Topband: Beverage Length vs F/B or (RDF?)

Fri Oct 18 11:27:29 EDT 2019

Jim

When you say it measured 70K was that DC, low frequency (60hz) A/C or at 
1.8/3.5 Mhz RF?

Big difference.
'
Here two 5' rods about 2' apart measure about 2K DC but measure about 
600 ohms at 1.8 Mhz...Still not sure how that correlates to a larger 
earth RF ground. The other thing is RF ground varies not only with the 
soil type but frequency

Dave
NR1DX

On 10/18/2019 10:51 AM, MU 4CX250B wrote:
> 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 at 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 at 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 at ArtekManuals.com
>>>> www.ArtekManuals.com
>>>>
>>>>
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>> Dave
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>> www.ArtekManuals.com
>>
>>
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Dave
Manuals at ArtekManuals.com
www.ArtekManuals.com

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