Topband: BOG - Selecting the Optimum Length

Mon Oct 17 12:01:36 EDT 2016

Just to be clear, my original 200 foot BOG was a success – much quieter on RX than the vertical !

In my particular environment, based on my particular soil conditions, I was not seeing a significant directional characteristic on 160m, but the 200 foot BOG still outperformed the vertical and allowed me to work Heard Island, South Sandwich and South Georgia last season!

If you only have 200 feet or even a bit less than 200 feet, I still think the BOG is definitely the way to go.

I apologize if anyone was misled.

73

Lloyd – N9LB

From: Mark K3MSB [mailto:mark.k3msb at gmail.com] 
Sent: Monday, October 17, 2016 10:35 AM
To: Lloyd - N9LB <lloydberg at charter.net>
Cc: topBand List <topband at contesting.com>
Subject: Re: Topband: BOG - Selecting the Optimum Length

Based upon N9LB’s comments,  I just emailed Bruce and told him to hold my order for a KB-1.

I have just enough room for 200 ft for a BOG.   Extending it to 250, 290 feet etc is NOT an option for me.

>From my reading,  I understood that 200 feet was not exact,  but I didn’t expect it to be 250 to 290 feet.   If I had known that I would not have even considered a BOG.

With the cable, KB-1 etc (my BOG will be unidirectional to EU only,  not bidirectional),  I really don’t want to invest close to $200 on an antenna that will not do any better on RX than my Inverted-L.    Saving it for a Hi-Z 3 may be the better option.

So, with only 200 feet to play with,  is it worth it?

I've no doubt BOGs work,  I may not have the room for them.  

73 Mark K3MSB

On Oct 17, 2016 9:35 AM, "Lloyd - N9LB" <lloydberg at charter.net <mailto:lloydberg at charter.net> > wrote:

I have been asked how I arrived at the 290 foot BOG length.

My original 200 foot BOG had a good F/B on 80m but showed almost no
directivity on 160m, so this indicated to me that the BOG needed to be
longer to improve the 160m performance with my particular soil conditions
and environment.

A search on the Internet produced recommendations for 160m BOG lengths of
247 to 290 feet.  Knowing that I could always shorten the wire, I went with
the longer number as a starting point.  That produced a greatly improved 15
to 20 dB Front-to-Back ratio.

The 290 foot length was not chosen for a good match, but that length just
happened to result in a good match.

Unfortunately, I did not measure the match on my 200 ft BOG before it was
dismantled.

The optimum 160m BOG length in your environment might be much different from
what I found at my QTH.

- - - I think the group would benefit from hearing what others have found to
be their optimum BOG lengths - - -

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com <mailto:topband-bounces at contesting.com> ] On Behalf Of Lloyd -
N9LB
Sent: Sunday, October 16, 2016 11:06 PM
To: 'Topband' <topband at contesting.com <mailto:topband at contesting.com> >
Subject: Re: Topband: BOG

My Reversible Bog uses the KD9SV transformer set.  It was originally 200
feet long, just increased to 290 feet and that made a very significant
improvement on 160m front-to-back ratio, but hurt 80m performance.

Conditions here are:
Wire run across a weedy field, as close to ground as possible (weeds
trampled down to allow the wire to be close to ground - mostly 2-4 inches
above the actual ground).  Soil is a few inches of decent dirt, about one to
two feet of clay, about one to two feet of sand, and then bedrock.  Tops of
the five foot ground rods can't be driven completely below the ground's
surface.

WX - a wetter than normal Summer and Fall here in Southern Wisconsin.

My Antenna Analyzer shows a 1.45 : 1 match at 1825 KHz ( 75 ohm system ).

I can send the analyzer plots to anyone that is interested.

73

Lloyd - N9LB

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com <mailto:topband-bounces at contesting.com> ] On Behalf Of Charles
Moizeau
Sent: Sunday, October 16, 2016 10:20 PM
To: Lloyd - N9LB <lloydberg at charter.net <mailto:lloydberg at charter.net> >; Topband <topband at contesting.com <mailto:topband at contesting.com> >
Subject: Re: Topband: BOG

Thanks Lloyd,

But pls tell us your wire height and approximate description of gnd condx
for your otherwise well-described bog.

73,

Charles W2SH
________________________________
From: Topband <topband-bounces at contesting.com <mailto:topband-bounces at contesting.com> > on behalf of Lloyd - N9LB
<lloydberg at charter.net <mailto:lloydberg at charter.net> >
Sent: Sunday, October 16, 2016 7:15 PM
To: topband at contesting.com <mailto:topband at contesting.com> 
Subject: Re: Topband: BOG

Hello Tony!

Ground conditions and wire height above ground make a huge difference in
best length.

I found the optimum for my BOG, using WD-1A wire and operating at 1825 KHz,
at my QTH is 290 feet.

73

Lloyd - N9LB

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com <mailto:topband-bounces at contesting.com> ] On Behalf Of N2TK,
Tony
Sent: Sunday, October 16, 2016 5:15 PM
To: topband at contesting.com <mailto:topband at contesting.com> 
Subject: Topband: BOG

Stretched out 200' of WD-1A along a stone wall. Kept it about 2" above the
ground and right up against the stones. Fed it with a 300 ohm secondary
transformer and left the far end unterminated.

Used the MFJ-259 to sweep the bands starting at 1.67 MHZ.  Saw on K1FZ notes
that to find the best single wire length for 160M is to sweep the bands and
check where the SWR goes to a low value and stays there.

I couldn't find that frequency. I get dips at

2.58 MHZ 4.3:1
3.36 MHZ 1.5:1
4.39 MHZ 1.4:1
6.033 MHZ 1.3:1
9.807 MHZ 1.2:1

I didn't check any higher in freq. I only care about listening on 160M with
it.
I twisted both wires together at the feedpoint.
Want to check it out first as a single ended BOG to see how it works before
I go to the trouble of making it a two direction BOG.
At one point the BOG is only 35' from my tower.
Is it too high and does it need to be against the ground?

Any feedback appreciated.

N2TK, Tony
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