VI. Alignment. Hammarlund SP-600 JX

VI

ALIGNMENT

The alignment of a mndcrn communications re' ceiver requires precision instruments ilnd a thorough kr)O\Vletl~c uf the circuits involved. This receiver, bemg

.1

douhle super-hcterooyne. the <llignmcl'lt procc' dure

is

even more involved than is usual.

UIH.kr normal service the receiver will stay in aliJ!I1' ment for extremely long periods of time. Cf'lIlscqucntly realiJ!nmcrH should not be attempted unless all other possible causes of a particular trouble h.\\'c been eliminated When

It has hCt:11 ddcrmincd that any rc,d(l!nmenl should be ,ltu:mptcd,

:1 g:rcat dc:d

(If caution

...hould be cl\crciscd in makin~ the adjustments. as an)' required readjustment should not entail mOre than a slight angu[M motion of lh..: aJjusting screw.

ALIGNMENT OF THE IF STAGES

The low frequency IF should be aligned first, The recommended method for aligning the low frequency

IF

involves the use of

11 sweep frequency si~nal generator and

;U\ oscilloscope. Since thcSi: instruments are not avaIlable at the average service station the alternate method using all amplitude modulated signal g.ma:\.lor and ;In output meter will be described first.

The additional information required for the visual dlignmcllt nlcthod

will be

cov..:recl in

a

later paragraph.

Th..: si~nal gencr.llor should

b..:

coupled to the grid of the mixer tube V5 thmugh a capacitance of ap' proximately .01 mfd.

A miniature tube adapter will be required to make the mixer grid connection avail·

.Ihle. Such an adapter is.mlll1\lfactured b}' the Akkn

Manufacturing

Co.

An output meter should be connected across the output terminals of the receiver or the speakl?r voice coil. The receiver controls should

IIOW be

Sd as follows:

COlilrol

Selectivity

Send

~

Recci\''':

CW~MoJ

Phasing

AVC~Man

AudIO Cain

RF

Gain

Hand Switch

Dial

Posilion

Sec text

Reccke

Mod

Arrow

Man

Set for approx. 20 volts

Sec text

1.35 3.45

me

2.5

me

The signal generator should be modulated

:iO

percent at 400 cycles. Turn the selectivity switch to the

3 kc Dosition :lnd advance the RF Cain control tll maxim'um. Sct the signal generator frequency to 455 kc and adjus.t Its output until some deflection is not;.:d on the Output meier. Refer to figure?> for the location of the various alignment adjustments.

Adjust L42.

1.4 [, L:i9, L?>8. L?>6 and L32 for maximum output. rc' ducing the signal generator output and the

RF

Gain contwl as required to prevent overload or excessive output. Now lurn the selectivity SWitch to the narrow' est position, .2 kc. and adjust the sign,ll KencTrI!Or frcquency for the maximum nutpuL This establishes the correct signal frequency by the 455 kc crystal for the

IF

amplifier and the frequcncy of the signal

~":llerator should not be disturhed for the rcm.tinUo:t of the low frequency

IF

alignment, unless it should be to recheck this establishment of crystal frequency to make sure th,lt the signal generlltor frequcn..:y h,ls not Jnftcd dllnng the alignment. The sekl:tivity switch is nnw lurned to the?> kc position and

L42, L41, U9. US.

L?>6 and

L:.2

:Ire ;Ig-al1l adJustct.l for maximum Output.

Now turn the selectivity switch to th..: I.:' kc pos:tit1n and :ldjust U7 for maximum output. llcJor..: ch:lng' ing this sct-up the

BFO

should

be

turned on by throw· mg the CW-Mod switch to

CW and checked for zero beat with the

BFa

knob dial at its :i:ero read mg.

If

necessary

LH

should be adjusted for :i:ero ompul. This check and adjustment of the

BFa

should be done WIth the signal generator carrier unmodulatcd.

The procedure for the visual method of aligning the

low

frequency

IF

should be the SJme

,u; the above

ex-

..:ept thJt the adjustments arc made for hoth m;u;imum

:Imphlud..: and coincidence of the oscilloscope images.

