Posts by SV1BDS

Hi,

Link

Hi,

Monopulse quad antenna array for finding both horizontal and vertical error angles, using GNURadio simulation flowchart.

Hi,

Monopulse direction finding GNURadio simulation.

It is used also for LEO satellites precise antenna positioning.

Hi,

Independent Rx and Tx with frequency hopping at 1.000.000 hops per second with 10240 different keys is archived. USB is used expanded to 1 MHz. Keys is from Python random generator with seed(0).

Hi,

Flowchart (for receiving) PDF and GRC attached.

Hi,

A two stations setup was operated successfully using a common RF path. Sample rate has to be adjusted in order to eliminate frequency drift between stations. It is possible for two stations to talk full duplex. Sweep rate is 10 per sec (100.000 numbers seed). In the photo it exists the two signals, one a voice and the other a pilot tone.

Hi,

Later spread spectrum experiments leads to a new possible way of spectrum management in QO100. This it would allocate 1 MHz in our example. Each spread spectrum station would sweep linear (saw-tooth) in this frequency range using for example 10.000 steps. This steps could sweep at 1 M rate. This is made them practically invisible to ordinary users. Each spread spectrum user can view other similar users as constant frequency ones but on different frequency. The difference is due to the propagation delay and different starting of 10.000 numbers seed. So multiple QSO can coexists between spread spectrum users viewing all each other and being together invisible to others normal users. Each spread spectrum user can change his 'frequency' by changing his seed initialization time.

Hi,

A direct sequence test Lab flowchart.

Hi,

Direct sequence was added and tested.

Hi,

A GNURadio flowchart was created that do frequency hopping using standard blocks. Initially a saw-tooth frequency hopping is used with progressive increment of sweep rate in order to find the correct delay using a carrier. After it was found, random key generator can be selected and also FreeDV for modulation. It must be noted that delay differs at each running. Also QO100 Doppler frequency must be known. In order for random generator to work, exact delay must be found. Random keys is produced at 1M/sec, so frequency change at this rate. They have 32768 different values leading to 32768 different frequencies. Frequency is spreading to 1 MHz. The hole system is GPSDO based.

Hi,

In DVB-RCS location of the client station is taking into account in order to estimate the variable distance from the satellite that is affecting the accuracy of the time slot. As I see the user is not giving grid locator. This is not affecting the slotting mechanism ?

Congratulations for you work !!!

Hi,

A experimental 1600 bps CODEC2 (used in FreeDV) mode is built using standard GNUradio block's. It's bandwidth is about 1 kHz, it uses QPSK and HDLC. I write it using GNUradio 3.10 using Pluto as SDR. As HDLC has CRC, no noise is heard. So it is a squelched mode.

Phase ambiguity problem is been solved for QPSK.

Hi F5OEO,

I was transmiting to QO100.

These are tests on the satellite.

Hi F5OEO ,

My setup is full duplex. There are two PC running Ubuntu 22.04 attached to a B210 USRP and to an ethernet Pluto. There is one transmitter and one receiver. A combiner for Tx and a splitter for Rx is used. Power is almost equal from two SDR and total output is not overdriving Tx. SDR Tx is at 430 MHz which is upconverted to 2.4 GHz. A split of 10 kHz is between the two signals.

Software is a TunTap interface, HDLC from gr-satellites, NRZI and BPSK as described.

No FEC is used so any error bit loose packet as it does not pass from CRC of HDLC. The bandwidth is about 2 khz from 2500 bps.

The flowgraphs must run in sudo.

If you need more info please tell me.

Hi,

HDLC from gr-satellites was used with 50 preample and response time reduced.

Hi,

An experimental IP over QO100 give positive results. It is far away from production state. BPSK,NRZI,HDLC and TunTap GNUradio 3.10 was used. 2 kHz bandwidth was used. FEC was not used yet. Delay was inserted as long packets keeps Tx on.

Hi,

A experimental 1600 bps CODEC2 (used in FreeDV) mode is built using standard GNUradio block's. It's bandwidth is about 2 kHz, it uses BPSK,NRZI, scrambling and HDLC. I write it using GNUradio 3.10 using Pluto as SDR. As HDLC has CRC, no noise is heard. So it is a squelched mode.

Hi Gerhard,

I just use FreeDV for testing my frequency hopping setup.

Hi Gerhard,

I use the 1600 mode of FreeDV. I use it's own data transfer.

Hi,

A GNURadio flowchart from my frequency hopping attempts.

100-300 KHz of spreading is archived with 10.000 hops per sec.