Grounding the coax shield to the tower at the feedpoint will allow the tower
to serve as the ground/radial portion of the antenna.  How well it performs
this task will depend on the height of the tower, how well it is grounded at
the base, how the guy wires are attached, etc.  It is quite possible for the
tower to be well grounded, but of such a length that it presents a high
impedance to RF at the feedpoint.  (Performance depends on the electrical
height of the tower in wavelengths, so it will vary from one band to the next.)

For lightning protection, the most important places to ground the coax
shield are at the base of the tower, and again before it enters the house.


With regards to your previous question about bending the wire, that will change
the radiation patterns, but the antenna will still work.

I'd hang the center of the vee from the tower using a meter or so of rope, and
let that wrap around the tower as it rotates.  This works best if the antenna is
being pulled away from the tower somewhat.  You can just allow enough sag
in the wires that they don't pull tight, or put a counterweight on the ends that
will maintain constant tension.

When the vee is exactly in line with the tower, probably the easiest way is to
put a counterweight on one end so it pulls the feedpoint in that direction, and
put a smaller one - or just a bit of slack - in the other side.  That allows the
mast to rotate without stretching the antenna.

Perhaps you are misunderstanding what the slug does:  it changes the inductance
of the coil, not the selectivity of the circuit.  There may be a small difference in the
selectivity due to a change in the L/C ratio and the Q of the coil, but it will be relatively
minor.  The capacitance required to tune to a specific frequency will change, of course,
as the inductance changes.

If the coil is designed to tune 6 to 18 MHz using a 40 - 365pf variable capacitor, then the
nominal inductance of the coil can be calculated as ~2uH.  That means it would require
around 1000pf to tune 80m.  From your data, we can see that moving the slug to the
bottom of the coil increases the inductance to about 20%, and at the very top of the
coil it lowers the inductance by about 20%.  This is typical of many such coils, though
sometimes there will be a peak near the middle with lower values at each end.

It doesn't really matter which setting of the coil you use, as long as you have the proper
capacitance across it to tune it to the desired frequency.  There are some practical limits
to the variable capacitor as it gets too big or too small, and you also need to consider the
tuning rate (whether you can adjust the capacitor accurately enough given the coverage
of 180 degrees of rotation:  in the regard using a larger fixed capacitor will tend to spread
the 80m band out over more of the range of the capacitor.)

So you can use a fixed capacitor on 40m and adjust the coil slug for resonance, then
switch in the variable (and possibly another fixed capacitor) on 80m to have the ability
to cover the band as desired.

But adjusting the coil slug really doesn't change the selectivity of the circuit.

It should still be able to charge batteries, but not in fast-charge mode. 
In standard charge mode it may be able to recharge a pack in one day
if it isn't fully depleted.

I'd agree that it would be optimum not to have to adjust the converter
tuning across one band, though if you needed to use two settings to
cover 80m that wouldn't be the end of the world.  In fact, if that is
the converter I'm remembering, I'd use a single band switch to select
the coil/capacitor combinations for 80/40m rather than relying on
a variable capacitor to tune between them.  Generally that would mean
a fixed mica with a small trimmer for each coil on each band, though
you could use a single fixed mica on 40m and adjust the coil inductance
for alignment.

Unfortunately I have EZNEC running on a computer that is not connected
to the internet.  I may be able to transfer the file off using a thumb drive,
but it probably is faster to create your own.  It isn't difficult:  Start with
a full wave dipole (two half waves) fed in the center, then add a quarter
wave wire going down, a single segment horizontal wire a couple inches
long, another quarter wave wire going up, and the final 1/2 radiator on each
end.  Just make sure you use the same number of segments in each of the
vertical wires that make up the stubs.

You could tweak the feedline length to see if it makes any difference, but if
you're happy with the SWR then just use it.

Isn't it great when you put something together and it works first time?  And
that SWR is pretty much what EZNEC predicted when it came up with a
feedpoint impedance of 1600 ohms.

The mast sections are about 1 7/8" diameter aluminum with 3/16" thick walls
(as near as I could tell in a dim corner of the garage.)  They're actually pretty
strong and relatively light, especially compared to steel.  But by keeping the
forces mostly vertical as I put them up there really isn't much sideways
pressure on the joints.

I have some similar fiberglass sections that I've stacked to 40' all by myself,
though they need multiple guy ropes at that height because the joints aren't
nearly as strong:  I've had some break out from the force of the wind sideways
on a 24' mast.

