transmitter and receiver range improvements

Discussion in 'General Electronics Chat' started by RodneyB, Mar 18, 2015.

  1. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    I often install automatic gate's and garage door openers. The question I am always asked is if the gate / door range can be extended.

    I would like to find out if this can be done and how
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    The answer is that it depends on how much you are willing to spend and how much time you want to invest in the effort.
     
  3. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    You now have my attention. Is it something I can build
     
  4. Papabravo

    Expert

    Feb 24, 2006
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    Maybe.

    First thing to determine is the frequency band used by the transmitter and receiver. Next thing to determine is transmitter output power and receiver sensitivity. You can rent test equipment in most places to make these determinations, but it won't necessarily be inexpensive. In every country on the planet there are legal limits for unlicensed radio transmissions, so you need to know what those limit are. If your transmitter is operating at the legal limit and the receiver can be tweaked to increase its sensitivity then you have a great starting point.

    If you don't want to fool around with the electronics then you need to work on the antennas. A wire stub radiates in an omni directional pattern. That is the available energy is directed in all directions. So the receiver has to pickup only a tiny fraction of the available power. So you need a transmit antenna that is highly directional and concentrates the available power in a single direction, in a very narrow beam. It helps if the antenna is closely matched to the transmitter's output impedance. This matching eliminates reflections which reduce the available radiated power. Plans for the consruction of a directional antenna can be found on the interwebs and are doable by anybody with a bit of maker skill. The problem comes in testing and debugging which requires some test equipment and some know-how.

    Alternatively you could hire someone to do it for you if it is important enough. What you could charge for this range extension in your environment is something only you can answer. I can imagine it might be a "price is no object" situation.
     
  5. Reloadron

    Active Member

    Jan 15, 2015
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    Part of this depends on how far is "extended"?

    I see you are located in Harare, Zimbabwe. Well I am in Cleveland, Ohio U.S. If I came to visit you and we were enjoying lunch I could open my garage door here at my home during our lunch through home automation and my smart phone over the Internet. :)

    Seriously it depends on how far is far and what Papabravo mentions. I have a little remote relay card laying here operated from a simple key fob with an easy 100 meter range outside or more. That being omnidirectional. Would something like that be far enough?

    Ron
     
  6. wmodavis

    Well-Known Member

    Oct 23, 2010
    737
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    Extend range by:
    1. antenna with higher gain on both receiving and transmitting end
    2. increase transmitter power
    3. situate T & R antennas so no obstructions.
    4. use externally mounted antennas and minimize transmission line losses.

    This is general only and not necessarily all inclusive.
     
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
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    not all remote recieve antennas can be changed, most of the door opener type remotes I have worked on use regenerative recievers, and it you change the antenna, the reciever stops working.
     
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  8. MikeA

    Member

    Jan 20, 2013
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    Push the remote transmitter into the neck under the chin and push the button. 200% range improvement guaranteed. :D
     
  9. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
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    I
    I have seen this done and it works WHY I have never had an answer to this
     
  10. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    100 meters is more than enough. I would like to build one. I am going to post information about the transmitters and receivers
     
  11. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    I think the option of the receiver attena having a higher gain may work but the transmitter may be a problem.

    Most of the time the receiver is mounted in the motor housing. And the antenna pushed through the vent
     
  12. Reloadron

    Active Member

    Jan 15, 2015
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    I have one of these and while they now advertise range over 50 meters I was getting about 100 meters in open line of sight. Originally we used them as a backup safety device. I had good luck at short distances going through thick concrete walls. I have also seen cheaper versions. The one I have was left over from the initial testing. The boards can also "learn" something like 15 key fob transmitters.

    Ron
     
  13. PlasmaT

    Member

    Feb 19, 2015
    40
    6
    Another method of improving range is to add a repeater. It can be used to re transmit the signal from the "key" with much higher power. So noting to manipulate with existing devices. You only have to make a repeater. The repeater can be mounted in the vehicle itself, so that the key can be operated as usual.

    Unfortunately, I do not know how to build one ;) . Perhaps another member can guide you on this.
     
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  14. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    We use the centurion Transmitters and receivers. code-hopping technology, 433Mhz operating frequency

    How do I determine the transmitter output power and the receiver sensitivity.

    I don't know how to tweak the sensitivity of the receiver.

    I think you are 100% right that working on the antenna will be the best. You mention that the problem comes in testing and debugging. What test equipment would I need the know how, I am prepared to learn what ever is required.

    Thanks for your help thus far
     
  15. alfacliff

    Well-Known Member

    Dec 13, 2013
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    the reason that changing the recieve antenna causes problems is that the regenerative recieverfs used in thys type of control are very simple devices, one tuned circuit, and an oscilator circuit just on the verge of oscilating. changing the antenna changes the rf loading on the oscilator, can "suck out" the rf causing the regeneration to stop, or change the load in otherwways to make it oscilate. both can shut down the reciever. just make sure the recieve antenna is clear of all metal (not in a box).l
     
  16. Papabravo

    Expert

    Feb 24, 2006
    10,148
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    Many commercial products have an available datasheet that gives the specifications. That is where I would start.
    An antenna analyzer is used to measure the impedance of the antenna. You would need one that went up to the band of interest, 433 MHz.
    What you do is start with a design, like a quarter wave vertical, and you make it bigger than it needs to be, which means that it is resonant at a lower frequency. Then you trim a bit off and test again until you get the minimum return loss. When you have minimum return loss on a transmitting antenna then you are radiating most of the output power. If you have a directional antenna matched to your transmitter then you can direct more of the transmitter's power in the direction of the receiver.

    Receiving antennas are not as critical as transmitting antennas when it comes to impedance matching. Receiver sensitivity can be enhanced in two ways. You can use an amplifier to boost the input signal and/or you can use a filter to narrow the bandwidth of the received signal. This is where having knowledge of the receiver design comes in. As has already been pointed out some designs are very cranky when you mess around with them.
     
  17. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    Thank you. At this point I am out of my depth. I better read a bit more then re visit this project.

    thank you for everything
     
  18. bertus

    Administrator

    Apr 5, 2008
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    PlasmaT and RodneyB like this.
  19. alfacliff

    Well-Known Member

    Dec 13, 2013
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    regenerative recievers used in these remotes do not have an rf preamp to buffer them from the antenna. an external antenna, or even a resonant antenna can stop the reciever from working. it has been tried here, and didnt work.
     
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  20. Papabravo

    Expert

    Feb 24, 2006
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    That is part of the reason that I said initially that it takes considerable know how and skill to do much of anything with commercial products, or build such a unit from scratch. RF engineering in the 433 MHz. range is not something a do it your selfer can quickly become proficient at.
     
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