29MHz trans Atlantic DX...

[radiogareth]

Found a spare MRF101 so fitted it up and then added ever more RF drive from a remarkably handy CA2832 HF to 200MHz 35dB gain block. This little amp really flies!! Its shown 75W (including harmonics....) on my power meter for a DC consumption of just 120W (50V DC).
So I hooked it up to my Slim Jim, having already heard the NY FM repeater today. I can't persuade my PD4=Pluto to send less than 125kS, but blow me down, I can see it on the Pennsylvania SDR!
Best I build or find a filter now......
How can I persuade a Pluto to do 66 , 35 or 20 kS? I tried using ExpressDVB Transmitter SW but it did not like the low SR's.

29.15_125ks.jpg (485.36 KiB) Viewed 6318 times

Gareth

[radiogareth]

OK, found a suitable filter and persuaded DATVEasy to send 66ks DVBS.
Now watching the SDR...
Gareth

[radiogareth]

Definitely an open path as 100W of FM makes it through fully quieting. But 1/2 the power spread over 20 times the BW is not visible. Need to sort out more power and my old ZL beam for 10m. Built in 1986, I knew I should keep it for 'one day'....
Gareth

[radiogareth]

Once I got things settled a bit, (amp output coax detached itself so proves the amp is robust into a very poor SWR...) turned it up to 75W and got the following screengrab. As its going down the garden to the Slim Jim Vertical, worth listening/watching for continentals on 10FM and having a look at some of the SDRs over there. With a 'Hamitup' converter they could theoretically receive it with a minitiouner.
Less bandwidth and more gain/watts needed I suspect.

66ks_DVBS.jpg (265.47 KiB) Viewed 6294 times

Gareth

[M0DTS]

Excellent!!

I have 0303 firmware on the pluto, it lets me go right down on DVB-S symbol rate.
You will have to generate the TS manually with ffmpeg as it's only 22kbps! at SR=18 and FEC=2/3, I have it to refine a lot yet and it's video only at 2fps right now.
Up till now it was not working right, but this gives a reasonable decode at 2fps!

Code: Select all

c:\ffmpeg\bin\ffmpeg -f dshow -i video="OBS-Camera"  -vcodec  hevc_nvenc -g 8 -s 213x120 -bf 0 -pix_fmt yuv420p -b:v 15k  -bufsize 22.1k -r 2 -preset fast -profile:v main -rc cbr_hq  -an -f mpegts -streamid 0:256 -streamid 1:257 -max_delay 120000 -pcr_period 40 -pat_period 0.4 -metadata service_name="Rob IO94IL" -metadata service_provider="M0DTS" "udp://192.168.1.68:8282?pkt_size=1316"
pause

ffmpeg can do codec2 audio encode (but maybe not now i read about it...) i'll look at that next but not sure if vlc can handle it.

SDRAngel only works well with low SNR on DVB-S hence my tests on that instead of DVB-S2.

Rob

[M0DTS]

I plan to do some more tests tomorrow, Saturday 12th Nov, between 10:00utc and 17:00utc, towards USA after 13:00 probably.
They will all be 29.150MHz, DVB-S and 18Ks to try other kiwisdr rx's.

To see if I'm on you can check my local Rx 2km away, here: http://planet3.dyndns.org:8073/?f=29150
A Map of online kiwisdr receivers is here: http://rx.linkfanel.net/

Rob

[M0DTS]

I've created a Zello channel '29MHz Digital Amateur Television' which maybe useful for coordination.

For some reason the channel can't be found in the search...
In your zello app go to the channels tab, press the add channel blue button then there's an option to add using QR code.
Scan the code below and it should be added to your list.

Rob

[g0mjw]

Working now. I am going to set up a 10m TX system today, I will also have RX should there be anyone else locally. I will try to get about 100W, but we might end up with 100mW...

Mike

[g0mjw]

OK, not as hard as I expected, 150W of DVB-S2 into a 3 element beam. All on the bench at the moment, some pictures.

lashup-1.jpg (610.27 KiB) Viewed 5971 times

It is now much cleaner, I have removed the first pre-driver amplifier as it wasn't needed and optimised the PA voltage and bias. I can get 100W at 48V, 4A from the NEC MRF300 pallet. I am using an HF low pass filter and auto ATU to match my beam.

The TX chain is a Pluto connected via USB running Evariste's 303 firmware on 149.150 MHz at 125ks or less. This is driving my 10m DATV transverter with a 120MHz LO so it comes out at 29.150MHz at about -10 dBm to 0 dBm, this is amplified by a broadband 5W PA which can produce 1W cleanly, but that's much more than needed to fully drive the MRF300. There is a 3dB attenuator before the main PA to aid stability and reduce the risk of oscillatory or user failure accidents. This then passes through a Drake TV3300-LP low pass filter to ensure the harmonics are suitably suppressed.

Still a lash up, reconfiguration into a neater system depends on the success of making contacts on 10m.

Mike

[g0mjw]

Pity everyone was out of 70cm this afternoon. Signals to the US were incredibly strong. I managed to receive my own signals via the KiwiSDR in New York and got some TS data and a few seconds of video. Still, there is work to be done. We just need someone at the other end of the QSO.

Mike