sqlldr- combine and insert two values - position(1:10) and position(20:30) into one column

i have to load a text file into oracle table using sqlldr.
I want to load characters from position(1:10) and position(20:30) into one column into my oracle table
I donot want to load characters from 10-20 since they are some invalid charactesr(like carriage returns etc) and it messes up my dataload of characters from position-20:30)
 
How can i do that using sqlldr
I tried
options( SKIP = 0 )
load data
infile 'myfile.txt' "str '\n'"
insert INTO
Table mytable
TRAILING NULLCOLS
 (  
allcols    position(1:10,20:30)  
 )

but that failed, I also tried using || concatenator but it did not work
pl help