Place TX/RX Antenna?

[mehdu]

Hello

I need help for TX and RX antenna in TRX system.
How to place antenna in uhf band?
How much isolation between TX and RX antenna?
Is the TX antenna influence in RX or not?

best regards

 

[FvM]

What do you specifically mean with "TRX system"?

Why not elaborate the question? What do you try to achieve, why do you require isolation between RX and TX antenna? Do you intend half or full duplex operation?

 

[mehdu]

i have a full duplex system and i think the TX coupling on RX antenna. because the RX going to saturation( I think.)

Now how can i fix it?

thanks and regards

 

[volker@muehlhaus]

Go and measure the coupling, instead of guessing.

 

[mehdu]

Ok, But how to measure it?

- - - Updated - - -

Hello

Look that noise floor when the PA is on and so off.
When PA is turn on, the noise floor more than 10dB than the PA is off.

https://pasteboard.co/J1sQWgU.png

how could i fix it?

regards.

 

[volker@muehlhaus]

Ok, But how to measure it?

Network analyzer S21 measured from TX antenna to RX antenna

how could i fix it?

More distance between the antennas, possible anechoic absorbing material to reduce leakage, reduce near field reflections ... it really depends on your setup and other antenna requirements.

 

[mehdu]

Hello Volker,

i couldn't measure S21 from TX ANT to RX ANT.

But when distance between the antennas as more as possible, it's better.

regards.

 

[volker@muehlhaus]

i couldn't measure S21 from TX ANT to RX ANT.

What is the reason? You need to know, so that you can verify possible modifications.

 

[mehdu]

Because i don't know how to measure it.
If possible help me more. ( with block diagram and description)

thanks.

 

[ktr]

Because i don't know how to measure it.
If possible help me more. ( with block diagram and description)

thanks.

I don't want to sound rude; but as the one who wants help; you need to give us a better description of your situation; so we can help you without giving you misinformation.

1- if possible show us a picture of your setup
2- is Tx and Rx antenna in same PCB, or are they on different planes i.e (distance between them) ?
3- What is the Frequency, Bandwidth (narrow or wideband antennas) and antenna type etc.?

 

[mehdu]

1- I can't take a picture. The antenna (RX and TX) installed on tower and have 5m distance between them and the cable length is about 20m and then connect to Device.
2- Yes, Both of them in same PCB.
3- UHF band with narrow bandwidth. and antenna type is omni like as "Laird Technologies FRX450 450-470 MHz 5dBi Fiberglass Omni Antenna"

 

[volker@muehlhaus]

antenna type is omni

Then perhaps a vertical offset helps, because the antenna radiation is smallest there.

If you have different TX and RX frequencies, you will need a diplexer
https://amphenolprocom.com/products/filters

Get an RF engineer on board to support you.