Increase the range of RF transmitter/receiver

[letsrelaythat]

Hi All,

I've recently (4:30am this morning :cry put in a car alarm.

Now I'm not too sure if it's just the batteries or not, but it seems to have a fairly short range. Now it's not too bad when you want to unlock or lock the car, but for the remote boot release the signal has to stay working for 3.5 seconds, which means if the signal is broken I have to start the process again.

What I really need to do is to increase the range. Preferable around 50m, but if possible 200 metres+ would be great. If anyone knows how to get it up to 1km.. I would very much like to know about it 8) 8)

I'm still unsure how I would go about it, whether I increase the range of the receiver or of the transmitter. My one problem is that its not one of the higher quality rolling code alarms, so if the transmitter receives the same frequency as someone elses remote puts out I'd be in trouble.

Thanks to all who at least read this, and I hope there are some ideas as to how I can increase the range.

Thanks in advance,

Tim.

 

[Nigel Goodwin]

These transmitters are 'licence free', which means there are strict restrictions on the power you can use - it will probably already be as high as it can be.

Your biggest improvement would probably come from the receiver aerial, if it's under the bonnet it will be screened and perform really badly. Moving the aerial outside the car will increase range considerably.

 

[letsrelaythat]

Is there any way I can extend the aerial from the main unit, I just had a thought about using the car aerial.

I was thinking of putting a relay in line, so that when the car is on ACC, the relay clicks over and gives the signal from the aerial to the radio, otherwise, the aerial picks up the RF transmissions and works a whole lot better..

Would this work or should I just get a new aerial.

Thanks in advance,

Tim.

 

[grrr_arrghh]

its not much aof a long term solution, but I know for a fact that if you put the remote against your head, you body acts as an aerial, and extends the range...

Tim

 

[letsrelaythat]

Lol I went outside and tried it, I hope it wasn't a joke cause I would have looked so stupid

My mate said that becuase the receiver is inside the car, that severly decreases range. Do the receiver units have like a one wire antenna? Could I use the car antenna like I hope??

Thanks in advance,

Tim.

 

[Klaus]

These things have precisely tuned antenna's, usually etched on a PCB.
Connecting external random wires would, IMO, not make much difference.

The remote is designed to work for a certain distance, why is it so hard to walk close enough for it to work :wink: , after all you are getting to YOUR car, are you not? :twisted:
Just push the button when you are standing next to the car.
Klaus

 

[dustinpruente]

These transmitters are 'licence free', which means there are strict restrictions on the power you can use - it will probably already be as high as it can be.

Exactly. its not restricted until you get caught. and what cop is gonna check the power going in to your car alarm receiver.

 

[dustinpruente]

if the antenna is just a wire, then run it and solder it to the body or chassis of your ride, man then the whole frickin thing works like a gigantic antenna. Problem solved.[/i]

 

[gerty]

if the antenna is just a wire, then run it and solder it to the body or chassis of your ride, man then the whole frickin thing works like a gigantic antenna. Problem solved.[/i]

If you do that you'll ground the signal and you'll get nothing, and possibly smoke your reciever

 

[audioguru]

Dustin,
Your idea will work only if you disconnect the receiver's ground from the car's chassis and connect it (and new power for it) to earth. Ohterwise, you are only shorting the antenna to signal ground.

 

[rookie]

hai guys,

I don't know if this is a good idea :lol: can we add an antena to the transmitter.

tq

 

[Nigel Goodwin]

I don't know if this is a good idea :lol: can we add an antena to the transmitter.

Again, that breaks the licence free conditions, and would be illegal - in response to previous comments about that, I know that the chances of being caught are slim - but it's still illegal, and it would be negligent not to make people aware of it!. If you want to then ignore it, fair enough

The main problems with any changes to the transmitter are it's small size, any changes (including a larger aerial) are going to make it considerably larger.

