Inovonics 375 User manual

INSTRUCTION MANUAL
MODEL 375
TAPE RECORDING ELECTRONICS
August, 1975
0-
INOVONICS
1630 DELL AVE ., CAMPBELL, CALIF 95008
INCORPORATEO
(408) 374·8300

SECTION
1.0
2.0
3.0
4.0
TABLE OF CONTENTS
PAGE
GENERAL INFORMATION ........ . 2
INSTALLATION AND USE . . . . . . . . 7
OPERATIJN AND FUNCTIONAL DESCRIPTION
9
ALIGNMENT AND MAINTENANCE
· 17
PARTS LIST.
· 23
SCHEMATICS.
• 28

SECTION 1.0 GENERAL INFORMATION
The lnovonics 375 is a compact, up-to-date magnetic recording elec-
tronicspackage, completely self-contained with integral power supply.
Available in several versions, the
375 is equally well suited to new
installations, or to improve the performance and reliability of older
professional tape recorders.
The 375 is delivered with proper interconnect cabling for whatever
tape
transport is specified for use with it. When no specification
is made, the unit is supplied with cabling for Ampex 350/351 series
mqchines.
Among the features incorporated are:
Calibrated positions
on Record and Reproduce gain controls.
Provision for remote switching of all monitor and equalization
functions,
and solid-state switching to eliminate contact noise
problems.
3-speed equalization to
accommodate any combination of NAB and
IEC characteristics.
Harmonic and phase distortion nulling circuits.
Able to accommodate a wide variety of original-equipment and
replacement heads.
Optional
SYNC Reproduce Amplifier with independent equalization
and automatic SYNC-INPUT monitor transfer switching (-03 version
only).
-2-

1.1 SPECIFICATIONS
NOTE: Performance of a magnetic recording system is limited in part
by the heads and tape employed. ihe Inovonics 375 is intended both
for upgrading older recorders in broadcast
and similar applications,
as well as for new studio installations. Hence two sets of specifi-
cations are given, each with respect to the heads, tape and standards
generally in use in each
installation situation. A third group con-
tains those specifications which are not application oriented.
1.1.1 Specifications derived using 3M 206 tape and a Taber full track
replacement
head assembly on an Ampex 351 t ,ansport.
Frequency
Response (in Hz)
15
; ps
+2dB 20
20k
7.5 ips
+2dB 20
15k
3.75 ips
+3dB
20
-
8k
Signal-to-Noise Ratio (in
dB, referred
to a "peak" record 1evel
6dB
above 200nW/m,
or approx. 3dB
below 3%
THO; 20Hz - 20kHz)
OVERALL
STANDBY
u'wtd. NAB wtd. u'wtd.
NAB wtd.
15 ips -67 -76 -76 -87
7.5 ips -69 -77 -76 -86
3.75 ips -66 -74 -72 -83
Erase/Bias Frequency
100kHz
Erasure
70dB erasure of 500Hz signal recorded 3dB below tape
saturation.
--
-3-

Recorded
Distortion (at 15-mil wavelength bias
peak - typical)
LIN out LIN in
Operating
Level .45%
.02%
6dB above Op Level
2%
.015%
8dB above Op Level
3% .02%
10dB above Op Level
5.5%
2.2%
1.1.2 Specifications derived using 3M 250 tape, an Operatinq Level
of 320nW/m and Nortronics 9227 (erase), 9203 (record) and 9213 (repro-
duce)
heads -70-mil track width format, typical of multi-track appli-
cations.
Frequency
Response (in Hz)
30 ips
+2dB
60 - 22k
(SYNC reproduce
response essen-
15
ips +2dB
30 - 22k
tially identical
7.5 ips +2dB 20 ~ 16k
to normal overall)
Signal-to-Noise Ratio (in dB, referred to approx. 640nW/m or 3% THO;
20Hz - 20kHz)
OVERALL
SYNC STANDBY
u'wtd. wtd. u'wtd. wtd. u'wtd. wtd.
30 ips
-71 -78 -71 -80 -80 -87
15 ips -67 -77 -67 -77 -75 -86
7.5 ips -67 -76 -67 -77 -74 -85
Erase/Bias Frequency
250kHz
Erasure
lOdB erasure of 500Hz signal recorded 12dB above Operating
level, or approximately 3dB below tape saturation.
-4-

