Function Description Modulation Generator.. t 1/6

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Q _ . _ _ _ _ _ _ _ _ _ 1 "-- "-- "-- "--. - - - --- -

-The MOD generator module consists of two AF generators which can be set indepen-dently of each other and whose output signals can be superposed. An external signal can additionally be added. In the RX mode, the AF signal is switched to the particular modulators, in the TX mode to an output amplifier with output trafo for direct decoupling. Up to 5 Vrms into 200 0 are available.

30 Hz ... 30 kHz Variable Modulation Generator

The variable modulation generator consists of a digital synthesizer in which the signal is first of all processed crystal-accurate in the digital range. A calculator determines the binary values for the signal-time function to be generated, which is converted by a digital/analog converter into a staircase function approximating the desired sine-wave oscillation. A subsequent, con-trollable low-pass filter then smooths the signal to produce a frequency-stable sine-wave oscillation of high signal quality variable in discreet increments.

Block Diagram: pP - _ - I Phase .Accum .•. fa Range

I I I

a) Phase accumulator

The numerical value of the frequency setting is passed to the phase accumu-lator as increment With each pulse derived from the divided oscillator frequency, the output is increased by the value If the range of values of the accumulator is exhauste, the output jumps back to 0... and the pro-cedure begins again. In this way, a sequence of numbers is produced with a sawtooth pattern. The slope of the sawtooth and thus its frequency is spe-cified on the one hand by the increment from through the PIA, on the other hand by the programmable divider 011, which divides the increment sequence frequency by 1/10/100.

b) Digital analog converter

The digital sawtooth generated in the phase accumulator is converted by the EPROM Pl into a digital sine equivalent. This contains a sine table cover-ing the range 0° ... 360° with 8 bit amplitude resolution.

Function Description

Modulation Generator 5h.t 2/6

r-- - -- ---The sine data are passed by a D flipflop for time synchronizing to a digital analog converter at the output of which appears a finely-stepped, staircase-shaped sine-wave voltage of the desired frequency and constant amplitude. c) Low-pass filter

A variable frequency low-pass filter is provided after the DAC to suppress interference due to amplitude and phase hops.

d) Frequency ranges

The variable modulation generator has 3 frequency ranges: 30.0 Hz ... 299.9 Hz

300 Hz ... 2.999 kHz 3.00 kHz ... 29.99 kHz

produced by dividing the clock frequency by different factors. Various in-crements are used to produce a fine division of the frequency in the 3 ... 30 range.

f

=

10 x increment

division factor

Range Division Factor 30 Hz ... 299.9 Hz 100 300 Hz ... 2.999 kHz 10 3 kHz ... 29.99 kHz 1 Increment Set frequency x 10 Set frequency x 1 Set frequency x

o.

1

To minimize set faults, the clock oscillator can be switched off by a control line.

Example:

a) f = 512 Hz

1. The frequency is in the range 300 Hz ... 2.999 kHz

The oscillator frequency of 655.36 kHz is divided by 10

= 65.536 kHz

= 216Hz.

2. The increment is 512 = 29

3. Since the phase accumulator has a length of 216 bits, it is full after

216

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_{128 increments. The sawtooth frequency and thus also the output} 29 frequency results in 65.536 kHz = 512 Hz 128 f

=

10 x increment A division factor 512 = lOx - = 512 Hz 10 b) f = 100 Hz 1. Frequency range 30 Hz ... 299.9 Hz

Division factor: 100 fclock

=

6.5536 kHz 2. Increment = f ) 10 = 1000 3. fA = 10 x increment division factor 1 kHz generator = 10 x 1000

=

100 Hz 100

The microprocessor clock 02 of 1 MHz is divided by 1000 to generate the crystal accurate 1 kHz signal. The square-wave signal at the output of

divider 018 is converted by a subsequent 1 kHz Chebischev 6-order filter into a sine wave of high signal quality. The divider can be switched off by a control line to avoid undesired digital interference.

Electric attenuator

An independent attenuator with identical circuitry is provided behind each of the two modulation generators. The voltages at the interfaces between modulation generator and attenuator are 1 V or 0.707 V . The attenuators

rr.lS

consist of a 0 ... 1000 fine attenuator and a x5/xl/xO.l/xO.Ol coarse attenu-ator. The fine attenuator is designed as a multiplying binary 10 bit DAC in which only 1000 steps are evaluated to obtaine an integral division from 0 ... 1000. The subsequent coarse attenuator divides in decades to achieve high resolution at low voltages.

Function Description

Modulation Generator

r - - - · - - - · · . .. .. .... ....

-The RX and TX modes each have their own output amplifier. RX mode:

The voltages of the two modulation generators and an external modulation voltage can be added with the OP amp. A13 to achieve dual modulations.

Since modulations are defined as peak values, the amplifier supplies max. 10 V for 100% AM, 8 V for 160 kHz FM deviation or 8 V for 64 rad to the particular modulators.

TX mode:

The voltages of the two modulation generators and an external modulation voltage can be added with the OP amp. A9 to achieve dual modulations.

The transistors T3 and T4 act as boosters for high output currents, T2 and T5 limit the output current in the event of a short-circuit to permissible levels. An output transformer between amplifier and output socket symmetrises the out-put vo ltage.

The output voltage at the socket is max. 5 V _rms into 200 Q.