I also don't quite see the reasoning behind wanting range from 50m to 1km - you may as well leave the doors unlocked and hang a 'please steal me' sign on the windscreen :lol:

 

[stevez]

Just to touch on the comments about ignoring the regulations - there are agencies that "listen" across the bands however it would be safe to conclude that there aren't enough enforcement personnel to go after small stuff. The risk you take is in interfering with something or someone else then they take steps to track you down.

An example - I am an amateur radio operator so I do what I do with RF for fun and to learn. I talk with others in my community many of whom are skilled technical folks who make their living in communications and broadcast work. I'll often hear from them about an "offending" signal and their efforts at tracking it down. The offense (or offence) isn't in the fact that regulations are ignored, it's that it's getting in the way of their operations that make them money. They may have paid a lot of money to use a frequency. Now and then an offending signal will appear on the amateur bands and we'll collectively work on it until it's gone. More often than not the source is found and usually the approach is to point out the interference problem - that works most of the time. When it doesn't we enlist the aid of the FCC or other agencies. Most of the time the offending signals result from commercial transmitters or equipment but now and then it's deliberate and unauthorized transmission.

I'd agree that the momentary push of a button isn't likely to get a lot of attention unless that momentary push was near the same location where it bothered something - and someone makes the connection to your activities.

 

[pike]

well seeing that the chances of being caught with an illegal RF device is pretty slim, there were reasons why it was illegal. Ambulance services also use radio communications, so if they fail because RF interference is being made an illegal device, somebody could die or something. It might even be you one day...

Then again 3.5 secs interference...pfft... just boost the supply voltage to the transmitter. This is the easiest way i know to increase range.

Off topic: England VS Australia -go the wallabies!!

 

[dustinpruente]

ive never tried my second idea, as i have put a new signal-sensitivity controller in mine and broken the "License Free" law completely, i get about a half mile range, and i changed the frequency crystals to a freq used only by the secret service when the prez is in town.

 

[letsrelaythat]

ive never tried my second idea, as i have put a new signal-sensitivity controller in mine and broken the "License Free" law completely, i get about a half mile range, and i changed the frequency crystals to a freq used only by the secret service when the prez is in town.

well i've looked into it a lot more, and I was also thinking about adding an aerial. I would rather add it to the recevier end, and possibly use the car aerial if that is possible. I thought changing the receiver module and adding a external aerial connector to it, then passing through some sort of amplifier, then onto the car aerial. If possible could I switch the aerial signal from radio to alarm through a relay?

I am getting very interested in this topic, and so far have done a lot of research on it. I will remove the alarm unit tomorrow and see if it could take an external aerial, however if this is a bad idea please let me know.

Thanks in advance,

Tim.

 

[letsrelaythat]

OK, well I spoke to the store that sold the alarm to me, and they said that the aerial needs to be away from metal, otherwise you get interference problems, and that most of them shipped with older batteries. Now it runs on a 12v battery, if available, would a 14volt battery be better?

The company is also replacing the batteries for free which is a good call seeing as the boxes have probably been sitting there for months

Any ideas on the external antenna theory?

Thanks in advance,

Tim.

 

[rookie]

another dicussion about tis topic
https://www.epanorama.net/phpBB2/viewtopic.php?t=666

 

[letsrelaythat]

Thanks for the link, basically had the same ideas as I did. I know the freqency of my alarm, is very close to the 433Mhz mark like most of them on the market are. I like the idea of the external aerial, with amplifier..

At this stage I'm not toooo worried about the FCC coming to get me, I just want an extremely effective car alarm. I found out the transmitter runs on 12v, so I can't really increase the power to that.. unless somehow I can get a bigger battery in there and I might have to change components around.

Is there a certain type of aerial I should be using??

Thanks in advance,

 

[grrr_arrghh]

perhaps a bit off topic or irrelevant, but how come sometimes you sime yourself as 'Tim' and sometimes as 'emtark'?