[600MRG] EIRP and such

[kl7aj at acsalaska.net]

Just to add more input to the discussion....the average ground 
conductivity in Alaska is a few orders of magnitude worse than the 
worst soils in the continental U.S.   The entire Interior of Alaska 
lies on a huge glacial silt lens.  This can actually be a mixed 
blessing.  Since the ground conductivity is SO bad, you can lay an 80 
meter dipole right on the ground and it works just fine....the "real" 
ground is down around 60 feet in most places. 

However, getting a real ground wave is a severe challenge.  I ws chief 
engineer at KJNP at 1170 KHz for 25 years, and we had a full half wave 
antenna, AND twice the number of radials required by the FCC to get 
anything like a stable ground field.   I had at one time calculated 
the miles of radial copper we had laid down.  For about half that time 
we had a 2 tower directional antenna.....I don't know HOW we ever could 
have done this with 1/4 wave 'sticks" since the seasonal ground changes 
would have been enormous.  The 1/2 wave antennas we had relied a lot 
less than most AM towers on the ground system, but it ws far from 
independent of it!

One thing that's notable here is that the dielectric constant is just 
as important as the resistivity when figuring out grounding systems. 
 In most "normal" places, the resistance dominates. :)

Eric

On Tue, 6 Oct 2015 11:24:55 -0700, Rudy Severns <n6lf at epud.net> wrote:
I think you guys need to read my recently published QEX article (Jul/Aug,
> Sept/Oct) on Rr and Rg at LF-MF versus HF. A copy of the prepublication
> draft is on my web site: www.antennasbyn6lf.com
> <http://www.antennasbyn6lf.com> . When I get a final .pdf of the
> published article I'll post it but the differences are small. 
>
>
>
> What I argue is that, because the soil characteristics are dominated by
> conductivity and LF-MF, the Rr for small antennas at LF and MF is very close
> to the value for ideal ground. The value for Rr is easily found using
> either modeling or calculation. As I show, this is not true at HF but who
> cares! We're not concerned with EIRP on 20m. 
>
>
>
> I argue that all you have to do is model/calculate Rr for ideal ground and
> measure your antenna current. The radiated power Pr= Io2Rr. The EIRP for
> the small antennas likely to be used by hams is simple Pr/3. For EIRP= 5W
> we are allowed Pr=1.667W. You can also determine Pr from a measurement of
> Ri and Pi: Pr= PiRr/(Rr+Ri). Besides the base article there are an 
> extensive set of appendices with the
> back-up for my argument. 
>
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