Delrin Casing

Jun 23, 2009 3 Replies

Doing a little work on a little transmitter to be placed in animal. Just seen a case made up of black Delrin. I thought, lets do the microwave test. It does start to get warm. I figure it might affect tunning of circuitry if case is too close. Transmitting through saline tissue has yet to be tested. I thought a saline sponge cut in half would make a good test fixture for the transceiver.



greg


I don't see a question here, but unless this transmitter is something that can pass safely through a natural orifice, and/or your work is supervised by properly qualified personnel, you would be mistreating said animal. This would not look good on a resume or a criminal record check.

RL

Maybe you can have an antenna sticking out a natural opening in the animal?

Hello Greg,

The microwave test is nice to compare losses of different materials at

2.45 GHz, but does say almost nothing with regards to the fitness for your application.

I don't know the frequency of the transmitter and the antenna type, but as soon as E-field lines cross the dielectric, you will get detuning when you change the dielectric from air to, for example, polyethylene. Polyethylene has very low loss, but has er = 2.5 (roughly), so will detune the antenna.

So heating effect in the microwave test, is not a good measure to assess detuning effects due to dielectric materials in the vicinity of the antenna. In case of VHF/UHF antenna inside the animal will probably result in poor efficiency. Measurements and/or modelling is required to make sure you have sufficient margin in the link budget.

Best regards,

Wim PA3DJS

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