[ARC5] Balanced antenna coupling...

[Brian]

Hello Wayne,

These matters are not new. I knew about them 40 years ago - they were passed 
down to me at radio clubs. And then I looked in various expert journals to 
substantiate the gossip.

The easy way to test the RF capabilities of the various plastics and cements 
is to put them in a microwave oven, of course with a small tumbler of water 
to act as a load, and see what happens. If the plastic or the cement gets 
noticeably warm, then they are conductive, through being carbon-rich or 
lead-rich (many of the older PVCs) and forming shorted turns in your oven. 
Then you will learn that not all PVCs, RTV and hot-melt cements are the 
same.

73 de Brian, VK2GCE.

On Sunday, December 28, 2014 9:00 PM , Wayne said:

The surprise I got was when I built one of those 2 meter collinear antennas
out of 300 ohm twin lead.  VSWR looked good.  Then I stuck it in a piece of
PVC pipe and sealed it in with silicone RTV.  VSWR went way up after that.

Also, not long ago I tried making some two section electrolytic caps by
seling some caps in pill bottles.  I used a hot melt glue gun to secure the
caps in the bottle.  On the one where the glue covered both the + and -
wires the leak rate went way up.

So RTV is not good at VHF and hot melt glue is not good at HV.  Who knew?

Wayne