Signal link problem with Force 4600c

Morning, we have a problem with PTP mode, can’t get more that -60dBm in link on 40KM, in the pass with other radio in same link we get -40dBm, the location of link is on Colombia. Please help us!

There is a difference between ePTP and PTP-TDD, so which were you using before?
Are you sure that the gain of your antennas is the same or close to the same at the new frequency? Also you may not have full EIRP power available to you due to your country limitations.

All It’s same as before, Same antennas, only change the radio for new one! How it can “free” the EIRP Power?

There is no way to “free” the EIRP. EiRP is the spectral power density and is determined by the antenna gain and the tx power. Your local radio authorities have set acceptable max EIRP for your country, cambium helps you stay compliant by setting a max TX power level based on country code.
So here are some basic pointers:

  1. I do not know what the acceptable EIRP is in Columbia
  2. set your country code on the radio correctly.
  3. doublecheck the old radio config to see if you missed something.
  4. if you believe everything is correct, open a support ticket.

I have a 10.2 km PTP link with a dish Algcom 6500-34-09-DP and Cambium 4600C, and I get the same signal strength. It is possible that there is an automatic power control that maintains the link at a target signal level of -60 dBm.

Therefore, it is impossible to access higher modulations than 64 QAM and consequently, to achieve the maximum possible performance of the link.

Please, Cambium team: We need help.

Hello, I’m sharing screenshots of my configuration.

Can you please share the eAlign page too?


My link is 10.2 km long, and my colleague’s is 40 km long. Both provide the same power despite having different distances.

Did you open the ticket with Cambium Support Team?


Yes!! have same problem in other link, look signal on different frequency

Guys, I’m very late to reply here but I want to say this [ and as I know myself, it will be very long ] :

40km means 141dB free space loss at 6.6GHz ; your receive signal level is -60dBm.
Forget all the planners, let’s do the simple math. This is what we have been doing 30 years ago and nothing changed in the physics since.

If you had 19dBm TX Power (you have more configured but that might not be a good thing, more to this later) and 31dBm antennas (you didn’t specify what you have, we only see 34dBi in the radio configuration but manufacturers occasionally tend to exaggregate), this would be the link calculation:

19dBm TX Power + 31dBi TX antenna gain - 141dB free space loss + 31dBi RX antenna gain == -60dBm receive signal level

So, at this distance and frequency, with 31dBi antennas and 19dBm TX Power, you would achieve -60dBm signal level.

Quickly about TX power : the more is not better. Analog circuitry doesn’t have unlimited scaling, signal purity, signal quality etc, there is something called inter-symbol-interference due to amplifiers being overdriven and signal distorted at transmitter etc. You SHOULD NOT use 28dBm TX Power in any case. Moreover, the higher modulation (MCS6 → MCS9 → MCS11 → etc), the LESS power you must use, this is clearly written in documentation. If you just blindlingly “crank it up”, you will decrease your resulting throughput.

Now, because you have more than 19dBm TX Power and most likely you have bigger than 31dBi antennas : at this frequency, 2ft antennas provide around 30-31dBi gain and I don’t think anyone clever enough tries to do long shots like this with 2ft antennas. I personally would not consider anything below 120cm = 4ft, they provide around 36dBi gain.

If you had 19dBm TX Power with 36dBi antennas on each side, this would be the signal :
+19dBM TX Power + 36dB TX antenna - 141dB free space loss + 36dB RX antenna == -50dBm receive signal

You are far far away from that, so you are doing something wrong. In real life, let’s substract two or three decibels for imperfect antenna aiming, coax cable loss etc. so you should be at around -53dBm.

At the same time, let’s quickly get into -40dBm signal from competitor. That’s extremely complicated to achieve ; mathematical explanation : to achieve -40dBm signal at this distance and frequency even with 25dBm TX Power (which is not going to happen at highest modulations and 160MHz channels), you would need 38dBi antennas on each side with absolutely perfect aiming and no other loss :

25dBm TX Power + 38dBi TX Antenna gain - 141dBm free space loss + 38dBi RX Antenna Gain == -40dBm receive signal.

Do you have 38dBi antennas ?

At the end, 4600c is capable of transferring almost 1.1Gbps at 110km. Yes you see that number right. One hundred and ten kilometers, more than a gigabit traffic.

there are other results at 71km and 46km in the video.

Check your configuration - examples what to look for have been provided already. Check your antennas. Pigtails. Coax cables. You didn’t say what the other radio is - you only said nothing changed, the same antennas etc. I have seen many cases like this : nothing changed, just the radios. When I got to site, there was a pigtail changed not just the radio, because old radio was using different connectors than new radio - guess what, those pigtails were broken.

Before I forget : 6600MHz is somehow high in the 6GHz range. BY FAR NOT ALL ANTENNAS ARE CAPABLE OF PROVIDING EQUAL PERFORMANCE IN THE WHOLE RANGE they are specified. Almost all “4.9GHz - 6GHz” antennas are not suitable of 6.6GHz operation ; many “6GHz” antennas are just simple forks/spin-offs of old original 5GHz models not capable of handing AX/MU-MIMO operations, with huge unoptimized VSWR and other low-level characteristics that make >6.4GHz operation problematic.

I personally look for “5.9 - 7.125 GHz” antennas when tasked to operate at around 6.5GHz.

There is absolutely no possibility how signal can change 20dBm by replacing just radios. Laws of physics apply to all vendors identically. Decibel or three is possible due to different output levels, but 20dB are not going to disappear out of nowhere.

Something is wrong either with your physical installation, or signal reporting by the “other radio”.
Good luck finding that, if you haven’t already since May as there was no reply in this topic for 2.5 months. First thing I would do in your configuration : change the antennas gain. Make it 20dBm for example on both radios - if your signal level changes, you know you hit some artificial limit, something that radios are obeying by due to local country settings (for example, EIRP has been mentioned already, but that’s a tough discussion with 34dBi antennas and 28dBm TX Power :slight_smile:

4600c are capable of miracles at 40km. Run them wild within physical limits (no more than 20dBm TX power) with big antennas and don’t plan to meet anyone from local telecommunication office :slight_smile:

Yeah, it was very long.

1 Like

just noticed right now : NetPoint guys are present here on the forum.