In Depth

The Lunar Module has been designed so that we can re-create 1960's and 70's style ground to space and space to ground communications from a Eurorack module, with either live speech and audio from an electret or dynamic microphone to the MIC input or samples / recorded audio to the synth INPUT.

 

Using the Lunar Module in a performance

Here's a short video from Wayne Taylor (Dreams of Wires) showing how the Lunar Module can be used to add some drama to a musical performance!

 

 

Video user guide

We have put together a video guide explaining all of the features of the Lunar Module and showing how to get the very best from it. The above performance video is included at the end.

 

 

How it all works

Ground to Space (Houston) mode:

Set the Capsule and Quindar toggle switches to off (up position). Press and hold in the grey Quindar PTT (push to talk) button. A short (250mS long 2525Hz Quindar on) tone will be heard, then talk into the microphone or trigger an audio sample. When the message is complete release the Qindar PTT button, a short (250mS long2475Hz Quindar off) tone will then be heard. The level of the Quindar tones is controlled by the QUIN LEV control, and the mic or sample level is controlled by the MIC LEV and INPUT controls respectively.

Space to Ground (Capsule Mode)

The following controls become active in Capsule mode - Distortion, Noise addition, HUM / LGM tone addition and Bandwidth Limitation.

Press and hold the grey Capsule PTT switch and talk into the microphone or trigger an audio sample. Adjust the Distortion control to add distortion to the audio stream, adjust the NOISE control and associated COLOUR control to add coloured noise to the audio stream and finally we can also add 50 or 60Hz mains hum or LGM tone using the LGM-H LEV control and its associated FREQ control. The signal is also bandwidth limited (LF and HF cut) to simulate transmission over phone lines - back in the day the received signal from ground stations was relayed back to Houston over phone lines.

We have added toggle switches for the Quindar and Capsule functions, so that these can be latched on if required, and we have also included Quindar and Capsule Gate inputs, so that they can also be controlled remotely with +5V modular gate signals - the toggle switches need to be off (up) in order for the Gate and PTT buttons to function correctly.. There are staus LED's for Quindar and Capsule which indicate when they are active.

 

Available with either Black (Dark Edition) or Silver front panels.

 

Control functions

MIC LEV control: Sets the level of signal from the MIC input

DISTORT control: Sets the amount of distortion applied to the input and mic signal. This is only active when CAPSULE is active (Led illuminated)

QUIN LEV control: Sets the level of Quindar tone generated when operating Quindar switch or PTT button.

INPUT control: Sets the level of signal from the INPUT jack, it is optimised for +/-5V p/p modular level signals.

NOISE LEV control: Sets the level of Noise that is added to the Input / Mic signal. This is only active when CAPSULE is active (Led illuminated)

COLOUR control: Changes the colour of the Noise source, LP filtering applied if rotated anti-clockwise of centre, or HP filtering if rotated clockwise from centre.

LGM / HUM control: Sets the level of HUM or LGM tone added to the input / mic signal. This is only active when CAPSULE is active (Led illuminated)

FREQ control: Changes the frequency of the HUM or LGM tuned Noise tone.

LGM / HUM three way switch: Selects between variable 50Hz, 60Hz HUM or LGM tone.

Jack Sockets

MIC IN jack: Input for an electret mic, dynamic mic or similar level signal source. It also provides power for electret capsules (NOT condenser phantom power)

INPUT jack: Input for higher level signals. This input is optimised for +/-5V p/p modular level signals.

Q GATE jack: An external +5V gate signal can be patched into here to allow external control of Quindar Tone function.

C GATE jack: An external +5V gate signal can be patched into here to allow external control of Capsule On / Off function.

OUT jack: Module output - the output signal is nominally at +/-5V p/p Eurorack audio signal levels,

 

What are Quindar tones and why were they needed?

The Quindar tones are the short sine wave burst that is heard at the start and end of a transmitted message from Houston Mission Control to the Apollo spacecraft, the end tone being a slightly lower frequency than the initial tone. They were necessary for two reasons -

1) Because the radio signals used were directional and rely on line of sight

2) In the 1960's the leasing of international telephone lines was hugely expensive.

In order to communicate with a spacecraft that is orbiting the earth a number of ground stations were needed at strategic places around the World so that line of sight could be maintained from ground to the spacecraft without of loss of communication when it went out of sight of Houston Mission Control. Each of these ground stations had transmitters and receivers, however the transmitters could only be switched on during transmission of a ground to space message, at other times they needed to be turned off so that they did not interfere with any signals being transmitted from the spacecraft to ground. So this would require two (very expensive) telephone lines connecting Houston to each of the other ground stations - one phone line for voice transmission / reception, and a second phone line that could be used to key on and off the remote transmitters as needed.

