PICAXE transceiver

[frankeltham]

If you wanted to make a 434MHz transceiver for PICAXE using separate Tx and Rx modules what's the best method of allowing them to 'share' an antenna?

I know little Tranceiver modules are available but they don't do what I want.
(I'm only talking about tiddlers here. 25mW Tx power max).

Thanks.

[Technical]

Best method would be to use a single module that both transmits and receives e.g. XBee

[BeanieBots]

What do you expect to do with a Tx/Rx pair that a transciever cannot do? If it is transmit and receive at EXACTLY the same time, then forget it. Almost impossible with totally seperate modules let alone ones which use the same antenna.

[frankeltham]

Thanks.

Transmission and reception would obviously be interleaved.
The current (small) modules on the market e.g. those from R F Solutions etc. are not powerful enough.
And also having separate Tx Rx means you could use separate bands on the 434 region.
e.g. RF Solutions can provide about 5 different frequencies happy to work through a 433/434 MHz antenna.

[BeanieBots]

Have a look at the LPRS (low power radio solutions) site. If they can't do it, you probably can't have it. Not sure what the legal limit in the UK is these days but as most are only 10mW I would guess that is it.
You can get more by using a high gain antenna, but that would actually be illegal in the UK.

[Stan. SWAN]

Check the Dec.'05 &amp; Jan.'06 &quot;Silicon Chip&quot; for typical Picaxe 433 data applications, including a repeater ( with 2 whip antenna). Refs at =&gt; www.picaxe.orcon.net.nz/433rpt.htm <A href='http://www.picaxe.orcon.net.nz/433rpt.htm ' Target=_Blank>External Web Link</a>point to all manner of layouts &amp; antenna least

[frankeltham]

Thanks. It ain't looking good so far.
I had already looked at the excellent LPRS Easy Radio and RF Solutions Transceiver modules.

I was intending/hoping to use the R7G/T7G modules from RF Solutions for this little project.

I have used these SIL RF modules - and similar - over many years in point to point simplex data radio as they are very good AND cheap. LPRS, RF Solutions and Radiometrix all good stuff .

The T7G has a 25mW output which should be attenuated for use in UK . And no gain antenna is allowed in UK at these unlicensed frequencies on the Tx O/P.

The nicely-priced standard ER and RFS Transceiver modules mentioned above will struggle at 300m. I need 2 or 3 times that range, which I have had from a T7G/R7G. And prices of more powerful 'proper' devices are too much.

With good circuit layout (i.e. real pcb not protoboard+wires) I could get a transceiver with 700m range for under &#163;60. And it would fit in half a fag packet with an antenna poking out of course.

I need full control over the Rx module for the PICAXE to perform duty-cycling and auto squelch (from the RSSI).

All the rest of the circuit is easy but my ONLY problem is the antenna switchover.

HELP?

But, so far it looks like 2 antenna.

[andypro]

I would jsut od it the way HAM's have done it for ages. Under normal operation, the antenna is connected to the RX...say through a DPST relay. On transmit, switch the relay to the transmitter, transmit, then return it to the RX. Google will turn up a multitude of TX/RX switching and sequencing circuits and schemes.

--Andy P

[Stan. SWAN]

I wish you'd mentioned healthy budget &amp; range needs to start, since there are numerous more upmarket offerings when longer range needed! What data speeds ? Perhaps the new Rev.Ed XBee 2.4GHz ZigBee Pro (100mW) will fit the bill, but also consider 27MHz units

[frankeltham]

Thanks.
I was really trying to keep it compatible (433/434) with what I'd done before. And 27MHz stuff would have (relatively) big components and antennas. (

However, now you've pointed it out, the XBEE-Pro (basic XBee not powerful enough) stuff looks very interesting.
As it seems pin swappable with std XBee I could prototype with Xbee then plug in the PRo when/if Rev-Ed start importing them(?).
That may be the way to go.

I have, by the way, after much nerding last night found a number of semi-cond RF switches. (Relays OK for bigger stuff, but a bit clunky for my requirements). The easiest and cheapest is an Analog Devices model from RS Components. I'm just getting some application notes on board layout.
But I don't enjoy surface mount...

Anyway, I have some options now and XBee looks easiest.

I assume you get a more comprehensive data sheet with the XBee starter pack than the AXE210.pdf sheet?

[andypro]

If your looking for a silicon RF switch in dip form, check out the Phillips SA630.

--Andy P

[frankeltham]

Thanks Andy. I found it with a bit of entusiastic nerding last night. I came across a couple of other makes which are similar - though I would have to buy bucket loads as a minimum order.
In UK I can only find Digi-Key as a supplier.

I've just noticed another thread on Transceivers... I'm just going over to listen.

[D n T]

Check this out.
Transmitters and recievers with over 1000m range
ATranciever with a ??? respectable range, its small enough to fit into half a cigarette packet.
You might have to wait a bit to get them or chase down the suppliers in your neck of the woods, good luck, if you order these the guys are good, they won't rip you off

[frankeltham]

Sounds good. Have you a link?

[frankeltham]

For anyone who wants a healthy range and doesn't mind a few more inches on their antenna check out:
http://www.radiometrix.com/pdf/bim1.pdf

This data sheet has a little bit of info on Manchester and FEC coding too. I think 3kM with 10kbs sounds good (no doubt with the wind behind you!). Though I'll leave it to the student to calculate the size of a half-wave whip at 151MHz!

[Gussy]

I found that transciver a while ago and i am still waiting for an email from the local (AUS) supplier to give me some prices.

3km is nice but 10km is even better, and at a nice speed too.

Good thing also is they are legal in AUS and UK