Just to point out that there is NO one-size-fits-all PHYSICAL length for
BOG best f/b.
There is an ELECTRICAL length that far better defines it. And the
electrical length of a fixed length of wire varies wildly all over the
place, depending on the ground underneath, and the spacing to actual dirt
ground. VF measured on 151 foot (46 m) dipoles-on-ground varied from 45% to
85%, some changing wildly just rotating the wire 90 degrees around its
center in the same back yard.
So you make a dipole on the ground, in the place you intend to put the BOG,
and at the same height and using the same installation method you intend
for the BOG. You trim it to make it resonant at 1140 kHz. Then you solder
and insulate the center and add the BOG stuff to the ends.
What you have done with that method is to create a series of 160m BOGs that
all have a certain design ELECTRICAL length.
73, Guy K2AV
On Sat, Sep 12, 2020 at 9:41 AM Artek Manuals <Manuals@artekmanuals.com>
wrote:
> Mike
>
>
>
> I have taken the liberty of changing to subject line to more accurately
>
> reflect the content of your reply on the Waller Flag thread
>
>
>
> After much reading and a lot of personal experience and experimentation
>
> I am of the opinion that BOG front-to-back is a function not only the
>
> length but the soil type as well.
>
>
>
> I experimented with 350', 300', 250', and 200' long bogs all in the
>
> same direction, In my case the shorter 200' long BOG, over very dry ,
>
> well drained, sandy soil clearly had better F/B than the 250' , 300',
>
> 350' ( F/B on the 350' was the worst of all of them..anyone want some
>
> 50' pieces of RG6?) . When I run out of other things to do I plan on
>
> trying a 175' and 150' but not in the next year.
>
>
>
> A friend of mine living in another part of the country compared his 200'
>
> BOG on laid top of rich Midwest farm loam to mine and was very
>
> surprised that my front to back was so much better than his. What the
>
> optimal length is for his particular soil is still TBD. Another friend
>
> with sandy soil but in a very near salt water environment ( he lives
>
> along a canal with ocean access, i.e salt water) also reported poor
>
> front to back , for sure we surmise his soil is much more conductive
>
> than mine) .
>
>
>
> The moral I guess is I would start shortening your BOG and see if the
>
> front to back improves
>
>
>
> Dave
>
>
>
> PS: I too use RG6 for all my BOGS and the feedlines and a dozen or more
>
> turns on a #31 torroid at each end of a 125' feed lines significantly
>
> reduces broadcast band induced signals
>
>
>
>
>
> On 9/12/2020 8:26 AM, Mikek wrote:
>
> >>
>
> >
>
> > My Technical knowledge is limited but, I have built directional AMBCB
>
> > antennas. Feed line isolation is critical to make a directional
>
> > antenna, directional! I have been criticized and been told, coax cable
>
> > does not pick up signal. Must be I don't use the right coax.
>
> >
>
> > This from a previous post I made after I ran out and tested a 230ft
>
> > Coax and a 230ft 18ga twisted speaker wire, to see what BCB stations
>
> > they received.
>
> >
>
> > "I found I received 13 stations with up to 5.5 S units on the
>
> > properly terminated coax. I tried many things to reduce signal pickup,
>
> > chokes, transformers, grounds, several chokes and transformers, but
>
> > could never get it to be quiet. So after reading some info about
>
> > phased antennas using speaker wire, I ran a twisted speaker wire out
>
> > to where my antenna was to start.
>
> > After terminating that, I found I only received 4 stations, 3 were
>
> > audible but at zero on my S meter and one that was almost 1 S unit.
>
> > Do I think the speaker wire has more loss than the coax probably, but,
>
> > I seem to have plenty of signal and it doesn't have much
>
> > signal ingress compared to the coax."
>
> >
>
> > I have since went to Cat5 cable for my receive antenna. I started in
>
> > my haste just connecting Cat5 to my radio, terrible idea, but I
>
> > learned from it.
>
> >
>
> > I tried several things to quiet the Cat5 and came up with something
>
> > that works very well for quieting the Cat5 in_MY_ situation.
>
> >
>
> > I have the 235ft of Cat5 connected to a 260ft (property limited) BOG
>
> > that I use mostly for the AMBCB. The BOG points N/S, it seems to have
>
> >
>
> > attenuated side lobes but not much front to back.
>
> >
>
> > After reading a Laird Cat5 common mode article, I used their info to
>
> > help me build my signal ingress reduction box. If you're interested in
>
> > seeing what
>
> >
>
> > worked for me, click here.
>
> >
>
> >>
> https://www.dropbox.com/s/e1lq7fxv0kggi5d/bog%20final%20design%20may%2030%202020%20common%20mode%20attenuator.jpg?dl=0
>
> >>
>
> > KF4ITA Mike Knowlton
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
> >
>
>
>
> --
>
> Dave Manuals@ArtekManuals.com www.ArtekManuals.com
>
>
>
> --
>
> This email has been checked for viruses by Avast antivirus software.
>
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>
>
>
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>
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>
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