We are having issues with a PTP820S 11Ghz link we are trying to get up.
The link is around 18km in distance and the PTP820S units have 2 foot Andrew direct mount dishes set at vertical. Link planner states we should be getting around 43 to 47dBm but we are unable to get anything better than 60-65dbm on the link. Of course the link rate is no where near what we wanted for this link.
At the moment the link has been installed and aligned twice on one tower, on failing that, we then moved it to a seperate tower and then tried again - same problem. Im reluctant to say 'alignment issues' as we have done this a number of times now and it is unlikely to be alignment.
Below is a screenshot of what we are seeing. You can see on one end of the link it has very high defective blocks, whilst the other end does not. The radio with the defective blocks has been moved on to two seperate towers (tower distance is around the same - but about 5km apart from the original tower). Same issue.
I am asking if anybody else has seen this and if so - what was the issue / resolution? I will be trying another known good PTP820S link shortly to disprove if it is 'alignment issues' by removing the PTP820S from the dish and putting on the known good PTP820S link pair without moving the dishes.
Hello, I have also seen this type of issue when the Hi and Lo transmitters are reversed or the frequency range for the channel is beyond the range of the radio. Can you supply the part numbers, frequencies being used (or call sign) and the channel size (configured script on the radio)? If you would prefer, you can email them to chris.fikert@cambiumnetworks.com. If you have a LINKPlanner file, that would also be very helpful.
Unfortunately those radios are in different sub bands and the low TX frequency is out of operational range of the radio.
C110082B015A PTP 820S Radio 11WGHz,TR500,Ch1W6,Hi,11185-11485MHz High TX channel: 11285 – 11365
C110082B028A PTP 820S Radio 11WGHz,TR500,Ch7W13,Lo,10915-11207MHz Lo TX channel: 10795 – 10875
The Lo transmitter would be better as:
C110082B016A PTP 820S Radio 11WGHz,TR500,Ch1W6,Lo,10695-10955MHz
I would highly recommend using LINKPlanner, especially for licensed microwave links, in order to generate correct part numbers for the coordinated frequencies. Normally, we also have a tuning guide that can help find alternate part numbers that aren't in stock, but with the Wide SKUs, both radios need to be in the same sub-band, or share an overlapping sub-band.
The issue lies with us - thanks to the above we can see that at one of our tower locations ( where we installed 3 links), the radios for 2 links have been swapped. By sheer luck the other link radio frequencies are working with a very good link - hence why it was never looked at.
So reminder for those out there doing multiple radio installs on a tower - check off the part numbers when going up on the tower with tower climbers doing the work.
Sometimes these problems can be really hard to debug.
I ran into a similar problem a year or so ago: Our link worked, but it had occasional random bit errors. We checked EVERYTHING, until we discovered that someone had fat-fingered one of the frequencies. It was off by no more than 1 MHz, and yet the link was up and passing loads of traffic, just with a few bit errors. Once we corrected the frequency entry, everything worked quite well, indeed!
