[HECnet] Help to identify tap file format

[blmink]

14.03.2013 19:25, Johnny Billquist           :
On 2013-03-14 16:07, blmink wrote:
Dear All,

I found several pdp-11 tape image files on the net which have ".tap"
suffix.
It isn't well known simh/e11/tap/tpc tape images.
Please help to identify which format they have.
How such file can be converted to simh .tap or .tpc or how it can be
used/mounted?

Below is the beginning of hexdump of one of these files named "F77.TAP":

[...]
Where did you find them? They look totally broken. I can't see any reasonable format in them at all. The first 512 bytes might be some kind of meta-information, but it's really weird.

Get some proper images instead, as from trailing-egde.

      Johnny

There's file on trailing-egde:
ftp://ftp.trailing-edge.com/pub/rsxdists/rsx11mplus_4_6_bl87_dsk.zip
It contains rsx11mplus_4_6_bl87.dsk disk image.
If you mount or boot this image,
you can find in [200,200] directory:

Directory DU0:[200,200]
14-MAR-2013 19:35

RT57MU.TAP;1               7040.           03-NOV-1999 21:53
F77.TAP;2                     2440.           03-NOV-1999 19:53
DNMP46EN.TAP;1           41840.         03-NOV-1999 20:43