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Re: [IRCA] How to phase BOG's? (Jim Glover)
Your thought about the hand capacitance makes sense in light of the connections you had made.
I would suggest a) at least 700' of length ( more on that in a moment ); b) grounding the receiver; c) terminating either end and listening at the other; and d) using a matching transformer - 9:1 is usual for BOG's. There are plans/details/specs for those in several places on the web.
My experience is largely with BOG's on the beach at Long Beach island NJ for our annual DXpeditions. We have used the fan termination I described in an earlier post. We have used lengths in excess of 1000' and as short as 500'. The optimum length in our experience is somewhere between 700 and 1000' Anything over 1000' doesn't seem to offer any significant performance nor directional improvement. Using the 9:1 transformers, we can then use coax to feed splitters and have enough gain for 8 receivers, with a radius in the desired direction of roughly 60 degrees from the direction of the wire.
We usually use two co-linear BOG's, with the terminations at the far ends and the feeds at the point where they nearly converge. For those who have or phasing equipment, we run a 100-200' length of wire unterminated // to one of the BOG's which can be used with either one.
Russ Edmunds
Blue Bell, PA ( 360' ASL )
[15 mi NNW of Philadelphia]
40:08:45N; 75:16:04W, Grid FN20id
<wb2bjh@xxxxxxxxx>
FM: Yamaha T-80 & Onkyo T-450RDS w/ APS9B @15'
AM: Modified Sony ICF 2010 barefoot
--- On Tue, 9/29/09, Jim Glover <psykey@xxxxxxxxxxxx> wrote:
> From: Jim Glover <psykey@xxxxxxxxxxxx>
> Subject: Re: [IRCA] How to phase BOG's? (Jim Glover)
> To: "Mailing list for the International Radio Club of America" <irca@xxxxxxxxxxxxxxxx>
> Date: Tuesday, September 29, 2009, 7:18 AM
> There is no internal ferrite bar
> antenna. My guess is that I was
> giving the antenna system a ground plane. The BOG was
> simply
> inserted into the center of the chassis SO-239. I'd
> made no
> connection to the outer section of the SO-239
> (ground). Under
> other circumstances--e.g. if I'd been powering the
> transceiver
> from the car battery--my transceiver would have been
> grounded to
> the car. But since I was powering the transceiver
> from its
> internal battery, there was no "other side" of the
> antenna. By
> placing my hand on the metal body of the transceiver, I
> was
> probably creating a capacitive coupling between my body and
> the
> transceiver. My body was also capacitively coupled to
> the car.
> The result was probably that the car's body became a
> "ground
> plane" or "counterpoise" or whatever you want to think of
> it,
> providing the antenna with an "other side".
>
> In a future test, I will try grounding the transceiver to
> the
> car body to see if I get the same type of result. If
> I do,
> that will, IMO, strongly suggest that I'm barking up the
> right
> tree here.
>
> I'm thinking there are two big factors limiting the
> Beverage-ish
> performance of my BOG. One is that 500' at 530 KHz to
> 1700 KHz
> is relatively short, in terms of a wavelength. Even
> if you
> allow for the antenna ending up much longer electrically by
>
> virtue of its proximity to ground, it still doesn't get
> long
> enough to become directional off the end. The other
> big factor
> is probably good soil conductivity. I had already
> been wondering
> about this factor--then Bruce Conti (replying on the NRC-AM
> list)
> mentioned that BOG's perform better over soil with low
> conductivity.
> According to the maps, the soil conductivity around here is
> on the
> high side.
>
> On Tue, Sep 29, 2009 at 03:50:15AM -0700, Russ Edmunds
> wrote:
> > There has to be some explanation for why there was so
> little difference between the car radio and the BOG. Part of
> that is the length, part is no termination and part is no
> matching transformer. But it seems as if there should be
> something else.
> >
> > That thought is magnified by the increase in signal
> strengths by putting a hand on the receiver, although since
> I'm not at all familiar with the receiver in question, if it
> has an internal ferrite bar antenna, that could partially
> explain it.
> >
> >
> > Russ Edmunds
> > Blue Bell, PA ( 360' ASL )
> > [15 mi NNW of Philadelphia]
> > 40:08:45N; 75:16:04W, Grid FN20id
> > <wb2bjh@xxxxxxxxx>
> > FM: Yamaha T-80 & Onkyo T-450RDS w/ APS9B @15'
> > AM: Modified Sony ICF 2010 barefoot
> >
> >
> > --- On Tue, 9/29/09, Jim Glover <psykey@xxxxxxxxxxxx>
> wrote:
> >
> > > From: Jim Glover <psykey@xxxxxxxxxxxx>
> > > Subject: Re: [IRCA] How to phase BOG's? (Jim
> Glover)
> > > To: "Mailing list for the International Radio
> Club of America" <irca@xxxxxxxxxxxxxxxx>
> > > Date: Tuesday, September 29, 2009, 12:51 AM
> > > On Mon, Sep 28, 2009 at 06:30:57PM
> > > -0400, Gil Stacy wrote:
> > > > Jim, Dave:
> > > > Dave, I doubt if Jim's car antenna was
> coupling with
> > > the BOG.
> > >
> > > I can rule it out. I rolled the BOG up, and
> then
> > > checked many
> > > of the stations again on my car radio. The BOG
> was
> > > now once
> > > again a spool of wire in the trunk of my car, and
> the
> > > sations
> > > were still rolling in.
> > >
> > > Thanks, Gil, for the additional information about
> phasing
> > > these things. I don't really need to spend
> another
> > > C-note or
> > > two on one of these phasers ... but oh my, it is
> tempting.
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