[TowerTalk] HF Antenna Planning Questions

[Chuck Rippel]

First post to the group.  Thanks to Floyd, W8RO for steering me your 
way.

I am currently using an M2, 20M4 (20M, 4 el on a 46' boom) mounted on 
a 100' Rohn 25G tower.  It is 100% guyed (14" X 10' screw anchors 80' 
from the base) with 3 sets of Phillystran 1/4" equiv. at 33, 66 and 
98'.  There are torque arms at the top and the rotor is 10' below 
the thrust bearing at the top.  My mast is 2" water pipe.  The tower 
is located 200' behind my house in a pasture and the co-ax run from 
the shack to the top is 367' of 9913.  From the house to the tower 
the cables are buried in 4" drain pipe.  I have some wire antennas 
off the tower also and switch all with a 5 positon remote co-ax 
switch.  

With the sunspots coming back, I'd like to add HF beam capability 
over 14mHz to my antenna inventory.  We live on a farm so room is not 
as much of an issue.

My thoughts are to erect another, perhaps shorter tower, or tall 
phone pole and add an M2 17-30LP7, 17-30mHz log perodic.  The cost 
v/s performance far outweighs the 1-2 db losses in advertised forward 
gain and 5 db shortfall in F/B over mono-banders.  I am also 
tentatively considering stacking a 40M3L, 3el 40M on a 30' boom 
under the 17-30LP7.  Since there is a harmonic relationship between 
40 and 15M, the jury is still out on that.

My questions for the Collective Wisdom are:

Any thoughts on using an LPA on 17-30 mHz?  Has anyone tried the M2, 
17-30LP7?

Any thoughts about stacking the LPA over the 40M beam?

How about suggestions for most optimum height.  (I suppose I ought to 
get un-lazy and get the software out of the ARRL antenna book, load 
it and work the problem but I thought I'd first get some thoughts 
here).

Anyone cost a phone pole v/s guyed tower?  I suppose you can get them 
80' tall which would yield 65' of so to work with considering 10-15' 
in the ground but 80' phone poles are not common.  The (35'?) ones 
are which is too short, IMHO. 

----

An 80' tower 170 or so feet behind my existing tower would work 
wonderfully for providing an additional support for E-W facing 
dioples but the co-ax run from the shack to the top would be in 
excess of 500'.  Even with 9913, 10M performance would suffer.  7/8 
hardline is too expensive for my budget and might not suit my 
lightning disconnection scheme (see below).

The tower is back so far due to a personal incompatibility with 
lightning.  There are 6-50' runs of buried 2" copper strap in a star 
at the tower base plus 3 approx 120' runs of buried #6 bare 
copper wire which go to 10' ground rods pounded into the bed of 
nearly always wet, drainage ditches.  All feed and control lines are 
connected at the tower base. I remove these and move the cables away 
then place the ends in an enclosure about 30' from the tower base.

I was hit once at our previous home where the strike vaporized a 
large fiberglass Diamond 2M antenna.  It was just plain gone.  
Nothing left but the mast mount.  No damage, all the cables were 
disconnected and outside and the rigs were unplugged from both the 
wall and ground bus.  

No, I don't like lightning at all and we get a bunch of it here in 
the VA/NC Coast.  

Thanks for the help.

==================================================
Chuck Rippel, WA4HHG
Reply to:
crippel@usa.net
==================================================

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