Recorded Distortion (at IS-mil wavelenth bias peak - typical)
LIN out
LIN ,in
Operating Level
.5%
.15%
3dB above Op Level
1%
.3%
6dB·above Op Level
2.5%
.8%
1.1.3 Specifications Independent of Application
Equalization
3 speed with pushbutton
selection, automatic switching be-
tween INTER and LOW when transport provides closure. Accom-
modates NAB, lEe (or mixed) characteristics for 3.75 through
30 ips operation.
Amplifier Distortion
Record:
~.1% THO
<:.25% THO
Reproduce:
<:.1%
THO
~.5% THD
at Op Level
25dB above Op Level
at Op Level
at +24dBm Line Output (clipping level +25dBm)
Input '
Sensitivity:
Impedance:
-20 to +8dBm (-8 to , -f : 8dBm
input transformer)
10K bridging
with
-01 option
Outputs Line
Out~ut:
Headphones:
feeds 600 line, balanced
terminated
or not, at +4
Front panel jack
or
or
unbalanced,
+8dBm for Zero-VU.
-5-

Panel Controls
RECORD GAIN (with pre-set CAL position)
REPRO LEVEL (with pre-set CAL position)
MONITOR: selects between INPUT, REPRO and SYNC (-03 versions)
SAFE/READY
RECORD
EQUALIZATION: manual selection of HIGH, INTER or LOW.
POWER
Power Requirement
105-130 VAC (230V available) SO/60Hz, .3A (plus transport)
Size
and Shipping Weight
x 19
11
3~1I X 10"
15 1 bs
-6-

SECTION 2.0 INSTALLATION AND USE
2.1 Upon receipt of the equipment, inspect for shipping damage.
Should any be observed, notify the carrier immediately; if not,
proceed
as outlined below. It is suggested that the original ship-
ping carton
and materials be saved for possible future reshipment.
2.2
The 375 is packaged to mount in a standard 19-inch equipment
rack, requiring
3~-inches of panel space. When replacing original
electronics in an overbridge above the transport, it may be necess-
ary to
drill and tap an additional two holes to accommodate the 375
panel.
2.3
The signal, head and transport connectors are directly compati-
b'~ with Ampex 350, 351 and 354 equipment. Units ordered for use
with other transports- or for use in stereo pairs are supplied with
appropriate interconnect cabling.
2.4 Unless supplied otherwise to special order, units intended for
mono or stereo installations are delivered properly aligned for use
with 3M 206 tape at an operating level of 200nW/m, with Ampex 351-
type heads (1. 5mHy erase, 5-10mHy record ,and ·lHy reprod'lce) and
100kHz bias. Units for multi-track use normally operate with lower
inductance
heads (O.5mHy erase, 4-5mHy record, and 400mHy reproduce),
utilize 250kHz bias, and incorporate the optional SYNC reproduce amp-
lifier: Heads with inductances other than those suggested above can
be accommodated. Section 4.1.4.2 outlines the necessary changes.
2.5
As delivered, the 375 is calibrated to operate at a +4dBm signal
level. Should operation at +8dBm be necessary, clip the jumper shun-
tingthe 4.7K resistor near the line output connector and recalibrate
as described in paragraph 4.1.2.8.
2.6 The low source impedance of the 375 line output results in only
about
~dB level change from an unloaded to 600 ohm loaded condition.
._.
-7-

The 375 should, nevertheless, be connected to its intended load prior
to final calibration.
2.7 Even with the optional input isolation transformer option sup-
plied (-01 version
only), the 375 input impedance is 10K ohms or
greater. Should the equipment feeding the 375 require a terminating
load, a
600-ohm resistor should be placed in parallel with the 375
input.
2.8
No provision for meter indication of bias or erase current is
made, as the inherent stability of the circuitry is greater than that
of the heads and meter at bias frequencies.
2.9
When two Ot' more 375's are employed in dual or multi-track ap-
plications, the interconnecting cablinq supplied delivers AC power to
all units and to the transport, if it derives power from the elect-
ronics. The cabling also "slaves" all erase/bias amplifiers to a
single oscillator, thereby avoid-ing bias "beats" or the necessity of
synchronizing two or more oscillators.
-8-

