying height often scattered signals and caused fading in the reception. Illicit spy broadcasts were referred to as les parasites , flickering covertly between the bandwidths of official transmissions, but sometimes his instructors seemed to use the French term for the knots of turbulent activity in the nighttime Heaviside Layer.
    He learned to file and tin a soldering iron, and where to use a metallic flux and where to use a non-conducting rosin flux in connecting wire splices; and he learned how to re-wire the heater circuit of a direct current radio set so that it would work off alternating current, and what socket and vacuum valve needed to be changed, and how to avoid getting squealing and dead spots from the more sensitive cathode valve. At various points on the roofs of the barn and the barracks-like farmhouse he practiced setting up a Herz off-center-fed aerial, stringing the enameled wire at maximum angles to existing power lines or house wiring to avoid picking up accidental induction currents, and using ceramic coffee creamers and Coca-Cola bottles as makeshift insulators.
    But mainly he learned the dit-and-dah characters of the International Morse code, concentrating on the numbers rather than the letters.
    And he learned to use one-time pads. These were tiny books whose flimsy pages were nothing but columns of random four-digit numbers; given a practice sentence to encipher, he would assign a number to each letter of it—usually just 1 for A, 2 for B, and so on—and then after having written the message out in this pedestrian substitution-cipher he would add to each of the numbers one of the numbers from the one-time pad, taking them in order off the pad page from left to right. None of the one-time pad’s numbers was so high that the addition of any two-digit number would make it a five-digit number. When he tapped out the resulting code groups, his partner on the other side of the table would copy the numbers and then use a duplicate one-time pad to subtract the pad’s numbers and derive the original substitution-cipher message, and then quickly convert that all the way back into letters. Immediately after sending and copying, both copies of the used one-time pad page would be formally burned or eaten.
    Accuracy was more important than speed here, and the students were constantly warned against the