Topband: ITINERANT 160 M ANTENNA PROJECT

[bills stuff]

The plan is to develop a simple, relatively inexpensive, relatively 
light weight and shippable/airline transportable 160 antenna kit for one 
man quick deployment for modest DXpeditions or contributed for use by 
resident hams in rare-ish (for 160 m) locations. The ability to make 
adjustments to actual deployments to provide matching is important since 
such antennas are famously variable due to soil and local obstruction 
environment and there should not be a need for antenna matching 
hardware, especially at the planned higher powers.

First cut electrical design: Inverted L using telescoping aluminum 
tubes, two elevated radials and “hairpin” matching.

Mechanical features of a prototype that was deployed:

9 Alum tubes 6’, .058” walls, 2” diameter through 1” diameter – this 
gives a 50’ or 15.3 m mast (it can be pulled upright by 1 person, or 
probably telescoped up also)

#14 wire ~ 28 m for top wire and 2X ~34 m radials (values after some 
adjustment, not unique, some tradeoff between the top and radials)

Base - 2 thicknesses of Walmart (cheap 8X11”) ¼” plastic cutting board 
resting on ground with a ~ 1.5” wood cylinder bolted in the center. 
SO-239 connector screwed to the board.

Guys – 4X 3/32” dacron rope attached at 7 tube height, angled at ~ 45deg

Guys held down by sandbags (very effective and moveable)

Inv L top wire end was at ~ 2.5 m height with a support of opportunity 
(e.g., a tree) ~ 25 m from base

Radials have their closest support near the base from plastic rings 
looped through each of an opposite pair of the guys at ~ 6 m high and 6 
m from the mast. The radials therefore go from the base to the rings at 
about a 45 degree angle. (Elevating the base and everything else, by a 
meter did not seem to affect the impedance. Beyond that, supports of 
opportunity were used - above neck height is always nice.

This produces, with some fiddling with wire lengths, an impedance around 
20 – j20 which can be matched using a practical “hairpin” coil shunt of 
inductive reactance ~ 45 ohms ( 4 microHenrys, say 5 turns 4” dia).

More details of the test case including the EZNEC example are shown on 
my website. There are obviously a number of ways this design could be 
modified/improved, several discussed on the website. However, the 
tradeoffs with size, weight and complexity must be considered in the 
light of the mission here which includes transportability and ease of 
deployment.

I am looking for collaborators to contribute ideas to help improve, and 
potentially, test design issues. Check out the website at

http://n6mw.ehpes.com

for the Itinerant 160 m antenna project expanded discussion toward the 
bottom.

The immediate target is designing and assembling a respectable 160 m 
antenna that might go to KH8 on a DXpedition.

Bill, N6MW

billsstuff(at)gotsky.com