I notice that when I configure a DekTec radio in my output, the gain value is automatically set to 50dB. When I edit the output to be interference, the gain value drops to 30dB. Why does Skydel set this to 30dB and do I need to change my hardware configuration to account for this?
30 dB is the nominal gain value on the interference output. It has been calculated to maximise the jamming power while keeping the noise floor of the jamming output under the thermal noise (not to jam the GNSS signal when no interference is activated).
Yes the setup must be adjusted to the RF gain configuration. With attenuators you must bring the absolute power of GNSS and interference outputs to the same value. For example, with RF Gain set to 30 dB for interference and 50 dB for GNSS, you have to put 20 dB more attenuation on the GNSS signal.
hello @pmleveel ,
could you, please, explain the reason, why we
must bring the absolute power of GNSS and interference outputs to the same value?
I understand why we must add 50dB attenuation between GNSS output and Antenna LNA:
for GSG-842 we have GNSS output GAIN = 50dB.
means, that output power of GNSS output is -130dBm + 50dB = -80dBm
in Live Sky situation on Antenna we shoudl have -130dBm
So we are adding 50dB Attenuation between GNSS output and Antenna LNA to get -130dBm - OK
consumer grade Jammers which you can buy on Amazon or ebay have output power around 0dBm
so in theory in Live Sky conditions i can have case when on GNSS Antenna is present Interference signal with power = 0dBm (lets consider distance between Jammer and GNSS antenna = 0m)
To get Interference output level = 0dBm we should set Interference reference power = -30dBm (-30dBm + 30dB (GAIN) = 0dBm)
is my connection scheme correct to have GNSS = -130dBm and Interference = 0dBm on Antenna LNA?
GNSS ref.power = -130dBm on Skydel, RF output GAIN=50dB (default) - > Attenuator 47dB → 2way combiner (3dB loss) → Antenna LNA
Interference ref.power = -27dBm on Skydel, RF output GAIN = 30dB (default) - > 2way combiner (3dB loss) → Antenna LNA
Hi @kchereshnev ,
We took a look at it here and the answer is yes. your connection schemes look correct.