Viavi 3900 Series Operation Manual page 244

7. 5. 1. A. 3 M eas ur emen t M od e
Of fse t M o de
Whe n O ffse t M o de is se le cte d this fie ld dis pla ys th e d iffe re nc e be tw ee n the T es t S et 's R F
Fr eq ue nc y an d t he R F Inp ut sig na l.
Th e Un its dr op -d ow n m en u be sid e the O ffs et field s ele cts th e un it o f m e as ure u se d t o
dis pl ay the F re qu en cy O ffs et m ea su re me n t.
C ou nt er M od e
Whe n C ou nte r M o de is se le cte d this fie ld dis pla ys th e m e a su red fre q ue nc y o f th e R F
In pu t si gn al. Th e freq u en cy is dis pla ye d in t he u nit o f m e as ur em e nt se lec te d fo r t he R F
Fr eq ue nc y.
7. 5. 1. A. 4 Le vel (AG C) M od e
Le ve l d efin e s th e A G C M od e o f o pe rat ion . With A uto is s ele c ted fro m the L ev el d ro p-d o wn
m en u, th e Au to m atic G a in C on tro l (A G C ) f un ctio n o ptim iz es th e a tte nu atio n o r g ain . With
M an ua l is se le cte d from the L ev el d ro p- do w n m e nu , th e Le ve l s ett ing fie ld m u st be s et a
va lue fo r th e ex pe ct ed le ve l of inp ut sig na l.
7. 5. 1. A. 5 I F BW
Th e IF BW fiel d s ele ct s th e IF Ba nd w idt h F ilte r in clu d ed in the d em o du la tion p ath . A M
U SB a nd L SB m o du la tion ty pe s a re lim ite d to a 4 kH z IF B an dw id th filte r.
IF Ba n dw id th o p tion s are :
7. 5. 1. A. 6 P re-A mp
Th e 39 00 is eq u ipp ed w ith an in ter na l 1 5 d B br oa db an d am p lifie r th at af fec ts the T /R
C on ne cto r a n d A N T (A nte nn a ) C on ne c tor. Whe n Pr e- Am p is tur ne d O N , t he 39 0 0 h as a
typ ic al n oi se fig ure o f -9 dB le a din g t o a n ois e floo r le ve l o f a pp ro xim a tely -1 40 d Bm in
th e S p ec tru m An a lyz er ( RB W = 3 00 H z) an d ap pr ox im ate ly -12 6 dB m fo r th e Inb a nd
Po w er M ete r ( IF = 6 .2 5 k H z). Us in g t he P re- Am p fe atu re in cre as es th e se ns itivit y o f th e
39 00 .
NOTE
7. 5. 1. A. 7 M od ul a tio n
D isp lay s t he ty pe of m od ula tio n me a su rem e n t of the s ign al , eit he r F M D ev iat ion or A M
M od ula tio n De p th. Th e me te r fie ld to the rig h t of the M o du lat ion M e as ure m en t T yp e
dis pl ay s th e m od ula tio n m e a su rem e nt .
7. 5. 1. A. 8 Res ol u tio n
Se ts th e R F In pu t S ign a l's f req ue n cy re so lutio n se ttin g. Se ttin g op tio ns ar e 1 H z o r
10 H z.
A n al og D up le x S y st em
A M (k H z)
6 .2 5
8 .3 3
10
1 2 .5
25
30
Wh e n P re -A m p is u se d, sp ec ial atte n tion is re qu ire d; it is a
b ro ad ba n d a m plif ier an d co uld le ad to sa tu rati on or co m pr es sio n
p ro ble m s i n th e rec e ive r c ha in i f th e s ign a l of inte re st is v er y lo w ,
b ut a s tro ng o ut of ba nd si gn al i s p re se nt.
7 - 34
F M (kH z )
6 .25
1 0
1 2.5
2 5
3 0
1 00
3 00