home *** CD-ROM | disk | FTP | other *** search
- Path: sparky!uunet!olivea!hal.com!decwrl!bu.edu!transfer!necis!rbono
- From: rbono@necis.UUCP ( NM1D)
- Newsgroups: rec.models.rc
- Subject: Re: Carbon fibre and radio interferance
- Message-ID: <1704@necis.UUCP>
- Date: 31 Aug 92 16:55:39 GMT
- References: <BUDD.92Aug28095613@drynix.dfrf.nasa.gov>
- Organization: NEC Technologies, Inc., Boxborough, MA
- Lines: 67
-
- In article <BUDD.92Aug28095613@drynix.dfrf.nasa.gov>, budd@elxsi.dfrf.nasa.gov (Gerry Budd) wrote:
- > In article <steveg-240892093900@52.10.18.134.in-addr.arpa> steveg@resntl.bhp.com.au (steve garlick) writes:
- >
- > I've just finished a mould for producing glider fuselages. I'm planning
- > to use carbon fibre tows to reinforce critical areas on the fuse. I want
- > to run tows down either side of the fuse and some from the base of the
- > fin and up. Does anyone have experience with RF problems with an aerial
- > inside such a fuse. (Note, I dont plan to completely cover with CF, just
- > 2 strips down either side for vertical stiffening).
- >
- > I've got carbon fiber tow laminated into the interior sidewall of my
- > Conquest 120 pattern plane. I run the receiver antennae and three
- > long servo extensions the full length of the fuselage. I've been
- > doing this for years with no problems. However, I fly JR radios. I
- > know some people who will not do this with their 1024 Futaba's. They
- > have had some problems with their receivers and don't want to take any
- > chances.
- >
-
- I don't know if this makes sense to me? Is carbon fiber conductive in
- anyway? Can it shield or absorb RF energy? I don't know. I wouldn't think
- so except that there are electronic devices made of some sort of carbon.
-
- There are "carbon composition resistors", is this the same type of carbon
- that is used to make carbon fiber? Generally, carbon composition (or carbon
- film) resistors can be used in an RF circuits because they will not react to
- the RF energy in a way that impeads the RF part of the signal (so to speak).
- They will only represent pure resistance (no reactance). If the carbon
- fiber that we use has similar properties, then this may mean that carbon fiber
- is partially conductive but shouldn't shield RF energy (I am not sure about
- this).
-
- There could be one way to find out. Many ham's (amateur radio operators) use
- the following test to determine if a certain material will absorb RF energy.
- NOTE: There is a bit of controversy over this, but most think it makes sense.
-
- Place some amount of the material in question into a microwave oven. "Cook"
- the material for one to five minutes (start with one minute at low power,
- if it passes this test, go gradually up to five minutes at high power).
- If the material DOES NOT HEAT UP, then it should be transparent to RF energy.
- Microwave ovens work by subjecting their contents to 2.6 GHz high power (600
- watts or so) of RF energy. If a material doesn't heat up under this, then
- there is a good chance that it will not absorb lower frequency or lower power
- RF energy.
-
- Be warned that some microwave ovens don't like to be run empty. In this case
- you can place a cup of water in the oven. Just be sure that your test material
- is not near the cup of water so that it is not heated by the steam or heat
- that is generated in the cup of water.
-
- Additionally, one could use an Ohm meter to try and determine if the carbon
- fiber will conduct any electricity. It may read in the MegOhm range. This
- could depend on the length and/or thickness of the carbon fiber (and whether
- the measurement was taken across the thickness or across the length of the
- carbon fiber).
-
- If someone has some carbon fiber and tries this test, please let us know.
-
- Of course the SAFEST thing to do (in ANY case) would be to have the receiver
- antenna exit the fuse immediately after the receiver away from any other
- wires, and run outside the fuse away from all surfaces.
-
- --
- /**************************************************************************\
- * Rich Bono (NM1D) IMRICH rbono@necis.ma.nec.com *
- * (508) 635-6300 nm1d@nm1d.nh.usa.na *
- \**************************************************************************/
-