MY QO100 SETUP

Hi,

My latest attemts to tune 2 POTY. One with white cap and one red as yours. The white prefix is W and red R. The B4 photos are before allignment. The white antenna was a first trial from someone that it seemed that it was beyond repair.

Quote from G0MJW

Yes. PLEASE DO NOT ADJUST LIKE THIS FOR MINIMUM VSWR. HOW MANY TIMES MUST I REPEAT THIS ? The same point comes up again and again and again. If you tune like that the chances are you will produce a linear antenna. HF DXCC types old antenna lore does not apply! POTY is a complex antenna.

To confirm that SV2RR get higher performance from a POTY with a little higher SWR !!! ...

Hi,

During testing a Nokia 160W max amplifier at 2.4 GHz the 250W 30 dB attenuator began to smell and then smoke. The amplifier did not burned !!! A semirigid cable was used to replace the faulty stripline PCB. Now a much better behaviour exists. More than 20 dB S11 is obtained, centred at 50 ohm while looking at Smith chart at 2.4 GHz. Replacing also the other stripline PCB is planned.

Hi,

My RF-sense probe for Nokia SSPA directional coupler out. It uses a 1N5711, a 1nF 0805 SMD capacitor and a 100nF. It produces 2V at 100W and 0.2V at 10W. It will be used for remote sensing RF power, temperature and current (using a ACS712/20A). The photo is just before adding the shielding cover.

OE3GBB A Pluto DATV repeater was tested using GNURADIO. Input was in 2.4 GHz and output at 1280 MHz. Signal was QPSK decoded and then QPSK re encoded. The tested rate is 250 ks. Stream at 2.4 was generated using F5OEO software and Rx is via Express. Signal can be received at 1280 but with Carrier lock problems.

Quote from OE3GBB

George, that's great news. To understand it right: You are transmitting using a Pluto with F5OEO software. The repeater is consisting of another Pluto running Gnuradio on a Linux PC. You are receiving with miniTiouner-Express.

Would it be possible to use a RaspberryPi for the Gnuradio repeater?
Please keep me informed about your further developments.
Regards and 73 de Gerhard

Exactly.

The final plan is to use a RaspberryPi or similar.

Also this project can be used at a satellite.

What I have to do is to improve behaviour when Carrier fails.

The idea come from the 9600 bit regeneration modem from the old days.

The advantage is that a clean signal is produced.

Hi,

It seems that carrier loss is due to CPU. So a I5 is required and R Pi seems too little.

Hi,

A DVB-S2 DATV 500KS transmitter for Pluto was tested based on Link.

A similar command produce content file.

ffmpeg -i adv16apsk910.ts -vf scale=696/392,setsar=1/1 -c:v libx265 -b:a 128K -metadata service_provider='KM17VX' -metadata service_name='SV1BDS' -muxrate 807000 temp3.ts

Tested also 8PSK & 16APSK. H265 was used.

Hi,

It is updated so 1000,500,333,250,125 can be used.

This project can be used for example as a beacon.

Hi,

A GNURADIO flowgraph is created to receive QPSK signals at speeds 1500,1000,500,333,250,125 and compute MER.

Two constants need to computed precicly.

The first is what are in constelation the coordinates of the ideal 4 points. The second is similar the ideal part of the ratio (see page 43 Link) .

Hi,

For the first this Link has the answer. For the second 1 it seems is the answer.

Hi,

A screen dump of the running app.

Hi,

8PSK is also implemented. The 2 windows below the constellations display the frequency difference between the Tx and Rx signal. If a GPSDO one is used it can be calibrated the other one. About 65 boxes was used and no Python code. It seems that 8PSK is rotated by pi/8. It seems that this is shifting the output complex data. It was tested using a Pluto but a RTL can be used. The 8PSK is a local transmission at 2.3 GHz using F5OEO.

Hi,

When I do DATV reception using a POTY feeder the MER drops to about 4 vs 10 without POTY. The same poty feeder receive NB fine. I have test various LNB and POTY feeders with out a conclusion. Any proposals or ideas?

Hi,

Thanks for the answers. The problem was that using MER for adjusting POTY position. It seems that it is suitable only for fine tuning. SNR of the beacon was too little to SR lock when I try by hand to find the best position. I found a good position using an RTL and zoom at the falling edge of beacon. A custom feeding arm must be designed. This is a project for better weather 😀 Thanks again for your notes.

Hi,

An interesting pdf about DVB S2.

You may look at fig 3 .

Hi,

OE3GBB I modify the example of DVB-T-8K of GNURADIO to receive SV8RV using 500 KHz bw 2K QPSK via QO100. I send it to VLC via UDP port. A Tx example exists also but not yet tried.

Update: A RTL was used as a receiver, so 24-1800 MHz Rx is possible.