Hi, I just installed a link to a PTP650 and have noticed some problems , the fact is 
that the slave receives perfectly but the master does not receive perfectly, is not
able to modulate over 16QAM with only 10.1km away . On the other side modulate at 256QAM It is possible that one is defective radios?

Thank you.

I suggest looking at Link Loss for both directions and comparing this with the LINKPlanner prediction, looking at Receive Power and Vector Error in the Diagnostic Plotter at the master, and looking at the Spectrum Expert page at the master.

If this doesn't pinpoint the problem, please collect the field diagnostics files for both ends of the link and contact our Customer Support team.


Hi Telysat,

Does the radios are in Line of Sight? Make sure that the radios are in line of sight. 

If they are in line of sight and issue still persist. As Mark said, create a link planner project and compare the values and troubleshoot accordingly. Below is the link to download the link planner software and its user guide. Refer the user guide for any help.

If you still find any difficulties or issue still persist. Please pull the field diags file from both radios by following the below steps and contact our Support team for assistance with Field diags and Link Planner project file.

1) Open web browser and type in IP address of first radio
2) Go to system administration in order to complete logon process (you must logon to get the field diags)
3) After logon, type into your address bar: http://xx.xx.xx.xx/field_diags.cgi (xx is the IP address of the Radio)
4) Click on the link displayed and download the file somewhere where you can easily find it.
5) Repeat same process for 2nd radio.
6) ZIP both generated files and contact our support team at


Vijay Gnanamurrthi.

1 Like

Thank you, i send both diagnostic file and link planner project.

Coming to the original issue.You are facing low modulation at Master end. The cause for low modulation can either can be 1.)Interference 2.)Can be obstruction at master end,which is affecting master end freznal zone 3.)Last and rare seen cause could be the faulty IF cable.which is transmitting bad or poor signals.

So in order to improve the modulation our first task should be comparing the predicted values from link planner and actual device stats.If the modulation is low than predicted.Look for predicted Rx power in link planner.If that's has issues than possible places on device stats to find real cause can be 1.)Spectrum Expert to check spectrum conditions. 2)Diagnostic Plotter to check Vector error.3)Any Rx/Tx CRC in Detailed Counter. 
Possible solution for Noise issue is 1)Reduce the channel size 2)Change the channel frequency to cleaner 3)Move to better band.

Possible solution for Line of sight issue 1)move to lower bands like 5.1 or 5.2 or 5.4 rather than 5.8 or 5.9. 

Possible solution for low Rx could be 1)Better Alignment.2) Checking noise level and performing Noise solutions mentioned above.3)Check for obstructions in path.60% of Freznal zone should be clean.

If the link good channel and good Rx as predicted in L.P than the modulation will be always high.If modulation is higher than the throughput will be at Maximum.

These things are co-related:- Distance---->Modulation--->Throughput. Or Noise/Obstruction--->Rx power--->Modulation--->Throughput.


Hope the above mentioned information will help everyone who sees this post in understanding the relation of each parameter in RF.