Simulcast Solutions NBL4 Narrowband Booster Limiter Installation and Operating Guide

Transcription

1 Simulcast Solutions NBL4 Narrowband Booster Limiter Installation and Operating Guide Copyright 2011 by Simulcast Solutions 18 Port Meadow Fairport, NY Phone: Fax:

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3 Table of Contents 1.0 Introduction NBL4 Front Panel Controls and Indicators NBL4 Rear Panel Connections Typical NBL4 Applications Connections and Pinouts NBL4 Configuration and Adjustments How to Enter the Setup Mode Audio Input Scaling Adjustment Audio Output Level Adjustment (Gain) Audio Limiting Adjustment Maximum Audio Output Adjustment Limiter Release Time Adjustment Audio Limiting Threshold Adjustment Function Tone Notch/Reinsert Adjust (optional) Miscellaneous Controls and Adjustments Bypass Audio Processing Restoring Factory Defaults Using the RS-232 Serial Port Specifications Theory of Operation Warranty Page 3

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5 Voice Optimizer NBL4 Narrowband Booster Limiter Installation and Operating Instructions 1.0 Introduction The NBL4 Narrowband Booster Limiter is a four channel rack-mounted audio processor for radio communication systems. Typically useful in transmit circuits, the NBL4 incorporates Digital Signal Processing (DSP) to boost low-level audio and limit the output to prevent transmissions outside FCC channel spacing envelopes. Boosting the low level audio and limiting the final output provides a consistent audio level in both transmit and receive applications without the need for constant adjustment. The NBL4 provides front panel adjustment of all parameters, front panel LED indication of average and peak audio levels, and audio level metering for all four channels on an LCD display. The NBL4 also provides support for EIA function tones (tone remote) by notching the F1 function tone sequence and reinserting it after the boost/limit functions. Power-off bypass is provided and connects the inputs directly to the outputs in the event that power to the unit is lost. All audio inputs and outputs are 600 ohm impedance, transformer-coupled, and balanced. The default nominal audio level is -10 dbm. 2.0 NBL4 Front Panel Controls and Indicators The NBL4 incorporates an LCD display on the front panel to aid in setup and to allow viewing of audio activity during normal operation. The display provides an audio level metering function for each of the four channels. Four LEDs provide a peak audio indication for each channel, allowing the input audio level to be set without the need for other measuring instruments. Finally, the NBL4 contains a single rotary control with a pushbutton switch which allows adjustments to be made to the operating parameters for each channel. These settings are saved to a non-volatile memory and automatically restored whenever the unit is powered on. NBL4 Front Panel Page 5

6 3.0 NBL4 Rear Panel Connections The NBL4 rear panel contains four RJ-45 jacks for audio inputs / outputs (two for the pairs of audio inputs and two for the pairs of audio outputs) and a coaxial power connector with a plastic lockdown, shown in Figure 1, for the included +12VDC AC adapter. A pushbutton switch on the rear panel allows bypassing of the audio processing for tests and configuration, and a DB-9 RS-232 connector provides an interface to upgrade firmware in the field and perform factory diagnostics. NBL4 Rear Panel Chassis Ground NOTE: For maximum ESD protection connect the Chassis Ground stud to a frame or Earth ground connection. Figure 1 Detail of Power Connector Lockdown Page 6

7 Units equipped with the ±48 VDC power option can operate from a ±36 to ±72 VDC power source. The input power is fuse protected with a 2.0 Amp Slo-Blo fuse. Power connections are made on a terminal block that accepts 1/4 spade lug connector or bare wire. Crimp style connectors are provided. 4.0 Typical NBL4 Applications The NBL4 may be used in transmit and receive applications. Some typical applications are shown in Figures 2 and 3. In Figure 2 the NBL4 is being used to boost received and voted audio prior to being sent to the transmitter. In Figure 3 the NBL4 is being used to boost console audio as well as the received audio from a repeater. Console Audio NBL4 Voting Application Voted Receiver Voter Channel To TX#1 or Simulcast Channel Additiona l Channel Channel NBL4 Figure 2 The 4 channels of the NBL4 are completely independent and can be used for transmit processing or for boosting audio going to a console. Page 7

