Larry Baysinger

On the night of 20 July 1969, Larry Baysinger recorded Neil Armstrong and Buzz Aldrin from a yard in south Louisville. He was a technician at WHAS, call sign W4EJA, and the antenna was one he built. Glenn Rutherford of the Courier-Journal was there. The story ran on 23 July 1969, on the front of section B: "Lunar Eavesdropping: Louisvillians hear moon walk talk on homemade equipment."

Baysinger recorded the transmission from Armstrong's backpack. The backpack was the transmitter, on 259.7 MHz, the short link meant for the lunar module. Armstrong's own voice is on it. Aldrin's voice is on it too, relayed: Aldrin's backpack sent Aldrin on 279.0 MHz to a receiver in Armstrong's backpack, and Armstrong's backpack put both men on the signal Baysinger heard. Houston, Collins, and the public-affairs commentator are not on that signal. Their voices went the other way, from Earth to the lunar module, and the lunar module sent them to the suits on 296.8 MHz.

Larry Baysinger and the antenna, Louisville, 1969. One story, an open yard, and the frame above the neighbor's roof.

The night

Baysinger had been building antennas for weather satellites and radio astronomy. Local advice was that the Moon was out of reach. The weather was cloudy, so he and Rutherford aimed by getting behind the antenna and sighting along it. The mount was motorized and had to be guided by hand. When the Moon drifted out of the beam, the signal went away. Pointed back at the Moon, it came back.

His wife and daughter watched the landing on television in the house. The same words arrived on his receiver about 5 to 10 seconds before they arrived on the television. He told Christopher Graney in 2009 that he had hoped to hear something NASA cut out before it reached the public, and that he did not. What he heard went out on television.

Rutherford wrote that they recorded about 35 minutes, including the walk. The first reel ran out while they were celebrating the signal. The reel that survives in recognizable form is shorter. In 2009 Baysinger transferred the usable stretches. The complete public file is about five minutes. Graney's account, the audio, and Baysinger's own log of that file are on the Otter Creek observatory page. The ARRL writeup is Eavesdropping on Apollo 11.

• 1969 article: the clipping, and a copy.
• 2019, Courier Journal: the article, and a PDF.
• The recording: WMA, and an MP3.
• His 2009 log of that file: WMAtranscript.pdf.

The frequency

He was listening on 259.7 MHz, amplitude modulated. That is VHF channel B. In the two-man moonwalk configuration it is the commander's backpack, transmitting to the lunar module, and it carries both men.

Three VHF channels were in use on the surface:

• 296.8 MHz, AM, channel A. Lunar module to both backpacks. This one carries Houston, relayed.
• 259.7 MHz, AM, channel B. Armstrong's backpack to the lunar module. Armstrong and Aldrin. This is the one on the tape.
• 279.0 MHz, FM. Aldrin's backpack to a receiver in Armstrong's backpack. Aldrin only. Armstrong's set folded that audio into the 259.7 transmission.

The lunar module and the command module also used those two AM channels, 296.8 and 259.7 MHz, for VHF voice between the ships. The 279.0 MHz link existed only between the backpacks.

The Earth link was unified S-band, a different band, and a different set of frequencies.

Lunar module (NASA TN D-6974, page 15):

• Transmit 2282.5 MHz
• Receive 2101.8 MHz
• The VHF transmitters delivered about 3.8 watts average at the diplexer

Command module (NASA TN D-6723, and the 1966 Unified S-band paper):

• Uplink 2106.40625 MHz
• Downlink 2287.5 MHz on the phase-modulated carrier
• A separate FM downlink at 2272.5 MHz

The downlink is the uplink multiplied by 240/221, so the two carriers stay coherent. During the moonwalk the lunar module was sending television, so its S-band carrier was in the wideband FM mode. Voice, picture, and telemetry were one broad signal. A small antenna had a chance on the VHF backpack carrier and none on that S-band mode. The pictures needed the big dishes.

The backpack transmitter in the range study is half a watt. NASA TN D-4915 (December 1968) uses "the newest astronaut transmitter of 0.5-watt output" at 279.0 and 259.7 MHz, and figures how far an astronaut could walk from the lunar module before the link dropped.

