Kanthal/Globar in Niagara Falls, NY makes some excellent noninductive resistors that can be used in a high-power aircooled dummy load. They are not cheap, but they will allow you to build a good dummy load that can handle a kilowatt or more of steady carrier without the mess of oil. Add a squirrel cage blower and you can make a dummy load comparable to the ones sold for commercial use. Shielding the load with perforated metal stock and grounding the shielding will prevent incidental radiation of your signal. You can see the Kanthal product line at www.globar.com .
The problem with the Heathkit "Cantenna" and similar paint can loads made by DenTron and MFJ is that the oil tends to migrate, making a mess. If the oil overheats, it constitutes a fire hazard. Light bulbs may be fine for tubed transmitters operating on relatively low frequencies, but they are unsuitable for solid state transmitters and the upper part of the HF spectrum. The reason is that the resistance of the filament changes as it heats up. At full brilliance, the filament may present a resistance of 50 ohms or so. But a cold filament represents a dead short! On the higher frequencies, you also have a lot of inductive reactance to deal with. Also, a light bulb will radiate over a short distance. I worked someone years ago by loading up a bulb with a small ham rig! Phil K2PG