8 NBL4 Application for 2 Repeaters RX Audio Channel 1 Repeat Console Audio Channel 2 Console RX/TX #1 Console Audio Channel 3 RX/TX #2 Console Channel 4 NBL4 Repeat RX Audio Figure 3 Page 8

9 5.0 Connections and Pinouts The NBL4 incorporates RJ-45 jacks for audio interfacing. Each RJ-45 jack contains the connections for two channels, either input or output. The pinouts are as follows: Pin CH1,2 IN pins 8 and 7 CH1,2 IN pins 2 and 1 CH3,4 IN pins 8 and 7 CH3,4 IN pins 2 and 1 CH1,2 OUT pins 8 and 7 CH1,2 OUT pins 2 and 1 CH3,4 OUT pins 8 and 7 CH3,4 OUT pins 2 and 1 Connection CH1 balanced input Tip and Ring CH2 balanced input Tip and Ring CH3 balanced input Tip and Ring CH4 balanced input Tip and Ring CH1 balanced output Tip and Ring CH2 balanced output Tip and Ring CH3 balanced output Tip and Ring CH4 balanced output Tip and Ring Table 1 - Rear Panel Audio Connector Pinouts NOTES: 1. Pins 3-6 on each RJ-45 jack are not used in the NBL4 and should not be connected. 2. If CAT5 networking cables are used for interconnect the brown/white pair will correspond to channel 1 or 3, while the orange/white pair will correspond to channel 2 or The NBL4 is completely bypassed (inputs connected to outputs) when the power is off, so interface cabling may be verified by removing power from the unit and verifying that audio passes from input to output. Figure 4 - RJ-45 Connector Pinout Page 9

10 Standard RJ-45 crimp-style connectors may be used for the RX audio inputs and TX audio outputs. A typical connector and the pin numbering is shown in Figure 4. NOTE: In the event that the NBL4 should need to be removed from service the audio inputs may be connected to the audio outputs by unplugging the cables from the rear panel of the NBL4 and connecting them together using the standard RJ-45 female-female couplers provided in the ancillary kit. Such a coupler is shown in Figure 5. Figure 5 - RJ-45 Female-Female Coupler 6.0 NBL4 Configuration and Adjustments Once the NBL4 audio interconnections have been made the unit must be adjusted for desired operation. The unit is shipped with the following default settings for each channel: Input scaled so nominal input level -10 dbm Output Boost +10 db Limiting threshold -15 dbm Compression 6:1 Ceiling 0dBm Compressor release time 250msec This means that each channel expects a nominal input level of -10 dbm and that the output is set to provide a gain (or boost) of 10 db over the input. When the input level reaches -16 dbm the unit will begin to limit the output level, and will only allow a 1 db increase in output level for every 6 db increase in the input level. The output is hard limited at 0dBm. Finally, the unit will continue to limit the output level for 250 ms after the input signal falls below the limiting threshold. For many installations these settings may be sufficient to allow proper operation and proper boost/limiting out of the box. The following section describes how to make adjustments to these settings when the factory defaults are not suitable for a particular application. Page 10

11 NBL4 Configuration, Basic Steps (described in detail below): Enter setup mode from the front panel. Scale the audio INput level to match your nominal level to the NBL4. The input gain control can be numerically set or can be adjusted until the LED corresponding to the channel being adjusted just lights on voice peaks (or when a test tone at the desired level is injected at the input.) Adjust the OUTput gain for the desired boost. Select the amount of limiting (COMPression ratio.) Select the ceiling the output shall not exceed (MAX level.) Select the point at which limiting begins (THRSHold.) Select the amount of time the limiter continues to operate after the signal drops below the threshold (RELease time.) Adjust the settings for function TONE notch/reinsert (if desired) 6.1 How to Enter the Setup Mode When the NBL4 is powered on the unit performs internal diagnostic tests and then displays a signon banner on the display showing the firmware version. After approximately 5 seconds, the NBL is operational and the display shows an audio input level meter for each channel as shown in Figure 6. Figure 6 - Default NBL4 Audio Level Meter Display To enter the setup mode press the ADJ/SEL control on the front panel. (This is a rotary control with a pushbutton.) When the NBL4 is in setup mode you ll see the display shown in Figure 7. Figure 7 - NBL4 Setup Mode Display Select the channel you wish to adjust by rotating the ADJ/SEL control until the triangular cursor is to the left of the desired channel. Then push the ADJ/SEL button. (If you enter setup mode and don t Page 11

