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how to increase F.M transmission range.

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dudedevil100

New Member
i have bought a new wireless fm tranmisster camera(survilliance camera) which antenna transmission distance is very low.. It specified with 100 mtrs range workng. but at range of 20 mtrs it transmitts distorted image's. i need to fix this cam on my wireless robot. so is there any kind a way to increase the ariel distance of the cam or reciever.. plez do rply i need ur help thnx in advance
 

audioguru

Well-Known Member
Most Helpful Member
Video is transmitted with AM modulation, not FM.
Either the transmitter or the receiver is broken for the range to be so low and the image to be distorted.
 

dudedevil100

New Member
no camera nor the reciever is broken. when it close transmiision is good with no distortion but when i take the cam far at 2o mtrs the video starts distorting.. cn i incresae the length of the antenna of reciever
.. and the cam has a smaall wire coming out of it as an antena
 

audioguru

Well-Known Member
Most Helpful Member
Look at the datasheet for the system. it should say what is the antenna for the transmitter and for the receiver for a range of 100m.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Ranges are often highly exaggerated, and are always done outside with nothing in the way. It's also probably using a shared frequency (usually WiFi), and other users are limiting it's range.
 
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shokjok

Member
What other interference is in your environment? Overhead power lines? Children's RC toys? Electric motors?
 

RadioRon

Well-Known Member
i have bought a new wireless fm tranmisster camera(survilliance camera) which antenna transmission distance is very low.. It specified with 100 mtrs range workng. but at range of 20 mtrs it transmitts distorted image's. i need to fix this cam on my wireless robot. so is there any kind a way to increase the ariel distance of the cam or reciever.. plez do rply i need ur help thnx in advance
I'm guessing that your transmission is in the 2.4GHz band using FM. Most devices of this type should be able to reach at least 50m outside, but this assumes it is using a directional antenna, one that you have to point in the direction of your receiver. Please post a photo of your camera unit showing the antenna.

The main issue is likely to be that there is interference from other devices on the same frequencies. This band is occupied by WiFi, bluetooth, cordless phones and other types of equipment and these can all interfere and reduce your range and also corrupt your picture. The only thing you can realistically do about this is to try changing channels on your unit, if it has more than one channel, and try adjusting the aiming of the antennas at each end for the least amount of disturbance to the picture.

If you have WiFi or bluetooth in your home, you could try turning them off just to experiment to see if the picture improves.

There is no easy way to modify the equipment to get more power or better sensitivity other than with better antennas, but first we need to see what you have. Please post photos.
 
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audioguru

Well-Known Member
Most Helpful Member
My cordless phones operate on 900MHz and on 2.4GHz and have tiny stub antennas. their range is pretty far.
 

RadioRon

Well-Known Member
My cordless phones operate on 900MHz and on 2.4GHz and have tiny stub antennas. their range is pretty far.
It may be that yours are FHSS (frequency hopping spread spectrum) which I've found to be quite good at punching through broadband interferers such as WiFi for example. Many of these phones put out a narrowband signal at relatively high power like 20 or 25 dBm (thats 100mW to 316mW to Duffy) and a few as high as 29 dBm (794 mW), and they may have bandwidths on the order of 50KHz roughly, which means that they have a power density advantage of as much as 30 dB (1000 times) compared to WiFi for example. This allows them to work fairly well in my experience. Their signal hops around from one carrier frequency to another, but the hopping is not lightning fast, maybe about 10 hops a second more or less. I find that when WiFi and FHSS signals have to fight it out, the FHSS one tends to win more often.

Analog FM television signals are very wideband, roughly 16 MHz or so and so are, I think, particularly vulnerable to interference. I note that microwave ovens are also known to cause interference to these devices. Just now I did a search for 2.4GHz TV discussions on other forums and it seems that interference is a common problem, especially from phones and ovens. A common symptom of interference is lines in your video, but it can take other forms too.
 

Hero999

Banned
DC motors are another source of interference. I remember my dad not allowing me to play with motors or my brother play with remote control cars when he was watching TV because it caused the screen to be covered with coloured lines. :D
 
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