PTP550 cannot deliver the required bandwidth

Dear Team

Currently I have a very bad experience with the Cambium PTP550 radio unit when used with a 34dBi Parabolic antenna dish over a distance of 12km.

I have done several spectrum scan and changed frequency and still yet all I could get on the wireless throughput test when I used Channel bounding is 18.9Mbps(downlink and uplink) during the night and 3Mbps(downlink and uplink) during the day.


The RSSI level have is -67dBm on radio1 and -71dBm on radio2.

Kindly advice what can I do?

What can I do better in-other to get the maximum capacity on the PTP550 radio?

Hi, those signals aren’t nearly good enough at those distances. With 34 DB antennas, your signals and modulations should be substantially better.

Your modulations are only DS2 - DS4 or even just SS (single stream) modulations. So your performance will be horrible.

Maybe if you post your radio configuration screen, your Monitor->Performance screen, your eAlign screen… maybe one of us can make good recommendations on what to do.

Properly configured, and properly aimed, your performance can be 50 times better. :+1:


Thanks for your prompt response

The link during the day it keeps disconnecting but at night it manages to come up.

How else can I effectively utilize this radio unit PTP550?

I would propose the following

  • Check with the link planner what you should get (RSSI) and compare with what you have. Then check alignment and LOS.
  • Change Channel BW to 40MHz from 80MHz. Less noise, better sensitivity and more output power in higher modulations.
  • Check your antenna specs. You are using frequencies at the edge of the spectrum, not all antennas may perform acceptable on these frequencies (even if the manufacturer claims that they do!)
  • Finally, you may use one radio (disable the second) in 40MHz, find a channel that performs as you expect and then proceed with enabling the second radio.

Hope it helps


Hi again. OK - the suggestions ndem makes are all exactly what I would have said:

  1. Check Linkplanner, and figure out what the target RSSI should be at 12km. With 34dBi dishes, it should be substantially better than this.

  2. Once you know what your signal should be - you’ll need to achieve that. That’s either tweak the aiming, or it’s obstructions, or it’s having your radio output set at 7dBm, or it’s using a channel where your antennas perform better (as ndem says, it’s not uncommon for higher gain antennas to fall of dramatically on the edges of the bands). You signals need to in the low 50’s (eg -53) in order to get the maximum modulation rates.

  3. I’d start with one radio mode - use 20 or 40Mhz mode, and simplify the situation down to just one radio. That should allow you to aim better, and should allow you to select a channel which performs well within our antenna’s “sweet spot”. And again, you’ll really need to achieve whatever Linkplanner tell you the ideal signal is. That’ll probably be signal in the low 50’s

And if I haven’t mentioned it already… SIGNAL. :slight_smile:
If you look at your eAlign, you’ll see a signal of only -65 (which doesn’t see to terrible at first glance) but when you look at what that -65 is comprised of… each of the chains ARE terrible.


So on a per-chain basis, that link is a -78, a -73, a -74, and a -73. So, we would never connect a customer as a -78, right? Likewise, we should never have a chain that’s a -78 either. I know a -65 seems kinda OK, but when there’s 4 chains… those are horrible signals, and that’s why your modulations are DS2 and SS2. A -78 is frankly close to not even working, and thats why you’re seeing SS (Single Stream) rates even. All your chains need to be -60 or better - ALL of them. And that’s going to mean an aggregate signal of -54 or better.

So, here is an example PTP550 link of ours. This is only 1 radio, and this is in 80 Mhz mode, and the signals are NOT perfect, but they are pretty good with an aggregate signa of -54/-57 (which really isn’t good enough actually) but this link does about 500 Mbit with 1 Radio.



Hi Ninedd what distance and what dishes are you using?

This particular 80 Mhz link above is a shorter, but has small antennas on it. It’s actually re-using some old Force110 antennas… so what were the Force 110 antennas really? 20dBi maybe? Small antennas.

However, this one below is a 14 KM link – and this has a 32dbI antenna on one side, and a 25 dBi antenna on the other side I think. That’s due to size constraints on each side. As you can see below, signals at 14 KM are a -51, and all the chains are -57 to -54 right now. It’s a rainy crappy day today (unless you’re a duck) so the signals are typically a db or 2 better… but this is what your link should be capable of at 12Km I think.


Also, I have this one configured in TDD 75%/25% and I’m using a single 40 Mhz channel, but even in only 40Mhz mode, I get 210 Mbit download, and 70 Mbit upload right now - so about 280 Mbit aggregate.

SO - again to @KOwopetu123 - what’d I’d recommend best thing to start with is:

  1. Cambium’s LINKPLANNER software, and you should be able to calculate with your antennas, and which channels, and which radio configuration should give you for expected signals. You’ll want them to be in the low 50’s
  2. Then start with a single radio link, in 40 Mhz mode, and then aim and tweak until you achieve the signals which LinkPlanner calculated - and make sure all chains are as balanced as possible.
  3. Then you should have an SNR in the 30’s or 40s - and you should get modulations of DS9/DS9
  4. And even in a single radio, in only 40Mhz mode, you should be capable of close to 300 Mbit aggregate

And then once you have that all dialed in with the proper aiming, a know narrow channel which works well, modulations and signals and snr which are as expected… after that, you can add in the second radio, and ramp up your bonded throughput.


