rf properties of PVC

Steve Lund stevel at hpsrfh.sr.hp.com
Fri Jul 23 11:56:05 EDT 1993

>Subject: Re: rf properties of PVC
>On Tue, 20 Jul 1993 jcoleman at ux1.cso.uiuc.edu wrote:
>> Is there any problem using pvc (schedule whatever water pipe) as an
>> insulator for 40m and 80m antennas?
>> Thanks de Jim, KA6A
>In the Dayton Contest forum this year, VE3EJ presented an interesting
>method of testing materials for their suitability as RF insulators.
>Put a piece of the material, along with a cup of water, into your
>microwave oven.  Nuke it for awhile.  The more the material heats, the
>less suitable it is as an RF insulator.
>Randy, K5ZD
This is a simple test, which should work most of the time.  The material
heats up because of the dissipation loss of the dielectric.  For most
plastics the loss tangent (tan d) of a material gets worse with frequency.
The only problem with this test is that a microwave oven works around
2400 MHz, while you are interested in 3.5 MHz.  If it stays cool in the
microwave, it should be good for 80m.  If it gets hot, it might still 
work for 80m use.

I've used PVC for 80m traps, but I only run 100W.

Another method is to place the trap in parallel with a dummy load.  If the
trap is any good it will be a high impedance and the VSWR won't change much.
If the coil is lossy, it will get hot.  I've used this method to test
cores for balun use.

Steve  WA8LLY/6

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