Version 3 Dongle

Main forum to discuss RTL-SDR related topics.
Post Reply
loureed58
Posts: 41
Joined: Tue Jul 05, 2016 11:27 am

Version 3 Dongle

Post by loureed58 » Mon Aug 22, 2016 3:28 pm

Hi

I am thinking of buying your latest dongle. I would use this with SDR# which I have successfully up and running with a cheapo dongle!!

I have what I'm sure is a stupid question! I notice that your dongle will potentially receive most of the HF spectrum down to 500khz. Is this as simple as plugging in an HF antenna and choosing a different input setting in SDR#? Do I have to input a frequency shift of -75,000,000 or -125,000,00?

Also, if I buy through your website and choose shipping from China will this be free delivery

I'm an enthusiast not a techie so hope my questions are clear!

David

rtlsdrblog
Site Admin
Posts: 2401
Joined: Mon Nov 19, 2012 11:54 pm

Re: Version 3 Dongle

Post by rtlsdrblog » Mon Aug 22, 2016 10:44 pm

Yes simply plug in a HF antenna into the antenna port. You'll need to select the "Q-branch" in the SDR# settings to enable the HF mode. No need to set the offset.

Delivery from China by airmail is free, unless you opt to pay for an express service which costs more, but is faster.

hfaero
Posts: 6
Joined: Wed Aug 24, 2016 8:32 pm

Re: Version 3 Dongle

Post by hfaero » Wed Aug 24, 2016 8:39 pm

OK, first posting but very familiar with SDR, dongles, Windows and Linux including RPi.

I bought a v3 and tested the HF using SDR# and all wen much better than I thought (https://hfaero.com/?p=3486), not bad at all.

The next thing I want to achieve is to run the v3 off my RPi on HF signals (recording audio only) at the command line. Does the CLI support just Q branch reception? I guess I'm looking for a list of rtl_fm switches that allow Q branch only rather than I & Q.

Has anyone attempted this yet?

Cheers,
Michael

rtlsdrblog
Site Admin
Posts: 2401
Joined: Mon Nov 19, 2012 11:54 pm

Re: Version 3 Dongle

Post by rtlsdrblog » Thu Aug 25, 2016 10:11 am

rtl_fm supports direct sampling, but i've never tried it before, so can't confirm if it works. To get the help screen type in "rtl_fm -h".

This gives the following regarding direct sampling:

[-E enable_option (default: none)]
use multiple -E to enable multiple options
edge: enable lower edge tuning
dc: enable dc blocking filter
deemp: enable de-emphasis filter
direct: enable direct sampling
offset: enable offset tuning

so you could probably use the "-E direct" flag. Though I am unsure if this would select the I or Q branch. Let me know if it doesn't work, I might be able to modify rtl_fm slightly to fix it otherwise.

hfaero
Posts: 6
Joined: Wed Aug 24, 2016 8:32 pm

Re: Version 3 Dongle

Post by hfaero » Thu Aug 25, 2016 8:34 pm

Thanks for the -E switch and I gave it a couple of goes using a command string like

Code: Select all

rtl_fm -E direct -f 1.548e6  -M am -s 192000 -r 4800 | sox -t raw -e signed -c 1 -b 16 -r 4800 - coast1.wav
I got a significantly larger file for the duration than if I recorded an AM airband signal, 1.2Mb vs 322kHz for about 30 seconds. This was the response when I hit ENTER on the command:

Code: Select all

Found 1 device(s):
  0:  Realtek, RTL2838UHIDIR, SN: 00000001
Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Tuner gain set to automatic.
Enabled direct sampling mode, input 1
Enabled direct sampling mode, input 1/I.
Tuned to 1836000 Hz.
Oversampling input by: 6x.
Oversampling output by: 1x.
Buffer size: 7.11ms
Sampling at 1152000 S/s.
Output at 192000 Hz.


Perhaps the "input 1/I" is a reference to the I branch?

Playing back the resultant .wav file produces a very low level noise and nothing else that I could discern.

Cheers,
Michael

rtlsdrblog
Site Admin
Posts: 2401
Joined: Mon Nov 19, 2012 11:54 pm

Re: Version 3 Dongle

Post by rtlsdrblog » Sat Aug 27, 2016 6:26 am

Hmm yeah looks like its turning on the "I branch" instead of the "Q branch" by default.

To use the Q-branch, I think the fix is very simple in the code.

Just open up rtl_fm.c with a text editor, and search for and change this line as follows:

Code: Select all

if (strcmp("direct",  optarg) == 0) {
	dongle.direct_sampling = 1;}
Change to

Code: Select all

if (strcmp("direct",  optarg) == 0) {
	dongle.direct_sampling = 2;}
Then recompile and reinstall as usual when installing the drivers on Linux. Now -E direct should select the Q-branch.

hfaero
Posts: 6
Joined: Wed Aug 24, 2016 8:32 pm

Re: Version 3 Dongle

Post by hfaero » Sat Aug 27, 2016 9:21 pm

Brilliant, worked a treat!

Command was:

Code: Select all

[email protected]:~ $ rtl_fm -f 8867000 -M usb -E direct  -p -1 -s 12k | sox  -t raw -r 12k -e signed -v 2 -c 1 -v 2 -b 16 - hf1test.wav &
and the return was:

Code: Select all

[email protected]:~ $ Found 1 device(s):
  0:  Realtek, RTL2838UHIDIR, SN: 00000001

Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Tuner gain set to automatic.
Tuner error set to -1 ppm.
Enabled direct sampling mode, input 2
Enabled direct sampling mode, input 2/Q.
Tuned to 9119000 Hz.
Oversampling input by: 84x.
Oversampling output by: 1x.
Buffer size: 8.13ms
Exact sample rate is: 1008000.009613 Hz
Sampling at 1008000 S/s.
Output at 12000 Hz.
And the recording was just great, clear, spot on 8867kHz.

Thanks,
Michael

Seasalt
Posts: 4
Joined: Fri Jan 22, 2016 8:46 am

Re: Version 3 Dongle

Post by Seasalt » Wed Aug 31, 2016 4:31 am

[quote="rtlsdrblog"]Hmm yeah looks like its turning on the "I branch" instead of the "Q branch" by default.

To use the Q-branch, I think the fix is very simple in the code.

Just open up rtl_fm.c with a text editor, and search for and change this line as follows:

Pardon me for jumping in but i would be very greatfull to know if the commands that work for rtl_fm will with rtl_tcp?

I would like to have my orange pi running armbian 5.18 being able to have my Q sampling Soft66q2 from Japan ending me tcp packet to my Ubuntu GQRX to decode.

George

hfaero
Posts: 6
Joined: Wed Aug 24, 2016 8:32 pm

Re: Version 3 Dongle

Post by hfaero » Wed Aug 31, 2016 8:42 pm

One way to find out, back up the rtl_tcp.c file, then make the change as per the rtl_fm.c file (if they exist in rtl_tcp.c), rebuild the programme and test.

Post Reply