Topband: Beverage terminations (was BOG wire)
donovanf at starpower.net
donovanf at starpower.net
Sat Nov 19 11:38:47 PST 2011
Over the last 20 or 30 years, the military spent many millions of dollars on research, development and installation of highly directive Beverage HF receiving systems using large arrays of Beverages. The largest HF Beverage array I'm aware of is still in use every day; it consists of 128 Beverages, 220 feet long and four feet high. Signal processing is performed by many SDRs.
Researchers found that that the most stable all weather Beverage termination (especially in very dry weather) is a ground mat, similar to KM1H's experience with verticals. The least expensive ground mat is chicken wire. They installed a chicken wire ground mat at each end of the 128 Beverages, each mat is about 6 feet wide and roughly 1/4 wavelength long at the lowest frequency of interest.
---- Original message ----
>Date: Sat, 19 Nov 2011 12:58:07 -0500
>From: Guy Olinger K2AV <olinger at bellsouth.net>
>Subject: Re: Topband: Bog wire
>To: w0rihps at sbcglobal.net
>Cc: ZR <zr at jeremy.mv.com>, topband at contesting.com, Bruce <k1fz at myfairpoint.net>
>In places where you can't get an eight foot rod to go down, there are
>alternatives. A four foot rod, or driving the rod down at an oblique
>angle will add some resistance, but not enough to change much.
>Another method is to dig a hole as deep as you can go (two or three
>feet), bury a metal plate of some sort with #4 bare wire bolted and
>soldered to it, and fill up the hole with dirt, bringing the wire up
>for connection. This will certainly be good enough for a beverage
>termination. The method is used with some mandatory guidelines as an
>alternative for driven rod power company grounds. Some have been
>uncomfortable with these in a given situation and have buried two
>equal length large bare wires at right angles to the beverage for the
>ground. 25 feet either side is probably more than enough most places.
>Anything is better than a trip hazard that someone can trip on or fall
>on and impale themselves.
>I would point out that some types of ground are fairly "transparent"
>at MF, and an eight foot vertical driven rod will pick up to some
>degree like a rod above ground. More fodder for the "two right angle
>short 'radials' at the end" method.
>There still is a fair amount of voodoo in this stuff, 80 years since
>any serious research money, and none in the era of modern equipment.
>On Sat, Nov 19, 2011 at 12:39 PM, Price Smith <w0rihps at sbcglobal.net> wrote:
>> not conduct well. If it is not possible to drive a rod all the way in, avoid
>> leaving a large amount above the ground. (Short metal lengths can pick up
>> signals like AM car radio antennas did years ago)
>> Carl and all,
>> For safety reasons ground rods should NOT stick out of the ground. If one
>> would fall on one it would do some serious damage.
>> I dig a hole about 1 foot deep and drive the rod to below ground level. They
>> go in easy in most soils with a large impact hammer.
>> 73 Price W0RI
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>UR RST IS ... ... ..9 QSB QSB - hw? BK
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