Problem with PTP820S Link - poor radio signal and high defective blocks on one end


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.

Have you aligned the irises properly for V polarization?

Please download and search the PTP 820S and 820S Assured Installation Guide here:

I hope this helps!


Hi Dave,

We have checked a few times. See photos attached - are we missing something?

Note we have also upgraded to the latest firmware as well - no change and no improvement.

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  If you have a LINKPlanner file, that would also be very helpful.

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Hi Chris,

Below are the details you are after -

Partno - C110082B015A - SN- F276G01701 - TX -  11325.00   RX - 10835.00

Partno -  C110082B028A - SN - F386100973 - TX - 10835.00  RX -  11325.00

We use an 80Mhz channel. Script name - mdN_A8080X_117_1501

The part number descriptions reveal the answer:

C110082B015 PTP 820S Radio 11WGHz,TR500,Ch1W6,Hi,11185-11485MHz
C110082B028 PTP 820S Radio 11WGHz,TR500,Ch7W13,Lo,10915-11207MHz

When I enter the Tx frequencies into LINKPlanner, here are the ODUs it recommends:

C110082B015 PTP 820S Radio 11WGHz,TR500,Ch1W6,Hi,11185-11485MHz
C110082B016 PTP 820S Radio 11WGHz,TR500,Ch1W6,Lo,10695-10955MHz

So instead of C110082B028, you need C110082B016.

Check out the supported frequencies. You need one that transmits on 10835 MHz.

C110082B028's frequency range is 10915-11207 MHz. An 80 MHz channel with center at 10835 MHz won't fit within 10915-11207 MHz.

 An 80 MHz channel with center at 10835 MHz will fit within 10695-10955 MHz.

I hope this helps!


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.

PTP 820S-W 11 FCC 80 10755.00 11245.000 490.00 Ch1W6  
PTP 820S-W 11 FCC 80 10835.00 11325.000 490.00 Ch1W6  
PTP 820S-W 11 FCC 80 10915.00 11405.000 490.00 Ch1W6 Ch4W9
PTP 820S-W 11 FCC 80 10995.00 11485.000 490.00 Ch7W13 Ch4W9
PTP 820S-W 11 FCC 80 11075.00 11565.000 490.00 Ch7W13  
PTP 820S-W 11 FCC 80 11155.00 11645.000 490.00 Ch7W13  

Interesting that we DID use link planner and Cambium reviewed this link before we purchased ...

Hope we have Cambium support on rectifying this issue with the link ...



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.

Again, Cambium appreciate the support.

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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!


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