The oscilloscope vcrtic,d input should be I:onllcctcd across the dIOde detector load resistance, from the junction of R64 <tnd

R65

to ch~lssis.

The high frequency

IF

should be aligned next. Set the band switl:h

[0 th..:

7.4~ 1~.8

mc b<tnd. The sc'

I.:::CtJvit}, switch should be in the:' kc position. Adju.st

Ihe si!!nal generator frequency to ;'.955

mc ami adjust

Ul, U:'

;1l1d

U4

ffIT maximum output.

The ?> .

.i

mc I:rystal used

III thlt s<;:cond ':(lllv.. rSIIHl oscillator circuit is held to :\ wry dose frt.:qucilcy tolerance :lIld may be used

<I.!' a frcqucney s[;:Uldard at multiplc-s of :1.5 me from 10.5

Ttl..: upwards.

III orda to do this. in \,iew of the .::umplete shlc1t.ling ag<tinst r,ldia.tioll from this os.6I1ator, it

will

be necessary

!(\ t..:.mpor:trily connect a two foot length of Insul;Hed wire to the antenna terminal and dress the fre..: end of chis le:td around the tulle shield

Oil th..:

.~

.

.s

m\'

CJscill,lwr tube V8. This t..:St kad should, of ..:our:...:.

he rcmov..:d exr..:pt

\vhd~' in us,'

,IS a fn:yu'·l1q·

.;t.lndard.

ALIGNMENT OF THE RF AMPLIFIER

& HF OSCILLATOR

To ;uJcquately align the RF Amplifier and HF OscIllator an accur.ttdy calibrated slj.:nal generator lind an output meter arc required.

The frequencies n:qui red arc shown in table :'t. The location

1)(

the ad-

Justments is showil in Figure ). The use of Table

~ and Figure:; should be made in following this put uf the alignment which

will

llOW be described for une ircquenc)' band. The s.1mc

procedure should then be followed for the other frequency bands.

To align the .54-1.35 me band the sign.d generator is coupled to the antenna input terminal through a

100 ohm carbon resistor.

The gcncr;llor should be modulated :;0 percent at 400 cycles and the outp\ll meter cnnnected across the receiver

Output terminals.

The nX:l.'i\'cr controls should be set as follows;

Control

Selectivity

S~nd·Reccive

CW-Mod

AVC-Man

Audio Gain

RF Gain

Band Switch

Limiter

Set the re..:.:iva and signal generator dIals to .56 m.::.

The RF Gam control should be set at maxmmrl"\ and

Ih;: AVe Man .o;wHch sct

Oll

A

ve.

The

HF Os,:. L

adjustmcm shown in Figure :;, should now

t-l:

set for maximum output. Then the Ant., 1st RF and 2nd RF

I.

adjustments should he .set for maximum output.

Th~ receiver and signal genc.r'ltor dIals are now set ttl I.:' me and the

C adjustments,

~hown in Figure

3, should be adjusted for maximum output in the same orJer, beginning with the Os.:

C

adjustment and then m,lk· ing: the C adjustments for the Am, 1st RF and 2nd

RF. This proccdur\: should

be

..:arcfully rcpe'ltcd un' til

110 inerc,,-sc in output can be r.::all:cd. The

AVe

Man switch should then be set

II)

Man and the sic-nal

I-:enerator should he set for ,ipproximatc1y :; n~icro

\'oIts.

The Land

C

adjustments should now

be

checked for maximum OutpUl, adjusting the RF Gain control as found necessary to m,lintaill the output at

;lpproximatc1y 20 vOllS.

PositiOn

:;kc

Recei\,c.

Mod

Sec

Text

Set (or appro:.:. 20 volts

Sec text set for band to be aligned

off

Following the frcqUl::ncit:s, shown in Table

3, align the rcmainlllg banus using the same procedure

.t$ above.

