We are using the devices which are mentioned in the subject. However we wanted to do simple RF tests to prove its performance for a distance of upto 20kms. I had posted an issue with these devices in another topic in the same forum which was answered by Mr.Jarda . However, we feel that there is a need to perform some basic RF tests using Spectrum Analyzer & Vector Signal Generator. Basically we wanted to perform some basic RF tests to prove the link capability & determine the maximum distance that can be obtained with these devices. Can anyone please suggest some basic tests that can be performed ? Please let me know if this is not the right topic under which I am posting. Thanks a lot for your time.
Thanks Inox, That is a good start. We can now compare the theoretical values we obtain with the practical ones. But basically I wanted to know if there are any practical tests which I can perform with the radio in a lab using spectrum analyzers ? I wanted to practically measure the distance that can be obtained by simulating the same conditions using a vector signal generator & a Spectrum Analyzer. Like using a variable attenuator to decrease the power levels at the receiver & verify the distance. So I wanted some direction towards this as I am new to RF testing. Thanks a lot for your time.
I was thinking with the variable attenuator we will attenuate the signals received & thereby check the signal power level in the spectrum analyzer. Will that not work ? Also for MIMO is there a certain set of test procedures that I need to follow ? I just want some basic RF tests to verify the distance at least approximately.
I am not a radio specialist but the distance is adding a delay also. How this are you going to simulate? When using attenuation, you attenuate the noise too. But it will not be attenuated in real life. And many more things that have influence on the link quality at bigger distances you cannot easily simulate. You can just see if the device works, make preliminary settings but that’s all you can do in lab. The rest need to be done outside…
That makes sense. Thanks a lot. I can probably check only if the rated power output is obtained from the radio. The rest needs to be checked on the field.
We did a simple test with the Mikrotik Metal & a 3W Power Amplifier (http://www.l-com.com/wifi-wlan-cellular-amplifiers-3-watt-24-ghz-80211b-indoor-amplifier) available with us. However the Power Amplifier is specified for 802.11b standards. On the ROS we were getting a Tx CCQ of only 28%, whereas without the PA we were getting the CCQ to be 90% and above. The distance between the TX & the RX is about 1m. Is it because the PA is not specified for IEEE 802.11n standards ? The input stream into the PA was an rtsp and was well below 2Mbps. Therefore I too feel it is a problem with the PA. I will update you soon with more tests from the field.
Each amplifier adds distortion to the signal. When you scream too much on the receiving antenna, the receiver is overbuzzed and cannot clearly hear the details. Imagine yourself on the concert right in the front of the speaker and 100m away… Where your reception will be clearer and richer in details?
Is it because the Tx & Rx are placed closer, the reception is not of good quality ? If they are taken farther apart then they should work better with the improvement in the CCQ ? I will try doing that as well & post the results.
Amplifiers are garbage. No matter the distance.
I don’t see the gain of amplifing 30dbm to 35dbm. 30dbm is enough. Also I’m pretty sure that’s a peak power. And if it is used indoors, it will be even worse.
Pigtail has some loss.
I do agree that the amplifiers add a lot of distortion & non-linearity. But we require transmission of HD quality videos for longer distances (about 10kms or so). So I thought Power Amps would greatly help in boosting the signals. Another solution for this might be better antennas on the transmitter & the receiver. However we are limited by the size of the antennas on the transmitter !!! So can there be any other solutions ? We already use a 15dBi directional antenna on the ground!!
Hmmm… I do have a 18dBi patch from L-Comm & a TP-Link Sector of 24dBi. Lets see if I can hook it up ! Also we have the setup the Mikrotik Metal on both transmitter & ground, the connections are as follows :
Transmitter : Configured as CPE & is connected to a HD camera whose encoder provides frames at a rate of 30fps & bitrate of 1Mbps to 5Mbps that is kept constant throughout the transmission (720p). We have a 3dBi antenna connected at the transmitter.
a) Band : 2GHz (B/G) (b) Mode :Bridge (c) Frequency : Auto (d) Tx/Rx Strength : 32dBm/-20dBm (e)TX CCQ : 91 - 100 %
Receiver : Configured as WISP AP to which the directional antenna is connected . The other parameters remain the same & the RX CCQ is also the same.
The above is tested in our assembly area and is working fine. But are the above parameters good for mobile links ? Or is there any other major parameter which needs to be taken care of ?
We tested with the above settings & obtained a distance of 3.5 Kms . The CCQ was around 54% & RSSI was -68dBm when the connection was lost. The next thing to do is to use a higher gain antenna on the ground. I will update with those results as well.
Thanks a lot for the suggestions. Did exactly as per your suggestions & now we are able to obtain a HD video for just above 10Kms. The CCQ & the RSSI were even better (about -60dBm) at that range. Overall the video was quite good. The time for testing was limited & hence we were not able to go further, but I am sure we will be able to achieve more than 15 Kms at least. Thanks a lot for the support jarda. Is it possible that in any way we can get your mail id (maybe not through this thread ) because we might have more orders that will be coming for mikrotik & might require support at higher levels !! Thanks a lot for your time.
!!! So can there be any other solutions ? We already use a 15dBi directional antenna on the ground!!
) because we might have more orders that will be coming for mikrotik & might require support at higher levels !! Thanks a lot for your time.