Topband: BOG - Selecting the Optimum Length

Mon Oct 17 12:04:21 EDT 2016

Typing on my iPhone from the woods now.  I am testing a JK BevFlex 4 deployed as a bog now. Early stages.  I think the optimum length will be determined by the local earth characteristics.  Started by measuring a wire dipole resonance on the ground to determine the shortening factor from earth proximity.  Based on this started at 225'.  Antenna hears well and shows good f/b but condx have been poor. Waiting for more favorable conditions to try optimizing.  Have Hi Z triangle and normal bev to test against. I can already say it works much better than my tx inv L on 160. Another update after more testing.  Back to work now.

73 Charlie N8RR
Sent from my iPhone

> On Oct 17, 2016, at 11:35 AM, Mark K3MSB <mark.k3msb at gmail.com> wrote:
> 
> 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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