The maximum base-referred ground loss number my system has is bounded at 0
and 15 ohms given a base R measurement of 15 ohms.
N6LF found that for a 90 deg monopole the method of summing resistances can
result in under estimating ground loss due to the radiation resistance
being less than 36 ohms. If we apply this reasoning to my short monopole
having (an assumed?) radiation resistance of 2 ohms the maximum ground loss
error due to this is 2 ohms.
Dave WX7G
On Sep 27, 2012 8:18 PM, "DAVID CUTHBERT" <telegrapher9@gmail.com> wrote:
> Tom, with this ground system and 90 degee monopoles I measure 5 ohms
> ground loss on 7 to 28 MHz. With the 30' vertical I measure about 10 ohms
> on 1.8 and 3.5 MHz.
>
> The 7 MHz measurement agrees with the N6LF papers (90 deg monopole and 1/8
> wavelength radials).
>
> I have no evidence that would lead me to doubt the measurements of the
> other bands.
>
> 160 meters measurenent:
> 15 ohm base R
> 2 ohm radiation resistance
> 5 ohm cool loss
> 8 ohm ground loss (rounded to 10)
>
> This is the accepted procedure for measuring base referred ground loss, is
> it not?
>
> Dave WX7G
> On Sep 27, 2012 7:54 PM, "Tom W8JI" <w8ji@w8ji.com> wrote:
>
>> I am presently using a 30' base loaded vertical. The ground system
>>> consists
>>> of 90 radials from 12 to 25 feet. The base referred ground loss is 10
>>> ohms.
>>>
>>
>> The problem is we really can't measure ground loss at the base.
>>
>> Let me give an example....
>>
>> A 40 meter vertical here, 1/4 wave tall of fixed length.
>>
>> Four elevated radials had less than 40 ohms feed resistance. About a
>> dozen buried radials had around 60 ohms base resistance.
>>
>> Field strength was identical despite the resistance difference with the
>> same length resonant radiator.
>>
>> Others have measured the same type of thing, and it is easy to duplicate
>> results like this.
>>
>> 73 Tom
>>
>>
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