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My Plan

Posted: Tue Apr 23, 2019 3:38 pm
by 2i0jmt
Hi Folks

I'm completely new to Amateur Satellite, and I just wanted to write down my current plan for those who are interested, and hopefully get some feedback.

Right now, I have an RTL-SDR connected to my Sky Dish (still pointing at 28.2). My LNB is powered by a satellite receiving using a splitter (the other output going to the RTL-SDR with a DC-block F connector)

I have the following things on order:
90cm offset dish, with an Octagon Green Single LNB
Dmyco V8 satellite finder
25m of RG-6 (twin feed)

Next steps:
1) Try and improve my SNR on NB SSB RX. Hopefully this should be pretty easy compared with my 60cm Sky dish pointing the wrong way
2) Try and receive the DATV signals from OSCAR-100. Using the above equipment, should I be able to receive the DATV signals from OSCAR-100 ? Or is my dish too small?

Once I get good RX, I'll then try to TX SSB ....

3) Purchase a LimeSDR-Mini and get it going with SSB RX (with SDRSharp on Windows)
4) Try and get SSB TX on 13cm working with the LimeSDR-Mini, probably using SDRAngel. I don't really know how to test this though - can the LimeSDR RX at the same time as TX?
5) Purchase an ebay 2.4Ghz 8W PA and build a 2.5 LHCP antenna that can fit infront of my Octagon LNB, and try to talk via Oscar-100!

Once all that works, I'll then try to TX DATV ....

6) Try and get DATV TX across the shack from the LimeSDR-Mini to my MiniTiouner (on 13cm). Probably use DATV-Express for this
7) Try and use my 8W PA + 90cm dish to send DATV to Oscar-100. Could this work with a really low bandwidth?

Any comments or suggestions welcome, thanks!


Jonny 2I0JMT

Re: My Plan

Posted: Tue Apr 23, 2019 5:08 pm
by g8vpg
I think you are wise to concentrate on receiving first and get this sorted before moving onto transmit. Setting up a satellite reception station will teach you a lot. I believe that the LNB you have ordered is a PLL type; this is essential. The Technomate TM1 is another good alternative.
A 90cm dish will give excellent results on the NB transponder for both transmit & receive, and good results on ATV reception. It might be a bit marginal for ATV uplink; most stations use 1.1-1.2m, which are available for less than £100 on Ebay.
When it comes to aligning the 90cm dish, ensure the support pole is vertical and preset the elevation according to the scale on the mount. The Sat-finder should have some preset beacon channels for BADR4/5/6 on 26E, so you can use these to align the dish. Do a scan and you should find BBC Arabic, which I use to fine tune the dish position. It can be a bit frustrating because as you tighten the clamps, it tends to pull the dish off heading.
Good luck with your plan. There is lots of information on this site and questions usually elicit some helpful responses.
73 Shaun.

Re: My Plan

Posted: Tue Apr 23, 2019 7:39 pm
by G3VZV
Hi Jonny,

As Shaun has said it sounds like a good plan...the satfinder may not be necessary as, if you are already able to see NB signals, albeit weakly, with the dish pointing at 28E, then it should be possible, using the same LNB, bias tee and SDR to align the new 90 cm one by looking for signals directly on the waterfall. They should be v much stronger of course.

To receive the WB transponder simply rotate the LNB 90 degrees and you will see the WB beacon (and perhaps other DATV signals) in the waterfall.

To decode/display these DATV signals just attach the minituner...and yes the Lime Mini can do TX and RX at the same time.

Graham G3VZV

Re: My Plan

Posted: Tue Apr 23, 2019 7:59 pm
by 2i0jmt
Thanks folks for the reply!

Indeed, the sat finder isn't really that useful for Es'hail2. Purchased it more just for regular TV sat finding.

Yes, I was thinking that 90cm might be a bit marginal for ATV uplink. If I were to stick to around 100KS/s, do you think it would be possible? If so, how much power would I need? Basically, I'm hoping to be able to ATV uplink *something* to the satellite with only 8W and 90cm dish, even if the image is very low resolution.


Jonny 2I0JMT

Re: My Plan

Posted: Tue Apr 23, 2019 8:10 pm

driving a 8W WiFi-PA with a LimeSDR will not work. The gain of those amplifiers is approx. 10dB and LimeSDR only provides 0dBm@2.4 GHz. You need another 20+ dB gain to drive the WiFi-PA.

Do it step-by-step. Narrowband works even with 25mW at the dish for CW.

Wilm, DL4OCH

Re: My Plan

Posted: Tue Apr 23, 2019 9:39 pm
by 2i0jmt
Thanks Wilm, that's good to know that I'll need a preamp. Hopefully shouldn't be too hard to find. Any suggestions on a model?

Also, I'm scrapping my 90cm dish order and changing it to 1m. Hopefully that will get me a bit further with my datv experiments

Re: My Plan

Posted: Tue Jun 11, 2019 5:47 pm
by 2i0jmt
Hey Folks

Just to update this post.

- Managed to RX both NB-SSB and DATV from Oscar-100 using my 1m dish. MER of the wb beacon is about 6.5, 6.9 on a good day. SNR about SSB is about 24. I can just about see the transponder noise floor, so I don't think a bigger dish will help me with NB RX.

- Managed to get my LimeSDR-Mini TX'ing DATV from 66ks up to 1000ks. This was tricky for me, but got there in the end. I'm using IPTSIN on the Portsdown. My Windows PC outputs OBS to a seperate running instance of ffmpeg, that makes the video a constant bitrate, then sends that off to the Portsdown.

- Using a bandpass filter, 3 small ebay gain stages, and the "8W" (prob about 2-3W) ebay WiFi PA, and a £10 wifi panel antenna (supposed to be 14dbi, but I doubt it) leaning on a box looking out the window, I managed to have a couple of QSOs on NB. Eyeballing the signal meater in SDR Console showed an SNR of about 13. Signal reports were 5/5 and 4/4. See photo attached.

I've also ordered a 17dbi Yagi WiFi antenna. Let's see how that fairs.

I know I should really work on doing my tx properly by using a dual-band patch on my dish, but I'll need to figure out another coax run (my shack is over 40m away cable length wise), outdoor gain stages and power. As I've mentioned in other posts, I enjoy doing things not using the best equipment to see how far I can go :)



Re: My Plan

Posted: Fri Jun 14, 2019 12:15 am
by 2i0jmt
Managed to upgrade my WiFi Panel to a 17dBi yagi. The audio modulation into the satellite seems to be improved, and visibly looking at the waterfall, you can now see the signal appear across the full SSB bandwidth (albeit faintly). It's still quite weak though, but getting readability reports of 5.