Posted by pegpare9 on
URL: https://www.es-forum.com/Intermodul-harmonics-mixing-signals-at-GSM-base-stations-Aaronia-Spectran-tp1543519p1543573.html

--- In [hidden email], "S. Andreason" <sandreas41@...> wrote:
>
> Hi Joris,
>
> Nice to find another Spectran !
>
> There is a changeover at 3100 MHz in the measuring/detecting that
> prevents accurate scanning across this threshold.
> I'll look up the exact wording the technical staff sent me last
year.
> The upper band can only be measured with a bandwidth of 3MHz.
>
> Do you have the datalogging software? I would be excited to
compare results. 6080).
> > The measurements in the GSM900 & 1800, and UMTS bands are (seem
to
> > be) good and normal.
> >
> > But at most GSM/UMTS base stations, I found that for example in
the
> > 5000-6000 MHz range and at 3000 MHz, there are several signals
which
> > are higher in intensity than the actual GSM or UMTS frequency
band
> > signals.
> > The signals are certainly coming from the base stations. The
high
> > values between 2099 - 3011 Mhz (and further) are only detected
at
> > base stations where GSM900/1800 and UMTS antennes are installed,
> > not at those without UMTS. The 3000 MHz frequency is normally
> > military. The high signals between 5000-6000 Mhz are almost
always
> > found at all base stations, and seem not to be WLAN (also not
the
> > typical sound from WLAN/WIFI).
> >
> > There might be some (small) errors in the measurements of the
> > Spectran
> > in these higher bands (?), and some "mirror frequencies" (not
real)
> > might exist in the range that I am measuring (at pulse mode),
but
> > I measure several ranges separately (for example the 2099-3011
MHz,
> > 5470-5725 MHz, 5725-5825MHz ranges) and found that the high
signals
> > are very clear and also hearable (audio analysis), in many cases
at
> > around 200 meters from the base ststions ca. 2-6 V/m, in
contrast to
> > the for example 0,2 - 1,2 V/m values in the GSM / UMTS bands !
> >
> > I think these high signals can be real, possibly 'intermodulation
> > interference signals' (and out of band). I read a lot on the
> > internet
> > about measured signals and that all spectrum analysers have the
> > problem
> > of second and third (...) "harmonic
frequencies", "intermodulation
> > interference" from several different base station
antennas, "mixing
> > products from harmonics", etc, and that the problem is becoming
more
> > important, as more different antennas are being installed at
each
> > base station.
> >
> > See for example
> >
http://www.tek.com/Measurement/App_Notes/2G_14758/eng/2GW_14758_0.pdf
> > and
> > http://www.summitekinstruments.com/oasis/documentation.asp
> > click on "White Paper".
> >
> > The 900 (gsm) and 2100MHz (umts) signals from base stations
could
> > indeed also mix and give something around 3000MHz, and the
readings
> > between 5-6 GHz could also be explained by (third order)
harmonics
> > and mixing ?
> > The not-real 'mirror' signals ("in" the measured range) are
normally
> > weaker, but can the real (really in the air) signals
> > like "intermodulation/mixing/harmonics" signals be more stronger
> > than
> > the original signals separately ?
> >
> > At 2400MHz, 3000MHz, 3500MHz, 5000-6000MHz, the sound (audio
> > analysis
> > of pulses/modulations) with Resolution Band Width (RBW) at 3 MHz
and
> > 1 MHz is a loud constant noice, almost the same (?) like at
> > GSM1800/UMTS
> > (base control carrier) but it seems a little different and in
most
> > cases
> > more intense. At RBW 300 and 100 kHz, the sound is clearly with
> > small
> > hard pulses (around 10 Hz ?, like woodpecker). Can anyone
explain
> > this ?
> >
> > I also noticed that when I put my GSM on (in speaking mode),
high
> > signals
> > in the 3000 MHz and 5000-6000 MHz range are also found (and in
audio
> > analysis also clearly the sound of a GSM). This can also be
> > explainedby "intermodulation/harmonics/mixing" signals ?
> >
> > Best regards,
> > Joris Everaert
> > Biologist
> > Belgium
> >
>This is why I stay a member of this group. Even though I only
understand bits of this, I know that with work I will succeed and
apply it to my situation.
Joris, I have found that locally here in N. Central Texas, we have
some techies that have found a way to combine several signals, from
several sources and the sound of taps like a woodpecker are found
like you describe depending upon the indentifier signal of the
device used. By reading your information on mixing of signals I have
determined how they are doing it.
Cities or regions are assigned numbers and that is the number of the
taps/pecks issued when activated, and a small pause, then the number
of the officer/person assigned. 5/2 for Region 4 of Kaufman County
Texas and person 2 for the person it is charged out to. The city of
Kemp is the city in region 4, and the number 5 stands for that city
I believe, or so forth. These devices are charged out to
governmental entities. Hijacking of these signals occurs.
These techies I speak of are not above harrassing others with the em
spectrum, and that is happening here, so any alleviation of RF
signals and info is welcome. Thanks again for the enlightening
information that I can understand and use.