CASE 1:
Source: 3C48
Fluxes in the SU table are 0. 

 BPASS INPUTS
DOSCALE SPECINDX     HISTORY FILE RECORDS        BP TABLE RESULT
-----------------------------------------------------------------------------------------
-1        0          no mention of SPECINDX     flux density increases with nu
-1       -5          no mention of SPECINDX     flux increases with nu; same as DOSCALE=-1, SPECINDX=0

0         0          SPECINDX(  1)= -0.769      flux density increases with nu 
0        -5          SPECINDX(  1)= -5.000      flux density increases with nu; nearly identical to
                                                       DOSCALE=0, SPECINDX=0 and DOSCALE=-1, SPECINDX=0

1         0         SPECINDX(  1)= -0.769       flux *decreases* with nu---opposite DOSCALE=0, SPECINDX=0 case
1        -5         SPECINDX(  1)= -5.000       flux decreases with nu; nearly identical to DOSCALE=1, SPECINDX=0 
                                                                                   

CASE 2:
Source: 3C48
Used SETJY to set ZEROSP=1, SPECINDX=-5 in SU table

 BPASS INPUTS
DOSCALE   SPECINDX   HISTORY FILE RECORDS     BP TABLE RESULT
--------------------------------------------------------------------
2           0        SPECINDX(  1)= -0.769    flux density increases with nu; identical to DOSCALE=0, 
                                                                  SPECINDX=0 case
    
CASE 3:
Source: Rename 3C48 as "3C99" in SU table (i.e., disguise as an unknown source)                 
Used  SETJY to set ZEROSP=1, SPECINDX=-5 in SU table

 BPASS INPUTS
DOSCALE   SPECINDX   HISTORY FILE RECORDS     BP TABLE RESULT
--------------------------------------------------------------------
2           0        SPECINDX(  1)= -4.998   flux density increases with nu; nearly identical to
                                                     DOSCALE=2, SPECINDX=0, 3C48 case