Today, we have installed a pair of 300-16 as a ptp link. The problem is that the endpoint are in a very close distance (almost 100m) and the link is too hot (rssi -42). As I see there is a difference on 300-16 and force 180 about how low we allowed to set the transmit power (the lower value is 3db compare to -25 on force 180). What are your suggestions? Are you planning to release some new firmware ?
Not sure if I follow your question entirely. What tx power are you setting for each side? F180 and F300-16 while they look similar are different inside so the range of power levels especially on the negative side is not the same.
Right now we are using two of f300-16 for operating a ptp connection. The distance between of them is 100m, the rssi is too high (-40) and im looking a way to lower the transmit power on these devices. As i saw the lower setting on f300-16 is 3db compared to f180 that is (-25db)..
on the AP side Set you TX power under the radio tab to 20 less that current, so if at 20 set to 0, if at 0 set to -20, then set sm RX power to -65
on SM side, check the box to auto control power. done.
-42 may be considered 'hot' but it will not hurt these radios to run with received power levels that are normally considered high.
Alternatively run 300-13's and your power levels will be reduced by 3dbor a 300CSM with a pair of stick antennas?
or run a cable for 100m? (this one is humor, or at least supposed to be)
Yeah i know these ,but i canot run a cable throught top of the buildings and i have select the lowest setting on the sm side and this is 3db (i have already say that this one on f180 is -25..).
So Cambium please create a new firmware with lower transmit power...
Try de-aiming them - for example, aim both down 30 degrees toward the ground instead of straight at each other.
j
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Lets look at this: (this is based on RF power of 30dB = 1W conducted as specified in IC RSS210)
IF 0db tx power is 100mW, -3 is 50mW and -6 is 25mW. if you keep going -9 is 12.5mW, -12 is 6.25mW, -15 is 3.125mW, -18 is 1.562mW -21 is 0.781mW and -24 is 0.39mW. anything less and the signal will not get through the RF network or the antenna connectors.
Firmware that provides a lower output power is not really possible as it is a physics problem, do not compare an f300 to a f180 as they are not the same under the plastic. They have different radios and different RF networks.
Your options are to choose a radio with a lower gain antenna or detune the look angles or both or ignore the -42 received power if the radios are set AP lowest setting with SM auto power level set to -65 and SM set to auto power mode. SM auto power mode can and will go to the lowest tx power setting possible, settings you can not access.
I had a SM at -40 (we swapped to a lower gain antenna as running an f200 at 600ft was really a waste of hardware when a f180 was all thats needed) and have an SM at -52 coexisting on the same AP with another SM at -80, no issues. As long as the receiver is not in the + region, it wont hurt it especially on on a ptp link.
@Douglas Generous wrote:......and -24 is 0.39mW. anything less and the signal will not get through the RF network or the antenna connectors.
Firmware that provides a lower output power is not really possible as it is a physics problem, do not compare an f300 to a f180 as they are not the same under the plastic. They have different radios and different RF networks.
If this was the case, everyone would need a RSSI above -24dbm to have a connection or else the receive signal would not make it through the antenna connections and RF network..
I used to align HF SSB radios on a daily basis. Many of them a day at that. The RF generators I used to align the receive section could go down to -130dbm. Many of those SSB receivers could actually faintly hear a signal at that level (-130dbm). The -130dbm signal made it through the RF circuitry and connectors of the RF generator, and into the radio where it was demodulated and turned into audio. I have used spec-ans, that I could never afford, that could -see- signals down to around -150dbm.
It is not a physics issue for why it does not go lower, at least not related to the RF network and connections. My -opinion- on why the 300 does not go as low as the 180 is due to 64-QAM vs 256-QAM. 64-QAM has 64 constellation points, 256-QAM has 256 constellation points. Or you can look at it as 256-QAM has four times the constellation points in the same bandwidth (20Mhz, 40Mhz, etc). The constellation points are closer together for 256-QAM compared to 64-QAM which means error control must be tighter for 256-QAM to keep constellation points in their intended locations. My -opinion- is the 180 can produce 64-QAM over a wider dynamic range. It can faithfully produce 64-QAM from -24dbm to 30dbm, where the 300 can faithfully produce 256-QAM from 3dbm to 30dbm. If the 300 was a N product where it also only produced up to 64-QAM it may also be able to go as low as -24dbm. Once again this is my -opinion- as to why the 180 has such a wider tx power range than the 300.
SSB, now thats something I havent played with in ages! Can be a bit tricky to get aligned properly, but once there they are hard to kill!
I routinely repair and test Motorola radios down to -115dbm, a few even get down to -120, but these dont pass data at speeds like the epmp's or other radios geared for data. I have had Wi-Lan and Wave Rider gear too, Wi-Lan wouldnt connect until you had a - 78dbm signal but would hold it to -90 once connected, Wave Rider would connect at -91(ish) but it would be flakey until you got into the -80 range. But in all fairness, SSB is a dirt bike vs epmp is more like a Genesis Coupe (not quite the sports car, but still just as sporty!)
Correct me on this but the receive side pre-amp input limitations of -95dbm (would be -100 but for the antenna switch and block filter) are what determines the RX sensitivity on the epmp's? The TX output amplifier is before the RF shaping filters and output antenna switch (I had a dead OOW radio so I opened it), this all has losses and takes power to get through.
To get the radio to switch to a higher modulation, the RX signal has to meet a few requirements seperate (but RX RF power is a consideration) of RF power: SNR, EBL, R-TX. These radios all start at QPSK1/2 which really does not need much for signal quality just to link.
All this is moot as using a high gain antenna and asking for less output power is the real problem. Incorrect antenna choice can create problems, it does not matter the radio used.