[600MRG] Transformer design

[N1BUG]

Hey folks, it's that dim bulb up in Maine again! Ya know, we haven't
seen the sun in so long everything here is dim. And waterlogged. I'm
sure the answer to this is out there on one of the info sites but I
am not finding it in a form that speaks to me.

I want to design an antenna impedance matching transformer for 630
meters. This will go between the coax and the variometer. I believe
a single 2.4" OD core of #77 material is sufficient at power levels
below 100 watts. Or maybe not, as I believe this depends on core
saturation which is related to number of turns. Hmm. That brings us
to the matter of how many turns. I believe the rule of thumb is that
the 50 ohm side should have an inductive reactance of at least 10
times 50, or 500 ohms. That would mean 7 or 8 turns minimum. The
antenna system resistance on 630 meters does change over time, but
not over a wide range. To that end I would like to have taps to
adjust it, but I do not need a wide range and prefer the ability to
concentrate on the range of resistances I will actually see. I would
like to do this with only one tap switch on either the primary or
secondary. This would dictate having more than 7 or 8 turns on the
50 ohm side in order to avoid having the impedance ratio change in
large steps. I have been through the math on ratios. Something
around 14 or 15 turns on the 50 ohm side would give me the matching
range and adjustability I want using the core and switch I have.

My question is, what is a practical upper limit for the number of
turns? Is this limited only by core saturation? Or are there other
factors I need to consider? I will admit to feeling a little shaky
on use of the core saturation formula, but *think* I can navigate it
from the notes I made last year when someone kindly walked me
through an example. I just need to know if core saturation is my
only worry with regard to using more turns.

73,
Paul N1BUG