Good question and I’m not sure of the long term answer. The carbon is very conductive but you MUST be in contact with the “carbon”.  The epoxy is a very good insulator.  I used conductive paint from Lancair as ground planes on my IV-P.  I scuffed the carbon skins real good before painting on the ground planes.  As you can see from the results below, the carbon is as conductive as the ground plane paint. The ground planes do not touch each other and are only connected via the carbon.

Biddle DLRO Meter (Digital Low Resistance Ohmmeter)

Full scale of lowest setting is 6000 micro ohms (setting for this test was 6 ohm full scale)

 

Probes at Center of antenna mounting area

Transponder  =  .040 ohm

Com1           =  .035 ohm

TCAD           =  .045 ohm

Com 2          =  .037 ohm

 

At far extreme of circle

Transponder  =  .106 ohm

Com1           =  .134 ohm

TCAD           =  .118 ohm

Com 2          =  .096 ohm

 

From one ground plane to another (this shows conductivity of the carbon)

Transponder to Com1  =  .130 ohm

Com1 to TCAD           =  .063 ohm

TCAD to Com2           =  .112 ohm

 

Craig Berland

N7VG