- This topic has 11 replies, 1 voice, and was last updated 15 years, 6 months ago by Pix.
22nd June 2006 at 06:45 #45275RFGuest
theses days we pass by strange interference really i have never see like it before , mostly of our site are affected by this interefernce and it’s happend on the sites near by the sea and not all ( there are some sites near by the sea and not affected) but all the sector which there azimuth are oriented to the sea are affected , and this interference happend at the same time , can somebody advice ?
for more details we have already analyzed the spectrum in whole the PCS band and also from 1.5 G to 2 G and the noise floor ( when the antenna oriented to the sea) is very hight ( -87dbm)
our frequency is 1.9G,
please advice22nd June 2006 at 07:41 #45276StveGuest
Problem seems due to different layer density of air. When the air density reaches a certain level where the refraction index becomes enough for total refraction of the signal then refracted signal reaches destination with different time difference which may cause this type of interference.24th June 2006 at 06:30 #45277RFGuest
what do you avice ?8th July 2006 at 00:55 #45278PixGuest
You could simply modify the density of the air… 😀
Don’t you think this phenomena shall be very rare ? Usually such refraction would propagate the radio waves further away (= ducting effect ?), but refracting back to the original emitting point… that’s weird. I know nothing about this, but your post is very interesting.
What about external interferer ? (army radar ?)
Did those intereferences occured only at certain time of the day ? Are they still occuring ?
When you did your spectreum analysis, did you shut down your sites ? Or are you measuring frequency bands that are not used ?
If you find -87dBm noise in frequency bands that you are not using, it’s either a very weird natural phenomena or an external radio device… a powerful one.
Please let us know 🙂8th July 2006 at 19:35 #45279RFGuest
this phenomena happen random but almost everyday , and when we made frequency scan our sites was on, we can’t switch off all of them!!!!
waiting your replay
best regards10th July 2006 at 16:49 #45280PixGuest
you’re facing a problem i’ve never seen before… i will not be able to help much, but doing frequency scannings and communicating with the local army is a good start ?
i undestand you can’t switch your sites off 😀
One thing you didn’t answer : are you measuring signal in frequency bands you’re not emitting with your sites ?10th July 2006 at 21:01 #45281RFGuest
yeah i have already scaned whole the CDMA band ( include the frequency that we dont emitting on it )
and i have another problem i have never seem before some subscriber make registration in two differents BTSs are from differents BSC at the same time11th July 2006 at 04:21 #45282TufailGuest
U said “some subscriber make registration in two differents BTSs are from differents BSC at the same time”
then its true tht the signal frm ur own n/w r ducting thru air to da area of interference..
in my opinion u better optimize those sites under which the subs r registering, without being in there area…
i feel like this..
hope it may help.
tufail11th July 2006 at 09:55 #45283Tech ManGuest
If I can correctly recollect it, there was a similar problem faced by another team elsewhere. The external interference problem in that case emnated from the sea too ! Then, the cause of the problem was found to be a High Power marine radio on a Merchant Ship parked off the coast, which illegally using the same frequency band as the GSM service provider.
Check it out, you might be facing a similar situation.11th July 2006 at 19:33 #45284PixGuest
Yep, you have an illegal external emitter somewhere above the sea. Better call the cops, mate 🙂
The two identical registrations might not be related to this issue. Are both cells using the same radio ID ? (i’m not sure about CDMA, the way the registration works ?)11th July 2006 at 20:00 #45285RFGuest
do you think this interference come from ships?we have already made frequency scan and show that all the band are affected by this interference(1.5G to 2G) CDMA Band 1.9G!!! and what more in the same site only the sector are oriented to the sea are affected and others are normal!! and in some others sites two sectors are oriented to the sea one affected and the other one are not affected
and for the registration it’s the same as frequency update in GSM
best regards11th July 2006 at 23:48 #45286PixGuest
you are saying : the whole frequency bands are polluted by noise, even the ones we’re not emitting on.
Therefore, something must create that polluting signal (signal = energy… you need a source somewhere because energy doesn’t appear by itself).
Something on the water, creating a strong high-freq radio signal ? Well, yes, a ship. Or a whale. A geeky one… 🙂