[Yaesu] FT-901DM Questions

[steve sutfin]

Hello to the list,
I am installing a little INRAD 30 meter conversion kit in my pre-WARC
FT-901DM. I will do the conversions on spare boards from my parts rig
and I see a difference in the two xtal units (PB-1711). The xtal unit in
my working radio has Q1-Q10, T1-T10, etc. and a blank space for Q11,
T11. The schematic in the service manual only shows Q&T 1-10 while the
parts layout pictorial of the board shows the xtra Q11 & T11.
Furthermore, the xtal board out of my parts rig actually has Q11, T11
and an empty xtal socket installed.
I hope I've been clear with this and I'm very curious to know what is,
or was, the purpose of this addition on the board (or lack of it) and if
there is a way to make use of it in any frequency conversion? I wonder
if there is a correlation with the two dead spots at the bottom of the
bandswitch?
Any thoughts or ideas?
tnx & 73,
Steve
k7dna