[Amps] Anyone know RF properties of Acrylic??

[Ian White GM3SEK]

Dr. David Kirkby wrote:
>Does anyone know how Acrylic behaves in the presence of RF? Will it
>significantly absorb RF up to 2.5 GHz?
>
Somewhat... meaning it isn't as low-loss as PTFE, but that doesn't 
automatically mean you cannot use it

Much more important is the electric field strength where you propose to 
use the material. For example, I have melted delrin within seconds of 
firing up a a 20W transmitter; yet one manufacturer uses delrin to 
support pi-tank coils in 1.5kW amplifiers with complete success.

The difference between those two experiences is "location, location, 
location". It is hard to visualize electric fields, but we can often 
take a good guess based on the gap between metal parts at different RF 
voltages, the size of the RF voltage, and the sharpness of the metal 
profiles.

For example, bandswitches score badly on all three of those criteria: 
small gaps, high voltages and sharp edges on the metal parts.

Another good way to create a high electric field is between two 
sharp-pointed screws into the opposite ends of a plastic insulating 
pillar. The electric field between the opposing metal points is also 
concentrated by the dielectric material. And then we wonder where the 
smoke is coming from...


-- 

73 from Ian GM3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek