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@@ -24,11 +24,11 @@ This software uses <a href="http://www.alsa-project.org">Alsa</a> kernel driver
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<p>
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Use a radio transmitter for 2-meter band to transmit to A-Netz or B-Netz phones.
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Use a radio transmitter for 70-cm band to transmit to C-Netz or NMT phones.
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An amateur radio can be used, but be sure it is not limited to amateur radio frequencies and channel rasters.
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For A-Netz the transmitter must be able to transmit arround 162 MHz.
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For B-Netz the transmitter must be able to transmit arround 153 MHz.
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For C-Netz the transmitter must be able to transmit arround 465 MHz.
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For NMT the transmitter must be able to transmit arround 463 MHz.
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An amateur radio can be used, but be sure it is not limited to amateur radio frequencies and channel spacing.
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For A-Netz the transmitter must be able to transmit around 162 MHz.
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For B-Netz the transmitter must be able to transmit around 153 MHz.
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For C-Netz the transmitter must be able to transmit around 465 MHz.
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For NMT the transmitter must be able to transmit around 463 MHz.
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</p>
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<p>
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@@ -39,8 +39,8 @@ This image shows a two-band amateur radio receiver without limitations for the f
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<p>
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I built several transmitters out of modified taxi radios.
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It features a simple digital PLL (configurable by junpers) and allows to directly connect the audio signal to the oscillator.
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This is highly recommended for the C-Netz, because signalling is done by sifting the carrier directly.
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It features a simple digital PLL (configurable by jumpers) and allows to directly connect the audio signal to the oscillator.
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This is highly recommended for the C-Netz, because signaling is done by sifting the carrier directly.
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One unit has a switch to change between A-Netz and B-Netz (2-meter version) and the other units to change between C-Netz and NMT (70-cm version).
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I added an input to switch between two channels for the B-Netz.
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(Whenever a B-Netz phone is paged, the channel must be temporarily switched to the paging channel.)
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@@ -51,13 +51,13 @@ I added an input to switch between two channels for the B-Netz.
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<p>
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Use radio receiver for 2-meter band to receive from A-Netz or B-Netz phones.
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Use radio receiver for 70-cm band to receive from C-Netz or NMT phones.
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The transmitter cannot be re-usedr, because all networks are full duplex.
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A seperate radio is required to simultaniously transmit and receive.
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For A-Netz the receiver must be able to receive arround 162 MHz and 157 MHz.
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For B-Netz the receiver must be able to receive arround 153 MHz and 148 MHz.
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For C-Netz the receiver must be able to receive arround 465 MHz and 455 MHz.
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For NMT the receiver must be able to receive arround 463 MHz and 453 MHz.
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The receiver must support both uplink and downlink frequencies, to make a test loop for the calibration process.
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The transmitter cannot be re-used, because all networks are full duplex.
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A separate radio is required to simultaneously transmit and receive.
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For A-Netz the receiver must be able to receive around 162 MHz and 157 MHz.
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For B-Netz the receiver must be able to receive around 153 MHz and 148 MHz.
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For C-Netz the receiver must be able to receive around 465 MHz and 455 MHz.
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For NMT the receiver must be able to receive around 463 MHz and 453 MHz.
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The receiver must support both up-link and down-link frequencies, to make a test loop for the calibration process.
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</p>
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<p>
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@@ -71,7 +71,7 @@ This image shows a two-band amateur radio receiver that supports all the frequen
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The best solution I could find for low price is the Uniden UBC360CLT.
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It is actually some kind of clock radio with scanner.
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It supports all relevant bands up to about 950 MHz.
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In all bands the channel raster is freely selectable.
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In all bands the channel spacing is freely selectable.
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Up to 300 channels can be stored and simply selected by using up/down keys.
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</p>
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@@ -79,14 +79,14 @@ Up to 300 channels can be stored and simply selected by using up/down keys.
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<p>
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I added a discriminator output to the radio, to get undistorted receive signal.
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This is highly recommended for the C-Netz, because signalling is done by sifting the carrier directly.
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This is highly recommended for the C-Netz, because signaling is done by sifting the carrier directly.
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</p>
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<center><img src="discriminator.jpg"/></center>
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<p>
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In order to keep RF emission low, use a dummy load for lab test.
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Use two seperated antennas for outside use of the mobile phone.
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Use two separated antennas for outside use of the mobile phone.
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Connect one dummy load to the transmitter and another one to the mobile phone's antenna connector.
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</p>
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@@ -99,11 +99,11 @@ My phone did not work correctly with a 5 Ampere 12 Volts regulated power supply.
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I suggest to use an amateur radio power supply with low ripple.
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In my case I use modified ATX-2 power supply for 12 or 13.8 Volts.
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The voltage can be adjusted in most power supplies, but 12 Volts is good enough.
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These power supplies have built-in overcurrent/overvoltage protection.
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These power supplies have built-in over-current/over-voltage protection.
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The ATX-2 power supplies are regulated on the 12 Volts rail.
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I added two plugs and a switch.
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The switch connects to the PS-On line.
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In case of an overcurrent, the switch can be used to reset the protection circuit.
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In case of an over-current, the switch can be used to reset the protection circuit.
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Note that opening a switching power supply can be dangerous and may cause death.
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If you don't have the knowledge about power supplies, ask an expert to help you.
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</p>
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@@ -111,18 +111,18 @@ If you don't have the knowledge about power supplies, ask an expert to help you.
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<center><img src="power.jpg"/></center>
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<p>
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Early tests were done without any wireing between radios and sound adapter.
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Early tests were done without any wiring between radios and sound adapter.
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This may worked for early tests with the B-Netz, but turned out to be a pain in the as.
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It is not possible to keep the levels and avoid feedbacks.
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It is not possible to keep the levels and avoid feed-backs.
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</p>
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<center><img src="headphone.jpg"/><img src="microphone.jpg"/></center>
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<p>
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The sound adapter must be connected to a transmitter and a receiver.
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Coils are suggested for galvanic seperation.
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Coils are suggested for galvanic separation.
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I don't use coils, instead I add extra grounding wire between earth (power supply) and sound interface.
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For adjustemnt I highly recommend to use variable resistors.
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For adjustmnt I highly recommend to use variable resistors.
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This makes the adjustment process faster.
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I use 4.7 K resistor for connecting headphone output to radio input.
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I use 10 K resistor for connecting radio output (discriminator) to microphone input.
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