DIGITAL ELEVATION INDICATOR
The methods I have tried to remotely read the elevation angle of the EME yagi, have not worked out. There are several devices like carpenter's levels that are made for a digital display. NJ6P and others have been working on remoting the display from the angle sensor. I decided to give it a try. The 10 inch "HUSKY" level was purchased from Home Depot for about $40.
Two screws hold the battery box on. Under the battery box is the back of the display that is held on with 4 screws. The sensor is tightly attached to the frame with 2 screws. The sensor and display are connected with a 4 conductor ribbon cable. I decided after blowing one sensor up, that I would place only the sensor on the antenna without the level's frame so I could shield it properly. Expensive lesson.
The cable is attached to the display with a connector that needs to be carefully unsoldered.
Once the connector is removed you can see that there is one hole with a square pad and the others are round. I numbered this square hole #1. The closest hole to #1 that is next to the side is #2, the other hole close to #1 is #3 and the hole furthest from #1 is #4. See the numbering below.
The cable attaches to the sensor on the back. The cable may be completely removed or cut off close to the board. You can solder directly to the pads either way. I color coded the new wires and made a chart to keep things wired correctly. The sensor is wrapped in "masking" tape that can be carefully cut off to expose the connections. As you look at the board from the ribbon cable end, the left tab will be #1 and the other 3 are in order. See the numbering below.
The display was mounted in a project enclosure from my junk box. A very odd shaped hole to fit the display was nibbled out of the panel. A small flat piece of amuminum was drilled to match the threaded holes in the back of the display. A pair of #8 threaded holes were drilled and tapped on the ends of the aluminum to allow the display to be held in place. A small PC board holds a 3-pin regulator circuit that provides the 3 volts DC to power the unit. The source voltage for the regulator comes from an external 12 volt regulated supply. The 35 Volt DC power supply is used to supply voltage to operate the elevation positioner. The toggle switch on the left turns the power supply on. The switch on the right is an "ON-OFF-ON" type to move the positioner up and down,
The sensor was mounted in a cast aluminum box. The PC board was attached with one #4 screw and a spacer that came with the board. All wires enter the enclosure with feed through capacitors and ferrite beads on the wires inside. Spade lugs are used for the 4 wires and the ground. The box was mounted to an aluminum angle to keep it vertical. The angle had a #8 clinch stud installed for attachment to the small shelf on the boom.
I wanted the 4 conductor cable to be shielded so I could bypass the leads. I found a cable that had 2 twisted and shielded pairs for the 100 foot run. I folded the 2 foil shields back on the body of the wire and wrapped and soldered the 2 drain wires around the foil. The bypass caps are double .001 units that bypass each pair and have a common wire that is wrapped and soldered over the foil along with the drain wires. A ground wire was attached and a length of shrink wrap was placed over the foil area.
The cable was measured before final testing and attached to the sensor and display. The sensor box was placed on a level block and adjusted for 0 degrees on the display. I don't know if different lengths of cable will give the same results. Once adjusted, a blob of silicone was glued to the corner of the sensor to make sure it wouldn't move.
When the equipment was installed on the antenna, I transmitted with the 1500 watts that had distroyed the first sensor. No problem at all. I was not willing to blow another $40 to test each shielding method at a time and recommend you use all the shielding you can.
The remaining level frame has excellent magnets on the bottom that will clamp to a tower leg when setting guy wires. Not a wasted tool.