NV Series
PA Modification
for Improved
Performance in
FM+HD and HD
Modes
IS10001
Issue 0.3 ....................... 02 March 2010
Nautel Limited
10089 Peggy's Cove Road,
Hackett's Cove, NS, Canada B3Z 3J4
T.877 6 nautel (628835) or +1.902.823.2233
F.+1.902.823.3183 info@nautel.com
U.S. customers please contact:
Nautel Inc.
201 Target Industrial Circle, Bangor ME 04401
T.877 6 nautel (628835) or +1.207.947.8200
F.+1.207.947.3693 info@nautel.com
e-mail: support@nautel.com
www.nautel.com
© Copyright 2010 NAUTEL. All rights reserved.
IS10001 - NV Series PA Modification for Improved
Performance in FM+HD and HD modes
INFORMATION SHEET
1 INTRODUCTION
This document provides instructions to modify the subject equipment in the field.
1.1 Reason For Modification
To improve performance in FM+HD and HD modes of operation for the NV series FM
transmitters. The modification will allow the transmitter to comply with spectral limits at higher
injection levels (elevated digital carriers).
1.2 Equipment Affected
This procedure applies to NV series FM transmitters operating in FM+HD and HD modes
which utilize NAPA20A Power Amplifiers in the RF power module and have two-hole core
ferrites installed on inductor L1. Note: If the RF power module or individual PA has a
DWA09-144 label, this modification has already been completed in the factory.
1.2.1 Minimum Software Required
Software version 2.7 needs to be installed. Please contact Nautel if the transmitter is running
with an older version of software.
1.3 Responsibility for Implementation of Procedure
This procedure should be carried out by qualified station maintenance personnel who are
familiar with the NV series FM transmitters.
1.4 Scheduling
Implement this procedure at the convenience of station maintenance personnel. The
transmitter can remain ‘on-air’ (reduced power) while RF power modules are being modified
individually; however, when the injection level is changed and settings are applied, there will
be a brief interruption in ‘on-air’ status (approximately 5 seconds). Additional interruptions
may be necessary during the subsequent steps that optimize the transmitter’s performance.
Prior to commencing the procedure, ensure that the power module shipping hardware has
been removed as per ‘Unpacking and Positioning’ section of the Installation Manual.
1.5 Manpower Requirements
The modifications described in paragraph 2 will require 15 minutes per RF power module to
complete. Depending on your familiarity with the AUI, it may require an additional 30 minutes
to properly create a new preset and optimize the transmitter’s performance as described in
paragraphs 3 and 4.
1.6 Special Tools/Test Equipment
The following test equipment is required:
•
•
•
Standard technician hand tools including a pair of long nose vice grips (Nautel
suggests vice grip model LN6)
Personal protective equipment - safety glasses/dust particle mask/gloves
Vacuum cleaner
NV Series PA Modification for Improved Performance in FM+HD and HD mode
IS10001
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1.7 Materials Required
No additional parts are required.
1.8 Identification of Modified Assemblies
Identifying modified assemblies will inform future maintainers of the current configuration.
Use indelible ink to mark ‘IS10001’ on each PA PWB (NAPA20A) along with ‘IS10001’ next to
the serial number sticker on the chassis for the RF power module (NAA56/01). You should
also add this label to the chassis of the transmitter next to the serial number plate.
1.9 Publications Affected
No publications are affected by this modification.
2 MODIFICATIONS
(a) With the transmitter operating on-air, disable (switch down) ac power and remove RF
power module #1 as described in the transmitter Troubleshooting Manual – ‘Removing
and Reinstalling RF Power Modules’.
(b) With the power module on a bench, remove and retain the 14 sets of M4 hardware
(screws and beveled star washers) securing the right hand side cover.
(c) Locate inductor L1 on the PA PWB and confirm the two-holed ferrite is installed (see
Figure 2). Position the power module on the bench in an upright position, fans down (see
Figure 1). In this position, debris will fall away from the module. Utilize personal protective
equipment as defined in paragraph 1.6.
Figure 1: RF power module positioned upright with fans down
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NV Series PA Modification for Improved Performance in FM+HD and HD mode
IS10001
L1
Figure 2: Location of L1 on PA PWB
CAUTION
Take care not to damage the insulation of the remaining L1 wire loop.
(d) Using a pair of needle nosed vice grips with the jaws set slightly smaller than the depth of
the ferrite, carefully break the ferrite away for the wire loop (see Figure 3). It is advisable
to slightly tilt the module to the side to ensure the ferrite falls ‘away’ from the module.
Clean away any ferrite debris from the module. If possible, operate a vacuum cleaner in
close proximity to L1 while the ferrite is being broken away to minimize ferrite dust
collection in the module.