Similar sections could be made from other local materials.  One limitation is the
weight:  you have to be able to lift the mast sections + antenna and rotator
enough to slip in the next section.  For longer sections a step ladder may come
in handy, but keeping the sections relatively short makes it easier.

A typical 43' vertical would have an impedance (ignoring ground losses)
around 12-j500 on 75m.  That's 12 ohms resistance and 500 ohms capacitive
reactance.  You can cancel the -j500 with a series coil, but that still leaves
you with 12 ohms.  Without the un-un, that's best case SWR of about 4 : 1.

If the un-un has a perfect 4 : 1 ratio, it would step the 12 ohms DOWN to
3 ohms, for an SWR of about 16 : 1.

Depending on your ground system, the ground loss could add 5 to 50 ohms
to the R value, which will improve the SWR (though at a corresponding loss
of efficiency.)

In this case, removing the un-un will improve the SWR considerably.  The
same goes on 160m, where R is perhaps 3 ohms:  you don't want to step
that down any further.  (In practice the un-un is not perfect, and the
shunt reactance may serve to increase the R value that you have to match.)

I use the 4' military surplus aluminum mast sections, and two people can
easily put up a tribander to 32'.  (I was going to do it by myself to show it
could be done, but another ham insisted on helping me.  Three people is
probably the most convenient number:  two to lift and one to feed sections.)

I put the antenna on top of two sections of mast, attach the guy ropes
(approximate lengths), and walk towards one of the guy anchors until the
other two guys are tight.  At that point I should be able to set the mast
on the ground and lean it against the two guys while I pick up the next
mast section.  Pick up the mast and antenna (moving slightly towards the
guy anchors, but while keeping it leaning slightly against the guy ropes),
slip in the next section of mast, and lower it back down.  Lather, rinse, repeat.

Though with a big antenna on top I'd generally put up just the mast and
get it positioned where I want it, tie off the guy ropes, then lower it back
down and put the antenna on.

The 4' mast sections are about as long as I can manage:  5' TV mast
sections would be too tall (though they could be cut down.)  There are
some 3' or 32" sectional masts available which would be better, or you can
make your own.

Because the mast is always vertical it doesn't have the bending moment, and
the weight involved is less than trying to tip up the same antenna load.

Because it is missing the tangent operator:

( 1 / tan( 16.26 degrees ) ) = 3.428

W4RNL included those designs in his survey of ground-independent
vertically polarized antennas.  Those articles are now behind the
AntenneX paywall, but you may find an occasional sample file to
read, or they'll be happy to sell you access.

But basically they are a fairly high Q, narrow bandwidth approach to
building a low vertically polarized antenna.  You still have ground losses,
both near field and far field that will depend on ground conditions, but
probably not as bad as for a conventional vertical antenna of the same
height fed against a set of ground radials.  I've modeled a couple such
designs and they seem to work about as claimed.

The exact height isn't critical:  as tall as possible will improve efficiency,
as will using reasonably large wire.  (Not a good time to use galvanized steel
fence wire or that spool of #32 magnet wire you have laying around.)
With the right height, folding the wire will give you a direct 50 ohm match,
but if you can make it higher the improvement might be worth a bit of
impedance matching.

While a 1 : 1 balun is the proper ratio to use, that particular balun doesn't
have enough inductance in the windings to work much below 10m or so.

The antenna itself won't do anything to your scanner.

Transmitting on 2m using an antenna close to your scanner antenna
may, however, damage your scanner, or at least cause it not to work
as expected while you are transmitting on 2m.  That effect is basically
independent of what antenna you are using for each:  the more critical
issue is the distance and coupling between the two antennas.

That said, I've seen any number of installations where a scanner antenna
was installed beside VHF/UHF transmitting antennas without damage.
(Our Search and Rescue van had at least 10 antennas on the roof, one of
which fed a scanner, and we didn't have any issues.)


What you do NOT want to do, however, is to run the coax for any other
antenna up through the middle of the yagi, as it will distort the pattern.
Mounting the yagi on a stand-off to the side of a tower or mast is a good
idea, as it also keeps the mast or tower itself from affecting the pattern.

Looks like a traditional air-core 1 : 1 voltage balun. 

With 12 turns of wire on 1" diameter pipe it might have enough inductance
to work at 10m.