QB450 TX and RX distance.

[Anonymous user]

Hi,

chosen model of QB450 in full duplex mode, with PTP link.

for the model QB450 , what will be Antenna separation for TX and RX antenna for SITE-A and vise versa for SITE-B.because the QB450 has two different antenna.

[Joel_Weder · Accepted solution]

Hello again @Anonymous user 

Typically the installation does not use two antennas. It can be done, but would require a significant separation. One antenna must be directly above the other (on the same tower) with (example only) probably 15 metres or more separation. This would cause the upper antenna to have a much better coverage area than the lower antenna, so it is rarely done.

Instead, Schneider offers a device called a band-pass duplexer. This is a mechanical filter that allows the high-powered transmitter to share the same antenna as the receiver, which is listening for very weak signals. A duplexer must be adjusted carefully at the factory for the exact frequencies used by the radio system, so you must state the frequencies when ordering.

A duplexer includes three type N connectors. One goes to the antenna, and the other two to the radio's Transmit and Receive ports. The Transmit port of the duplexer is adjusted to pass the transmit frequency to the antenna port, and the other is adjusted to pass the receive frequency from the antenna port to the Receive port and then out by cable to the radio's receiver. You can see the duplexer on page 13 of the attached document.

Schneider also sells the short (1 metre) cable kit to connect the duplexer to the radio. TBUMRFJP-DUPLX-BP is the part number.

[Teaan]

Hi Joel and Ahmed,

If I may give my experience as well. We used to use duplexer's at all our high sites but at those really requiring extra distance we opted to remove the duplexers and go with the extra spacing, depending on your frequency. Typically we worked at 440 an 445Mhz for Tx and RX. With between 7-10m separation of our antennas, we have found the isolation adequate and have increased our distance and receiver sensitivity by about 3-4dB. 

I would recommend this only if your tower heights are 30m and above. 

Again this would depend on your distance requirements two antennas also means twice the co-ax, connectors, strapping and labor. 

A good start would be to do a pathloss analysis and see if you really have border conditions for communication. If that is not the case then definitely  opt for the duplexer.