Valcom 85' Monopole buit out in 2022 and 2023
In today's broadcast landscape station operators can find themselves in a situation where the real estate that an AM station is sitting on becomes quite valuable and in this case selling the old AM site was able to facilitate building out a new non directional site complete with a new grounding system and 85' FCC type approved loaded monopole antenna. These units are made by Valcom in Canada and they are very high quality and even better than that they radiate very well! Valcom has FCC type approval for these units down to 1200 Khz for US AM use if they are built out on the specified ground system design that Valcom sends with their kit. When it was completed the coverage with equal power on this new antenna far exceeded the 90 degree quarter wavelength "full sized" antenna at the old AM site. In all fairness this is in part due to a new ground system but the Valcom performs very very well and I have no hesitation recommending this setup to any broadcaster who has an old AM site on good real estate. They tune up with a simple L or T configuration and they just work.
The rainbow however is a custom order, call for details.
Below you see the ground system and the monopole base. 120 radials all terminated and silver soldered on the far end to 120 ground rods. There is a 16x16 screen under the center section and 6" coper strap around the hinge plate, the hinge plate is cad welded with #2 tinned copper to the 6" strap which is in turn silver soldered to the mesh which is all silver soldered together. The 6" copper strap and the 8 pieces of tinned #2 solid copper (2 on each side of the bottom of the hinge plate) are not included in the Valcom kit, I added them on this build because it seemed like an easier way to do the layout and connections. Each of the 120 ground radials is terminated into a 1/2" copper ring which sits under the mesh and has #8 copper wires that go to the copper strap and are silver soldered. The entire system was covered with 2-4" of scoria and scoria fines. As you can see the ground system sits on sedimentary soils, mostly fine sand and clay. The ground impedance is staying very constant with soil moisture conditions and tuning has been a non issue.