SECTION 3.0 OPERATION AND FUNCTIONAL DESCRIPTION
3.1 OPERATION
3.1.1 The RECORD GAIN and REPRO LEVEL controls are provided with a
detented
CAL position at full CCW rotation. They are normally left
in these positions except for temporary correction for an improperly
recorded tape
or abnormal line level. Range is adequate to record
from a -20dBm line level (-8dBm with optional input transformer) and
to produce normal line output from a tape under-recorded by 10dB.
3.1.2 The MONITOR buttons determine whether the line amplifier will
derive
its si9~al from the incoming program (INPUT), the reproduce
head (REPRO), or in versions with -03 option, the record head (SYNC).
When any button is only slightly depressed to release all three to
their "out" position, the monitor selection is transferred to the
rear panel REMOTE connector. On versions with the -03 option, mon-
itor is automatically switched from SYNC to INPUT when entering the
record
mode.
3.1.3 The alternate-action SAFE/READY switch, when depressed, per-
mits the
375 to enter the record mode when the transport is in "record".
When this button is "out", the 375 will not enter the recoY'd mode,
thereby preventing accidental erasure of a tape or that track of a dual
or mult-track recording.
3.1.4
The RECORD button places the transport in the record mode. The
button will not illuminate, though, nor will ~he 375 go into "record"
unless the
SAFE/READY button is depressed. In dual or multi-track in-
stallations, depressing any RECORD button will place the transport in
the record
mode; only those 375
1 s in "ready" wi.l record,
however.
3.1.5 The EQUALIZATION buttons select record and reproduce equal-
lizationappropriate to the transport speed employed. Three independ-
ent
sets of equalizers are provided, although most transports are only
-9-

dual speed units. In these cases the third position may be used for
a
European or other non-standard curve. In the event of use with a
transport providing
an equalization-switching pole on the speed
switch, the equalization
selection can be transferred to change auto-
matically
between INTER and LOW (if the transport is appropriately
wired)
by depressing an EQUALIZATION button slightly so that all
three buttons are "out".
3.1.6 The alternate action POWER switch controls AC power to the
375 and to the transport, if it is powered by the electronics.
3.1.7 The PHONES jack is connected ahead of the output transformer
through a
470 ohm resistor. It is suitable for headphone monitoring
or as an unbalanced, uncalibrated line output for servicing.
3.1.8
The recessed slide switch behind the adjustment cover panel
enables or defeats the
linearization circuit, (see paragraph 4.2.1).
-10-

3.2 CIRCUIT DESCRIPTIONS
3.2.1 General
Electronic
circuitry for the Recording, Reproducing and Erasing
Amplifiers
iS ,contained on a single "piggy-backed" plug-in assembly.
The lower board (Reproduce) carries the Reproduce, optional SYNC and
Line Amplifiers; the upper board (Record), the Erase/Bias and Record
Amplifiers. Another single PC assembly within the chassis contains
the
power supply and bias oscillator circuits.
3.2.2 Reproduce Amplifier (sche~atic 129000).
Signals
from the reproduce head enter on pins 13 and 14. An option-
al
head input transformer (-04 version only) can be strapped in to
permit
use of low (4-5mHy) inductance heads. Resistor Rl is selected
to
dampen head resonance and yield smoothest playback response (see
paragraph
4.1.2.4).
Transistors Ql and Q2 form a complementary feedback-pair input stage,
Q3 serving primarily as an emitter-follower buffer. DC feedback is
maintained through RIg and Rll, bypassed at audio frequencies by C2.
AC feedback . is routed througli an appropri ate equa 1i zat i on network by
FET switches Q4, Q5 or Q6. A secondary function of Q3 is to provide
a phase-inverted reproduce signal
(at the collector) for the repro-
duce phase compensation circuit. This signal, coupled through C7, '
interacts with the in-phase emitter signal fed through R25 to provide
an adjustment of reproduce phase shift to complement and cancel the
phase
shift which normally occurs during the recording process. FET
switch Q7, normally on, defeats this compensation, except at the one
speed for which the adjustment is made (see paragraph 4.2.2.2). IC2
imparts voltage gain to the reproduce signal, with R28, the REPRO CAL
adjustment, providing a controi over the gain and a means of obtain-
ing a given signal level for a
variety of head outputs. This amplified
signal
is fed through R29, bridged by the front panel REPRO LEVEL con-
-11-