12 wish to make any adjustments just press the ADJ/SEL button again when the cursor is beside the EXIT label and you ll return to the main operating display.) If you selected CH1 (channel 1) above you ll see the display shown in Figure 8. Figure 8 - Channel 1 Setup Display You may select the parameter you wish to adjust by rotating the SEL/ADJ control and pressing it when the cursor is beside the desired parameter. Note that parameters can only be changed when the NBL is active. While in bypass, no settings can be changed. 6.2 Audio Input Scaling Adjustment When IN is selected from the menu in Figure 8 you ll be presented with the display shown in Figure 9. Figure 9 - Audio Input Level Adjustment The factory input default is set to -10dBm, and can range from +17 dbm to -28 dbm. Alternatively, with an input signal present at the desired level, adjust the ADJ/SEL control until the front panel LED corresponding to the channel being adjusted just comes on during voice peaks or when a test tone is injected at the desired level. The audio meter on the LCD display should indicate approximately halfscale when the audio input gain is adjusted correctly. When you have adjusted the input gain to the desired setting press the ADJ/SEL button to save this setting and return to the previous menu. Note that many of the adjustments are relative to the audio input value selected and changing the input scaling value may readjust other settings. Page 12

13 6.3 Audio Output Level Adjustment (Gain) NBL4 Manual Revision 1.32 The NBL4 comes from the factory with the Boost set to +10dB. If you want to empirically set the boost level, from the Channel Setup Display (Figure 8) select OUT and press the ADJ/SEL control to adjust the output level. In the CH Output Gain menu rotate the ADJ/SEL control for the desired output level. This should be the amount of gain or boost that you require in your system. The output gain setting goes up to db in 1.5 db steps. When you have adjusted the NBL4 output level for this channel to the desired level press the ADJ/SEL control to save this value and return to the previous menu. 6.4 Audio Limiting Adjustment Figure 10 Audio Output Level Adjustment From the Channel Setup Display (Figure 8) select COMP and press ADJ/SEL. You ll see the display shown in Figure 11. Figure 11 Audio Limiting Adjustment (Compression) The compression value controls how much the NBL4 limits the output signal when the input signal increases. Figure 11 shows the default value of 6.0:1. This means that for every 6 db of signal increase on the input the output will only increase by 1 db once the limit threshold has been exceeded. This setting controls how aggressively the output is limited, and is adjusted for the preference of the user in the particular application. Extremely high compression values will allow for a wider range of input signals, but may cause the audio to sound squashed while lower values will have less effect on the audio but will allow less boost to be added without exceeding the desired output level. The range of compression settings from 1:1 (no compression) to 11:1 in 0.5 db steps. Press the ADJ/SEL control to save the desired setting and return to the previous menu. Page 13

