3 Dec
2020
3 Dec
'20
4:04 p.m.
Dear forum,
I am setting / running GSM network with LimeSdr and Osmo-packgaes:
osmo-bts-trx
osmo-bsc
osmo-hlr
osmo-msc
osmo-pcu
osmo-stp
osmo-trx-lms
and as i understand the only option to vary / set up output power is through the →
osmo-bsc →
trx 0
nominal power 23
! to use full TRX power, set max_power_red 0
max_power_red 20
So does this mean that 23-20=3 dbm?
With this set up i instruct LimeSDRmini to transmit 3dbm signal into the air? If so —
when i brought phone just into the very vicinity of LimeSDR antena (touching phone and SDR
antena) on my smartphone screen i got signal -60 dbm …why did i get such a low figure ?
Also if you know is there any supporting application / software that can tell at what dBm
LimeSDRmini is sending RF into air?
--
Mario Lucas
4 Dec
4 Dec
2:42 a.m.
No, AFAIK that value is the attenuation in the PGA stage, with 0 being no attenuation. You
will need to measure the output power at the required frequency yourself, these devices
are not precision calibrated.
Depending on frequency, the Lime boards can output as high as 15 dBm CW with 6-9 dBm being
the medium value across the whole supported spectrum.
Adrian
On December 3, 2020 9:04:22 PM UTC, Mario Lucas <mariolucas75(a)mail.ru> wrote:
Dear forum,
I am setting / running GSM network with LimeSdr and Osmo-packgaes:
osmo-bts-trx
osmo-bsc
osmo-hlr
osmo-msc
osmo-pcu
osmo-stp
osmo-trx-lms
and as i understand the only option to vary / set up output power is
through the → osmo-bsc →
trx 0
nominal power 23
! to use full TRX power, set max_power_red 0
max_power_red 20
So does this mean that 23-20=3 dbm?
With this set up i instruct LimeSDRmini to transmit 3dbm signal into
the air? If so — when i brought phone just into the very vicinity of
LimeSDR antena (touching phone and SDR antena) on my smartphone screen
i got signal -60 dbm …why did i get such a low figure ?
Also if you know is there any supporting application / software that
can tell at what dBm LimeSDRmini is sending RF into air?
--
Mario Lucas
15 Dec
15 Dec
5:23 a.m.
A very later follow up, sorry:
On Fri, Dec 04, 2020 at 12:04:22AM +0300, Mario Lucas wrote:
and as i understand the only option to vary / set up
output power is through the → osmo-bsc →
trx 0
nominal power 23
! to use full TRX power, set max_power_red 0
max_power_red 20
So does this mean that 23-20=3 dbm?
OsmoBSC and OsmoBTS have been developed primarily for GSM-specific radios with
calibrated,
defined output levels.
Using a general purpose SDR we really have no way of knowing what the output power will
be,
and it differs from unit to unit as well as on the frequency you use. It's all a big
mess :(
In the ideal world one would actually be able to purhcase factory-calibrated SDR
boards that came with a data file (or even stored on internal EEPROM) that would
tell you on which Tx port at which frequency and temperature dbFS (full scale)
results in what kind of absolute output power in dBm.
If the SDR manufacturers would ship such calibration data, life would be so easy.
--
- Harald Welte <laforge(a)osmocom.org> http://laforge.gnumonks.org/
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participants (3)
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Adrian Musceac -
Harald Welte -
Mario Lucas