Figure 3: Vice grips used to break away ferrite core
(e) Repeat step (d) for all nine PA PWBs (8 PAs A1-A8 and 1 IPA – A9) within the RF power
module. Vacuum away any debris from within the module.
(f) With an indelible marker, mark each PA PWB and the RF power module chassis with
‘IS10001’. Also mark the transmitter chassis on the rear upper left corner next to the
serial number plate/label.
(g) Replace the right hand side cover and secure using the hardware retained in step (b).
NV Series PA Modification for Improved Performance in FM+HD and HD mode
IS10001
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(h) Reinstall the RF power module and enable as described in the transmitter
Troubleshooting Manual – ‘Removing and Reinstalling RF Power Modules’.
(i) Repeat steps (a) through (h) with all remaining power modules including any spare power
modules or spare PA’s.
3 OPTIMIZE FM+HD / HD PERFORMANCE
The following paragraphs describe how to configure your transmitter to operate within
spectral limits and at optimal efficiency. It involves:
•
•
•
•
•
recording the transmitter’s current configuration settings and creating a new preset
monitoring and optimizing the transmitter’s ramp-up behavior
optimizing spectrum and efficiency
saving and recording the new configuration settings
saving the new LUT (Look Up Table)
Use the “Process Flow Diagram and Worksheet” in Figure 7 as a guide to perform this procedure.
3.1 Preliminary Tasks
Verify the transmitter is operating without alarms in FM+HD mode, at the licensed Analog
TPO with standard modulation (audio) present or HD mode. It is recommended that the
Controller Average PA Dissipation and Controller PA Volts meters be loaded on the main
screen to assist with this procedure (refer to the Operations and Maintenance Manual; see
Figure 4). A passing spectrum plot displays 3 dB or more margin (-77.4 dBc) between the
IBOC intermodulation products and the blue mask (limit lines) on the analyzer (see Figure 4;
red arrows represent margin). From the transmitter AUI, set the transmitter for Local control.
Figure 4: Spectrum Analyzer with Average PA Dissipation and PA Volts meters
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NV Series PA Modification for Improved Performance in FM+HD and HD mode
IS10001
3.2 Optimize Transmitter Performance
(a) Go to the AUI Menu / Hardware Configuration / HD Settings screen and record the
“Default LUT Height” (forward gain) value on the worksheet (see Figure 7). Exciter A and
B may have different “Default LUT Height” values. The value displayed on the AUI
represents that value stored in the active exciter. Temporarily change over to exciter B, if
applicable, and record the “Default LUT Height” on the worksheet. Change back to
exciter A. From the AUI Menu / Presets screen, while viewing the active preset, record
the current mode, power level (Analog or Digital), injection level and HD PA Volts on the
worksheet.
(b) Save a “new” preset by pressing the Save button in the “Presets” box on the left hand
side of the AUI. The “Save Preset” window will appear and will display the current
presets. Press the “Please Enter a Name” field and enter a new preset name via the popup keyboard; press the Save New button and then press Activate. The new preset will
now be the active preset.
(c) In the new (active) presets Other Audio Settings sub-menu, set LUT Index value to
“Flat”. This is at the bottom of the drop-down menu.
(d) At the top of the preset page, change the IBOC Injection value from the current setting
(e.g., -20 dB) to the new desired injection level. See Table 1 to determine the maximum
allowable Analog TPO vs. injection level vs. frequency vs. transmitter type for FM+HD
(hybrid) mode; or maximum allowable Digital (Total RMS) output power vs. transmitter
type for HD (all-digital) mode.
NOTE
Note that for any FM+HD mode, the power level displayed in the AUI’s Presets page is the
desired analog power setting (TPO). The power reading at the top of the home page is also
the analog portion of the FM+HD output.
Table 1: Transmitter Maximum Power Levels vs. Injection Level vs. Frequency vs. Transmitter Type
Xmtr
Type
NV40
NV30
NV20
NV15
NV10
NV7.5
NV5
NV3.5
FM Max
44.0 kW
33.0 kW
22.0 kW
16.5 kW
11.0 kW
8.3 kW
5.5 kW
4.13 kW
FM+HD
Max
-20 dBc
FM+HD Max
87.5-91.9 MHz
FM+HD Max
92-108 MHz
(Linear Int. b/w -20 & -10)
(Linear Int. b/w -14 & -10)
-14 dBc
-10 dBc
-14 dBc
-10 dBc
32.0 kW
24.0 kW
16.0 kW
12.0 kW
8.0 kW
6.0 kW
4.0 kW
3.0 kW
23.0 kW
17.3 kW
11.5 kW
8.6 kW
5.8 kW
4.3 kW
2.9 kW
2.2 kW
17.0 kW
12.8 kW
8.5 kW
6.4 kW
4.3 kW
3.2 kW
2.1 kW
1.6 kW
29.0 kW
21.8 kW
14.5 kW
10.9 kW
7.25 kW
5.44 kW
3.63 kW
2.72 kW
21.0 kW
15.8 kW
10.5 kW
7.88 kW
5.25 kW
3.94 kW
2.63 kW
1.97 kW
HD Max
12.8 kW
9.6 kW
6.4 kW
4.8 kW
3.2 kW
2.4 kW
1.6 kW
1.2 kW
* Maximum Power is guaranteed into a 1.2:1 or better VSWR only.
