Topband: Salt-Water Qth!

[Herbert Schoenbohm]

This is fascinating stuff.  My 160 meter vertical is less than 2 
wavelengths away from the Great Pond Bay and the salt water lagoon 
inside which includes a floodplain of very brackish water. This is 
proven my taste and by the fact that there are plenty of mangroves 
there.  Before I knew any better I ran 1000' coax and then a 600' 
Beverage from on side of the salt flat muck to a post on the other using 
an existing series of fence posts.  The results were horrible and my 
inland Beverages over a former hay field worked but the salt pond 
beverage did not. All I can say that to a moral certainty that whatever 
that proves it proves.

Herb Schoenbohm, KV4FZ

On 4/2/2015 3:59 PM, Grant Saviers wrote:
> Since this thread continues, I thought I would share some EZNEC Pro/4 
> modeling results I have submitted for publication to QEX, with a focus 
> on "verticals on the beach" for DXpeditions.  EZNEC Pro4 can segment 
> ground along a line into two arbitrary ground properties, in my 
> modeling 4 S/m, 80 for salt water and 0.005 S/m,13 for land. W3LPL's 
> and other's guidance is roughly consistent my modeling of a vertical 
> at various separations from the tide line.
>
> The brief summary of modeling results is there is significant benefit 
> at elevation angles <20 degrees towards the salt water IF the antenna 
> is less than 0.7 wavelengths (WL) from the tide line. The pattern is 
> asymmetrical in azimuth as a result, favoring the salt water. The -2db 
> azimuth pattern at 5 degrees elevation is 140 degrees wide at peak 
> 4.5dbi gain towards the water when the vertical is 0.3 WL from the 
> tide line, with 2 radials elevated 0.025 WL.  In this case the F/B is 
> 11 db.  Around 0.45 WL from the tide line the elevation gain -2db 
> point starts to fall below 20 degrees and continues to fall as 
> separation is increased.  Since my objective was to better understand 
> the tradeoffs for DXpeditions, only 1 or 2 elevated radials were 
> modeled and additional radials did not enhance seaward performance.   
> In this case, elevating the radials helps the peak gain, about 0.15 WL 
> is optimal.    Further than 1 WL from the tide line, there is 
> essentially no low angle gain benefit from the sea and the vertical 
> pattern is whatever you have as ground + radials.   The results for 
> azimuth and elevation gain and pattern showed no fractional wavelength 
> peaking, the values all smoothly trend out to more than 1 wavelength 
> from the tideline.
>
> These are only gain results, so the seaward path may have much lower 
> skip and/or ground wave losses.
>
> Grant KZ1W
>
>
>