Bandwidth Reduction from 800 kHz to 200 kHz

ON4VRT-OO1A · 2021-03-09T18:53:09.455Z

Thanks Syed.

maxboysdad · 2021-03-09T21:55:35.062Z

@Syed
@kenbarbi
I haven’t seen it addressed in this thread yet, but Syed stressed to us in the past that SKEW was really important. It really didn’t cause a lot of change with the old setup, but on this new bandwidth, I discovered this morning for the first time that skew was making a huge difference at this frequency and LNB. If you are receiving or not receiving, check that your skew is set correctly, and when receiving, manipulate your LNB a bit clockwise or counterclockwise and watch your SNR. You, like I did, may get a very pleasant surprise.

BillMc · 2021-03-09T22:59:53.861Z

So does anyone have a Maverick LNB working? I have scanned through multiple frequencies 5kHz at a time, I can get the frequency error within 100Hz but never achieve lock. I am on an old DISH500 dish and used to get about +3 SNR(dB) before the change. Now I seem to see about -11. I like the idea of checking the skew but I have to wait for about 2 feet of snow to melt before I can reach the LNB.

maxboysdad · 2021-03-10T00:24:20.622Z

Hi, Bill. I was at -13 and -14 with no lock since the change over. My Maverick just couldn’t hold the frequency, I guess, either. I then put my dual frequency LNB on the unit, and still could not get a lock, sometimes not even a signal. This particular LNB didn’t work well when it was new, either, as I recalled. Ken @kenbarbi logged into my unit and worked pretty hard one night and got it to work for an hour or so, but it didn’t hold, either. This morning I took the LNB from my portable v.3.05 Dreamcatcher, and installed it on my old Moto-Sat dish. After a little tweaking of the frequency, I got it to receive, but it was still -11 to -14 without lock. Finally, I twisted the LNB in both CW and CCW and found a spot where SNR jumped up to +6, so I got down off the roof and came inside. Fortunately, our snow is just about all gone for this storm, so it was just basically climbing up with the 8-ft ladder to the patio roof.

Mr_B · 2021-03-10T02:55:29.612Z

Just a technical thought about the problems with the Maverick LNB. I split my dual freq LNB output again and feed it to my HackRF to see what the spectrum around our target signal looks like. Here’s what I saw-(frequencies noted are center frequencies of signal).

12088.650 MHz–600 kHz wide signal
12089.400 MHz–200 kHz wide signal-Our Target Frequency
12090.850 MHz–600 kHz wide signal
12091.600 MHz–600 kHz wide signal

I looked for the adjacent frequency rejection specs for the Maverick but couldn’t find any. If the receiver section of the lnb is weak on rejecting nearby frequencies, there could be bleed over from a nearby frequency corrupting the transmitted data and not allowing the Dreamcatcher to lock-on. I also looked at the spectrum for the previous Americas downlink frequency to see what conditions were there but the satellite company has re-channelized that area of the spectrum so that didn’t help. Anyway, just some techno-geeky thoughts. Have fun.

Tysonpower · 2021-03-10T21:40:46.965Z

Maybe the little App i made helps people finding the right Frequency faster, Feedback is welcome of course

Satellite Frequency Finder App for Skylark Othernet Software

I made a small App based on javascript that uses the API of Skylark on the Dreamcatcher 3.x that should make it a lot more easy to find the right Frequency for the new Beam. It has the Following Features so far: Showing the current Beam / Frequency Settings that are Setup in Skylark Showing the Current Tuner Status in Realtime (updates every 500ms) Setting the EU / US Beam to the newest Frequencies that are in the Script in/decrease the Frequency of the Custom Profile by 5khz with one Button p…

Cheaha · 2021-03-10T23:24:32.370Z

@Tysonpower This is awesome! I’m still not able to find a signal but man this is so much easier to use. Thank you.

I have tried everything I can think of to get any kind of signal at all. No joy. I have re-aimed, added a horn, and used a short run of cable. Still no joy.

LNB:
Avenger PLL321S-2
Single KU LNBF
L.O.: 9.75 & 10.60 GHz
N/F.: 0.1 dB

Capture

Update #1: I have purchased a replacement LNB of the same model, in hopes that my LNB is the issue. I will let you know when I have swapped and tried again.

Update #2: New LNB and I can finally get some signal on 12089.6 but only for a few seconds. It’s strange if I make small changes to the freq (12089.55, 12089.65,etc) I get signal for a few seconds but then it stops. After that, nothing happens unless I make another small tweak to the freq…then a few more seconds and it stops again.