trol, to the LineAmpl ifier.
3.2.3 SYNC Amplifier
The optional SYNC reproduce amplifier (-03 version only) is essen-
tially identi~al to the Reproduce Amplifier just discussed, except
that the head input transformer is always used, and the value of
R53 is increased over that of its counterpart R3 to reduce overall
gain. This
is required as the record head used as a reproduce head
has greater output than a true reproduce head of similar inductance.
3.2.4 Line Amplifier
FET's Q8, Q9 and Q28 perform an input switching function for the Line
Amplifier, passing
signals from the Reproduce Amplifier, input source,
and SYNC Amplifier, respectively. The gates of these switching tran-
sistors are normally held at -20 volts, introducing an effective open
circuit between the source and drain. When the gate is brought to
ground potential either by the front panel MONITOR switch or through
the
REMOTE connector, the source-drain resistance drops, passing the
selected signal.
Transistor Q29 and associated circuitry is part of the SYNC reproduce
option (-03 version
only), switching the line amplifier from SYNC to
INPUT monitor when the 375 enters the record mode.
R34, 36, C10 and 12 are part of an active low-pass filter with cutoff
beginning at about 30kHz. This aids in reducing whatever bias signal
might appear
at the line output, primarily in the SYNC reproduce mode.
IC1 performs the vcltage gain function of the Line Amplifier, with
gain
established by feedback resistors R35 and 37. Transistors Q10,
Ql1 and associated components provide the output current required for
driving
low impedance loads and long cables. Protection from output
short circuits is afforded by diodes CR3 and 4.
-12-

3.2.5 Reproduce Line Amplifier
Although not
available as a factory-installed option, provision is
included in the PC artwork to incorporate a second Line Amplifier
dedicated
to the reproduce function. Use of this user-installed
option is relegated to special applications or effects generation.
3.2.6 Record Amplifier (Schematic 129100)
Input
signals from the front panel RECORD-GAIN control are further
attenuated by the RECORD LEVEL calibration control, Rl. Resistors
R2 and R3, capacitors Cl and 2 and first gain stage ICI form an
active low-pass filter with cutoff beginning about 30kHz. The filter
removes RF and other spurious signals outside the audible range which
mi ght otherwise cause hi gh frequency ollerl oad-j ng duri ng recordi ng. A
portion
of the mplified input signal is directed to the Line Amplif-
ier through RECORD CAL control R7 for spurce monitoring.
C4 imparts a 6dB/octave rising characteristic to the imput signal as
required
for recording pre-emphasis. Depending upon the tape speed
and equalization characterisitc used, however, only a rise at very
high frequencies
or no increase at all may be required. C7, connec-
ted in the feedback path of IC2, therefore provides a complementary
falling characteristic which cancels the effect of C4. Record equali-
zation trimmers R34, 35 and 36 are introduced into the lC2 feedback
loop
when the appropriate FET switch is activated, and "shelf" the
falling characterisitc. This affords control over the inflection
point of the effective pre-emprasis curve provided by the combined
network characteristics.
Rll and C5 modify the pre-emphasis curve slightly, causing a droop
in the 5kHz-and-above region. These component values
can be changed
for smoothest overall response, but are supplied as the best com-
promise for heads typical of the application for the version order-
ed.
0 ---
-13-

A 3dB boost at 50Hz (required for the NAB record characteristic) is
effected by shunting C4 by RIO. FET Q5 is normally off, but can be
turned on for one or more equalization positions if IEC or other
IIflat-low-end
ll
record curves are desired. This is accomplished on
the Power Supply PCB (see paragraph 3.2.9).
CR3 and 4, IC3, and associated circuitry forms the IIlinearizer
ll
net-
work. When Q9 is turned on by activating the LINEARITY switch under
the adjustment cover panel, a
variable non-linear characteristic can
be imparted to the record signal that when properly adjusted cancels
a major portion
of the tape-gener~ted third harmonic distortion (see
section
4.2.1).
1C4 and associated components form the constant-current head driver
stage. Relay Kl connects the record head to the output of IC4 in '
the record
mode, and to the input of the SYNC amplifier for SYNC re-
produce (-03 version only). A bias trap composed of L2/C22, C24 and
L3/C23 keeps bias from disturbing the head driver stage or overloading
the
SYNC amplifier. FET switch QI0 opens the input to IC4, except
when the 375 is in the record mode.
3.2.7 Erase/Bias Amplifier
The bias signal generated on the Power Supply PC assembly is raised
to the required power level for erasure and bias by Ql, 2, 3 and 4.
Q1 arid 2 raise the 1Vrms signal to a proper level to just saturate
the class lie' output stages, Q3 and 4. · R23 and 25 control drive and
symmetry, respectively, and are factory-adjusted.
Transformer T1 raises the amplifier output vol~age to approximately
the
150 volts P-P required for erase head driving requirements.
Capacitor
C16 resonates the erase head at the operating frequency. C25
and BIAS ADJUST control R50 couple the required bias signal to the
record head.
In the case of erase heads of lower than nominal induct-
ance,
an inductor, L4, is inserted in series to bring erase head
-14-