14 6.5 Maximum Audio Output Adjustment NBL4 Manual Revision 1.32 When MAX is selected from the menu in Figure 8 you ll be presented with the display shown in Figure 12. Figure 12 Max Audio Output Ceiling The factory input default is set to 0dBm, and can range from +17 dbm to -28 dbm. When you have adjusted the input gain to the desired setting press the ADJ/SEL button to save this setting and return to the previous menu. 6.6 Limiter Release Time Adjustment From the Channel Setup Display (Figure 7) select REL and press ADJ/SEL. You ll see the display shown in Figure 13. Figure 13 Limiter Release Time Adjustment The release time is the amount of time the limiter continues to operate after the input signal falls below the input threshold you are about to set in the next step. Stated another way, it s the amount of time before the system begins boosting the input signal again after a large signal has cause the system to limit the output signal. Setting the release time too low may cause the system to limit and boost between words or syllables, causing a pumping effect. Setting the release time too high may prevent the first few low level signals not to be boosted after a large system has limited the output. The release time is adjustable and has a factory default set to 250msec and a range of values from 100 ms to 1650 ms in 50 ms steps. Once you ve adjusted the release time to a suitable value press the ADJ/SEL control to save the desired setting and return to the previous menu. Page 14

15 6.7 Audio Limiting Threshold Adjustment NBL4 Manual Revision 1.32 From the Channel Setup Display (Figure 7) select THRSH and press ADJ/SEL. You ll see the display shown in Figure 14. Figure 14 Audio Limiting Threshold Adjustment The threshold is the point at which the system begins limiting the output level. The unit comes from the factory set at -16dBm, that is, when the input is at -16dBm, the compression starts. You can also use the visual method to fine tune the audio shaping. The upper line of the display is an expanded audio level meter, while the lower line shows the input level at which limiting will begin. This makes it easier to set the threshold while an input signal is present. Note that there is some hysteresis in the limiter operation, so the threshold may not correspond exactly to the audio level, but it is useful for adjustment purposes. If the threshold is set too high the input audio may never exceed the threshold and the limiter will never be activated. If the threshold is set too low the limiter may be activated all the time, and there won t be any boost apparent in the output signal. The threshold range is --34 to - 4 dbm. Once you ve adjusted the threshold properly press the ADJ/SEL control to save the desired setting and return to the previous menu. 6.8 Function Tone Notch/Reinsert Adjust (optional) If you are using the NBL4 in a transmit audio application and you are using the EIA F1 tone keying sequence you may wish to adjust the tone notch/reinsert parameters. The NBL4 has the ability to notch out the function tones and reinsert them into the audio stream after the boost/limit functions. This prevents the NBL4 from changing the amplitude of the function tones, and also prevents the function tones from triggering the boost or limiting functions of the NBL4. The following adjustments are only relevant if you are using the EIA F1 function tone in your system. From the Channel Setup Display (Figure 7) select TONE and press ADJ/SEL. You ll see the display shown in Figure 15 & Figure 16. Figure 15 Function Tone Notch/Reinsert Adjustment Page 15

16 Figure 16 Tone Attenuation There are two adjustments available in this menu. You may turn the notch/reinsert function on or off, and you may reduce the level of the reinserted tones relative to the output gain setting. The level adjustment ranges from no tone attenuation to 30dB of attenuation. Setting the attenuation to the same value as the gain, negates any boost on the keytone levels. As with other menu selections, use the ADJ/SEL control to select and adjust the desired setting and press the control to save it. 7.0 Miscellaneous Controls and Adjustments 7.1 Bypass Audio Processing During input and output level adjustments all effects of the limiter can be turned off temporarily by momentarily pressing the BYP switch on the rear panel. Limiter functionality for all channels will be turned off and the LEDs on the front panel will flash at a one second interval. This can be useful for making adjustments to input or output levels without the limiter interfering with the output level. When the unit is in Bypass, the controls cannot be adjusted. Press the BYP switch again to restore normal operation. 7.2 Restoring Factory Defaults Should you ever need to start over and restore the NBL4 to its factory default settings: 1. Remove power from the NBL4. 2. Push the rear panel BYP switch and hold it down. 3. Apply power to the NBL4. 4. The NBL4 will display the normal power-on banner on the LCD display and then the display will clear. Continue to hold the BYP switch down for at least two seconds after the display clears. 5. Release the BYP switch. 6. The NBL4 will restore its settings to factory defaults and display a message confirming this. Press the BYP switch again to acknowledge. 7. Finally, the NBL4 will report an abnormal reset which is the result of resetting the factory defaults. This is normal. Press the ADJ/SEL control and the unit will then start normally with all settings as they were when the unit was shipped. 7.3 Using the RS-232 Serial Port The serial port connector on the rear panel is not used in normal NBL4 operation. It may be used for firmware updates if additional features are added to the product. You will be provided information on upgrading the firmware in the NBL4 when such updates become available. Page 16

