35 mhz radio control reciever

[shaun_c_m]

hello,
i have recently started to fly radio controled helicopters and have discovered that it can be quite difficult to place the reciever's antenna.

there are a lot of metal parts that can shield the signal from certain angles so i was wondering if it would be possible to use the tail boom which is typically anodised aluminuim as the antenna.

i was considering using a conductive epoxy to form the join as it is difficult to connect to aluminuim.

the type of helicopter is a raptor 30v2

electrically the tail boom is insulated from the rest of the structure but it is a completely different diameter to a standard antenna. also although it is a different length to the fractions of wavelengths, most radio control recievers use a standardised 1 meter wire.

im afraid my knowledge of RF systems is limited and i havent found anyone that has attempted this before, but it would seem that using this element of the structure as an antenna would mean that it isnt going to be able to shadow the aerial wire.

an example picture of a raptor can be found at:

http://www.raptor-mad.com/raptor_30_v2_rc_helicopter.htm

any thoughts and ideas would be appreciated,
thanks,
shaun

 

[flatulent]

At this frequency the wavelength is about 10 m and so whatever you use, it will be poor. Your idea will work as an antenna if you feed at the junction of the body and tail boom.

 

[fcfusion]

At this frequency the wavelength is about 10 m and so whatever you use, it will be poor.

Most RC low frequencies (around 20 or 30 MHz) and they don't need long antennas. A short antenna does the job but range decreases. That's not a problem when you only want a few meters range, like for those RC choppers. I think your ideia will work.

 

[shaun_c_m]

thanks for your replies. i didnt realise any had been sent at first because i was expecting an email, so sorry i didnt talk back sooner.

im glad to hear that my idea isnt completely stupid. i know antenna theory is a complex subject and all.


i dont want to reduce the range of the system if at all possible. with planes and gliders which are generally made of wood and plastic there is less of a problem.

the transmitter uses 100mw and a telescopic aerial of 1 meter.
the reciever uses a 1 meter wire as the antenna.
the range varies but is over a kilometer in most cases.
i would guess that the reciever compensates for the fact that the antenna is the wrong length electrically

with helicopters there are so many metal parts it is difficult to find a way to route the antenna without either running it parallel to something metal like the boom or with serious angles and potential doubleing back in places. the most common way to attatch the antenna is to run it near parrallel to the tail boom/ support struts. from the little i know this is a perfect way to cause inteference problems.

currently i have it so that it actually runs in more than one plane of direction. i was hoping that if one polarisation was blocked another might still be viable. this seems a very crude way of making the antenna work when there is a large metal tube out the back.

thanks again,
shaun