Model Forum / Radio Controlled / Water Models / November 2003

If you alter the lenght of your reciever antennae your will probably
not be able to operate as the areal lenght is set to correspond to
your radio wave lenght.To get the right answer post it on The
SubCommittee message board.
Malcolm  NZ

Oooh.  Nice.  :)

Yup, salt water is a surprisingly good EMI/RFI shield... and what is a
radio transmission but a designer form or EM/RF interference?

Around?  Sounds like you've created a coil of sorts.  Maybe not one
with many turns, but a coil nonetheless.  RX antenna wires work best
when kept as straight as possible, and at right angles to the TX
antenna (the ONE good thing those damned pistol grip radios have going
for them - the TX antenna's vertical).  May I suggest running the
antenna up out the top of the conning tower then forward to the bows?
If it doesn't reach, extend it with a piece of string, fishing line,
or other non-conductive material.

Yes.  Well, a hesitant yes.  When you say "double", stick to that like
glue.  Antenna length matters.  Double it *exactly* and see how you
go.  Be prepared to put it back to original spec though... results
with a double-length antenna are NOT guaranteed.

No, quite the opposite - salt water's RF shielding (actually
absorbing) qualities are frequency dependent - the higher the
frequency, the greater the absorbtion.  This is why 1:1 scale subs use
ELF (extra low frequency:  100KHz (0.1MHz) or even lower) for comms.

You can, but you'll be hunted down and tortured with hours of endless
toil playing with micro/nano RC cars if you do, and rightly so.

Boosted RF transmitters (be they RC, CB, broadcast band mini audio
TX's, whatever) tend to be loose canons, splattering the crap out of
all channels either side of their set channel/frequency, overloading
(and potentially damaging) RX's in close proximity, interfering with
legitimate users on the same channel miles away, etc.  Yes I know
amateur radio operators use "linears"/"footwarmers" (high power RF TX
amps) all the time, but they're the exception to the rule - their amps
tend to be built by very well clued in people who know what they're
doing, and are operated on frequencies where A) such devices are
allowed (usually;) and B) standard RX equipment is designed to be
operated in close proximity without adverse behaviour.  You could get
an engineer to design a 27MHz linear for your TX, but it'd cost you
more than a whole fleet of serious RC subs, and you'd still have the
problem of interfering with people miles away, and potentially
damaging nearby RX's.  And you'd be operating outside the guidelines
of your country's radio regulations, coz RC TX's are limited to x
watts of effective radiated power.  So, sorry but no.  Don't go there.

What you *could* do, if you're willing to sacrifice a little bit of
scale authenticity, is fix the end of your RX antenna in a cheap 1"
dia styrofoam ball (get'em at any decent craft shop).  Cut it in half,
fix the end if the wire to one of the flat surfaces, glue it back
together and paint the whole thing black.  Dunno how youre gunna
control it on the surface, but submerged, it'll float (or at least
stay as close to the surface as it can).  Caveat:  RX antenna wire and
props don't mix.  ;)

I'm on the virtual wagon.  :(  I'd settle for an emailed pic or two of
your sub though, if you're that appreciative and any of my rambling
was correct enough!  ;)

Good luck... :)

DS

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hmmmmm. if you can fold it exactly in half, as the other poster said. better
yet (if room) is to fold it exactly in half, tie a wire to the ground an do
the exact same thing to it pointed in the opposite direction and you have a
folded dipole. If you cant, do a loose coil (think spiral notebook wire, but
with more space between coils)

remember that antennas on both the reciever and transmitter "should" be
oriented in the same direction, if the antenna is along the subs length, you
should also have the transmitters antenna horizontal

get your tech liscence and convert it to the ham bands. test aint that hard