17 8.0 Specifications Audio NBL4 Input Level Boost Limiter threshold adjustment Compression adjustment range Release Time Ceiling Input / Output Impedance -10 dbm is factory default (adjustable from -28 to +17 dbm) 10 db is factory default (adjustable up to 23 db) -16dBm is factory default (-20 dbm to 0 dbm is range) 6.0:1 is factory default (1:1 up to 11:1 in steps of 0.5) 250msec is factory default (100msec to 1650msec is range) +5dBm is factory default (-20 dbm to +10 dbm is range) 600 ohm nominal, Balanced and transformer coupled Channels 4 Connectors Notch Filters with Reinsert Latching Bypass Frequency Response Crosstalk Total Harmonic Distortion Attack Time (fixed) Internally generated noise 2 x RJ-45 input 2 x RJ-45 output User selectable. (Allows 1950 and 2175 Hz tones to pass without affecting boost/limit) Manual Selection, Automatic on Power Fail 300Hz to 3000Hz <40 db < 1% at 0 dbm < 10 msec < 50 db Page 17

18 Power requirements Misc NBL4 +11VDC to 500 ma with VAC to 12VDC adapter included 48VDC option available Model numbers NBL4-12/115 for +12VDC version w/ac adapter NBL4-48 for 48VDC version RS-232 Port for firmware updates DB-9F, ,200 baud Size 1U high 19 rackmount, 6 in. deep Operating conditions FCC Compliance -30 to 60 C operating, up to 85% humidity non-condensing <discuss w/doug> This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation. Note: Shielded cables were not required to achieve FCC compliance. Page 18

19 9.0 Theory of Operation This section describes the theory behind the operation of the NBL4 Narrowband Booster/Limiter. The NBL4 is a 4 channel device which provides audio compression and limiting functions for narrowband land mobile radio (LMR) systems. Since all 4 channels operate identically this section only describes the operation of a single channel. Limiter Operation In normal operation the user selects a channel to adjust and makes adjustments to the audio levels, limiting threshold, compression value, and limiting release time. These values are saved in the microcontroller s non-volatile memory, and are sent to the DSP where the audio processing firmware uses the values to make the necessary adjustments. An audio signal input to the CH1 input connector is transformer coupled through T1 to U13, an op-amp, and from there is capacitively coupled to the A/D converter input. If the user has adjusted the audio input and output levels, commands are sent to the programmable gain blocks in the A/D and D/A converter to achieve the desired input and output gains. The boost desired by the user is handled by the programmable gain blocks prior to any DSP operations. The DSP then samples the audio input at an 8 KHz rate, and saves the resulting 16 bit digital value in memory. This audio level value is compared to the threshold level selected by the user. If the peak audio value is above the limiting threshold value then the audio signal must be limited. The past history of the input level is also tracked to determine where audio peaks occur, and the peak value is updated accordingly. The resulting peak digital value is used as an index into a lookup table to determine how to attenuate the current input signal based on the desired compression level. Compression levels are specified and applied in terms of decibel ratios. For example, a compression ratio of 6:1 means that for every 6 db of signal increase on the input the output value will only increase by 1 db. The values in the table are logarithmic values which represent the amount of attenuation which must be applied to the input signal in order to limit the change in output level to that specified by the user. When the attenuation value (which is a number between 0 and 1) is fetched from the table it is multiplied by the input signal to produce the limited result. This signal is then sent to the D/A converter which produces an analog output. This output signal (now limited based on the user s settings) is interfaced to the TX1 output jack via the U6 op-amp and output transformer T5. Now the DSP software starts a timer which is based on the user s selection of limiter release time. While this counter is non-zero the DSP continues to limit the output level, even if the input signal falls below the limiting threshold. If the signal rises above the limiting threshold before the timer has expired then the timer will be reset to the original release time value, ie. the release time starts again. But if the timer expires and the input level has not exceeded the limiter threshold then the DSP will no longer apply any attenuation to the output signal, and the system is no longer in limiting mode. Function Tone Reinsert (Side Channel) Operation The NBL4 DSP software also provides a side channel for EIA function tones. The side channel is implemented by a digital notch filter at the two frequencies used by the EIA F1 tone. In this way the function tone is not presented to the limiter algorithm, and therefore does not affect limiter operation. But the function tone values are preserved by bandpass filters (again implemented by the DSP) and saved for reinsertion after the limiter processing has been applied. The user has the option of specifying additional attenuation for the function tone values if desired. Before the final NBL4 audio Page 19

