He bounced around from site to site for a while until he finally exclaimed, “Got it.” He had navigated to a website that was devoted to collectors of the various electronic parts and equipment that the long-out-of-business Haverkit company had made. Pointing to a rectangular metal box that looked like it belonged on a rack of computer parts, he said, “Your friend is looking for a repeater.”

“Which is what?”

“It’s a device that amplifies the range of a broadcast signal by repeating it from one source to another.”

I thought about that for a moment and something clicked. I told Jack, “Before she flipped out on me, Ravenette said that the radioman was describing a huge broadcast network that covered . . . well, she said galaxies. Many galaxies. It can’t be possible that one Haverkit repeater could help boost a signal that much?”

“Of course not,” Jack explained. “These types of repeaters were meant to be used by amateur radio operators trying to extend the range of their broadcasts over relatively finite distances. But sometimes, repeaters like these were used as the hub of what’s called a linked repeater network. With that kind of system, when one repeater is keyed-up by receiving a signal, all the other repeaters in the network are also activated and will transmit the same signal. So if there is a chain of repeaters waiting to hear from this one . . .”

“Just this one?”

Jack shrugged. “Maybe. If that’s how the network is set up.”

“So why doesn’t whoever gave the radioman his job just ship him another one? Send him a replacement for the hub repeater?”

“I don’t know,” Jack said, though he seemed to have a guess. “Maybe,” he said, “for something to exist where the radioman is, it also has to exist here. If it disappears from where we are, it disappears from where he is, too. Or maybe the supply train from his home base—wherever it is—only shows up once a millennium.”

“Do you think that’s funny?” I said to him.

“I think this is a very strange conversation,” Jack replied. “I’m just going with the flow.”

Something else suddenly occurred to me. “You know,” I said, taking another look at the repeater that was still displayed on Jack’s computer screen, “I don’t remember ever seeing Avi fiddling with something like that.”

“It wouldn’t have been something he would have carried back and forth with him, like the radio. It would have been permanently installed somewhere, on high ground.” Then, pointedly, he added, “Like a roof, for example.”

I closed my eyes for a moment, picturing Avi and me on the fire escape of the Sunlite Apartments, listening to the pinging sound of Sputnik’s 10 telemetry signal—and then Avi, frowning, as the radio suddenly went silent. Laurie, he’d said, looking up at the roof, I have to go fix something . . .

Still there was something that puzzled me. “Why would Avi even need a repeater?” I asked Jack. “He was just listening to satellite signals on his receiver. He wasn’t broadcasting.”

“Well,” he replied, “he sort of was.”

Jack asked me to give him a minute and left the room but was soon back, carrying a brown accordion folder. I thought I remembered seeing it months ago when he had told me about the ghost signals, but it turned out that this was a different folder. And it held some very different material.

As he sat back down at the desk and started taking papers out of the folder, he said, “So, I have to tell you that when I did the original research about the ghost signals, I also used the Freedom of Information Act to get whatever I could on Avi, too. I had to know if there was anything . . . well, off about him.”

I realized that he thought I might have been upset by the fact that he had been digging into Avi’s life, but I wasn’t. At this point, I just wanted to hear the rest of the story: what was Avi broadcasting? And why?

“Was there anything strange about what he was doing?” I asked.

“No,” Jack said. “Not at all.”

I looked down at the papers he was pulling out of the folder. They were color photocopies of documents that looked vaguely familiar to me. I had a feeling that I had seen them before, but I couldn’t remember where, or when.

“It turns out that Avi was a member of a Distance Listening Club,” Jack said. “You never heard him mention anything like that?”

“No,” I said. I started leafing through the dozens of documents that Jack had now laid out on his desk and realized that they were copies of what looked like postcards from foreign destinations—some familiar, like Paris and Moscow, but others from places with odd names like Tannu Tuva, or breathtakingly distant, like a town in Tasmania. There was also one from what appeared to be a weather station in Antarctica. Some were in English, some in languages I couldn’t recognize, let alone read.

Suddenly, something focused in my mind; a clouded memory became clear. “I do remember these,” I said. “Avi kept these—the originals—in an album that he used to let me look at. All he ever said was that people had sent them to him.”

“People did send them to him,” Jack told me. “They’re what’s called QSL cards. In radio lingo, that’s a code meaning, ‘I confirm receipt of your transmission.’ If you were a DX-er, which is what distance listening guys were called, you’d send a signal on the short or medium wave band to another DX-er in some distant location, and then the two of you would exchange these QSL cards to confirm that you’d received each other’s broadcast. Some of the cards were very colorful, some had pictures, some were just plain, typed confirmations. From the 1950s up until about the time he died, Avi was apparently a very active member of a Distance Listening Club that had members all over New York. And that’s probably why he maintained a repeater out at Rockaway Beach. It may not even have been his, but it’s also likely that he shared it with everyone else in range. Repeaters are often used by large networks of amateur radio types.”

Interesting as all that was, it still didn’t explain why copies of Avi’s QSL cards had turned up in some government file. I asked Jack about that and he explained, “It was the Cold War era. A lot of these cards are from countries behind the Iron Curtain. Maybe some federal agency kept records of correspondence that went back and forth between the United States and countries they thought of as problematic.”

“Antarctica?” I said, holding up the copy of the QSL card from the weather station, which included a series of call signs and a drawing of a penguin with a big smile on his face. The happy bird was wearing a striped scarf around his neck and on his head, a set of oversized headphones.

Jack shrugged. “It was just the job of some guy at a government desk to intercept these things and make copies. He probably didn’t even know where Antarctica was.”

“Can I have these?” I asked Jack.

“If you really want them, sure.”

I did want them. I was feeling a little nostalgic about these lost-and-now-found postcards, but looking at the penguin again, I was still a little puzzled.

“I can’t really imagine that anybody needed to worry about Avi. I doubt that he was sending secret messages to the Communists. Or to penguins.”

“No, of course not,” Jack said. “And I think they actually gave up on worrying about him pretty quickly. But maybe somebody else heard him and decided to piggyback on his repeater. Remember the story I told you about Howard Gilmartin’s encounter with the gray man on the radar tower during World War II? What if he—and your radioman, and however many others there are—well, what if they were stationed here?” Jack’s voice had a note of incredulity in it even as he confirmed, for himself, that he had come up with the right terminology. “Yes, I guess they’re stationed here. So what if these guys were always trying to find some way to boost their signal? I guess at one point they were trying to use radar towers—where one of them ran into Gilmartin, senior—but eventually it turned out that, of all things, the Haverkit repeater in Rockaway worked best. Maybe because of the thin, cold air out at the beach. Maybe the fact that it was always kept in good working order. Maybe the moon, the tides, and good luck. And maybe,” Jack said, speaking more slowly now, as if he were thinking through every word, “they’d been trying for a very, very long time to find just the right place to link up their network to get the maximum distance out of their signals. Maybe one of the places they tried was in Mali, a couple of centuries ago.”