inductance up to the nominal value (see paragraph 4.1.4.2).
3.2.8 Record Logic Timing
In order to insure inaudible "punch-inls" and "punch-outls", the
375 must enter the record mode with the proper sequence of events.
IC5, C26 and R58 form a Miller Integrator which generates a linear
ramp when the unit goes -into "record. II At the start of the ramp,
the Line Amplifier is first switched from SYNC to INPUT monitor
(-03 version only).
Next K1 is energized, transferring the record
head to the output of the record amplifier. A short delay intro-
duced by R45 and C19 applies the input signal to the head driver
stage concurrent with the relay closure. At this point the bias
and erase field begins to build. UpOh leaving the record mode, the
opposite chain of events occurs. "Punch-in"
and "Punch-out" time
is symmetrical at about 100 milliseconds.
3.2.9 Power Supply (Schematic 129200)
Triac Y1 operates in conjunction with the front-panel POWER switch
to control primary
AC power to the 375 and associated tape transport,
if deriving power from the unit. This saves the switch contacts from
heavy surge currents and inductive loads.
The chassis-mounted power transforme~~pplies AC to the bridge re~t
ifier, diodes CRl-4. A bipolar "raw" supply of about +30 volts
appears across filter capacitors C1 and C2.
IC1 is the positive supply regulator, with Q1 connected to provide
up to 250mA, at +2~ volts (nominal). Resistor R3 and circuitry in-
ternal to IC1 limit the available current to this value and establish
short-circuit protection. The negative power source is
referenced to
the regulated
positive supply, and utilizes Q3 and Q4 as
a
di fferent-
ial input pair driving the compound output stage Q5/Q6.
CR6, 7, and
-15-

8 and RI provide current limiting and . short-circuit protection.
Transistors QIO and II are connected in an emitter-coupled multi-
vibrator configuration, oscillating at the erase/bias frequency
established by the value of C7 and trimmed by FREQ adjustment R33.
QI2 amplifies the oscillator signal and applies it to the parallel-
resonant network LI/C8, transforming the square wave into sine wave
form. Transistor Q9, an emitter-follower buffer stage, provides a
low output impedance for the IV rms bias oscillator signal.
Transistor Q7 and its associated components form part of the equal-
ization switching system, placing the 375 i ~ INTER EQ when no other
command is received, either from the front panel EQUALIZATION switch,
or a
transport speed switch closure.
Transistor Q8, normally off, disables the reproduce (and SYNC, on -03
versions) phase compensation network, except
at the one speed for which
the network is optimized and for which a strap is connected (see sec-
tion 4.2.2).
Similarly, the record amplifier pre-emphasis characteristic includes
a
low frequency boost, as required for NAB equalization, which can
be defeated at one or more speeds by the installation of diodes as
shown on the schematic.
SCRI, a silicon controlled rectifier, replaces the electro-mechanical
"record"
relay usually required by Ampex 300-,350-, and 440- series
transports. The SCR is triggered "on" in the transport PLAY mode
when the front panel RECORD button is depressed, and latches until
the transport leaves the PLAY mode. An optical coupler Al and tran-
sistor Q2 isolate the ground-referenced Record and Erase/Bias Amplifier
logic signal from the transport control function voltages.
-16-

