I can't speak to switchable bi-directional arrays but I can speak to my
900ft terminated beverage (450 Ohm resistor to a ground rod with 2 - 1 / 4
wave radials per band). It has 20db plus front to back ratio on 40 - 160M.
The gain is sometime not much more than half an S unit to one S unit vs my
ank
W3LPL
- Original Message -
From: "MU 4CX250B" <4cx2...@miamioh.edu>
To: "Artek Manuals"
Cc: topband@contesting.com
Sent: Friday, October 18, 2019 2:51:50 PM
Subject: Re: Topband: Beverage Length vs F/B or (RDF?)
Thanks for the suggestion, Da
Jim
When you say it measured 70K was that DC, low frequency (60hz) A/C or at
1.8/3.5 Mhz RF?
Big difference.
'
Here two 5' rods about 2' apart measure about 2K DC but measure about
600 ohms at 1.8 Mhz...Still not sure how that correlates to a larger
earth RF ground. The other thing is RF
Thanks for the suggestion, Dave. I’m using DXE hardware and relay
boxes for switching, and twin lengths of WD-1A mil surplus telephone
cable for the wires. The lengths are spaced roughly 6 inches apart to
approximate 450 ohms. The end terminations are three 8ft ground rods
spaced out about 4 ft
Jim
Poor front to back can indeed be a result of being too long. Although
w8JI would argue that at 700 feet your just about at optimum (1.5
wavelengths) I would think it would be easy to add an insulator /jumper
and a set of terminations and grounds at ~500 feet and see what the
difference
