Poor signal with activated TII

Question

Poor signal with activated TII

andimik opened this issue 6 years ago · comments

I tried to activate TII but then my Sticks and radios either don't lock at all or get a very poor signal (Microspot 4 squares instead of 16).

Seems the null symbol causes a gain issue on the receiver side.

andimik commented 6 years ago

Qt-dab

Matthias P. Braendli · Answer 1 · Wed May 16 2018 22:31:24 GMT+0800 (China Standard Time)

What version did you use?

andimik · Answer 2 · Wed May 16 2018 22:35:11 GMT+0800 (China Standard Time)

The latest from the next. I've posted the version in the (closed) issue about edi.

andimik · Answer 3 · Wed May 16 2018 22:35:57 GMT+0800 (China Standard Time)

ODR-DabMod version v2.0.0-26-g9ef3824, compiled at May 13 2018

andimik · Answer 4 · Wed May 16 2018 22:40:12 GMT+0800 (China Standard Time)

Digital gain is 0.8

Matthias P. Braendli · Answer 5 · Wed May 16 2018 23:30:34 GMT+0800 (China Standard Time)

Ok. I also used next to do a test, enabling/disabling TII with the remote-control. I wasn't able to see any effect on my receivers :-/
Can you post your .ini file in a github gist or on https://paste.ubuntu.com/ and send me a link?

andimik · Answer 6 · Thu May 17 2018 02:14:34 GMT+0800 (China Standard Time)

Well, now I remember. When I started the issue I still had Ubuntu 16.04. Some days ago I re-installed a clean 18.04 Kubuntu. And tested it again right now. Seems we can close now.

andimik · Answer 7 · Thu May 17 2018 02:15:53 GMT+0800 (China Standard Time)

btw: My ini is:

[input]
transport=file
source=/dev/stdin
loop=1

[modulator]
gainmode =1
rate=2048000
digital_gain=0.8

[output]
output=file

[fileoutput]
format=s8
filename=/dev/stdout

[tii]
enable=1
comb=4
pattern=11
old_variant=0

more foo.eti | odr-dabmod foo.ini | hackrf_transfer -t - -f 215072000 -x 25 -a 1 -s 2048000 -b 1750000

Deleted user · Answer 8 · Thu May 17 2018 03:19:15 GMT+0800 (China Standard Time)

Hello, I'm surprised that this can work because you are using the native sampling rate which does not push the image frequencies far enough into the stop-band of the 1.75 MHz monolithic filter inside the transceiver chip. Trust me - it looked truly awful on a spectrum analyser!.;-D If you have sufficient cpu resources, try to operate odr-dabmod and hackrf_transfer at a higher sampling rate, ideally at least 4.096M. It will clean up your signal a lot and the image won't be there to clobber reception. Disable the FIR filter if you have too because it would still much better than the close-in image interference. Hope this is useful! R.

…

On 16 May 2018 at 19:15, andimik ***@***.***> wrote: btw: My ini is: [input] transport=file source=/dev/stdin loop=1 [modulator] gainmode =1 rate=2048000 digital_gain=0.8 [output] output=file [fileoutput] format=s8 filename=/dev/stdout [tii] enable=1 comb=4 pattern=11 old_variant=0 more foo.eti | odr-dabmod foo.ini | hackrf_transfer -t - -f 215072000 -x 25 -a 1 -s 2048000 -b 1750000 — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#24 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AIbPH7pf41K-ufXSFBCW1Hfu-eq5WsT7ks5tzGzbgaJpZM4Tz6_J> .

andimik · Answer 9 · Thu May 17 2018 03:28:26 GMT+0800 (China Standard Time)

Ok thanks, I'll try that instead.

Matthias P. Braendli · Answer 10 · Thu May 17 2018 03:34:16 GMT+0800 (China Standard Time)

If you read from a file, better specify the filename in the .ini over using more. cat would be more appropriate (pun not intended) because more is a pager, it could actually mess with file contents.
Thanks for reporting issues, even if this was (luckily) a false positive!

andimik · Answer 11 · Thu May 17 2018 04:30:07 GMT+0800 (China Standard Time)

Ok, thanks.

I also had to change rate=2048000 in the ini-file to 4096k.

andimik · Answer 12 · Thu May 17 2018 13:43:42 GMT+0800 (China Standard Time)

Well, I don't see a difference between 4M and 2M beside of higher traffic and CPU usage. Signal is the same. Both work here.

Matthias P. Braendli · Answer 13 · Thu May 17 2018 13:45:58 GMT+0800 (China Standard Time)

How do you measure your signal? Do you have a spectrum analyser?

Matthias P. Braendli · Answer 14 · Thu May 17 2018 13:57:48 GMT+0800 (China Standard Time)

qt-dab doesn't show a wide enough bandwidth, so you won't see the effect Rash is talking about.

andimik · Answer 15 · Thu May 17 2018 14:05:34 GMT+0800 (China Standard Time)

4096k and CPU usage 40%

2048k and CPU usage 35%

For testing (and helping FMSCAN to be updated with CSV files from Andreas Gsinn's Player) this is absolutely ok.

Matthias P. Braendli · Answer 16 · Thu May 17 2018 15:21:51 GMT+0800 (China Standard Time)

Sure. It's interesting to see that the spectrum looks a bit flatter in 4096ksps. Maybe it's just an impression though.
As long as you are aware of the limitations and consequences of using 2048ksps, this is fine.