Dear Team

Thanks a lot for all the responses.

As advised above I have reduced the bandwidth to 20MHz I have also used Radio 1. I have done a link plan its attached to this mail.

Festac POP to Ilupeju POP.pdf (135.4 KB)

Our engineers while re-aligning the link observed that on the LOS path passes through a very high transmission electricity power line.

Please can a power line affect the quality of the link? If so what other option do I have?

Kindly advise on what to do next

Our engineers while re-aligning the link observed that on the LOS path passes through a very high transmission electricity power line.

In my experience normally you have to be pretty close to them but they can cause all kinds of problems when they are close enough. I suppose if they are dead center of your link then maybe they and cause more problems a farther distances.

Something is most certainty interfering with both ends of your link since your RSSI is good but your link speeds and MCS are trash both directions.

Turn on the “spectrum analyzer” and let run for bit, be curious to see what it shows.

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Dear Brubble1

Kindly see the spectrum scan from the AM

while from SM I have this

what else can be done?

Extremely narrow beam width antennas?
HighGain Horns with no back or side lobes?
Flamethrower to melt all the other gear in the area?

Cambium does also have DCS (Dynamic Channel Selection) in the 4.6.1 firmware, so you could experiment with DCS and see what it can find. In theory, the DCS will move around channels dynamically, and keep track of noise and performance, and can figure out the best channel. I haven’t really heard any results from it - but in theory it sounds great.

You could even try DCS with narrower channels as an experiment (10Mhz) and see if it can find room in between other gear out there? And once it figures out the best channels, then you could manually widen out the widths on those same channels.

BUT - above all else - SIGNAL. Get whatever antennas you need to get, with perfect aiming, and get the signals to a low 50’s. Right now, your signal on your chains were in the high 60’s, and if your background noise is a -60, then a -69 chain isn’t going to be able to do anything. Get bigger/narrower beam antennas (with better shielding if possible?) and meticulously aim them - so that your signals get down to the low 50’s and you’ll have a chance.


Hello @KOwopetu123 ,

the spectrum analyzer shows that you are in a very interfered area.

You chose the right dishes, but you need smaller channels to transmit more capacity and have a good Received signal level. The power lines will not affect your link at all. Also, can you share a picture of how the jumper cables are connected from the radio to the dish? They must be similar on both sides of the link, otherwise the signal will not be optimized at all. If now, at night you get good capacity, it is because there is less traffic over the air and radios are not busy transmitting.

Please, do share a picture of the installation. I will assist you further to sort the issue.

From LINKPLanner, you should expect this signal:

Sincerely yours,

Niragira Olympe

Yeah, wow… I think what ninedd says is pretty much your only hope.

The only thing I might add is, if it was me and that was an important link then I would be looking into something besides 5Ghz. I don’t know if 3Ghz is an option where you are or we now pretty much go with licensed, at least here in FCC land, 11Ghz Ubiquiti.

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Here is a great video on antenna alignment that I highly recommend.

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Ninedd is on the correct path. You have a lot of interference as shown in your spectumrum scan and this is what is killing your link.

Unlike what olympe has asked, the ptp550 series does not care which jumper cable is attached to which port on the radio or antenna, the radio will correct for this if there is any cross polarity. Some systems do care but the wifi based radios (epmp and the ptp550) do not care about which radio goes to which.

I would turn one radio off on each end and realign with a 20 or 40mhz channel. 34db on each end is enough for your link but that is assuming quiet spectrum, in your case you may want to look for a tighter beamed antenna with a narrower respose range. Not using 4.9 or 5.9 then done get an antenna that is as wide of band.

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I am curious what became of this link?

was this issue fixed?

We have many PtP550 running on long, noisy links and they perform extremely well.
You can split Radio 1 and Radio 2 which gives you a lot more granular control. 20MHz on Radio 1, 40MHz on Radio 2 - find some clean air and get the best performance.

We have a 32km link doing 200Mbps Full Duplex all day, every day.
We have 10km links doing 400Mbps Full Duplex all day, every day.

These are both in very, very noisy metro environments.

It’s all about making sure you have your radios in clean air and make sure you’re alignment is right.
All too many times people align to a side lobe and wonder why it’s running poorly.

Do your plot in LinkPlanner and it should be very close.


Dear Glipschitz

Wahooooo that’s a good link for 32km and 10km but in my case there is an electric high tension power line is on the LOS path of the link this seems to be affecting the link performance. We have had riggers at both ends who has realigned the link and still yet the link performance has been terrible during the day and manageable in the night.

Interference is very high in my case.

However I am still trying to relocate the PTP550 radios to a path that wont pass through the electric high tension power line to see if I will get better performance.

Yes I have plotted this link on cambium link planner. But the real life scenario has not been good at all.

Hello @KOwopetu123 ,

the power line should not be an issue as its power oscillation is around 50/60 Hz very far from the 5 GHz. Do scan your air to have cleaner channels or move the radio to a location with cleaner channels. Else, invest in a licensed radio like the PTP 820S with a band between 11 and 15 GHz.

Sincerely yours,

Niragira Olympe