Driving Modulation Generator 208 040

PIA 1: Frequency Control Variable Modulation Generator

PIA 2: PIA 3: PB 7 PB 6 PB 5 PB 4 PB 3 PB 0 PA 7 PA 0 CA 2 Mod.off 0 0 1 1\ MSB " LSB

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-3 ... -30 kHz 1 0 mod. var. on increment 1 := active 1 kHz gen. on

Level Setting Var. Mod. Generator

Level Setting 1 kHz Mod. Generator

PA 7 PA 0 PB 7 PB 6 PB 5 PB 4 MSB LSB x 0.01 0 0 1 eve 1 setting 1 := active x 0.1 x 1 0 1 1 0 0.3 ... 3 kHz 0 1 0 same drive x 5 1 1

Off Ext.Mod.Gen. 1 kHz Mod.Gen.

PB 3 0 1 1 PB 2 1 0 1 PB 1 1 1 0 PB 0 1 1 1 PIA 3: CA 2 30 ... 300 Hz 1 eve 1 range Var.Mod.Gen. 1 1 Signal 1 Distrib. 0

o

Ext. Mod. normal

"'-1 Ext. Mod. through 1 kHz level controller (Spec. 27)

Function Description

Modulation Generator 5h,t 6/6

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(") I'D 0.. c: ...., I'D OJ 0 rl" -'. 0 o ::::l Ci> ro ::::l ro -s OJ rl" o -s REQUIRED TEST EQUIPMENT PROCEDURE

Var. Mod. Generator Oscillator Frequency range 30 .... 299 Hz 0.3 ... 2.99 kHz 3 ... 29.9 kHz

D/A

converter

Test for voltage peaks and drops with Ocsilloscope at 511 Hz. Output voltage: Test:

_UA

Distortion FREQUENCY POINT ADJUST MP 1 MP 2 MP 2 MP 2 MP 3 MP 3 MP 6 MP 6 MP 6 MP 6 fvlP 6 MP 6 655,36 kHz + 10 Hz 6,5536 kHz 65,536 kHz 655,36 kHz 1 kHz 100 Hz R 37 1 kHz R 35 10 kHz R 33 30Hz ••• 30 kHz 30HZ •••

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3kHz ••• 30kH

REQUIRED VALUE IMEASURED VALUE Urv TTL TTL TTL TTL 5,1 V ss 1,8 V rlilS + 0,1 V u - 2,55 V 0,707 V .:!:.. 1 mV 0,707 V + 1 mV 0,707V.:!:..1mV 0,707 V .:!:..10 mV < 0,3 % < 0,8 %

REQUIRED TEST

REQUIRED VALUE MEASURED

,

PROCEDURE _{FREQUENCY ADJUST}

VALUE EQUIPMENT _POINT

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n 1 kHz Mod. Generator • ' - - . C lJl MP 7 1 kHz _rTL

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•

3

(1) Mp'tJ _{1 kHz R 73} 0,707 V .:!:. 1 mV ::J _{Output voltage} iii"

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0,1 %

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c: MP 9 1 kHz It ::J _Distortion » n ... it

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c. N II) Electric Attenuator

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c z _{Setting TX} VI _? -U _...., a) Var.Mod. Generator 0 0 n I> _I'D ;; _n Setting: 1000 mV _{MP 11 1 kHz R 53} 0,707 V .:!:. 1 mV C ...., 10 mV _MP '11 _{1 kHz}

7,0'1 IIIV.:!:. U,3 IlIV

(1) Test: z

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3 100 mV _{MP 11 1 kHz} 70,7 mV.:t. 2 mV It 3000 mV _{MP 11} 1 kHz _{2,12 V+ 50 mV} :;u

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'0 P _n

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1 kHz Mod. Generator N b) 0 ;; co 3: 0 0 0. Setting: 1000 mV _{MP 14} 1 kHz _{R 85 0,707 V .:!:. 1 mV} .+0> c: 0 - ' OJ .+0> ):> .-+ 0 Test: 10 mV _{MP 14} 1 kHz _{7,07 mV .:!:. D,3mV} -'. -l='> 0 0 :::l G'l 100 mV MP 14 1 kHz _{70,7 mV .:!:. 2 mV} C'D :::l C'D 3000 mV _{MP 14} 1 kHz _{2,12 V .:!:. 50 mli} -s OJ .-+ 0 -s ... !'w

REQUIRED TEST _MEASURE

MEASURED

•

_EQUIPMENT PROCEDURE _{FREQUENCY ADJUST REQUIRED VALUE}

POINT _VALUE l> 0-""-. TX Amplifier rt> _C

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Ul

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...

3

_{Setting: TX} (l) ::J

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Gen.Var.:

a

mV MP 12 1 kHz _{R 132}

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_{mV + '1 mV} . " I ..loo. III

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C P

..

_::J 0- 1000 mV _{MP 12 1 kHz} ca 1,4 V "" 0 _it N _Ii 1000 mV 0' _VJod.Gen. 1 kHz _{R 143 1,0 V .!. 2 mV} tJ :l lJ)

...

0 _z U'\ _-U Gen. 1 kHz: 1000 mV 1 kHz _{1,0 V .!.2o mV}

...,

0 0 ₀

Gen. Ext. : 1.0 V "Iod.Gen. 1 kHz _{1,0 V .2:,20 mV}

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..

0. C (t) z RX Amplifier

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3

..

\ :;0 Setti ng: RX frequency: 100 MHz

..

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Mod.Var. : 20 kHz FM MP lEi 1 kHz _{5,EiEi V.:!:. 0,1 V}

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..

Mod. 1 kHz: _{20 kHz FM MP lEi 1 kHz} 5,Ei6 V.:!:. 0,1 V .... Q _::s: N 0

Mod. Ext.: _{0.5 V MP lEi 1 kHz}

5,0 V .!.0,1 V a 0-ro c:: - ' a OJ rt a a ...I. 0 a ::t:o :::l GJ ro :::l ro } OJ rt 0 } \J')w