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
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@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
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.
baseband-devel@lists.osmocom.org
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Adrian Musceac -
Harald Welte -
Mario Lucas