The Quindar tone system was devised to reduce the number of international leased phone lines from two down to one. It worked as follows:

When a PTT (push to talk) transmission signal is sent from Mission control it triggered a 2525Hz sine wave with a duration of 250 milliseconds which was sent over the phone line before the massage was spoken- this tone turned on the transmitters at all of the ground stations around the world, so that the message from Houston was sent to space from all of the ground stations, so no matter where the spacecraft was in orbit it would not be in a transmission blind spot. As soon as the PTT button was released at the end of the voice message a second, but lower 2475Hz sine wave with a duration of 250 milliseconds was sent over the phone lines and this lower frequency tone keyed off the transmitters. By doing this only one telephone line was needed for both voice and keying on off of transmitters. The frequencies of 2525Hz and 2475Hz were chosen because international telephone lines at the time were restricted to 3kHz of bandwidth, and these frequencies sat nicely in the "sweet spot". Quite an ingenious system!

The tones are so named because the Qunidar company was the Telecoms equipment supplier to NASA, and it was convenient to refer to the sine wave burst switching as "Quindar Tones". It is interesting that they actually remained in use until the STS-134 Space Shuttle mission of February 2011, after which all communications were digital and no in-band signalling was needed.

What kind of microphone do I need for the MIC input?

An electret microphone is probably the most authentic as we understand that they were used on the Apollo missions, however all electret microphones capsules require 1.5v to 3v of phantom power to function, and this is either supplied from a battery inside the mic itself, or (more commonly) the power is fed to the mic capsule from the mic socket itself - so we need to use an electret mic with a TRS (stereo) 3.5mm jack plug, where the ring of the jack is powered. Some electret mics only have a mono jack socket and require the tip to be powered, unfortunately these will not work as the MIC IN socket on the Lunar Module only has +3V of phantom power connected to the ring.

We have got pretty good results from low cost tie clip microphones, which are readily available from Ebay, Amazon, AliExpress etc, and here is a photo of a suitable tieclip microphone. Just search for "tie clip microphone" or "Lavalier microphone" and you should be able to find something suitable, just ensure that it has a 3.5mm TRS (stereo) non-locking jack plug.

If you would prefer something rather higher quality then the Rode Lavalier Go is a very good solution.https://www.rode.com/microphones/lavaliergo There are similar mics available from Sennheiser and other manufacturers.

Alternatively, there are low cost desktop electret mics available from Amazon, Ebay etc which are also suitable, we have tested the model shown below and it works well too. The mic shown sells for around GBP10 and the performance is good for such a budget mic. Do note that it states on the label "Condenser Microphone" however this is a bit misleading as this particular model is actually an electret rather than condenser mic.

Don't be too concerned if the mic you see has a different brandname from this one, if it looks the same then the chances are that it is the same model as this mic is an OEM product and the branding tends to be done by the distributors rather than the manufacturer. It is also sold as SF-666 Condenser Microphone. Just make sure that the one that you buy has a "stereo" 3.5mm jack plug as shown which provides the phantom power to the electret capsule from the Lunar Module Mic socket. This model is also produced as a USB mic with a USB cable attached, however the USB version is not compatible and cannot be used with the Lunar Module.

Electret mics tend to be omnidirectional in response, so you may well encounter feedback if it is in close proximity to your system speakers. Either use headphones or keep the levels low and it shouldn't be a problem.

Dynamic microphones such as the Shure SM58 or similar can also be used, the only slght problem here is that most dynamic microphones have a cable terminated with a 1/4" jack plug, so a 1/4" to 3.5mm mono jack extension cable or adapter would be needed to connect it. Please note that we only need a mono 3.5mm jack in this case , TRS (stereo) is not required because we do not need to power the microphone capsule itself.

Studio condenser mics are not really suitable here, as they usually require +48V of phantom power which is fed through an XLR socket, and the signal level may be too low even if external powering is used.

But can I use the Lunar Module for anything else?

Of course - it's a Eurorack module and can be used for signal processesing and a few other creative tasks too.

The most obvious use is to feed a modular level audio signal into the INPUT jack, we can then add coloured noise, tuned LGM noise or mains hum to this signal in any mix desired, and it can be switched remotely between this and a clean sound by patching a gate signal to the C GATE input.

The onboard Noise Generator offers a variety of coloured / filtered noise from the output when the capsule toggle switch is latched on. This is very useful in a multitude of modular synth patches, particularly percussion.

The LGM tone is also available at the output, and this offers a variety of tuned noise sounds - a particularly useful patch is to connect a microphone to the MIC Input and then place it in close proximity to a loudspeaker that is connected to the output of the module - this gives a howling feedback if placed too close, but if it is taken a little further back and some LGM noise is added to the signal then some interesting Theremin like tone can be created by moveing the microphone nearer or further from the speaker while manually adjusting the LGM frequency.

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Internal signal flow of the Lunar Module

Having an idea of how everything is connected internally in a module can give a much better idea of how to get the best from it, so here's a useful block diagram of the main component parts of the Lunar Moduler:

 

More demos

Here's a demo video from our distributors and good friends Alex4.de

The original Alex4 youtube video can be found here

 

 

 

 

 

 

 

 

 

 

 

 

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