AE6K Antenna project
After several months of suffering along with a low-slung dipole as my single band (20m) antenna I decided to buy a beam and mount it on a rotatable mast atop my roof. I purchased a used Force-12 C-3SS triband Yagi and a used hy-gain CD-4511 rotator. I decided to open up the rotator for a cleaning and lubrication before installing it on the roof. I discovered that the position sensor was shot and that the pinion gear was also in bad shape, so I replaced them. This project was started in October 2008 and was completed on December 18, 2008. The shack also received a power upgrade using an Ameritron 811.
The engineering drawing. Not the back of an envelope....but almost.
The upper bearing has about 0.030" clearance and requires good alignment with the lower bearing to turn smoothly.
The lower bearing and equipment shelf
will eventually have a foot at the end to distribute the load onto the roof
shingles. It will
support the rotator at the base of the mast as well as the lightning shunt routed to an outdoor ground rod, to keep Phil and his
radio equipment from getting fried.
Inside the hy-gain rotor. Trouble with the wiper on the position sensor ......
Old potentiometer with broken wiper and broken resistor winding
...and more trouble with the pinion gear.
Old pinion gear with worn teeth
New pinion gear with shiny, new teeth.
Bottom bearing design with steel brackets and aluminum pipe for base of rotator
Bearing is designed to tilt over in case I decide to hoist up the antenna by assembling horizontally first.
Assembled and tested. Everything was aligned and rotating smoothly. Direction indicator also smooth due to new potentiometer.
Top bearing on painted cross-member. Bearing will be lubricated with synthetic bearing grease at final assembly.
The lower mast is tipped to receive the upper mast and antenna, then tipped up into position....
First bird (a dove) arrives a few seconds after the antenna is locked into position.
The rf, antenna and ground connections are made inside of a protective junction box.
The PolyPhaser impulse suppressor is used to protect the radio and radio operator from static and lightning.
AE6K (me, on the left) and K6YP (John) enjoy a beer after testing the antenna.
John and Al. Could not have put this antenna up without their help.
Power Amplifier repairs and upgrade now
Ameritron 811. Purchased used, I discovered that the variable plate capacitor was arcing.
The blobs of melted aluminum on some of the fins. Caused by arcing while tuning the plate circuit.
I figured I would try filing and polishing with 800 grit paper to see if I could resurrect the capacitor. Otherwise a replacement was in order.
The procedure worked well and the amplifier is up and running now.
The RF power is transferred from the
load capacitor to the output terminal via a piece of bell wire routed under
one of the power tubes.....
...this was replaced (upon the
recommendation of K6YP) with a piece of properly grounded RG-141 and rerouted
from the tube socket.