Road trip to HQ tower.. Below 5150 Rfi
last updated 20jan16
The U-NII band is an unlicensed band that starts
at 5150 MHz. Many internet providers use this band to provide
Chris salter and tapasi have been reporting (.. for many months)
illegal interference below 5150 MHz.
dana and i looked for this rfi from the 12meter site.
- Strongest rfi peaked up when pointing in the general
direction of the HQ/radioRedentor towers.
azimuth swings showed lots of rfi below 5150 MHz. It also showed
the azimuth direction where this rfi was strongest (in the cband
- 18jan16: dana and i went
back to the 12meter site. We again saw the rfi below 5150
peaking up in the HQ/radioRedentor tower direction. This time
the direction was the same to within a few degrees of the tower
(from google maps).
- 19jan16: dana and i went out to the HQ/radioRedentor towers
The road trip
We took the anritsu spectrum analyzer and
the cband (5GHz) and sband (2380MHz) helix antennas.
This page describes the cband results (find sband results here..)
We made 2 stops before arriving at the towers:
- We tried the rest stop on route 10, but it is now blocked off
with a cement divider.
- First stop was the intersection of 6612 and routine 10
- coordinates: 18.31576, 66.68288
- This is west,northWest of the towers.
- We looked at hq,radio redentor towers at cband and 2380
- 2nd stop was across from colmado torres up R611 on the way to
the HQ tower
- coordinates: 18.28576, 66.68934
- We looked out at yiyi's tower, and the tower to the east of
yiyi's tower using 5100 and 2380
- The final stop was at the base of the HQ/radio Redentor
- coord: HQ: 18.2887, 66.6606, radio redentor: 18.289535,
Radio Redentor Emissions:
The first plots show the 5 GHz
rfi from the RadioRedentor tower direction (.ps) (.pdf):
We met some people from KSXpress.net (787 487-6466.. used to be
ViVinet) working on the tower while we were at the RadioRedentor
- Top Plot: pointing at the RadioRedentor tower from the first
stop (intersection R10 and R6612).
- Black is a 5 sweep avg, red is a peak hold. the RBW was
- The dashed green line is the lower edge of the U-NII band.
- The internet channels are usually 20MHz wide.
- The signal was maximized when we pointed at the
HQ/radioRedentor tower direction.
- Bottom plot. This was standing between the HQ and Radio
- The rbw was 3MHz.
- the signal was about 15 db stronger when we pointed at the
RadioRedentor Tower (compared to pointing at the HQ tower).
- We also went under the RadioRedentor tower (to shield us
from the radio Redentor tower) and pointed back at the HQ
tower. The signal was about 20db lower than when pointing at
the Radio Redentor tower.
- Why are the relative signal strengths so different
between the two plots?
- Talking with some of the ksXpress workers we met at the
- different frequencies are used to cover different sectors.
This directional dependence is probably what caused the
large relative power differences.
- We explained the rfi problem we were having with emissions
below 5150 MHz. They volunteered to turn off their 5 GHz xmiters
for a test.
- While monitoring the RadioRedentor tower from below it, they
turned off their 5 GHz xmiters.
- I saw no change in the 5 GHz rfi coming from the tower.. so
it looks like it wasn't them.
- They told me that other Internet providers using the tower
We need to coordinate turning off the 4net and
dmWireless 5 GHz xmiters while monitoring the tower to see if it
It is interesting to note that we've had trouble with ViVinet
(old name for KSXpressnet) and 4net before..
04jun13 during a road trip to yiyi avila's tower, these
two companies were found to be broadcasting illegally below 5150
5 GHz rfi coming from yiyi avila's tower
looking for 5 GHz rfi when looking at yiyi's
The 2nd plot shows the 5 GHz
rfi when pointing at yiyi's tower from colmado torres (.ps) (.pdf)
- From the 12meter site we didn't see any.
- From our first stop on the road trip, yiyi's tower was blocked
- On the 2nd stop of the road trip (colmado torres) we
were able to get a clear look at yiyi's tower.
- The rbw was 1MHz.
- the clouds lifted before this data was taken and we could
clearly see yiyi's tower.
- The rfi peaked up when pointed at yiyi's tower. It was
weaker when we pointed at the tower to the east of yiyi.
- While talking to the workers from KSXpressnet, they mentioned
the 4net also had internet service being broadcast from yiyi's
- Looking back at the 04jun13 trip to yiyi's tower, 4net was
broadcasting around 5100 or 5110 MHz back then..
- strong rfi below 5150 MHz is coming from the radio Redentor
- When ksXpressnet turned off their 5 GHz xmiters (on the radio
redentor tower) , i didn't see any of the strong rfi go away
- If their emissions were overlapping with someone else,
i might not have noticed the change.
- DMwireless and 4net are also using the radio redentor tower to
provide wireless internet services.
- We have had trouble with 4net in the past (04jun13 on yiyi's
- When looking at yiyi's tower, there is rfi at 5110 to 5130
coming from his tower.
- i was told that 4net is also broadcasting from yiyi avila's
- Coordinate with radio Redentor tower engineer to turn off 4net
and then dm wireless 5 ghz radios.
- I'm not sure if we should be at radio redentor tower or not
when this is done. if we rely on the cband receiver, we might
miss some rfi because of the azimuth dependence.
- using the 12meter site is probably not optimal since many of
the birdies we saw at the tower, were not seen at the 12meter
- The azimuth spins also showed some weaker rfi with different
- This may be the reply signal from house back to the tower.
- We need to make sure that not only does the tower not
transmit below, 5150 MHz, but they should not request the home
users to reply at frequencies below 5150.
- After radio redentor is cleaned up, we should look again at
yiyi's tower for emissions below 5 Ghz,.