Topband: BOG - Selecting the Optimum Length

[Mark K3MSB]

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> 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] On Behalf Of Lloyd -
> N9LB
> Sent: Sunday, October 16, 2016 11:06 PM
> To: 'Topband' <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] On Behalf Of Charles
> Moizeau
> Sent: Sunday, October 16, 2016 10:20 PM
> To: Lloyd - N9LB <lloydberg at charter.net>; Topband <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> on behalf of Lloyd - N9LB
> <lloydberg at charter.net>
> Sent: Sunday, October 16, 2016 7:15 PM
> To: 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] On Behalf Of N2TK,
> Tony
> Sent: Sunday, October 16, 2016 5:15 PM
> To: 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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