Hi there,
I’m hoping there is something simple I’m missing out on here…
I recently just purchased an RB711UA-2HnD and set it up, the goal was just to add a short 1km boost on my existing wireless network.
For this I made a 12db gain yagi antenna and got it all set up. I had some radio guys I know test the antenna on an Anritsu SiteMaster and it came back looking good with just shy 2% reflection. I configured the router to use Antenna-B on Chain-1 as indicated on the wiki and set the transmit power to 29dbm. Then I did a quick coverage test, which basically showed only a tiny bit more signal than my non-directed retail linksys router, (just about 15 meters away from the window my yagi is set up in). Any further than that and the signal disappeared. From the napkin math I did I should easily have enough signal to make a decent connection 1km away, so I’m at a loss as to why the signal strength is so poor.
When I log into the RB711 RouterOS reports the device as outputting 27-28db, (Even when it’s configured for 30db). To be sure it wasn’t the antenna or the cabling I tested the antenna on the Anritsu all the way up to the MMCX connector on the pigtail that hooks up to the router.
I also did the test of the connector as described in the hardware wiki and that came up milhouse so I’m kind of at a loss here.
The only thing I can figure is that the radio power amplifier is broken or not working. This thing is new out of the box and I didn’t play with it at all until it was all setup. Also I noticed that there are a bunch of test points on the circuit board, would any of these allow me to test whether or not the power amplifier is working? Is there some other way to see if the output power is off?
Any ideas would be appreciated, I’m way beyond my own level of comfort with this!
I did some simple tests…
It still seems like the power is off. The amount of drop I get from one spot to another seems to hint at the transmit power not being reported properly… is this normal???
Most of these high powered cards and boards have a note that the actual power output may vary by 1 to 2dB. 27 instead of 30 is a bit more, but we’re talking a sub $100 board here.
99% of the time if you can’t do it with 27dB you can’t do it with 30 either.
If you check the link here it shows a test that I did.
The transmit is reporting between 27dBm and 30dBm,
But the receive is tested at -30dBm only a few feet away on a spectrum analyzer.
Here is the test setup:
The antennas are both highlighted with red boxes.
The router had an MMCX to R-TNA adapter and a standard WRT54G omni connected.. The spectrum has a R-TNA to BNC connector with the same WRT54G omni.
For the first test the transmit power was reported by the router at anywhere from +25dBm to +30dBm.
This had both of the radio chains enabled and the antenna configured as “antenna-b”.
As shown here:
The spectrum analyser reported the receive at -24.23dBm at the distance described in the test setup.
The second test I only had chain-1 enabled and the antenna was again configured as “antenna-b”. The transmit power mode was set to ‘Default’. The router reported that it was transmitting at +23dBm to +27dBm
When tested on the spectrum my receive was at -30.86dBm. Which is about a 60dBm loss across the space of less than 2 meters. From other posts I’ve read on here the napkin math calculation for 2.4Ghz loss is 100dBm per Kilometer?
I’d like to reiterate I’m not an expert by any means but it doesn’t seem to me that this is correct. This as well replicates what I had found in my coverage test with the Yagi attached.
The spectrum analyzer was set to measure max dB. When I browse the config site, this would be communicating, at least in the fact that it’s a TCP connection that is ‘open’ and the spectrum analyzer would be reporting the maximum dB measured during that period. How much of a dB loss would it have when ‘not communicating’? Would that account for a 60dB difference? Or a difference of 5 to 10dB which only scaled when transmitting files?
What is the standard dB that the radio transmits at when it isn’t communicating?
My only point of reference is a regular radio repeater, which when configured to transmit at 5W will transmit at 5W.
A signal of -28dBm as reported by the spectrum analyzer is roughly 0.0015mW. How would you initiate a 1K link, between two devices that perform like this at all? Let alone a 100M link? There is a baseline for transmit power and it surely would be greater than 0.0015mW measured at a distance of 2 meters.
I have access to a spectrum analyser. What can I do to determine if this is functioning properly or not?
