>
>> >Sorry this is not stictly about amps, but I guess someone here might
>> >know the answer.
>> >
>> >We have a student working on using a 10 GHz transmitter (burgler alarm
>> >type, using a 10GHz Gunn diode) and detector (Schottky diode) to measure
>> >attenuation caused by cloathing soaked with water (to determine the
>> >amount of water in the cloathing). We need to find a plastic (or other
>> >material that we can machine things from) that *absorbs* microwave
>> >energy at 10 GHz. I don't want a good reflector (metals), but something
>> >that will attenuate by absorption (ie it would get hot if we used enough
>> >power).
>> >
>> Nylon. Vinyl. Delrin.
>>
>> Rich...
>>
>> R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
>------------
>Howdy,
>Nylon, vinyl and delrin are poor absorbers at 10 GHz.
This issue came up during the "grate vhf parasitics debate", so I went to
the local plastics distributor to get some info. on dissipation factor -
a.k.a. D-factor Nylon has a high D-factor at 1MHz and an even higher
D-factor at 10MHz. The various vinyls and Delrin have a lower D-factor,
however, not nearly as low as the stryrenes, polyethelynes or Teflon.. .
. I had PVC water pipe catch fire at the end of a 40m dipole. I had a
40m dipole that was supported with nylon line reliably decend to the
ground when the linear amplifier was switched on. . Does it seem likely
that nylon would have high absorption at 7MHz and poor absorption at
10GHz.? - - - To check it out, put a styrene cup half full of water,
along with a sample of the plastic you want test, in a microwave oven and
blast away for a dozen or so seconds. .
- later
> They do work well if you want to change the phase of a signal @ 10 GHz.
>
>Cuming Corporation, 230 Bodwell St., Avon, Ma 02322 manufactures
>machinable, absorptive materials that will do what you want.
>
>Good luck,
>Bob, W5AH
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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