How the backpack reached Earth

The portable life support system radio did not talk to Earth. It talked to the lunar module, and the lunar module relayed.

NASA TN D-6974, page 26, on the two-man set that flew:

"In essence, the first EVCS transmitted voice and data to the second EVCS. Then, the combined EVCS-1 and EVCS-2 voice and data were relayed to the LM by the second EVCS."

NASA TN D-8093, page 41, on the same hardware:

"The composite signal of voice and four subcarriers is relayed from the LM to the Earth by S-band, and the S-band communications signals from Earth are relayed to both crewmen through the LM."

The April 1967 lunar-module communications study guide says the same thing as a switching path. EVA voice and suit data arrive on VHF channel B and are routed to the S-band equipment for transmission to the ground. Voice from the ground arrives on S-band and is routed to VHF transmitter A for the astronauts.

The lunar module operations handbook puts it in one sentence: "When both astronauts are outside the LM, the LM relays communications between the astronauts and MSFN." The rover relay in the next sentence is later hardware. Apollo 11 had no rover.

So the path that night was:

1. Aldrin's backpack transmitted on 279.0 MHz FM to Armstrong's backpack.
2. Armstrong's backpack combined both voices and transmitted on 259.7 MHz AM to the lunar module.
3. The lunar module retransmitted that audio to Earth on 2282.5 MHz.
4. Houston's reply came up on 2101.8 MHz to the lunar module, and the lunar module retransmitted it to both suits on 296.8 MHz.

Baysinger heard step 2. He did not hear step 4. A recording of a Louisville television station would have had Houston, Collins, and the commentator. The tape has the two men the 259.7 MHz carrier is built to carry.

The same relay is why the Nixon Apollo 11 phone call could reach the suits at all. Nixon's voice went to Houston, to the lunar module on S-band, and then out on 296.8 MHz. It was never on the frequency Baysinger was recording.

What is on the tape

The surviving file starts at ground elapsed time 110:20:06 on 21 July 1969, 03:52 UTC, 11:52 p.m. Eastern Daylight Time in Louisville. Aldrin is describing the soil he has just kicked. It runs through his remark about feeling cooler in the shade at 110:25:09. Baysinger's annotated pages of the NASA commentary carry the recording on through Aldrin's description of contrast and color at 110:28:22.

The air-to-ground transcript below is the Apollo Lunar Surface Journal. Houston's lines are in that journal, between these, and they are not on the tape. On the noisy carrier his own log gives a few of the cable lines to the other man. Both voices are on the one transmitter.

110:20:06 Aldrin: Houston, it's very interesting to note that when I kick my foot (garbled) material, with no atmosphere here, and this gravity (garbled) they seem to leave, and most of them have about the same angle of departure and velocity. From where I stand, a large portion of them will impact at a certain distance out. Several (garbled) percentage is, of course, that will impact (garbled) different regions out (garbled) it's highly dependent upon (garbled) the initial trajectory upwards (garbled) determine where the majority of the particles come down, (garbled) terrain.

110:21:24 Aldrin: I've noticed several times in going from the sunlight into the shadow, that just as I go in, I catch an additional reflection off the LM that, along with the reflection off my face onto the visor, makes visibility very poor just at the transition (garbled) sunlight into the shadow. I essentially have so much glare coming onto my visor (garbled) shadow until (garbled) helmet actually gets in the shadow. Then it takes a short while for my eyes to adapt to the different lighting conditions. (Garbled) inside the shadow area, visibility, as we said before, is not too great, but with both visors up (garbled) you can certainly (garbled) what sort of footprints we have and the general condition of the soil. Then, after being out in the sunlight a while, it takes ... Watch it, Neil! Neil, you're on the (TV) cable.

110:22:40 Armstrong: Okay.

110:22:41 Aldrin: Yeah. Lift up your right foot. Right foot. It's still... Your toe is still hooked in it.

110:22:45 Armstrong: That one?

110:22:46 Aldrin: Yeah. It's still hooked in it. Wait a minute. Okay. You're clear now.

110:22:51 Armstrong: Thank you.

110:22:55 Aldrin: Now, let's move that over this way. Okay. I've got it.

