Sharing a single antenna, is this possible?

Hi

I have an Arduino Nano project which is using 433Mhz for TX and RX comms.

I am in fact using the QAM-TX1 and QAM-RX4 modules for 433Mhz comms.

At the moment the two Antenna pins I have wired to separate aerials.

Do you think its possible to connect the pins together and share a single antenna?

I am concerned about power differences if wired together. The TX will transmit a higher power than the RX module is expecting to directly receive.

Do I keep them on separate antenna's?

If I can connect together can I just direct wire them together or is there some load/impedance matching/balancing circuit I need? If so any pointers and diagrams would be appreciated

Datasheets for both modules are below

QAM-TX1
QAM-RX4

Your thoughts?

At the moment the two Antenna pins I have w

ired to separate aerials. [/quote]

You can clearly see there is only one pin (4) labeled ANT on the transmitter and only one (1) on the receiver, so are you trying to say that you have the antenna pins on BOTH transmitter AND receiver connected to something else ?

or (god forbid), you are trying to say that you connected a wire from the transmitter ant pin to the receiver antenna pin ?

Do I keep them on separate antenna's?

If I can connect together can I just direct wire them together or is there some load/impedance matching/balancing circuit I need? If so any pointers and diagrams would be appreciated

I think you should stay away from any electronic circuits until you learn the rules and some basic theory.

The questions you are asking should never be asked.

Look up the definition of antenna and then read your questions .

Why on earth would you ask such questions ? (assuming that what you meant was hardwire the transmitter and receiver antennas together. Good god man. Why would you want to do that ?

Assuming you know what RF means , why do you want to take the RF out of an RF Module by eliminating the electromagnetic wave altogether and short circuiting the transmitter to the receiver ?

Do you understand the absurdity of your question ?

If I understood your question correctly, you want to convert a WIRELESS Module pair to a WIRED module pair.

Does that make any sense ?
If you don't want WIRELESS , why are you using a WIRELESS module pair ?

I'm both shocked and confused.
Please explain.

What is your final objective ?
What is your project ?
What are you trying to do ?

As a general rule, injecting a large signal into a receiver, which would happen if the antenna pins are connected together and the transmitter is on, will damage the receiver.

If I can connect together can I just direct wire them together or is there some load/impedance matching/balancing circuit I need? If so any pointers and diagrams would be appreciated.

Assuming that there is some good reason for doing this (I totally agree with raschemmel; doing this is barking), then, yes, with a suitable attenuator it should be OK. You can buy RF attenuators ready made. You can make them. You need to understand impedance, impedance matching, attenuator design and what a decibel really is. Look those subjects up and understand them. You need to know the power output of the transmitter and the expected power at the receiver.

I can't repeat what raschemmel said enough though; this is madness.

I can't repeat what raschemmel said enough though

I love hearing that... :sunglasses:

Doing this is barking

OK, so maybe I'm being harsh, why do you want to do this? In any case, if you wire the Tx to the Rx, why do you think you need an aerial at all?

NEWSFLASH !

If you connect the antennas, it no longer called an antenna, so the post title is wrong..

Most transmitters and receivers that use the same antenna switch it over with a relay. But at those sorts of frequencies if you use a normal relay the signal will, to use a technical term, just piss right through it.

You need to use a coaxial relay that is rated for the frequency you want to use. I am assuming you know you can’t transmit and receive at the same time on the same frequency. You can do this at the same time on different frequencies if the two are far enough apart and you put a very good high order notch filter in the receiver antenna to notch out the transmitted frequency. But then you need separate antenna.

Unless you use a device known as a circulator

ichilver:
Your thoughts?

If your objective is to have a transceiver (both a transmitter and a receiver) at each node sharing a single antenna, it would be far better to use a device that is intended to be used that way.

The HC-12 is one such option. The NRF24L01 is also popular for modest range communications.

The modules you've proposed are intended for one-way transmission applications such as a remote control unit while your application presumably involves two-way transmission.

The standard way to switch RF power upto a few watts is PIN diodes, not coax relays. Google "PIN diode antenna switch" perhaps?

MarkT:
The standard way to switch RF power upto a few watts is PIN diodes, not coax relays. Google "PIN diode antenna switch" perhaps?

Quite clearly you are not a radio ham.

Be that as it may, he is correct. Hand-held radios have not used relays for some considerable time. Generally a λ/4 stub and diodes, or similar. Circulators on SHF.

Just got the cable today to program my two BF-888S that I bought to play with. Amazingly inexpensive. The silly thing is that toy stores offer toy radios that are total crap, for higher prices! You just pay for the pretty livery like My Little Pony or Spiderman. :astonished:

MrMark:
If your objective is to have a transceiver (both a transmitter and a receiver) at each node sharing a single antenna, it would be far better to use a device that is intended to be used that way.

The HC-12 is one such option. The NRF24L01 is also popular for modest range communications.

The modules you've proposed are intended for one-way transmission applications such as a remote control unit while your application presumably involves two-way transmission.

Hi

Many thanks for your reply. Yes the idea was to use a single antenna.

I know you can't just wire them together (@raschemmel), especially with the power on TX vs the RX, hence why I put a post on here.

The project I was given was using the QAM-RX and QAM-TX modules but the outside design needed to go from two visible BNC antennas to a single Antenna.

The answer to my problem is in fact the HC-12 module.

Many thanks.