4.1
SECTION 4.0 ALIGNMENT AND MAINTENANCE
Routine Calibration
4.1.1 Equipment Required:
Head Demagnetizer
Appropriate Reproducer Alignment
Tapes
Audio Oscillator
AC Voltmeter
4.1. 2 REPRODUCE
4.1.2.1 Depress INPUT monitor button. Clean and demagnetize all
heads, moving very slowly while the demagnetizer is near the
heads,
and withdrawing it about a yard from the head assembly
before unplugging
it.
4.1.2.2 Depress REPRO monitor button and thread an alignment tape
appropriate for the
equalization to which the electronics is
switched.
4.1.2.3 While reproducing the highest frequency on the tape, adjust
reproduce head azimuth for maximum output.
4.1.2.4 If the resonance of the reproduce head with its cable is near
the top
of the passband (as is usually the case for best
signal-to-noise performance), a peak in response will be ob-
served
at the highest frequencies. R1 on the Reproduce Amp-
lifier card is provided to damp this resonance. To determine
whether
its value is correct for the head used, set High Speed
H.F. control so that 5kHz playback is flat with respect to the
reference frequency tone
on the alignment tape. Note response
at the highest frequencies, and raise the value of R1 to in-
crease, or lower to decrease,
this level.
4.1.2.5 Set H.F. control for smoothest response from reference fre-
quency to highest frequency.
-17-

4.1.2.6 If alignment tape track width is the same as reproducer
track width,
set L.F. control for smoothest response from
reference frequency to lowest frequency. If not, as with
full-track tapes and half-track reproduce heads, wait until
step 4.1.5.4 to trim the control.
4.1.2.7 Repeat the preceding two steps for the other speeds. It is
advisable to make final azimuth setting at the lowest speed
to be used.
4.1.2.8 Turn front panel REPRO LEVEL control fully ccw to CAL posi-
tion u nd adjust R34 REPRO CAL on Reproduce card for an indi-
cation of Zero-VU while reproducing a reference tone recorded
to the desired operating
level. If it is wished to operate
into a
+8dBm line, remove the jumper across the 4.7K resistor
near the output connector before making this adjustment.
4.1.3 SYNC REPRODUCE (-03 version only)
The SYNC reproduce function, on 375
1 s
so equipped, is aligned
in the
same manner as the normal reproduce section described
in
4.1.2.1 through 4.1.2.7. Playback is from the record head
in this case, and there is no front panel level adjustment.
4.1.4
ERASE/BIAS
4.1.4.1 The Model 375 is available with the option of 100kHz (-00
version)
or 250kHz (-02 version) era~e/bias frequencies. The
lower frequency is intended for operation with older metal
heads, as are
found on the earlier Amrex vacuum-tube recorders.
Heads for operation at 250kHz must be of lower inductance and
greater efficiency.
4.1.4.2 For 100kHz operation the 375 is designed to drive an erase
head in the 1.2 to 1.8mHy range. At 250kHz, the requirement
-18-

is 0.4 to 0. 6mHy. If a head of lower inductance than specif-
ied is intended for use at either frequency, remove the short-
ing strap in place of L4 on the Record PCB and install a choke
coil, the inductance of which when added to the erase head in-
ductance, will equal
1.5mH (in the case of 100kHz operation),
or 0.5mH (for 250kHz units). Similarly, the optional (-04
version only)
head input transformer on the Reproduce PCB can
be strapped as shown on the board to accqmmodate low-Z {4-5mHy
reproduce heads.
4.1.4.3 NOTE: Present-day tapes with higher coercivity oxides may
require a biasing procedure slight~y modified from the trad-
itonal 15-mil wavelength "peak" method described below. Follow
tape manufacturer's recommendation for best performance.
Depress the
REPRO monitor button, connect an audio oscillator
to the INPUT connector, and thread transport with a good sample
of the type of tape to be used subsequently. Place machine in
record
mode at 15 ips and adjust input to 1kHz at about oper-
ating level; adjust R13 BIAS control for maximum reproduced
signal. (Use 500Hz at 7 ~ ips on units which do not operate
at 15 ips.)
4.1. 5 RECORD
4.1.5.1 ' With conditions as for 4.1.4.3 above, place recorder in re-
cord mode at highest speed and set input signal to 700Hz at
+4dBm (+8dBm if reproduce was calibrated for this level). Re-
duce level by about 10dB in the case of transports which do
not operate at 15 ips.
4.1.5.2 Raise the frequency
for
maximum output.
record
head azimuth
be repeated.
to
15kHz and adjust the record head azimuth
Note:
on -03 versions, the adjustment of
was made in SYNC calibration and need not
-19- '-