RF Modules Tranceiver on ONE Antenna

Chicago Mike

SO the RF modules are great, but I'm looking at making a project into a smaller package, and I'm interested in using ONE antenna instead of the 2 (One for receive and one for transmit. Yes, the unit needs to be a transceiver). From reading the cut sheets on the Linx site (The RF chip parallax uses in these modules), its not recommended to simply tie the ant. pin of the RX and the TX units to one antenna, because during transmit it will overpower the receiver. Does anyone have experience with this? Obviously this is done commonly on many products (Cordless phones being the most basic). Linx recommends using an Antenna Switch, but I can't seem to find any of these for the 433Mhz product range?

I'm fine with setting up a handshaking routine to check for collisions, so I don't attempt to send and receive at the same time on the unit, but I'm more worried about the electrical side (and the warning the Linx says about this).

Anyone try this before? Its more that I don't want 2 antennas sticking out of the package, but I also don't want to damage the RX module.

Thanks!
Mike

Post Edited (Chicago Mike) : 5/26/2007 11:23:31 PM GMT

Mike Green

Here's one link for a limiter using a PIN diode: www.edn.com/article/CA486567.html.

There are other transmit/receive switches using PIN diodes that you could use, but I don't have any links.
You might try searching the web for PIN diode transmit receive switch circuits for UHF frequencies like 433MHz.

Kevin Wood

If you're planning to do a lot with RF in your projects, you might want to check out some of the technical books published by the ARRL, such as the ARRL Handbook.

Robert Kubichek

Chicago Mike said...
SO the RF modules are great, but I'm looking at making a project into a smaller package, and I'm interested in using ONE antenna instead of the 2 (One for receive and one for transmit. Yes, the unit needs to be a transceiver). From reading the cut sheets on the Linx site (The RF chip parallax uses in these modules), its not recommended to simply tie the ant. pin of the RX and the TX units to one antenna, because during transmit it will overpower the receiver. Does anyone have experience with this? Obviously this is done commonly on many products (Cordless phones being the most basic). Linx recommends using an Antenna Switch, but I can't seem to find any of these for the 433Mhz product range?

I'm fine with setting up a handshaking routine to check for collisions, so I don't attempt to send and receive at the same time on the unit, but I'm more worried about the electrical side (and the warning the Linx says about this).

Anyone try this before? Its more that I don't want 2 antennas sticking out of the package, but I also don't want to damage the RX module.

Thanks!
Mike

There ARE transciever modules already.
Here are some;

www.active-robots.com/products/radio-solutions/radio-modules.shtml

www.saelig.com/miva/merchant.mvc?Screen=CTGY&Category_Code=RW

www.sparkfun.com/commerce/categories.php?cPath=16_114

To get longer distance, you put an amp inline, at the cost of power usage..


Bob N9LVU

PJAllen

Chicago Mike said...
I'm looking at making a project into a smaller package

Consider this: an "antenna switch" will take up (a lot more) space than an antenna.

LoopyByteloose

Yeah.
Why do half-duplex when you can have full-duplex with two antennas? I suspect PJ Allen is correct, the antenna switching may take up as much space as a second antenna. After all at 418Mhz, a 1/4 wave antenna is merely 7" of wire above a small ground plane.

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Chicago Mike

Thanks for the help. The pin diode is an interesting method, but I think I'm going to give the EasyRadio Transcievers a run. They seem remarkably easy, and everything is packaged already. Thanks!