(e) Press Activate and monitor the transmitter behavior.
NOTE
The transmitter output power will be interrupted briefly as the system resets and the
Spectrum Analyzer limit lines will change to account for the elevated digital carriers.
NV Series PA Modification for Improved Performance in FM+HD and HD mode
IS10001
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(f) If the transmitter overshoots (i.e., exceeds the set-point) or the ramp-up time is too long
(i.e., PA failures occur), press RF Off immediately and perform the “Optimizing
Transmitter Ramp-Up Behavior” procedure in paragraph 3.2.2 to correct or fine-tune the
ramp-up characteristics, then return to step (g).
(g) Perform the “Optimizing Spectrum and Efficiency” procedure in paragraph 3.2.1.
Continue to perform the “Optimizing Transmitter Ramp-Up Behavior” procedure in
paragraph 3.2.2 unless already done in step (f).
NOTE
Consider the effects of paragraphs 3.2.1 and 3.2.2 simultaneously, as either procedure
affects the other slightly.
(h) Steps (e) through (g) will be repeated for exciter B (if applicable) after all steps have been
completed for exciter A, which includes step 4 – LUT Re-Saving [see step 4(f)].
Figure 5: HD PA Volts setting in the FM+HD (or HD) Preset.
3.2.1 Optimizing Spectrum and Efficiency
(a) Once the transmitter output power settles at the “set-point” power, monitor the 3rd order
inter-modulation products (spectral re-growth – the “humps” that are just outside of the
digital carriers) and the Average PA Dissipation meter reading and take the appropriate
action based on the following two possible conditions:
NOTE
The HD PA Volts value should be decreased as much as possible to bring the intermodulation products within the 3 dB margin. This optimizes efficiency by reducing the
Average PA Dissipation reading. The HD PA Volts can be set under Menu / Preset; change
the HD PA Volts value, then press Activate after each adjustment. It can take up to 30
seconds for the spectrum plot to re-stabilize.
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NV Series PA Modification for Improved Performance in FM+HD and HD mode
IS10001
NOTE
For dual exciter systems, when optimizing HD PA Volts with exciter B (already performed
with exciter A), if it is determined that the HD PA Volts can be further decreased to improve
efficiency – DO NOT (remember that exciter A needs this voltage setting to have 3 dB of
margin and both exciters share the preset setting). Instead, only increase HD PA Volts to
improve exciter B’s spectrum if B is worse than A with the same HD PA Volts (noting the 3 dB
margin and average PA dissipation limits).
i.
Does the spectrum FAIL but Average PA Dissipation is less than
130 W (87.5-91.9MHz) or 150 W (92-108 MHz)?
If so, in the Preset menu (see Figure 5) INCREASE the HD PA Volts value
by 0.5 V (e.g., increase from 48.0 to 48.5). Repeat until the spectrum has 3
dB margin (see Figure 4) and Average PA Dissipation is less than or equal to
the limits specified.
ii.
Does the spectrum PASS but Average PA Dissipation is more than
130 W (87.5-91.9MHz) or 150W (92-108 MHz)?
If so, in the Preset menu (see Figure 5) DECREASE the HD PA Volts value by
0.5 V (e.g., decrease from 48.0 to 47.5). Repeat until the spectrum has 3 dB
margin (see Figure 4) and Average PA Dissipation is less than or equal to the
limits specified.
(b) If the requirements of step (a) cannot be satisfied, the injection level selected (or digital
carrier power) is too high for the transmitter’s configuration (i.e., licensed Analog TPO).
Reduce the injection level in the preset menu (e.g., from -10 dB to -11 dB) and repeat
step (a) until the requirements are satisfied.
3.2.2 Optimizing Transmitter Ramp-Up Behavior
The following steps involve turning the transmitter on and off while monitoring its behavior.
The optimal “Default LUT Height” (forward gain) value will be determined. Repeat these steps
until the transmitter does not overshoot, and ramps up quickly and smoothly without alarms.
