PMP450 vs 450B Modulation Issues

We recently turned up a new AP running in 5.4GHz for a customer.  The first 2 installs off the AP we've run into issues.  We have clean spectrum on both sides.  20MHz channel.  The issue I'm running into is that I can get an acceptable RSSI on the 450b radios but my modulation doesn't get to a point where I can allow an install.  I've seen 3X MIMO-B Modulation at the highest.  The links are 1.1 and 1.2 miles from the AP with clear LOS and fresnel zone.  If I swap out the 450b for a 450 with a reflector dish, I get the same RSSI but my modulation jumps dramatically in some cases and the installs are considered acceptable.  I saw one of the links go from 3X up to 8X and another go from 2X up to 4X.  Radios were installed at the same height at the same exact spot with the azimuth and up/downtilt as precsribed by LinkPlanner.  I have 16.1 released to the production network at this time and have reveiwed the release notes for 16.1.1. and 16.2 and don't see any bugfixes for something like this or any issues that look close to this.  Has anybody else run into this issue?    

1 Like

So two things... the 450b high gain seem to take more time and care to align, and second... did you remember to update the SM's antenna gain field with the appropriate dBi increase from the reflector dish?

Many people that have reported better values from the SM + reflector dish weren't putting the gain in, so they were typically going above the allowed DFS EIRP.


Thanks for your reply.  In regards to the gain I checked and the installers missed setting it on one of the SM's but did set it on the other.  Same result.  Our typical process is to hold the radio by hand to ensure we get accepable signal we've done this since the PMP100 days.  I'm going to do some additonal testing this afternoon to see what we come up with however I think it sounds like we are going to need to work with our installers better on getting them to be a bit more patient on the installation side with the initial aiming.  

There are a couple of additional considerations when moving to the 450b that you should be aware of as well... you can find these here and here 


Thank you for that information.  I will certainly review it.  Just so everybody knows, I had one of my more senior techs go out and do some testing on this sector with me.  In all 3 cases of test points we were unable to recreate this issue, so I'm thinking it may be an issue with some our installers being too impatient perhaps.  I'm going to test this theory the next install by sending one of our senior folks out with them.  

Yes, the 450b takes a bit more time to properly align, and it's just *different* than the old 450 SM (even with reflector)... once they gain a bit of experience, things will become more efficient.

There is a useful video on this process here or directly on YouTube here.