20 output value is sent to the D/A converter the saved function tone value is added to it. The resulting analog output is properly limited without being affected by the function tone, while the function tone level is unaffected by the NBL4 processing. Miscellaneous Functions In addition to communicating with the DSP, the NBL4 microcontroller also monitors the bypass switch to see if the user has requested that all DSP processing should be bypassed. If the bypass switch is pressed then the digital input value is simply passed directly to the D/A converter, resulting in an output signal with no processing applied. At power-on the microcontroller also checks for proper DSP operation and communication, handles firmware upgrades, and checks to see if the user wishes to reset the NBL4 settings to factory defaults. Hardware Description The NBL4 consists of a DSP-based audio processor which is controlled and monitored by a separate microcontroller. The DSP is a Texas Instruments TMS320VC5509A, and the microcontroller is an Atmel Xmega128A3. The microcontroller communicates with the DSP via a dedicated high speed serial port. The user interface consists of a rotary encoder and a push button control and an LCD display. The user selects desired settings using the rotary control, and results and status information is displayed on the front panel LCD. All user interface functions are performed by the microcontroller, while all audio processing functions are performed by the DSP. Audio input and output is via RJ-45 jacks on the rear panel. These connectors are transformer coupled to analog interface circuitry in the form of low-noise op-amps. The op-amps are interfaced to 16 bit analog-to-digital (A/D) and digital-toanalog (D/A) converters, which are, in turn attached to the DSP. All audio processing is done in the digital domain. Programmable gain blocks in the A/D and D/A converters handle audio input and output level adjustment. Page 20

21 10.0 Warranty The NBL4 is warranted against defects in materials and workmanship for a period of one (1) year from the date of shipment. No other Warranties are Expressed or Implied. Simulcast Solutions LLC disclaims all warranties of any kind with regard to products provided by Simulcast Solutions, including without limitation any implied warranty or merchantability or fitness for a particular purpose. Simulcast Solutions LLC shall have no liability or responsibility to the original customer or any other party with respect to any liability, loss, or damage caused directly or indirectly by this product, provided by Simulcast Solutions, replacement parts or units, or services provided, including but not limited to any interruption of service, excess charges resulting from malfunctions of hardware or software, loss of business or anticipatory profits resulting from the use or operation of this product, whatsoever or howsoever caused. In no event shall Simulcast Solutions be liable for any direct, indirect, special or consequential damages whether the claims are grounded in contract, tort (including negligence), or strict liability. Simulcast Solutions LLC s obligation under this warranty is limited to the cost of in-factory repair or replacement, at their option, of the defective product or the product s defective component. This Warranty does not cover any costs for installation, reinstallation, removal or shipping and handling costs of any warranted product. In all cases, the customer is responsible for all shipping and handling expenses in returning product for repair or evaluation. Simulcast Solutions will pay for standard return shipment via common carrier. Expediting or special delivery fees requested by the customer will be the responsibility of the customer. Contact Simulcast Solutions LLC at nblsupport@simulcastsolutions.com for warranty support. Page 21