[600MRG] NDB Antenna Calculator

[Warren K2ORS]

Coupling to trees, buildings etc will also introduce a lossy resistance 
to the antenna impedance.

See Bill Ashlock's article:
http://www.geocities.ws/mike_staines/bill/loop1.doc

   I can vouch for his conclusions from personal experience.
73 Warren K2ORS


On 10/5/2015 9:17 PM, Edward R Cole wrote:
> Rudy,
>
> I assumed when you write ground resistance you mean for the ground, only.
>
> When I originally calculated my ERP in 2012, I used EZNEC to provide the
> radiation resistance which was about 0.83 ohms and I measured ground
> resistance with my modified MFJ analyzer by tuning the loading coil
> until I got R +j0; R read 20-ohms.
>
> Rr/Rg is used in the calculation of EIRP.
>
> So if the variable given in the "NDB calculator" is Rg+Rr that should be
> made clear instead of saying "ground resistance".    It seems this
> imprecision in specifying variables is what keeps the analysis from
> being accurate.
>
> 73, Ed
>
> At 03:22 PM 10/5/2015, Rudy Severns wrote:
>> Steve, he's going to have a real problem.  Rg depends not only on soil
>> electrical characteristics and details of the radial system but also
>> on the
>> antenna over the radial system.  If you have NEC4 determining Rg from
>> modeling is easy.  Direct calculation is also possible, I've done it, but
>> it's complex because you have to start by deriving the E and H field
>> intensities associated with the antenna in the near-field.  From that you
>> can calculate the soil losses which determine Rg for a given Io.
>>
>>
>>
>> Too many people believe that a given radial system, at a given frequency,
>> with given soil characteristics, has a fixed Rg.  This is false.  Rg will
>> depend on all those things plus the details of the vertical.  This is
>> carefully explained in section 3.2.3 of the 22nd edition of ARRL Antenna
>> Book which shows among other things the dependence of Rg on the vertical
>> height for a given ground system.
>>
>>
>>
>> 73, Rudy N6LF
>>
>>
>>
>>
>>
>> _______________________________________________
>

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