Shortened BOG Array

[Gr0undPlan3]

In the past, I had a 180 feet low Beverage (~3 feet) terminated in 470 ohms facing about 340 degrees. Antenna wire was THHN stranded fed to a transformer to 75 Ohm coax. It was quiet and worked. But it was 'facing' North so somewhat limited. I was also using a crude vertical at the time.

Then I put up a proper multi-band quarter wave vertical. Still quiet and omni-directional. I could hear much more than the Beverage, including noise, especially in the lower bands. The Beverage and crude vertical came down at this point and I used only the quarter wave vertical.

I have gotten to the point where I would like some directivity, especially in the lower bands. I have a HOA lot, so towers are out of the question.
To keep it stealth, I'm going to try a 4-way BOG array, that will be far shorter than ideal. I’ve had decent results with 180 feet. And, this is a RX only array.

To implement all four directions, I need a little over 1,000 feet of coax. I currently have about 600 feet. The feedlines eat up much of the coax since there are two equal lines per feedpoint. My longest run will be for the E-W Beverage, 400 feet of feedline. I will start with the E-W leg since I have everything I need to start on hand.

Also, it may easy to test F/B using WWV to the West. I should see a signal decrease when listening to WWV on the East leg compared to the West leg. Maybe I’m wrong or my F/B will terrible.



The lengths listed above are the total length of the coax. The feedline run measures to just over 200 feet (x2). Sections D, E and F will require connecting each section into the total 218 feet. Not certain how I will join those sections yet.

The reversible BOG is based on section 2.15.5 in ON4UN’s Low-Band DXing. Excellent book with an excellent section on receive-only antennas. The concept is based on using both the braid and center conductor as two separate wires. 2:4 transformers wound on binocular cores are used at each end to terminate either the center conductor, or the braid.

Since my ‘wires’ will be on the ground, Z_SURGE is estimated to be 300 Ohms. I’m using 75 Ohm coax and my transformers (T1 and T3) are measuring between 305 and 308 Ohms.

The feedpoint contains both the feedpoint to the shack (2X) and the other 2:4 transformer for the antenna section. Gas discharge tubes (GDT) to ground rods are used at each end for lightening protection.



The end termination will go on the West leg and the feedpoint/termination will go on the East leg.



I’m currently getting rain at the QTH and I’m hoping to get the E-W leg installed externally this week. Much easier to pound ground stakes into soft ground. Not much rain recently and very dry.

I’ve also built an entrance panel with GDTs and braid-breaker transformers on each line. More on that to come as this progresses this week.

Thanks for looking.

[Gr0undPlan3]

UPDATE#1

ENTRANCE PANEL

The entrance panel is straight-forward.



Each coax/direction will feed through a GDT and then a 2:2 transformer to isolate common mode currents. There is a pair of double coax + ground that comes into the house for a total of 4 coax and 2 grounds. I’ll tie those outside grounds together and attach a ground rod for QTH ground. The inside grounds will attach to the entrance panel.

To check for losses through the entrance panel, I performed a 5 Vpp sweep from 600 Hz to 30 MHz with my SG and saw no loss and no spill-over to adjacent lines.



E-W Beverage – 255’

Physical length of the installed E-W Beverage is 255 feet and works surprisingly well.

Even in the AM broadcast band where the antenna is really short, I am able to null out a local AM station to the west of my QTH. 1270 AM WDLR 500 W. The N-S null is also strong with the major local stations to the south almost completely nulled. Did not specifically check yet, but under the assumption the clear channels in Cleveland and Detroit would be knocked down or nulled completely.



WWV is more difficult to null although there is a 3-5 S-meter drop listening to WWV on the east Beverage.

I appear to have mis-labelled the feed ports, east was actually west and west was east. Glad I waited to WX proof until after testing! Switched the feedlines to the correct ports and WX proofed them.

Due to tree roots, I was no able to get the feedpoint ground rod very deep. I’m going to add a second ground rod 5 or 10 feet away and bond it to the existing ground rod. I’ll bury the new one to ease mowing in the area when the time comes again next season.

E-W performance has surprised me, I did not expect much nulling considering the lack of space for a proper Beverage. Working on the N-S Beverage next.