900 450i dynamic filtering

When installing a 900 SM, we select all 3 center channels; 906, 915, 924. However, does the dynamic filter then allow more noise to pass thru on the adjacent channels than if we selected only a single channel? In orher words, how would the link performance be affected if at all if we set the SM to only a unique frequency to match with a unique AP?

Simarly when in spectrum analyzer mode, does the reported noise also show the self generated AP noise on the selected frequencies? That is with the 900FSK in SA mode, we had to turn APs off to remove self generated signals reported as noise. I am thinking maybe with the 450i in SA mode the filter does not report as noise signals coming from the APs themselves on the selected channels? We had a case where we were operating a 450i AP (5mhz) on 924mhz and the 450i SM in SA mode did not report any strong signals at 924mhz. But when we did a SA using a 900FSK SM, it indeed reported our familiar 5mhz pattern as noise at 924mhz.

So first off the PMP450i 900MHz platform does not employ the dynamic filtering design of the 450i for 5GHz. After testing both the dynamic filtering and direct conversion designs, it was found that the direct conversion design actually performs better.  It does however have a paging filter where frequencies at 920 MHz and above will not work when enabled. Assuming that there's a pager at the top of the band, and the filter is enabled, the SA will typically show far less energy at 920MHz and above.


As far as your second question is concerned, I'm not entirely clear what you're asking. AP's in SA mode do not transmit any energy, they're simply listening. SM's in SA or scanning mode do not transmit any energy, they're simply listenting. If there are adjacent PMP450i or PMP100 900MHz AP's that are transmitting, an AP in SA mode should def see this on an SA. One possibility might be if you're running an SA from an AP with the pager reject filter enabled, and you have an adjacent AP that's at 920 or above, then you would see very low signal levels from that AP.



Ty for your response.

So u are saying that cambium opted not to design in the dynamic interference filtering as presented in their August 2015 roadmap? See below excerpt.
• 900 MHz ISM band Operation – 902-928 MHz – 5, 7 or 10 MHz channel
• Next Generation Architecture – Utilizing PMP 450i architecture – Includes Dynamic Interference Filtering
Geez am I behind.

And yes on my second question i was referring to in band noise as generated from collocated APs on the same tower or even from adjacent towers both fsk or 450i. Yes I think gps sync should make that irrelavent anyway but we have some overlapping frequencies / sectors beyween fsk and 450i as we transition our network.

I guess my questions are irrelavent sonce 900 450i does not include dynamic interference filtering.

That's right Phil... testing was done with the "dynamic filtering" circuit vs. the "direct conversion" circuit late in the development cycle, and due to the relatively narrow bandwidth of the 900 MHz band (only 26 MHz) and the hardware filters being used, the "direct conversion" circuits actually performed much better, so that's what we went with.