SKCC 5123T----- FISTS 14979----- Flying Pigs 2331----- NAQCC 3610-----QRP ARCI 14176-----Polar Bear 257

Sunday, August 13, 2017

A Test of the Saltwater Effect for Vertical Antennas using WSPR

Saturday, August 12th
1620 UTC to 17:20 UTC
St Andrews State Park near the boat ramp on Grand Lagoon. 
The antennas were two identical N6BT Bravo 7K verticals each with a WSPRlite Beacon on 20 meters running 200 milliwatts.

Vertical 1: WSPRLite callsign N4KGL located on the Grand Lagoon shore (salt water)
Vertical 2: WSPRLite callsign W4RYZ located on a dirt area near about 700 feet inland.

The Bravo 7K verticals were at the endpoints of the line above.

The overhead view of the inland location

The beacons were started at the same even minute, and both had a 20% duty cycle. Over the course of an hour, each beacon transmitted seven times. However, to my disappointment only the first transmission was simultaneous. The simultaneous reports showed a mean 10 dB SNR advantage for Vertical 1 at the shore using DXplorer. The shore vertical also showed a DX10 advantage in the average distance 2960 km vs 2386 km. I did further analysis taking an average SNR for receiving stations common to both beacons over the test. The SNR-DELTA was well in favor of the shore vertical as shown in the table below. 

I surmise that the overwhelming difference is due to reduced ground losses. The dirt in this area is sandy and has a conductivity of 1 milli-mho. The salt water has a conductivity of 1500 milli-mho. Note since the Bravo 7K has a tripod we put it over the shallow water at the shore.

Now to increase the confidence in the data perhaps the test could be repeated switching the position of the two verticals. Also, I would consider increasing the duty cycle to 100% to get more simultaneous spots. Note this test was a two ham effort. I could not have pulled it off without the assistance of Dennis Walker WA6QKN. We had fun doing it.

I think my favorite spot to operate at the Grand Lagoon shoreline is well chosen. It does seem to supercharge a vertical. The Bravo 7K has never the less served me well at National Parks for NPOTA that were inland. It has an advantage that it does not require trees for support.

Shore Bravo 7K vertical

Inland Bravo 7K vertical