deleting strings where special characters are missing

Hi everyone, I have a text strings. This is just a little portion of the file but the original is much larger. Sometimes I get a row were something went wrong, like the third row of this example just below. On the third string part of the coordinates are missing, sometime part of the Northings, sometimes part of the Eastings, sometimes both. The rows that are right do not always have the same length. So I was thinking to look for those rows where either the 'N' letter or the 'E' letter are missing. I tried the 'strfind' and 'isempty' commands but I am not managing to get it right, it returns the same data as before. Can someone please help me??????? Thank you.

 '$GPGLL,5341.65350044,N,00713.34866656,E,104325.00,A,D*64,$SDDBT,00023.2,f,0007.1,M,0003.8,F*08'
    '$GPGLL,5341.65358961,N,00713.34455216,E,104327.00,A,D*6C,$SDDBT,00023,M,00.0,N,,K*4A'

'$GPGLL,5341.65523146A,D*68,$SDDBT,00023.2,f,0007.1,M,0003.8,F*08'

    '$GPGLL,5341.65527973,N,00713.29472566,E,104351.00,A,D*69,$SDDBT,00023.2,f,0007.1,M,0003.8,F*08'
    '$GPGLL,5341.65542543,N,00713.28847321,E,104354.00,A,D*6E,$SDDBT,00023.2,f,0007.1,M,0003.8,F*08'
    '$GPGLL,5341.65550430,N,00713.28218422,E,104357.00,A,D*6F,$SDDBT,00022.9,f,0007.0,M,0003.8,F*03'

$GPGLL,5341.71916345,E,105127.00,A,D*6E,$SDDBT,00032.8,f,0010.0,M,0005.4,F*0F'

'$GPGLL,5341.65570054,N,00713.27593477,E,104400.00,A,D*65,$SDDBT,00022.9,f,0007.0,M,0003.8,F*03'

'$GPGLL,5341.65608654,N,00713.26774575,E,104404.00,A,D*62,$SDDBT,00022.9,f,0007.0,M,0003.8,F*03'