Beverage performance is optimum when installed over poorly
conductive soil. Harold Beverage's first "Wave Antenna"
(later named after him) was a BOG several miles long (used at 50 kHz)
laid on sandy Long Island, NY soil.
In order to achieve good directivity (especially front-to-side ratio)
its absolutely essential that a Beverage be installed over lossy
soil. Why, you may ask... The front-to-side and high angle signal
suppression of a Beverage is dependent on suppression of
horizontally polarized signals. This is achieved by placing the antenna
as close to lossy soil as possible but not so low that signals levels
suffer excessively. Seven foot (two meter) height is an excellent
choice for 160 and 80 meters. A Beverage installed over conductive
soil suffers from significant horizontally polarized signal reception
at high angles resulting in very poor directivity, the Beverage is
behaving more like an NVIS antenna than a low angle DXing antenna.
Its not necessary to have a low resistance ground connections at each
end of a Beverage, after all you're going to install a termination resistor
at the far end and there's plenty of excess signal at the feedpoint of
a 7 foot high Beverage (but not on a BOG). What you do need is a
ground connection with fairly stable resistance at the termination end
of the Beverage. In most cases this can be easily achieved by:
- multiple ground rods (they don't have the be installed vertically),
- multiple radial wires tightly laid on the ground (use sod staples) or
buried; or
- chicken fence wire (preferably galvanized and welded) laid on the ground.
For good front-to-back ratio you must have very good common mode
signal isolation at or very close to the feed point especially if:
- you're using a BOG antenna
- you're using only a single ground rod
- any part of the feed line is elevated (buried feed line or tightly laid
on the ground with sod staples is ideal)
Beverage directivity can also be significantly degraded by re-radiation
from nearby antennas, towers and utility wires.
73
Frank
W3LPL
----- Original Message -----
From: "MU 4CX250B" <4cx250b@miamioh.edu>
To: "Artek Manuals" <Manuals@artekmanuals.com>
Cc: topband@contesting.com
Sent: Friday, October 18, 2019 2:51:50 PM
Subject: Re: Topband: Beverage Length vs F/B or (RDF?)
Thanks for the suggestion, Dave. I’m using DXE hardware and relay
boxes for switching, and twin lengths of WD-1A mil surplus telephone
cable for the wires. The lengths are spaced roughly 6 inches apart to
approximate 450 ohms. The end terminations are three 8ft ground rods
spaced out about 4 ft apart (12 ft total).The soil is soft, silty, and
relatively alkaline, but not as sandy as yours seems to be.
I did try to measure the ground resistance once. My 160/80m
transmitting vertical (70 ft self-supporting aluminum mast,
base-loaded with a switchable vacuum relay) is about 800 ft from my
shack and fed with hardline. The end-to-end resistance of the hardline
shield is only an ohm or two. The vertical has sixty 120ft radials
strewn out across the soil, and an 8 ft ground rod at the base. In my
test, I disconnected the hardline from the vertical, but left it
connected at station end, where it was well-grounded. I measured the
resistance between the ground rod at the base of the antenna and the
disconnected hardline shield, and it was about 70K ohms. With 800 ft
separation, the soil resistance approximates a two-dimensional
conductor and is independent of the spacing between the measurement
points. Thus the 70K resistance is an approximation of the actual soil
resistivity. I wish I could compare that value with measurements on
other soil types.
73,
Jim w8zr
Sent from my iPhone
> On Oct 18, 2019, at 7:53 AM, Artek Manuals <Manuals@artekmanuals.com> wrote:
>
> Jim
>
> Poor front to back can indeed be a result of being too long. Although w8JI
> would argue that at 700 feet your just about at optimum (1.5 wavelengths) I
> would think it would be easy to add an insulator /jumper and a set of
> terminations and grounds at ~500 feet and see what the difference is.
>
> What kind of grounds do you have at the ends? Living on a granular quartz
> plane myself with very poor ground conductivity ( I can push a 5ft length of
> 1/2" copper pipe 3ft in the ground by hand (pure sand!) and easily tap it in
> the last two feet with a hammer) I would think that the grounds at the end
> would indeed have an effect on front to back or RDF which is the latest
> popular figure of merit ( how do you actually MESAURE RDF?).
>
> I often wonder how one knows when one has a "good enough ground". I have read
> https://www.w8ji.com/beverages.htm many times. Tom suggest a proxy method
> using temporary radials which I don't have the topography to install in a
> meaningful way. The net result is I take Tom's measurements with a grain of
> salt since they are done on soil with much better conductivity than you
> (apparently ) or I have
>
> Dave
> NR1DX
>
>> On 10/18/2019 8:51 AM, MU 4CX250B wrote:
>> On this general subject, I’m using bi-diectional beverages 720 ft
>> long, suspended 7 ft above sandy desert ground. The F/B ratio is poor
>> (not important for New Mexico) but I’m wondering if the antennas are
>> too long? I use them on 80m/160m.
>> 73,
>> Jim w8zr
>>
>> Sent from my iPhone
>>
>>> On Oct 17, 2019, at 9:31 PM, Artek Manuals <Manuals@artekmanuals.com>
>>> wrote:
>>>
>>> Tim
>>>
>>> Which antenna will you be using ; BOG, Beverage or a FLAG/Pennant
>>>
>>> I have been doing some experimenting with the BF-4X with BOGs and Beverages
>>> in both very poor sandy soil and then again at a water front (salt) canal
>>> location. Eventually I will get around to trying out a FLAG/Pennant style
>>> as well. Seems to work pretty well in my dry sandy location� the
>>> performance has been less than stellar so far next to the saltwater canal,
>>> I think this may have more to do with the seawall near by. This is a BOG
>>> issue and not any problem with the BF-4X boxes. with BOGS i tried it in an
>>> end fed and center� fed configuration� and an of center feed with a
>>> beverage.
>>>
>>> The for BF-4X literature says BOGs from 100 to 300' . For my poor soil
>>> conditions I find that 200' ( as many other s have reported for BOGs) is
>>> the upper limit> performance was noticeably poorer at 225', 250' and 350' .
>>> This is a function of soil conditions and not the boxes and YMMV.
>>>
>>> Dave
>>> NR1Dx
>>>
>>>> On 10/16/2019 11:35 AM, Tim Duffy wrote:
>>>> Thinking about the Fall Stew coming up this Saturday, I will be trying out
>>>> the BevFlex-4X that W9XT is now manufacturing.
>>>>
>>>>
>>>> Here is the flyer:
>>>>
>>>> <https://static.dxengineering.com/global/images/technicalarticles/ums-bevfle
>>>>
>>>> x-4x.pdf>
>>>> https://static.dxengineering.com/global/images/technicalarticles/ums-bevflex
>>>>
>>>> -4x.pdf
>>>>
>>>>
>>>> And the BevFlex-4X details:
>>>>
>>>> <https://www.dxengineering.com/parts/ums-bevflex-4x>
>>>> https://www.dxengineering.com/parts/ums-bevflex-4x
>>>>
>>>>
>>>> 73
>>>>
>>>> Tim K3LR
>>>>
>>>>
>>>>
>>>> _________________
>>>> Searchable Archives: http://www.contesting.com/_topband - Topband
>>>> Reflector
>>> --
>>> Dave
>>> Manuals@ArtekManuals.com
>>> www.ArtekManuals.com
>>>
>>>
>>> --
>>> This email has been checked for viruses by Avast antivirus software.
>>> https://www.avast.com/antivirus
>>>
>>> _________________
>>> Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
>
> --
> Dave
> Manuals@ArtekManuals.com
> www.ArtekManuals.com
>
>
> --
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
> _________________
> Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
|