XBEE Pro

tim griff

Member
Dear Forum,

i'm trying to use one xbee on the PICAXE "connect" board" to 3 other xbee's also on AXE210 connect board.

All worked!

However, there was limited some range so I changed the xbee( series 1) to xbee pro ( series 1); I also upgraded the 3.3v regulator.

But it has not increased the range. I've tried another xbee pro. I've used the wizard to reset factory default so the power setting is 4(which is maximum). I've also measured the 5volt rail current( before the 3.3v reg) and both xbee and xbee pro boards draws 80mA ( on board led's). I transmit every sec so expected some deflection of the current meter to reflect what should be TX Current: 270 mA (@3.3 V)[ from the data sheet]


Any thoughts please ----- Tim
 

techElder

Well-known member
It is very possible that your meter will not respond quickly enough to measure a pulsed current. You might have a "peak reading" switch function. My Fluke has that.
 

tim griff

Member
Hi Tex,

You could be right, but I thought as I Transmitting every second it would " push" the meter up. Oh I it does not improve range.

Kind Regards
Tim
 

Janne

Senior Member
Are you 100% sure your 3.3V voltage rail is not sagging under transmit load? That might explain the lack of increased range. Also, are you measuring range indoors or outdoors? To rule out other things you should do the testing outside, or use the RSSI function on the receiver to decipher signal level.
With the Pro-modules working properly they should achieve quite a nice range. I've used both 900MHz and 2400MHz PRO-xbees in outdoor applications, and both will happily do over 500m with line on sight. Also, it's always a good idea to use the "biggest" antenna your design allows, only use the pcb antenna module if you can't work with anything else.
 

tim griff

Member
Morning Janne,

Some interesting ideas.

I connected my bench power supply to the input of the reg to eliminate pcb tracks ,wires; and it does not drop.

The range required, xmt through 9 inch cavity wall, 70metres of open space and then a glass window.
The standard xbee just covers this but not reliabily. I thought the pro version would "eat it" and give me more range.

I'm using the onboard RSSI led to "walk test" both variants and annoyingly they still seem the same.

i did not know I could alter the antenna, are you saying just solder an extra piece of wire of any length irrespective of wave-length.

Another question which I've just thought of, on the remote unit were I need extra range do I fit a "pro" module into this as well as the xmt station? [ I only need one way data transfer)
 

hippy

Senior Member
Another question which I've just thought of, on the remote unit were I need extra range do I fit a "pro" module into this as well as the xmt station? [ I only need one way data transfer)
That could be the problem. It's been a long time since I have used an XBee but recall that in some configurations they can undertake automatic retries. If that's the case then both will likely need to reach one another.
 

tim griff

Member
I've just extended the aerial( on Receive remote) and fitted a pro and the walk test /range lookks much better. I'll change the aerial on the transmitter next.

Thanks for all the help
By the way the transmitter

transmits wind speed, wind direction , rain fall every 0.1mm, ozone levels,pressure,humidity,temperature, uv level, and sunshine hours, soon when I built it visibility.

The other xbee's are in remote stations either logging or displaying data ,trend or sendind data over GSM etc
 

srnet

Senior Member
Not a good idea to just add bits of wire to an antenna on the assumption it will make things better.

On receivers its often of little consequence, it may make reception better it may not.

On transmitters however, its often important that the antenna is tuned correctly for the frequency in use.

Adding 'random' lengths of wire to a transmit antenna may damage the transmitter, or it may not.

Then there is the issue that improving the antenna will breach the legal restrictions on radiated power in your part of the world, but I dont think you said where you are.
 

tim griff

Member
I'm fully aware of this issue , I referred to maintaining wave length in a earlier post. Which is why I've only done this on the receiver. If I alter the xmt aerial I shall ensure correct standing wave ratios
 

srnet

Senior Member
If I alter the xmt aerial I shall ensure correct standing wave ratios
OK, so assuming the output stages of the module are circa 50ohm as the often are (but not always) what wire lengths can you 'add' to the antenna and still maintain a good 50ohm match ?
 

techElder

Well-known member
I cannot imagine that an XBEE module would not already have a carefully and efficiently tuned transmitter final stage.

PS. There's a lot of screwing off of the legal restrictions on this forum due to the inconvenience and additional expense of following the rules. (Not saying anything about the OP ... yet. :) )
 

tim griff

Member
Hi, The wire on the module is 1/4 wave, the piece of wire i've added to rec module takes this to full wave. Digi say the pcb ground plane is not efficient and suggest adding your own. When I've done these I think I'll get the range I need.

I also decided to use some of the xbee's as repeaters so as well as receiving will re-transmit. As I'm using 18M2 I can set the timeout to look for another valid signal if one fails( not exactly a MESH network, but good enough).

I've also downloaded ver 6 of the editor which now provides a way of checking/setting the power level AT PL = 4
 

srnet

Senior Member
Hi, The wire on the module is 1/4 wave, the piece of wire i've added to rec module takes this to full wave.
In terms of a safe match to a transmitter designed for 50ohm output (normal for these modules) a full wave (or half wave) end fed wire is about as bad as it gets, dont do it.
 
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