Re: BOG antennas


Russ Edmunds <wb2bjh@...>
 

For our annual DXpedition at Long Beach Island, NJ, we use a fan of 3-4 wires of 15' or so length fanned out through a similar resistance. This is on the beach on sand, so the conductivity is likely different, however this not only suffices for directivity. Ground rods proved disasterous as they were very hard to drive in, and even harder to remove owing to whatever driftwood, etc. was down there.

Our BOG's are 800 - 1000'  but they don't really seem to degrade near the top of the band - again perhaps a result of the sand.

Russ Edmunds
15 mi NNW of Philadelphia
Grid FN20id

FM: Yamaha T-80 & Onkyo T-450RDS w/ APS9B @15'; Grundig G8
AM:  Modified Sony ICF 2010's barefoot


--- On Mon, 10/31/11, neilkaz wrote:

From: neilkaz
Subject: [ultralightdx] Re: BOG antennas
To: ultralightdx@...
Date: Monday, October 31, 2011, 3:12 PM

 

Ten years ago I laid down my first real BOG, 625 ft due west from here 35 miles NW of Chicago. In contrast to the elevated mini-Bev it replaced it had considerably better directivity and was a considerably better DX antenna except on the very high end of BCB, where 625 ft is a reasonable length for a Bev, and where BOG's start becoming somewhat lossy at that length. A few examples of daytime reception on my initial BOG... 540 KWMT was loud, 570 WNAX which I could barely tell it was there on previous antennas was quite listenable. Even 880 KRVN was generally audible weakly. I was happily amazed and sunset and nightime DXing also didn't disappoint.

Typically I terminate BOGs to ground with something on the order of 230 to 270 ohms. The termination is not broadbanded and only provides a decent F/B improvement over some of the band. I've sometimes added some series L (10 to 25 turn handmade coils, wires around a toilet paper tube or paper towel tube) to try to better tune the Rt to frequencies of interest. Basically this is a black art and done empirically. If you want to try to terminate a BOG, experiment. I find that a 5 foot section of 1 in copper pipe (the thicker walled kind so it doesn't buckle much when driven into ground) provides a good contact to ground and I prefer it to a solid thinner typical 8 ft rod as I think there's more surface area incontact with ground.

For any quickish DXped I don't worry about termination and phase one // BOG vs another shorter one, typically 100 to 200 feet shorter. Using the Quantum Phaser this typically gives me great back nulls across about 200 KHz (sometimes more).

BOGs have some built in F/B. However, I've never experienced anything nearly as extreme as Rick did with his R75 and 30 ft wires. Here's a link to some measurements I made from both ends of a rather long unterminated BOG.

http://www.dxing.info/community/viewtopic.php?f=17&t=371

I have experienced exactly the same effect at my rural DX site in Grafton WI.

Phased BOGs changed the hobby for me, due to the more narrow beamwidth than can be obtained when using a flag type antenna, such as a KAZ antenna, and the nice F/B when compared to a typical small loop figure 8 pattern (like ULR internal loopsticks) which while having great side nulls, has no F/B.

Over the next couple of weeks I'll reply to some of the BOG posts here, mentioning my experiences from the past decade.

73 KAZ Barrington IL/Grafton WI

Join main@UltralightDX.groups.io to automatically receive all group messages.