Ignoring lines and create new file

Shell Programming and Scripting
1

Hello,
I have a requirement to ignore few lines in a file before keyword FILEHEADER . As soon as there is keyword FILEHEADER is identified in file , it will form another file with data from FILEHEADER to whatever in file after FILEHEADER.
I wrote

filename=$1
awk '/FILEHEADER/{a=$1;sub(".*FILEHEADER","",a);b=$2}/FILEHEADER/{print > a"_Src_"b".txt"}' $filename

but this is not working . Also its a fixed width file
Data format example

FILEHEADERTESTA     212012234234
test1
test2

File to be formed with name like TESTA_Src_21.txt

2 
awk '/FILEHEADER/{p=1}p' $filename > TESTA_Src_21.txt
3 
sed '/FILEHEADER/,$!d'
4

How about this one:

awk     '/FILEHEADER/ {p=1; sub(/FILEHEADER/,""); fn=$1"_Src_"$2".txt"}
         !p {next}
         {print > fn}
        ' file

$ cat TESTA_Src_212012234234.txt 
TESTA     212012234234
test1
test2
5

Does 'from' mean 'from the first character of' or 'from past', 'from beyond' ? Anybody can write code from good requirements, but it takes skill to write good requirements.