110:23:32 Aldrin: The blue color of my boots has completely disappeared now into this... Still don't know exactly what color to describe this other than (a) grayish-cocoa color. It seems to be covering most of the lighter part of the boot (garbled) color that (garbled) very fine particles.

110:24:23 Aldrin: Roger. I'll try that.

110:24:30 Aldrin: Well, I had that one inside my mouth that time.

110:25:09 Aldrin: In general, time spent in the shadow doesn't seem to have any (garbled) thermal effects. (garbled) feel inside the suit. There is a difference, of course, in the (garbled) radiation and the helmet. So I think there's a tendency to feel a little cooler in the shadow than we feel out in the Sun.

110:28:22 Aldrin: As I look around the area, the contrast, in general, is... comes about completely by virtue of the shadows. Almost (garbled) looking down-Sun at zero-phase very light-colored gray, light gray color (garbled) a halo around my own shadow, around the shadow of my helmet.

110:28:40 Aldrin: Then, as I look off cross-Sun, the contrast becomes strongest in that the surrounding color is still fairly light. As you look down into the Sun (garbled) a larger amount of (garbled) shadowed area is looking toward us. The general color of the (garbled) surrounding (garbled) darker than cross-Sun. The contrast is not as great. Surveying all the dusty area that we've kicked up (garbled) considerably darker in texture.

That is the salvage. The 35 minutes in the 1969 story are the reel they made that night. What could still be heard forty years later is this stretch.

The neighboring house

The house used for this check is on Deanna Drive, in the Okolona section of south Louisville, on the east side of the street. The street runs north-south. The claim was that a neighboring house would have blocked the signal.

The Moon's position is from JPL Horizons, DE441, for that house, with atmospheric refraction included. Azimuth is degrees clockwise from north. Elevation is the center of the Moon. West is 270°.

• 02:39 UTC, hatch open: azimuth 247.9°, elevation 16.0°.
• 02:56 UTC, Armstrong steps off: azimuth 250.7°, elevation 12.9°.
• 03:15 UTC, Aldrin down: azimuth 253.7°, elevation 9.5°.
• 03:48 UTC, the Nixon call: azimuth 258.7°, elevation 3.4°.
• 03:52 UTC, the surviving tape starts: azimuth 259.3°, elevation 2.6°.
• 04:08 UTC, the center of the Moon on the horizon: azimuth 261.7°.

The Moon was west-southwest, moving toward due west as it set. The next-door houses are north and south of his lot. From the front yard they are not on that line. The houses across the street are. They are one story, which is what the 1969 photograph shows.

A roof about 5 meters high, 30 meters away, seen from an antenna a few meters up, covers the bottom 4 degrees of sky. The Moon was above those roofs from the opening of the hatch through Armstrong's step, Aldrin's descent, and the Nixon call. It comes down to that roofline only at the end, in the minutes on the surviving tape, when the center of the Moon was 2 to 3 degrees up.

The photograph shows the antenna in an open yard, with the frame higher than the one-story roofs and open sky over the neighbor. And 259.7 MHz has a wavelength of 1.15 meters. A roof edge that hides the Moon from the eye does not make a hard wall for a wave that long. The signal on the tape is the one that got through that geometry, aimed at the Moon, and gone when the Moon set.

Antenna gain

Three accounts follow. Each summary uses only that source.

ARRL

Eavesdropping on Apollo 11, by Christopher Graney, retells Glenn Rutherford's 23 July 1969 Courier-Journal story. The antenna is "a fully steerable 8 by 12 foot corner horn," built from spare aluminum, nylon cord, and chicken wire. The receiver was a rebuilt 20-year-old set from an Army tank, which Baysinger had modified. The mount was motorized and had to be guided by hand. On the night of the landing he and Rutherford aimed it by getting behind it and sighting along it. The weather was cloudy and the Moon was hard to see. Once the antenna was on the Moon it could be left for a little while. When the Moon drifted out of the beam, the signal disappeared.

