[Towertalk] 160 Mtr Phased Verticals -Problems and Trivulations

[Rick]

I have two Force 12 160VX antennas.  For those not familiar, they are 60 ft
tall (46% of full size) and use two sets of linear loading wires that attach
at about the center of the antenna.    The manual recommends the use of two
tuned elevated radials, 16 ft above the ground.   The claimed bandwidth for
2 to 1 SWR is 42 kHz..

My antennas are  spaced 1/2 wavelength apart; and for reasons still unknown
to me (maybe some subliminal message I received from the ham gods while
asleep, combined with advice from "experts" on this reflector),   I decided
to use ground radials rather than two tuned elevated ones.    The more I
read on this subject, the less I seem to know and the more confused I
become;  it is worse than trying to figure out what a politician is telling
you.

Anyway,   after walking the better part of 10 miles I laid out  slightly
more than 100 ground radials under each one.    The radials are spaced
evenly and  most are 130 ft or so long  (there are a few that I could only
get about 100 ft  - to the W thru NW and then a couple to the N on one of
them).

Each antenna is fed with RG-213 phasing line (3/4 wavelength)  for in-phase
use, and I can switch in a 1/2 wave delay line (also RG-213) to one antenna;
allowing the pattern to change from broadside to endfire.

 I tuned each vertical  using about 30 watts of power at 1.830 KHz, and a
SWR meter right at the base of each vertical.   By manipulating the linear
loading and the hairpin matching coil,  a 1 to 1 match was achieved.

I have two questions/problems that I hope someone might be able to help me
with.

(1)   Problem:   The 2 to 1 SWR bandwidth is only about 21  KHz;  exactly
the same on both antennas.    This is the same when checked at the antenna
or  in the shack;   I don't seem to have any "added bandwidth" due to SWR
smoothing  with the long coax run to the shack.   Additionally, I erected
one and got it working before I even started on the second one.    It's
bandwidth was 21 KHz and stayed the same when I installed the second one -
installing the second one did not seem to de-tune or otherwise effect the
original one.

    Question(s):   Does tuned elevated radials increase the bandwidth of an
antenna as compared to standard old ground radial?    If not, does anybody
have any idea why the bandwidth is narrower than other hams seem to get with
the antennas?     Should I go to the trouble of walking  another  520 ft
(plus or minus) and install a couple tuned elevated radials?     If I do
that, do you use them in tandem or disconnect the ground ones?

(2)    Since I am not using any L network at the "T" where I split the
signal to the verticals, I  obviously lose the 1 to 1 match when feeding
the antennas together.     The effect of this (I believe which is due to
coax length and SWR) is to "shift" the apparent resonant freq of the array
at the radio to 1.846 KHz with a min SWR of 1.4 to 1 when feeding in phase;
and to 1.840 KHz with a min SWR of 1.2 to 1 when feeding 180 degrees out of
phase.    I am not a "double E",  but I believe these readings would vary
considerable, depending on just where you happen to insert the SWR bridge.

Question:    Is it best to "just live with it" and use the antenna tuner in
the shack to make the amp "happy"; or would it be prudent to make a couple
of L networks and switch them in out at the "T".     I am not sure how
effective this will be since the bandwidth is so narrow anyway, and I will
still need to use a ant tuner some of the time.

Hope someone out their has some answers, opinions, or ideas for another
hobby.

Thanks

Dick  K8ZTT
Franktown, CO