Posted by Joris Everaert on
URL: https://www.es-forum.com/Intermodul-harmonics-mixing-signals-at-GSM-base-stations-Aaronia-Spectran-tp1543519p1543593.html


Hello Stewart and others,

Thank you for your last message.

Yes, with a known transmitter nearby at 900 or 180O MHz, and the
Spectran set at 5-6GHz with a bandwidth of 3MHz, I am hearing
signals that can be definitely linked to the GSM. This is in
peak/pulse mode.

Here below is another test that I did (see also the messages in the
forum http://www.ralf-woelfle.de/elektrosmog/redir.htm?
http://www.ralf-woelfle.de/elektrosmog/forum/forum.php )

I checked this weekend for the "intermodulation" signals near base
stations with my Spectran HF-6080.
Oliver Bartels told me in a forum that the high signals can come from
both "real intermodulation" signals (several GSM bands, etc) and
spurious intermodulation products from "inside" the Spectran.
One way to know the difference (real/ not real) is to change the
attenuator. If the display changes by appx. 10dB with an attenuator
change of 10dB, then we talk about intermodulation products inside
the receiver, if they stay constant, then they are probably true.

Here first the results from the low (ground) signals that I have
everywhere, also without the antenna, in dBm (all with RBW 3 MHz).
All signals shown below are getting stronger with higher attenuator
setting (but not the same change), so they could be intermodulation
products created inside the Spectran (but shouldn't the signals
become less with higher attenuator then ??).

2400-2484MHz (WLAN band), peak hold.
0dB atten: -78
10dB atten: -69
20dB atten: -59
30dB atten: -57

3000MHz, 10MHz span, peak hold.
0dB atten: -32
10dB atten: -22
20dB atten: -12
30dB atten: -8

3410-3594MHz (WIMAX band), peak hold.
0dB atten: -
10dB atten: -
20dB atten: -
30dB atten: -

5150-5350MHz (WLAN band), peak hold.
0dB atten: -49
10dB atten: -46
20dB atten: -37
30dB atten: -35

5470-5725MHz (WLAN band), peak hold.
0dB atten: -43
10dB atten: -39
20dB atten: -29
30dB atten: -28

5725-5825MHz (WLAN band), peak hold.
0dB atten: -41
10dB atten: -38
20dB atten: -28
30dB atten: -26

And here below the results from near (ca. 150m) a GSM base station,
with the unexpected high signals (see previous posts).
You can see that the signals in the GSM and WLAN bands do not
change with changing attenuator, so also the high signals in the WLAN
bands could be real (not created inside the Spectran), probably
intermodulation products from the base stations signals .... because
I also hear the more typical GSM base control carrier signals and
some GSM (217Hz) pulses in these WLAN bands... Strange.
Moreover, in the GSM downlink band, the noice is much less than
in the "WLAN" bands ! In the WLAN bands I can better hear the
GSM base control carrier (or something that seems the same) and
GSM signals, than in the actual GSM bands...Hmm.
So I guess intermodulation products from the GSM base station
antennas. I will try to check that with another meter from an
official service in Belgium.
The 3000Mhz signals get stronger with higher attenuator,
so they could be intermodulation products created inside the Spectran
(but shouldn't the signals become less with higher attenuator
then ??).

So here are these results from near that base station.

GSM900 band (seem to be OK for real signals)
0dB atten: -28
10dB atten: -28
20dB atten: -28
30dB atten: -40 (?)

GSM1800 band (seem to be OK for real signals)
0dB atten: -51
10dB atten: -52
20dB atten: -51
30dB atten: -52

2400-2484MHz (WLAN band), peak hold.
0dB atten: -37
10dB atten: -42
20dB atten: - (no detection)
30dB atten: -

3000MHz, 10MHz span, peak hold.
0dB atten: -28
10dB atten: -21
20dB atten: -10
30dB atten: -7

3410-3594MHz (WIMAX band), peak hold.
0dB atten: -38
10dB atten: -39
20dB atten: - (no detection)
30dB atten: -

5150-5350MHz (WLAN band), peak hold.
0dB atten: -29
10dB atten: -29
20dB atten: -30
30dB atten: -31 (less detection)

5470-5725MHz (WLAN band), peak hold.
0dB atten: -17
10dB atten: -16
20dB atten: -18
30dB atten: -19 (less detection)

5725-5825MHz (WLAN band), peak hold.
0dB atten: -21
10dB atten: -19
20dB atten: -21
30dB atten: -23 (less detection)

That was it for now.

Best regards,
Joris Everaert