TABLE No. 3

RF AND HF OSCILLATOR ALIGNMENT FREQUENC.IES AND ADJUSTMENT DESIGNATIONS

!'REQ.

BAND

IN Me

H-l.3~ t.H-3.4S

3.45-7.4

7.4-14.8

\4.8-297 29.7-54.0

Rf

"

:\DJUST

HI' OSC

L

."T.

RF

Ei

HI' OSC

ADJUST C AT

.56

I.'

3.75

7.'

15.0

30.0

J.j

~.4

7.1S

14.5

29.U

52.0

TABLE No.4

APPROXIMATE SIGNAL INPUT AT IF

&

AF STAGES FOR 20 VOLTS OUTPUT

Output measured across a 600 ohm resistive load at output terminals of rccciva.

RF signals modulated

30 percent at 400 cycles. Signals :lpphcd to tube ltrids through ,I .01 mfd capacitor. Selccllvity switch ;n 3 kc

AVC-MAN .o;wit.::h On MAN. CW-MOD switch on MOD, RF Galli ;Ind Audio Gain at maximum.

BAND SWITCH

Any

Aoy

U5-).4~ me

1.35

3.45 no.:

1.3 .•-345 Ill('

1.35-3

4~ nit"" l,l~-345

In,'

7.40~ 14 8

In".

7.40-14.1I

me

FREQUENCY

AudIO 400 cyel.:s i\udlO 400 eyell's

Mod

RF 4H kc l'o.·lod

R!' 455 ke

Mod Rf 455 ke

Mod RF 455 k.-

Mud ItF

45~ k..

Mod R!' ~_955 me

Mod :~I' l.9~S me

INPUT TO

1'",5,V17

Pin

2, VI6B l)in I, VI t

Pin l.

VIO

Pm t.

V?

Pm I, V7

Pm 7. V5

P'" 7. V5

Pin 7, V6

APPROX. INPUT

U

,"olts

,

.

,"olt•

.35volt<

ClOOO 'meru\'olt.,

110 nllcnwolts

40 lI"n"volts

65 Oller' "'olts

40 Il"novolu

2501llICrtwolts

13

§

8

L41 L42

OT50

e

L38 L39

OT40

e

L37 L36

OT30

8 e

L34 L33

OT20

,

,

i------ --,

,

,

lee!

L..: ________

J

6

8 e e

80@

1/

'\

T8

0

OND

0

~c

0

ANT

GC

0

0

L

'RF

0

e~

- - . "

0

L32

0

2RF

0

@~

0

Tl

0

L3\

0

0

HF

8?

1"'/

~

V3

I 2

:5 4 5 6 e

0

L44

rn

0

0 0 0 0 0 0

0 0 0 0 0 0

0 0 0 0 0 0

TOP VIEW OF CHASSIS

SHOWING ALIGNMENT ADJUSTMENTS

5

<Xi

o

z o

....

::>

....

::> o z o

5

~

::> i1i \

0

....

\i

5

2

0

5

,-

~

100

FIG.3

'AUDIO AND OVERALL FIDELITY CURVES'

CURVE - Audio frequency amplifier.

Input

to

phono 'terminals.

CURVE - Overall fidelity at 2.5 me.

Modulation 30 percent.

Selectivity switch in 13 kc position.

RF Gain set for 20 volts output at 400 cycles.

Output measured across 0

600 ohm resistive lood.

Audio goin control at maximum for bath curves.

1000

CYCLES PER SECOND

FIG.4

-

~

,

\

10,000

100

0

1

• SELECTIVITY CURVES

Overall at 2 Megacycles.

2

NUMBERS DENOTE SELECTIVITY SWITCH POSITIONS

1,2 AND 3 NON CRYSTAL 4

1

5 AND 6 CRYSTAL

3 456 654 3 2

1

1\

>-

:::>

z

(fl

W

:;;

>w u

Z

<I

Z

0

(fl

W

0::

10

0

1a

,

i

I

I

I

15 10

"'

.... ~

l.o::'

5 0 5

KC OFF RESONANCE

!.I

FIG.5

/5

10

15