N2CKH/R 6 meter Repeater System Terrain Analysis

The image below shows the location of the N2CKH/R 6 meter repeater system located in Lakewood, New Jersey area as georeferenced on a map created using Sight It!™ LOS Calcuator™ terrain analysis software by N2CKH.

This map is created by imaging 1 degree by 1 degree Digital Elevation data distributed on the Internet free by the U.S. Geological Survey (USGS), it is called Digital Elevation Model (DEM) data, and is provided in 1 degree, 30 minute, 15 minute and 7.5 minute coverage areas, most amateurs are familiar with 7.5 minute topographical maps for determining their exact coordinates and elevations.

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In the image above, what we are looking at is an image created to display in colors for each elevation bin set in the software, as can be seen on the elevation bin color/range box in the lower left, with Black as sea level and Dark Blue 1 to 17 meters in elevation, also we have turned on the Cities overlay layer for a point of reference, we could also have or instead of Cities turned on political boundaries and shown County and or State boundary outlines.

We also have the Sun shading of the elevation data so that you can now see the hills and ridges of the terrain, now go back and look at the 360 degree coverage fans in the image below and you can see really see where the blockages are to the LOS from the repeater site to the north.

The image below shows the coverage of 53.430 taking into account the height of the antenna at the 6m repeater site out to a 25 mile radius in a 360 degree fan pattern.

This coverage does NOT take into account foliage, man made obstructions or even the antenna pattern of the repeater site antenna.

As you can see the plot depicts the mobile coverage pretty darn close to what is haas turned out to be in the real world. Where you see the PURPLE is Line-Of-Sight to the repeater antenna for the average terrain, thus is it is also the basic mobil coverage of the repeater when using at least 20 watts and even better with 50 watts.

This does NOT mean that outside the PURPLE area that you can not get into the system. I have worked the machine from Red Bank and Middletown with 20 watts, but only when in the clear and at higher road elevations. The longest range base station on a regular basis to date is W2ESH, Alan up in Hawthorne, NJ, he makes it DFQ with 50w and his Comet tri-band antenna at 25 feet, but he has elevation on his side.

However, the ridges to the Northwest, North and especially the Holmdel hills to the North East really block the line of sight and the signal. In the future a number of satellite receiver sites will be added to improve the situation.

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Also, do to the nature of the 1 degree DEMs from the USGS and the fact that Sight It!™ has been written to combine DEMs, you do not see the actual full 360 degree sweep as the physical location of the repeater is in the lower right quadrangle of the DEM thus the cricle goes off the coast line where land mass ends.

The image below depicts the 15 mile (24km), 20 mile (32Km) and 30 mile (48km) radius coverage area for the transmitted signal of the repeater when mobile. You can hear and work the system solid in most places in the clear while mobile within the inner cirlce (15 miles).

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Between the 15 mile and 20 mile circles the machine is still excellent copy while mobile in most places in the clear, but getting back into the system with the typical 1/4 wave mobile antenna is subject to many variables, the planned satellite receivers will be a big aid.

Between the 20 and 30 miles radius and beyond hearing the system while mobile is subject to mobile location, getting back in without satellite receivers will require a lot of high hill. Basically the range of the repeater for mobile operations is limited to about 30 miles. Base stations will easily work the system from 30 miles and more with good antenna installations unless they have blockage bewteen them and the repeater site.

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Entire contents Copyright © 1999-2001 by Stephen B. Hajducek, N2CKH. All Rights Reserved Worldwide.