(a) Press the Activate or RF On button and monitor the transmitter behavior.
NOTE
While overshooting of the transmitter power is quite easy to identify, determining optimal
ramp-up time is subjective.
i
Does the transmitter output power overshoot? If so, press RF Off immediately and, in
the Menu / Hardware Settings / HD Settings screen, decrease the “Default LUT
Height” by 0.01, press the Set button and repeat RF Off/On while monitoring
transmitter behavior.
ii
Does the transmitter power ramp up quickly (i.e., does it achieve 70-100% of power
in less than 30 s) and smoothly without alarms (e.g., PA/Module Failures or
Foldback)? If not, fine tune the ramp-up performance as follows:
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IS10001
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(1) When the transmitter finally settles at the setpoint power, monitor the AUI’s AMAM Correction instrument panel. Place the marker on the plot at the Table Index
value shown in Table 2. Note that the values are based on the mode/injection
level. Ensure the measured (LUT) Gain falls in the range specified.
NOTE
The Table Index Full Scale value in the lower right corner of the
AM-AM Correction plot is actually 255, not 2047. The instrument panel can be
increased in size by selecting the small, red up arrow. The left and right blue
arrows adjust the position of the marker. The LUT Index value and Gain are
displayed in the upper right corner of the instrument panel.
Table 2: AM-AM Correction Table Index Values and Expected LUT Gain vs. Mode
TABLE INDEX
(LUT) GAIN
MODE
VALUE
RANGE
FM+HD Low Injection
(-20 dB to -16 dB)
120
FM+HD High Injection
(-15 dB to -10 dB)
80
HD
All-Digital
30
0.36 to 0.44
(2) If the Gain value in step (1) above is greater than 0.44, increase the “Default LUT
Height” value (and subsequently decrease the LUT Gain) to:
Current Default LUT Height x (Measured Gain/0.44)
Example: In step (1), if you measure a Gain value of 0.48 and your “Default LUT
Height” value is 0.500, increase the “Default LUT Height” to 0.545 (or 0.500 x
0.48/0.44).
(3) If the Gain value in step (1) above is less than 0.36, decrease the “Default LUT
Height” value (and subsequently increase the LUT Gain) to:
Current Default LUT Height x (Measured Gain/0.36)
Example: In step (1), if you measure a Gain value of 0.32 and your “Default
LUT Height” value is 0.500, decrease the “Default LUT Height” to 0.444 (or
0.500 x 0.32/0.36).
(b) Record the new injection level, HD PA Volts and “Default LUT Height” (exciter A and B)
on the worksheet.
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IS10001
4 LUT Re-Saving
* LUT is an acronym for Look-Up Table.
(a) With the transmitter operating at the preset power level with all objectives from paragraph
3 satisfied, go to the AUI Menu / Hardware Configuration / LUT Storage screen to
review the stored Index details vs. the Index # in the table. For example, Figure 6 shows
index 1 with a mode of FM+HD, a power level of 3.65 kW, a frequency of 98.1 MHz and
exciter A active. In this example, index 1 is the only index to have a LUT stored. If others
were stored in exciter A, they would appear under index 2, 3, etc. (maximum 12), and
may have different modes (FM+HD or HD), power levels, frequencies and even injection
levels (default is -20 dB if not shown). The table shows the stored indexes for the active
exciter. If applicable, exciter B indexes will have \B at the end in place of \A and there
should exist an equivalent B index for every A index (same index # and description).
(b) Select the LUT Name field and enter a name using the same convention as the existing
LUT index (max 20 characters and \A or \B is not required considering each exciter
stores its own LUT index details). Press the Save New button to create and store a new
LUT. Note the index value.
Figure 6: LUT Storage Sub-Menu
(c) In the currently active Preset, change the Other Audio Settings -> LUT Index value to
the index value noted in step (b) (e.g., 2 in this case, if only 1 was used). Press the
Activate button.
(d) Press RF Off then RF On. The transmitter should satisfy the requirements for ramp-up
and spectral compliance.
(e) If the transmitter is expected to operate exclusively at the licensed mode/power
level/frequency (typical scenario), only one LUT (per exciter) is required. New LUTs for
different transmitter configurations can be saved at any time, and selected for a given
Preset by configuring the LUT Index for the associated stored index.
(f) If exciter B is installed manually change over to exciter B (using the AUI Menu /
Changeover screen) and repeat the procedure starting from step 3.2 (f) – Optimize
Transmitter Performance. Once complete, manually change over to exciter A.
(g) Select the desired preset or operating mode.
(h) The procedure is complete.
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Figure 7: Process Flow Diagram and Worksheet
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