The article says Baysinger recorded 35 minutes of VHF conversation transmitted among Armstrong, Aldrin, and Collins, and that those minutes included President Nixon's message of congratulations. It says he did not try to receive the S-band signals from the main Moon-to-Earth link, which the article calls encoded. The signal on his receiver arrived about 5 to 10 seconds before the same words on television. It was noisy, but you could hear what was going on. Rutherford wrote that the receiver worked to perfection that Sunday night. This page names the antenna and the size. It does not give a gain, an efficiency, or a link budget.

Phil Karn

Phil Karn, posting as ka9q on 1 March 2010, ran a preliminary link budget: Larry Baysinger's recording of A11. He found the link quite marginal, and consistent with the noisy recording.

He used a backpack transmitter of 500 milliwatts on 259.7 MHz, cable and diplexer losses of -1.2 dB, and a backpack antenna gain of -2 dB. Those backpack figures came from a Bellcomm analysis of Apollo 15 surface propagation that used Apollo 14 backpack figures. He called them probably good, and he called the -2 dB figure pessimistic. The distance was 386,000 km: JPL Horizons for the center of the Moon as seen from Louisville at 0400 UTC on 21 July 1969, minus the Moon's 1700 km radius. The receiving antenna was 96 square feet, taken from the article he was reading. The system noise temperature was 300 kelvin. In a 3 kHz bandwidth the signal-to-noise ratio was -10.8 dB.

The efficiency is his assumption. He wrote: "Every antenna has an efficiency factor, but it is not given here so I assumed unity, which is perhaps a little optimistic." He entered that assumption as 100 percent. He was least confident in the 300 kelvin noise temperature. An antenna pointed at the horizon sees the Earth in half the beam and the sky in the other half. At 300 MHz that sky noise is already low, in the tens of kelvins, and the preamplifier noise has to be added. He did not know what preamplifier Baysinger used. The result, he wrote, is certainly not broadcast quality or even good quality, and neither is the recording. The Moon was setting, so the antenna would also take a reflection off the ground, which can add to the direct signal or subtract from it. On the tape the signal fades slowly, and at times it is pretty much gone. If he knew the antenna height above the ground, he could calculate the fade period.

Empirical Earth

Empirical Earth gives the 8 by 12 foot aperture a theoretical ceiling of 19.25 dBi at perfect efficiency. If the antenna is read as a horn, the page assumes 60 to 70 percent efficiency and gets 17 to 18 dBi. If it is read as a corner reflector, a dipole feed in front of flat screens, the page uses the published range for that type, 10 to 15 dBi. Baysinger's sketch is a folded-dipole array in front of flat chicken-wire screens, and the newspaper photograph shows the same flat mesh, captioned as a reflector. The page calls it a corner reflector and uses the 10 to 15 dBi range. The sketch shows four folded dipoles, which the page says sits above the single dipole that published range assumes. The design source allows a 90 degree corner or a 60 degree corner. The page says no surviving image is sharp enough to show which one he cut.

The budget uses a 0.5 watt transmitter, -3.0 dBW. It subtracts 1.7 dB of cable and triplexer loss, measured on Apollo 14, and 2.0 dB of antenna pattern loss. The effective radiated power is -6.7 dBW. Free-space loss is 32.45 + 20 log(259.7) + 20 log(384,400) = 192.4 dB.

• 13 dBi, noise figure 8 dB, 6 kHz: signal-to-noise -27.9 dB, or -21.9 dB with a ground reflection.
• 16.2 dBi, noise figure 5 dB, 3 kHz: -18.7 dB, or -12.7 dB with a ground reflection.
• 18 dBi, noise figure 2 dB, 6 kHz: -13.2 dB, or -7.2 dB with a ground reflection.

The page keeps the higher rows as a ceiling. Even granting the horn, it says the link does not produce clean speech. At no assumption in the table does the page get ordinary real-time speech. The most favorable case is about -7 dB, where the noise is five times the signal. What the arithmetic permits is intermittent fragments. In a 100 Hz bandwidth the carrier reaches -1.9 dB, so the carrier was findable and the speech was at the edge. A receiver noise figure of 2 dB against a stock tube set at 8 dB is 6 dB, which the page calls the difference between fragments and nothing.

See also

• Moon landings
• MCToon Big List
• Nixon Apollo 11 phone call