Topband: Several BOG questions

Mon Aug 6 14:20:08 EDT 2018

Hi Mike, 

Congratulations on your first post regarding BOGs. They're a great 
antenna when stealth is the driving requirement, but here are better 
choices when stealth isn't so important. 

The front-to-back ratio of a BOG results mainly from its laying on the 
ground. A signal arriving from the back of the BOG is already greatly 
attenuated before it arrives the termination, the value of the termination 
resistor isn't as important as it is for an elevated Beverage. You can 
clearly see this affect with a TDR or an antenna analyzer as you 
install/remove the termination resistor on a BOG vs. an elevated Beverage. 

Do you have enough space to install another BOG at least a few feet away 
from your existing BOG? That would give you a reference to compare 
attempted improvements made to one of your BOGs. 

The RF resistance of a ground rod used with a Beverage or BOG isn't very 
important, more important is the stability of the RF resistance during 
varying wet/dry weather conditions. Stability can be improved by using 
multiple spaced ground rods or by adding radials or a ground screen 
such as chicken wire. Lowering the resistance isn't important because 
you lower the resistance you'll need to increase the value of the 
termination resistor to compensate for the lower resistance of the ground 
rod. 

73 
Frank 
W3LPL 

----- Original Message -----

From: "Mikek" <amdx at knology.net> 
To: topband at contesting.com 
Sent: Monday, August 6, 2018 5:06:12 PM 
Subject: Topband: Several BOG questions 

I have installed a 253ft Bog, 
I used WD-1A a pair and just twisted the two wires together. 

Any reason I should separate the pair and just use a single wire? 

Can the WD-1A be used for a Bi-directional BOG, or is the spacing too close? 

I have installed a variable termination on the North end of the BOG and 
a matching transformer 
on the South end, for receiving from the north. I'm in the Florida 
panhandle about 1 mile from the gulf. 

I'm a little disappointed that the Variable termination does not have 
much effect between 200 ohms and 1300 ohms. 
I use AM Band stations as a guide to the directionality of the BOG and 
it does seem to have good directionality, 
just no noticeable difference while adjusting the termination. It is 
also quiet when compared to a 150ft long wire. 

In an effort to make the antenna seem 'apparently' longer I have loaded 
the BOG with 9 ferrite binocular cores. 
Using info from W8JI's page, 
> https://www.w8ji.com/slinky_and_loaded_beverages.htm 
I originally measured my Velocity Factor as .78 and by installing the 
cores I was shooting for a VF of .55 

I made a single pass through a single hole in the binocular core. 
A single pass through a single hole in the binocular core is about 
8.9uh. My calculation said I needed 
11.8uh, but I installed all the cores I had and ended up with a VF of 
.67, lower but... when I get more cores 
I'll install them and test VF again. 

Your thoughts? 

I have measured my ground rod resistance using the method on page 24 of 
the this pdf. 

> www.weschler.com/_upload/sitepdfs/techref/gettingdowntoearth.pdf 

I got 117 ohms on both ends, I bought some calcium chloride and put 
2.5 lbs into and 
around my 3 copper pipe rods. I pre-drilled the rods every 3" to allow 
the solution to 
distribute more evenly around the pipes. (5ft rods/pipes) I did this at 
one end. 
A day later I retested the ground rod resistance, and it was 73 ohms, 
some improvement, 
and another couple days I remeasured and it was down to 60 ohms. 
A week later I added more Calcium chloride and I'm at 34 ohms now. 
I just finished retesting ground resistance, North end 34 ohms, South 
end 23 ohms. 

Is the method in the pdf article a reasonable way to measure ground 
resistance? 
I used 60 hz, because it's available. My last test used ~ 25V and 
supplied 600 mA. 
I have no other AC source at a different frequency that would apply 
that much power. 

I bought a 74AC14 TDR and used it to measure the characteristic 
impedance and VF. 

I measured the Characteristic Impedance, which I then use to calculate 
the matching transformer. 
Does the ground resistance show as part of the Characteristic Impedance? 
ie. If my ground was 117 ohms and I treated it and it is now 23 ohms, 
will my Characteristic Impedance, 
impedance drop by 94 ohms? 

I measured my Characteristic Impedance as 358 ohms before Binocular core 
installation, 
and measured 501 ohms after Binocular core installation. 

OK guys, this is my first post, there are a few questions, I hope to 
get some help on this project. 
btw, I did make a video showing how it compares to my long wire antenna 
using AM band stations. 
> https://www.youtube.com/watch?v=QuMwGDK6IhQ&t=51s 
Thanks, Mike Knowlton 
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