Update #3: Changed LNBs again. This time the Bullseye. Now I can find the frequency where it should be and the signal is much more stable. I went ahead and stuck it on an old DirecTV dish and now I’m getting a +4dB SNR.

maxboysdad · 2021-03-11T00:27:38.945Z

Pretty snappy! Thank you!

image1000×561 50.1 KB

BillMc · 2021-03-12T00:44:40.699Z

I tried the app and it seems very helpful, although I figured out the settings page the first day. The problem remains that while I am able to cancel out Frequency error from the LNB, the Maverick WON’T get lock. What say you, Sayed? Is the only option to upgrade the LNB or is there another option in the works? Has ANYONE gotten lock with the Maverick?

Snow is down to 18" from 24". Once it gets down to 6", I can play with skew or put my Bullseye LNB on it.

I appreciate this is difficult but I don’t think I am the only one this affects. BTW, I signed up for 2 years on the LibraPay.

Syed · 2021-03-12T02:04:46.014Z

I prefer that you do not purchase a new LNB. One thing to understand about the Maverick is that it is the least stable of the LNBs. It can be off by as much as 1000 kHz.

Also better to wait until you can adjust skew.

donde · 2021-03-18T05:46:08.141Z

Syed … It is possible to make a change in software so Status is not blank at any time. This would help because now we have to deal with more variables than before. Antenna orientation, the right frequency and drift, Maverick maybe not good enough, much narrower bandwidth. Just started today. Blank Status. Made small incremental frequency changes up from 12.0894 as shown by others. Absolutely no signal. Changed out LNB. Same thing. Pointed 35 cm dish close to what I had before. If Status wasn’t always blank until it got a signal, should it not be easier for success?

Syed · 2021-03-18T06:00:11.434Z

I don’t think I understand. How would a non-blank Status help? The reason that it’s blank is because no packets have been received. The packets provide the signal information to the software/UI.

caveman99 · 2021-03-18T09:17:54.309Z

I’ve been reading up a bit on codec2, which indeed seems to have a very good speech quality on low bitrates. Since i still not have given up the newsradio idea, i stumbled upon this article:

http://www.rowetel.com/?p=5966

That means, using codec2 as-is for a good shortwave quality signal (DC4 standalone), but using a deep learning postprocessor to improve the sound way above the Shortwave level (listen to the audio samples linked from that article). That would mean either using powerful deep-learning hardware on-the-fly or using a pre-trained neural network which would exceed the tight memory on the ESP32. That would be another use-case for our ‘Front-End’ ARM device, providing better sound quality through a WaveNet (from the same narrowcast signal).

Tysonpower · 2021-03-18T11:07:44.040Z

I already had a look at Codec2, despite that it it is really nice i wasn’t able to find a way to generate a File that can be played in a Browser. As an Alternative i had the Idea to use a 5min News summary in 6kbs opus format, it would give us great sound quality and some what useable file sizes to transmit 5min of audio every hour or so besides the other files.

If you get a small codec2 file that can be played in a Browser let me know

caveman99 · 2021-03-18T11:37:37.652Z

The offline/podcast of a newcast in ogg format is doable. Attached a sample NPR news bulletin in 8kb/ss (for this quick test, VOA only offers 32kb mp3 files which sound awful converted.) and the original file in 128kb/s mp3nprnews.mp3.gz (4.4 MB) nprnews.ogg.gz (390.5 KB)

Tysonpower · 2021-03-18T11:43:48.912Z

I made a VOA 5min news in opus 6KB/s that sounded okay in the past as a test, with only 230kb it is very small: https://tynet.eu/storage/downloads/VOA_Newscast_6Kbps.opus.

caveman99 · 2021-03-18T11:48:16.092Z

codec2 is still brewing up something here… you can always expand it to something uncompressed before sending it to the client browser.

donde · 2021-03-18T13:16:35.552Z

OK. I thought it would go blank if no valid RF signal on the tuned frequency was present. My mistake.

caveman99 · 2021-03-18T14:55:36.448Z

I have done a few offline tests with the same NPR news bulletin in codec2. Source material was converted to 8khz 16bit mono. At 2400bps (which is roughly the current payload of the downstream) it sounds (in my opinion) better than the 8k opus files on the old broadcast. At 1200bps it still produces good intelligable audio (of course not music, but news and special interest programming), and we could interleave that with the file stream. That would mean about 50/50 files and radio. Im just hoping i don’t falsely assume that the entire bandwidth is available for payload data… :-). What would it take to run a test over the current system, maybe even using a DC 3.06? the running aplay needs to be changed from 48kbit to 8kbit sampling, the rest of the format is right. Biggest task would be a modification to the current audioserver binary supporting codec2 in addition to opus.

Syed · 2021-03-18T15:11:38.476Z

A test only requires clear instructions on what you need. To be clear, this wouldn’t be compatible with Skylark. Are you thinking about running it on DC3 with Armbian?