PMP 450i

How are you? I would like to know if anyone could support me, my ptp link fell in the morning, I do not know why this sudden change is falling. Annex pictures. Already try to change frequencies and improve alignment. Please help.

Annex catch of July 30, where he worked well


Two things have happened:

1. Power level has dropped from 4 to 5 dB on both the Downlink and Uplink.

2. On the downlink, the SNR has gone from a good 27 dB to 10 dB.

For #1, please check for any water intrusion in the cables or other cabled issue. Also, please try alignment again.

For #2, it appears that an interferer has cropped up at the SM location. Have you done a Spectrum Analysis on the SM? What does it look like?



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Thanks for the answers, I will apply each point described.

1. If the wiring has moisture, is it necessary to change everything?
2. Is it likely that the radio has failed?

Annex images of how is working at the moment.

Good Morning Jose,

I thought I'd throw some thoughts out there if you haven't figured this out yet.

From my training/experience, the modulation rate is solely determined by the Signal to Noise Ratio (dB).  if you notice a substantial drop in this value, it is most likely attributed to noise.  I believe that the signal to noise must be at least 32dB to get an 8x/8x, but I haven't had that always be the case.  

I would check the following:

  • Timing of AP's in the area that may affect/cover this SM. (SM may be "hearing" other AP's and they are contributing to the noise floor)
  • Do a spectrum analysis to see the noise floor on the frequency this AP is set to. ¬†(You can swap the AP to another, cleaner, frequency)
  • Review the alignment of the equipment and peak in if necessary.

With moisture in the cable, the biggest "symptoms" I have seen in the field are a 10-BaseT ethernet connection, as well as CRC errors (Statistics->Ethernet).  

A failure of the SM, from what I've seen, would include symptoms such as not sending/receiving RF on either the Horizontal, or Vertical (so... 0V/-54.6H for example), or "no link" on the ethernet.  But again, with a failure of the SM many things can be the cause or result as the equipment has a lot more that can fail than a cable so if the SM is suspsected a quick swap out may be a good idea to try. 

I hope this helped.  


Great suggestions Scott... thanks for contributing.