netgear prosafe gs110tp network switch emissions
The netgear prosafe
gs110tp is a network switch with:
- 8 10/100/1000 Mbps autosensing copper Ethernet ports
- 2 dedicated gigabit sfp (fiber) ports. It can take 1000base
sx,lx, or zx modules.
- Power over Ethernet available on the 8 copper ports.
- A power supply module.
Jorge is planning on using these
switches at the observatory/vsq's.
Luis checked this
device in the screen room on 06sep12.
- the netgear prosafe gs11t is the same switch but without
the power over Ethernet.
06sep12:netgear gs110tp switch
emissions in the screen room:
Luis measured the emissions of the netgear
prosafe gs110tp switch in the screen room on 06sep12.
and results (.pdf)
The setup was:
- Agilent E4445A spectrum analyzer:
- average 20 sweeps
- 8192 points/spectra
- 6db attenuation , preamp on
- 100 MHz span, 12.5 Khz/rbw. covering 0 to 3000 MHz in 30
- 904 Efield probe with a 15 foot coax cable.
- copper port 8 was plugged into ao net
- linksys 1GbE SX Mini-GPIC SFP module installed, but no
fiber connected to the module.
- Luis measured the emissions with the 904 Efield probe
close to the connected copper Ethernet port 8.
- He also measured the emissions at the power supply module
(external to the device).
The plots show the emissions from the
- The first page shows plots of 0-1000 MHz, 1000-2000MHz and
- The 2nd page shows some blowups around some of our
- 300-500 MHz (327,430)
- 1350-1550 MHz (lbw)
- 2000-3000 MHz (lbw)
- Emissions at
switch port 8 output (.ps) (.pdf)
- The strongest birdie is around 800 MHz at -78dbm
- page 2 shows that there are 3 combs:
- 14.2854 MHz .
- You can see it from 200 MHz up to 2000 MHz
- The strongest birdie within our rcvr bands is:
428.55 MHz at -84dbm.
- 20.8358 MHz
- You can see this from 300 to 3000 MHz.
- the strongest birdie within our rcvr bands is:
2812.83 at -89dbm
- 100.00 MHz comb
- this is seen 100 through 3000 MHz.
- I thought it might be coming from somewhere in the
screen room (our 100 MHz distribution), but it is not
seen in the power supply plots, so it must be coming
from the network switch.
- The strongest birdies is at 800 MHz at -78dbm.
- The strongest birdies in our receiver bands:
- 1600 MHz -87 dbm
- 2500 MHz -92 dbm
from the power supply (.ps) (.pdf)
- These emissions are similar but much weaker than the
port8 output. Nothing is seen about 800 MHz.
- The emissions from the switch are much stronger that the
- there are 3 combs
- 14.285 MHz
- 20.836 MHz
- 100.00 MHz
- 0 to 3000 MHz
- This comb over laps with the two previous combs:
- 7*14.285=100 MHz
- 12*20.836=250 MHz.
- The table below summarizes the strongest birdies
strongest element in 327 rcvr
strongest elements in 430 rcvr
|14.285 and 100 MHz
combs overlap here.
strongest birdie 0 to 3000 MHz
strongest birdie lbw rcvr
|100 MHz birdie
strongest values in lbw
overlaps with combs:
combs . largest value in sbw rcvr
- 'comparing the gs110t ad gs110tp switch
- The birdies occur at the same frequencies
- the gs110tp birdies are stronger
- the 20.836 comb is seen all the way down to 300 MHz in
the gs110tp device. In the gs110t it is weak below 2ghz.
- gs110tp baseline has large variations (15db) over
10 to 700 MHz with a period around 100 MHz. Part of this
is also seen in the power supply. I don't know if
this is coming from the switch or maybe the cable from the
probe to the spectrum analyzer.
- This switch probably needs to be shielded.
- We also need to test this switch with a fiber optic cable
installed to check on the fiber transceiver.
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