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Youi

80 posts

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#195867 9-May-2016 11:55
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So we've had a mail thief problem which seems to have stopped for now, but to prevent future issues, I like to grab the mail as soon as the postie delivers it. I work from home/I'm always here, but we cant see the mailbox from the flat (we're set back behind another flat). Ive got one of these cheap driveway alarms from ebay and have stuck the sensor in the mailbox; getting my partner to play 'postie' and testing by posting replicas of the package sizes we normally get works well, and the receiver chimes as its supposed to (which would be my queue to leap into action and swoop upon the mailbox to retrieve said mail).

 

Only problem is the receivers range falls short of the front door by 1.3m. Sigh lol. The mailbox is insight of the front door, but has a wooden flap for the signal to go through, so thats already some of my 'range' taken up by having to go through said flap (non-removeable). Its about 18m from the mailbox to the front door. I would like to stick the receiver on the inside of the front doors glass panel, which is still juuuust insight of the mailbox without having any added walls to go through, bar the glass panel. So I somehow need to give the receiver (yes? not boost the signal being sent by the transmitter?) a boost to get the signal another 1.3m further away and through + one glass panel. Is it possible for a novice like me to add an aerial to the receiver? Its 315Mhz if that makes a difference. I DIY everything else in the house but fall short when it comes to anything electronic and hoped someone here might have a solution?

 

Cheers in advance, oh helpful people :)

 

 

 

This is whats inside the receiver:

 

 

 

Edited: to make the pictures smaller, sorry about that!

 

  Edited again: to add the link to the ebay page for the driveway alarm.


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MikeAqua
7773 posts

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  #1548632 9-May-2016 12:05
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Shouldn't;t you boost the output of the transmitter?





Mike




Youi

80 posts

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  #1548683 9-May-2016 13:15
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MikeAqua:

 

Shouldn't;t you boost the output of the transmitter?

 

 

 

 

Quite possibly! I just guessed at the receiver needing a boost to pick up the signal, but if its the otherway around, I can go and wrestle the transmitter out of the mailbox (stuck it in there rather well lol) and take a picture of its insides if that helps anyone help me?

 

As I said, complete novice at anything electrical, have little to no idea but quick at learning :)


wellygary
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  #1548690 9-May-2016 13:30
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Change the back flap of the mail box to a piece of plastic :),

 

I'm guessing it's currently a chunk of wood with the thickness of a fence paling, and that when it's wet your coverage is even worse

 

 




Youi

80 posts

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  #1548696 9-May-2016 13:41
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wellygary:

 

Change the back flap of the mail box to a piece of plastic :),

 

I'm guessing it's currently a chunk of wood with the thickness of a fence paling, and that when it's wet your coverage is even worse

 

 

 

 

 

 

If the landlady wasnt one of the most awful people ive ever met, i'd ask about changing the mailbox flap, but as its one of several identical boxes built into each other, she would lose it about things being 'different'. Its about 15mm thick btw and that side is kind of protected by the rain so it dosnt get soaked all the way through but yea, changing that would help if I were able :)


shk292
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  #1548702 9-May-2016 14:04
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Youi:

 

MikeAqua:

 

Shouldn't;t you boost the output of the transmitter?

 

 

 

 

Quite possibly! I just guessed at the receiver needing a boost to pick up the signal, but if its the otherway around, I can go and wrestle the transmitter out of the mailbox (stuck it in there rather well lol) and take a picture of its insides if that helps anyone help me?

 

As I said, complete novice at anything electrical, have little to no idea but quick at learning :)

 

 

It doesn't matter which antenna you improve, the overall effect on the signal strength is the same

 

You need to remember that increasing antenna gain only works by making the antenna more directional, ie you don't get anything for nothing

 

http://www.tp-link.us/FAQ-3.html


blackjack17
1705 posts

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  #1548707 9-May-2016 14:27
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Could you not install a lock into the back of the mailbox?





 
 
 

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SepticSceptic
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  #1548713 9-May-2016 14:37
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I think using some tricks that are used for extending Wifi would help.

 

Off the top of my head, cutting a metal can in half, length-wise, and placing the receiver inside could help ...

 

Place the receiver ( even better, the antenna) in the middle of the can, so the radio waves bounce off the metal towards the antenna, like a mirror does. You could use a bright led pointer to get the correct alignment.

 

 

 

 

 

 

 

 

 


ubergeeknz
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  #1548719 9-May-2016 14:46
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Try soldering a 25 cm wire to each instead of whatever antenna they have now, let the wire hang down, see what happens


dirtydutchman
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  #1548980 10-May-2016 07:23
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ubergeeknz:

 

Try soldering a 25 cm wire to each instead of whatever antenna they have now, let the wire hang down, see what happens

 

 

 

 

Why limit to 25cm?

 

 

 

I have used 27Mhz transmitters with the original aerials and had problems with range until I simply lengthened the aerial with some 6mm green conduit wire which I always have lying around in the back of my work truck.

 

That said if you were to replace aerials with some second hand proper whip aerials you should increase the range a lot.

 

Only way would be trial and error


SepticSceptic
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  #1549281 10-May-2016 13:26
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dirtydutchman:

 

ubergeeknz:

 

Try soldering a 25 cm wire to each instead of whatever antenna they have now, let the wire hang down, see what happens

 

 

 

 

Why limit to 25cm?

 

 

 

I have used 27Mhz transmitters with the original aerials and had problems with range until I simply lengthened the aerial with some 6mm green conduit wire which I always have lying around in the back of my work truck.

 

That said if you were to replace aerials with some second hand proper whip aerials you should increase the range a lot.

 

Only way would be trial and error

 

 

 

 

Best reception is either a whole length of the frequency wavelength, or a 1/4, or 1/2 wave length. This is more important at higher frequencies, than lower frequencies - 315MHz, vs 27Mhz.

 

So the entire antenna length for 315 Mhz is 952.4mm, or 476mm 1/2 wave, or 238mm 1/4 wave - antennas are more effective at these proportions, and not a random length. "Entire Antenna length" is the full length, including circuit tracks, etc, from the actual transmitting coil, or whatever.

 

Full length antenna for 27Mhz is 11 meters, and has more tolerance for out of spec lengths.

 

25cm is pretty close for 1/4 wave. 1.2 cm shorter would be even better :-)

 

 


ubergeeknz
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  #1551329 12-May-2016 09:55
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^^ Pretty much what he said

 

25cm should be near enough but technically speaking the optimum 1/4 wave for 315.000Mhz is 23.8cm

 

Try 25cm and if it's not good enough trim a cm off

 

 Also will work best if as straight as you can get it and the same orientation for both antennae


Youi

80 posts

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  #1552561 14-May-2016 11:45
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thanks for the answers guys! I dont suppose any of you could tell me how to actually attach an aerial? Thats the bit I dont know, i.e. I dont know what part of the inside of the receiver (the picture I posted) needs to be removed so an aerial can be attached (it has no external aerial, I assume one of those black knobs is the receiver/nubby aerial?).


richms
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  #1552594 14-May-2016 14:45
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Antenna will just be a trace on the circuit board. Need to solder wire to the other side of the circuit board.

 

But try adding some wire to the negative battery terminal. That is often enough to get some more range on things like that.





Richard rich.ms

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