[Lowfer] Testing material for losses

[ToddRoberts2001 at aol.com]

In a message dated 9/27/2009 3:55:17 P.M.  Eastern Daylight Time, 
weazle at hurontel.on.ca writes:

Hello  Lowfers,

I've read a number of posts lately where the losses of various  possible
coil or antenna forms has been mentioned.  We're all aware of  using
the domestic microwave oven to test material for RF suitability,  but
wouldn't a better test be at the frequency of the intended  use?

_________________________________________________________


No  need to go through a lot of work to try to test different 
materials for coil  or antenna form losses. It is already
accepted that the best materials for  low RF losses are Polystyrene,
Polyethylene, Teflon and glazed ceramic  or porcelain.

Polystyrene is the easiest material to work with as  it
can be easily glued, sawed and drilled. Polyethylene is 
almost  impossible to glue together. Teflon is hard to glue 
and both Teflon and  Polyethylene are flexible and
harder to use for structural shapes.  Teflon is a great dielectric 
for high power, high voltage RF capacitors  though.

So the best all-around material to use for a VLF-LF-MF-HF coil  
form is Polystyrene. For really high-power use glazed 
porcelain might be  a better choice if heating of the coil
occurs. Polystyrene can be softened  from heating. 

Plexiglas looks good but it is a Q-killer. Likewise stay  away
from phenolic.

Paul's suggestion of using a Q-meter is good  advice also if
you want to check different materials at the actual  operating
frequency.

73 Todd WD4NGG