PTP 650 Split Frequency


I can't understand how "split frequency" works.

Could someone give me an example?

I mean: if I choose a 45MHz channel, how much bandwidth does the system use on TX channel and how much on RX channel using a different frequency on TX/RX?

PTP 500/600/650/700 all work using Time Division Duplex (TDD) meaning that in a periodic TDD frame, the first end of the link transmits whilst the second end receives, and then the second end transmits whilst the first end receives. We have a figure illustrating this in the PTP 650 User Guide. Search for "TDD Cycle".

TDD operation can be symmetric, where both ends transmit a burst of the same duration, or asymmetric where one end transmits a longer burst and the other end transmits a shorter burst.

Normally, the master to slave direction and the slave to master direction use the same radio channel. The "split frequency" option means that the master to slave direction is on one channel and the slave to master direction is on a different channel.

So, to answer the original question, if you choose a 45 MHz channel bandwidth with split channel, both directions occupy 45 MHz, meaning that the total occupied bandwidth is 90 MHz. However, the capacity is unchanged because each channel (and thus each direction) is only in use for part of the time.


It’s a pity… Even AirFiber5 from Ubnt doubles the capacity if you do split frequency, and it’s not in the same price range :slight_smile:
Hope this will change in the future!

Here's a screenshot of the Spectrum Expert page using Fixed Frequency with different master to slave and slave to master frequencies:

Another option in PTP 500/600/650/700 is to select DSO in the Wireless Configuration page and Asymmetric DSO in the Spectrum Expert page like this:

Asymmetric DSO.png

Asymmetric DSO is basically DSO with the option of split frequencies. Asymmetric DSO is not available in regulatory bands that require DFS (Radar Detection). This limitation arises because each end of the link must monitor its own transmit channel for the presence of radar signals. This monitoring would not be effective if the unit received on one channel and transmitted on a different channel.


Thank you!
Can I choose overlapping channels, as the radio doesn’t transmit when is receiving?

Yes, overlapping channels will work just the same.