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Topic: is there anyway to make smaller antenna for FPV system ? (Read 1 time) previous topic - next topic

firashelou

Sep 13, 2013, 01:18 am Last Edit: Sep 13, 2013, 08:13 am by firashelou Reason: 1
hello guys,
i have this antenna that comes with the FPV system (attachment file)
but i need to know how to make one myself that is not huge as this one i want it the smallest possible for 900mhz FPV system : http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=21327

i need the antenna to have a good look and the smallest possible and the best range because i want to put it on an rc car but dont want it to be ugly so any idea ?
Aiming for the unreachable !

mauried

Its not possible to make the antenna smaller without adversly affecting the range.
Depends on how far you want to transmit.

firashelou


Its not possible to make the antenna smaller without adversly affecting the range.
Depends on how far you want to transmit.



i want to transmitt about 150m or 200m on ground not on flight

and if not possible to make it smaller then can i make it flexible and attach it to the body of the car without affecting the range ?
Aiming for the unreachable !

doughboy

these from hobbyking, but for 2.4 and 5.8ghz



I don't know if you can make any smaller antenna for 900mhz system

patryk

actually you are in luck. since it's 900MHz, you'll find planty of different antennas on ebay. just look for GSM antennas (yes - for cell phones).
it all dependes on your transmitter's output power, but i'd imagine that you could easily install tiny antenna on your RC car, and compensate for weeker signal by using higher gain antenna with your reciever.
that's how people usually do fpv - small stuff in the air/field/whatever and high gain antenna (usually directional btw) next to the monitor

firashelou


actually you are in luck. since it's 900MHz, you'll find planty of different antennas on ebay. just look for GSM antennas (yes - for cell phones).
it all dependes on your transmitter's output power, but i'd imagine that you could easily install tiny antenna on your RC car, and compensate for weeker signal by using higher gain antenna with your reciever.
that's how people usually do fpv - small stuff in the air/field/whatever and high gain antenna (usually directional btw) next to the monitor


well i want to build it myself if its possible, and i can't use ebay where i am because it will cost me very big money to get something for 5$ which i can't afford now

@doughboy well those antennas would be great in quality but i am looking for different ones, for example is there anyway to build a rolling antenna like the induction shape and what kind of wire can i use if i want to make something that is similar to an RC car antenna like this one flexible :
http://s7d5.scene7.com/is/image/horizonhobby/LOSA4002_a0?$pdpLand$
but without the cover ?
Aiming for the unreachable !

patryk

#6
Sep 14, 2013, 03:02 pm Last Edit: Sep 14, 2013, 03:21 pm by patryk Reason: 1
if you really want to build your antennas, then that's how i would do it:

wire antenna for the car:
1/2 or 1/4 wave lenght. your wave lenght is ~333.333mm so the antenna would be 166.666mm (1/2 wave) or 83.333mm (1/4 wave). use copper wire and keep it as straight as possible. curved antenna won't perform too well, but might work for you on short distances.

if you want high gain directional antenna for your reciever:
bi-quad design is probably the simplest to build. you can calculate dimensions here: http://www.changpuak.ch/electronics/bi_quad_antenna_designer.php



firashelou


if you really want to build your antennas, then that's how i would do it:

wire antenna for the car:
1/2 or 1/4 wave lenght. your wave lenght is ~333.333mm so the antenna would be 166.666mm (1/2 wave) or 83.333mm (1/4 wave). use copper wire and keep it as straight as possible. curved antenna won't perform too well, but might work for you on short distances.

if you want high gain directional antenna for your reciever:
bi-quad design is probably the simplest to build. you can calculate dimensions here: http://www.changpuak.ch/electronics/bi_quad_antenna_designer.php



aha that's a good info and about keeping it straight can i use for example the glue paper for electronics apps like the skotch i mean or that will affect the transmission ?
and about the width of the wire how much should it be ? 1mm is good or a lot ?
Aiming for the unreachable !

patryk

any not coductive adhesive should do. i usually use simple hot glue for that stuff
1mm should be fine ;)

firashelou


any not coductive adhesive should do. i usually use simple hot glue for that stuff
1mm should be fine ;)


what do you mean you put hot glue ? oh i was saying to make a cover for the copper wire
Aiming for the unreachable !

patryk

i would use a wire with insulation on it.  this way you won't have to worry about it. 1 - 1.5 mm^2 copper wire should be riggid enough to keep it's shape on it's own anyways.
in any case any plastic/rubber will do (as long as it's not coductive)

firashelou

#11
Sep 15, 2013, 01:37 pm Last Edit: Sep 15, 2013, 02:55 pm by firashelou Reason: 1

i would use a wire with insulation on it.  this way you won't have to worry about it. 1 - 1.5 mm^2 copper wire should be riggid enough to keep it's shape on it's own anyways.
in any case any plastic/rubber will do (as long as it's not coductive)


actuly i have to buy a copper wire without any cover on it, so i have to do my own so that way u saying that adhesive will be good to go :)
and about the extremity which i want to attach to the RF link, i just have to solder it right ?
this is the rf link i am using is this one 433mhz attachement file:


can i use one of these wires instead of the normal copper wire for antenna ? http://www.ekt2.com/products?cat_id=9c121e12-7483-4034-84e5-cb69f3bebdfa
Aiming for the unreachable !

patryk

youse whatever wire you have. a piece of old extention cable will probably work good btw.
of course you'll have to solder it. how else would you attach it? ;)
the only question is if you want to connect your antenna directlt to the PCB or you want to put it somewhere else in which case you'll need to use a piece of propper coaxial leed (soldering antenna directly would be way easier though).

firashelou

ok i guess i might 80% need the coaxial i have one already which used it before for satellite, so how would i connect the copper wire to it ?
Aiming for the unreachable !

patryk

if you have a piece of decent 75 ohm coax, why would you want to attach antenna to it?
just use cable's core as the antenna. strip it to needed lenght making shure that the screen doesn't touch it, then solder other end to the antenna output, solder screen to the ground and you should be fine.

tv coax will be a pain to work with though. those are rather thick and not very flexible. not exactly something good for RC imo

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