[Elecraft] NVIS HF vs VHF line-of-sight & CB

[kevinr at coho.net]

I lose my antennas about once each year to straight line winds. Flying 
branches knock them down.  But if the wires are still intact I can run 
the nets with the lowered antennas.  Using less than optimal antennas 
works; just not as well as perfect antennas.  In an emergency I really 
don't care about perfect performance, I simply want to contact someone 
for assistance.  By all means put up the best antenna you can just 
remember any antenna can make contacts.

Years ago I wrote some software to display antenna propagation patterns 
as a half wave dipole was lowered from 1 wavelength above ground until 
it was on the ground.  The results were pretty interesting.  By using 
the program I found many heights would work well depending on where I 
wanted to contact.  At less than 1/10 wavelength above the ground the 
radiation patterns got rather odd but still worked for in-state comms.  
Once I had modeled what was going to happen I tested it by dropping my 
antennas to different heights and tested comms.  Theory and practice 
correlated quite nicely.

     Kevin.  KD5ONS

P. S. The application also modeled 1/4 wave verticals and loop 
antennas.  I never found the time to model the Yagi-Uda, the math got 
too hairy.  Using Euler's equation a few times got me through the three 
antenna types I was able to model.  Beating on the Bessel functions 
would have taken longer than the time I had allotted to me.

      K.


On 4/30/2017 1:22 PM, Bill Frantz wrote:
> I have always wondered how towers hold up during earthquakes. Being 
> able to work with ad-hoc antennas seems a good attribute for any 
> emergency plan.
>
> 73 Bill AE6JV
>
> On 4/30/17 at 11:34 AM, kevinr at coho.net wrote:
>
>> Please try NVIS on 40 or 80 meters. You'll find you can cover most of 
>> the state with its use.  Plus the antennas can be ad hoc - tossed 
>> into trees or even an old fence line.
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