[TowerTalk] Optimum antenna location re multiple towers

[Patrick Greenlee]

My plan for an antenna farm is as follows:  I have a Hy-Gain Hy-Tower 
vertical atop a metal barn roof that operates 160, 80, 40, 20, 17, 15, 12, 
and 10M.  I have a 270 ft Carolina Windom OCF dipole hung from 10 -15 ft  of 
black Dacron at the 24 ft level of the Hy-Tower (base is about 22 ft AGL) 
with the other end supported  by another antenna rope on a pulley supported 
by yet more antenna rope in a tree top. The foregoing is what I have to 
date.

I am erecting 3  towers:

1. crank-up/tilt-over guyed tower consisting of two each 20 ft sections with 
some overlap.  Tube mast at the top more than makes up for the overlap so 
antennas can be mounted over 40 ft AGL. This tower is  for VHF and UHF only.

2. a 50ft tilt over which will get my K4KIO HEX HEX beam (hexagonal shape/6 
bands) 6, 10, 12, 15, 17, 20

3. an as yet unidentified electrically raised and lowered crank-up/tilt-over 
tower which will be mounted atop (or nearly so) a 40 ft tall triangular 
tower consisting of 6 each (three pairs) of 20 ft sections of 4 1/2 inch OD 
tubing (1/4 inch wall) with the legs a bit over 14 ft on centers (not a 
typo, feet not inches.)  This tower "base" is what is left ofv a 100 ft 
tower that held a wind generator before the genny and the top 60 ft (3 
sections) did a swan dive into the dirt due to fastener failure brought on 
by variable wind direction generating gyroscopic forces in the rotating 
parts. Great tower for antennas, not so great for wind generators where the 
wind is both strong and variable.

I would entertain suggestions as to the concrete base dimensions required to 
handle the guyed tower, #1 above and the guy anchor scheme for it.

I have designed and won approval from my mechanical engineering consultant 
for a tower base for the 50 ft free standing tilt over that will get the hex 
beam. Overkill but still a far better design than a big dumb rectangular 
lump of concrete. Uses about 60% of the concrete used for the big ugly lump 
designs and maybe a bit more rebar but it is massively overdesigned and can 
accommodate changing towers without obsoleting the mounting bolts as it uses 
an intermediate steel plate( 1/2 inch) between the concrete and the antenna 
base. Expanding grout stiffens the 1/2 inch steel plate by filling the 
interstitial space. Yet by unbolting the plate you can remove the grout and 
remount the plate after attaching a different base plate for a new tower and 
regrouting.

The electrically raised/lowered crank-up/tilt-over to go atop the 40 ft base 
was originally installed on three 18 inch diameter piers down 7 ft. I will 
use three each piers at each leg. Each set of three will be collinear and 
connected by a horizontal steel reinforced concrete beam which will more 
than compensate for my 12 inch diameter augur capability vice the original 
18 inch diameter piers and my max augur depth of about 6 ft will do very 
well.  The center pier of each set of triplets will attach to a tower leg.

Two of the legs are hinged for tilt-up.  ( I would like to have seen the 
original 100 ft of this tower tilted up with the wind genny on top.) I will 
build a platform at the 40 ft level and a set of stairs to access it rather 
than a ladder as I intend to use the platform for multiple purposes which 
will include but not be limited to nature photography, 1000 meter rifle 
range, observation platform, hammock support etc.

I have sited the 50 ft crank-up/tilt-over destined to hold the hex beam over 
100 ft north and uphill of the barn on which the Hy-Tower is mounted. 
Hopefully this is enough to avoid strong deleterious interactions.  I would 
be pleased to receive advice regarding locating the other two towers 
(VHF/UHF and the one with the BIG BASE.

1. How close is too close HF tower to HF tower?  (horizontal polarization)
2. How close is too close HF tower to VHF/UHF tower. (Horizontal HF 
polarization, either or both horizontal and vertical polarization for VHF 
and UHF)
2  How close is too close HF tower with horizontal polarized antennae vs 
vertical polarized HF antennae (HY-Gain Hy-Tower)

Please include consideration for increased feedline length (I will be 
running 1/2 inch hardline) if the towers are daisy chained for efficiency of 
sharing the trenches for  conduit to hold the feedline and control lines.  I 
was thinking that running the control lines and coax in the same conduit 
would be OK but using a separate conduit for 120 or 240 VAC service. It is 
just money and a few more hours of sweat equity to do additional trenching 
and add more conduits if needed. I have a ride-on trencher, like a small 
backhoe but free standing not on a tractor so I dig all my own trenches and 
can excavate for tower bases. I like to run 3 inch minimum ID PVC conduit 
(S&D.) I clean, prime, and lavishly glue each joint. I have yet to have a 
water ingress problem contrary to any of the laments posted here.  I did, 
however, run the 3 inch S&D through 4 inch steel pipe where it crossed my 
circular drive so I didn't have to worry about the shallow depth of cover 
while avoiding conflict with French drain lines.

Thanks in advance for any consideration applicable to any of the above 
queries.

73 de
AF5CK Patrick