Good evening - I am trying to make modifications to rtl_fm so that I can change frequencies, gains, modulation types, and squelch values on the fly (and thus avoiding a restart).
Its unclear to me what functions need to be called in order to apply changes to the sdr device so that I can do the above. The rtl_fm code isnt documented so I dont have much to go off of...
GQRX doesnt run reliably on any RPi3's I've tried so I hoping to use a modified rtl_fm in its place. Any help would be appreciated. Thanks :)
Any reason that you couldn't use rtl_tcp instead?
It's pretty common to run rtl_tcp on a remote RPi server, then use a different, local computer to host GQRX. Squelch, frequency changing, and other features should be available via that protocol presently.
At first I thought rtl_tcp was the way to go, but after looking at the code, it doesnt seem to support wide band FM, which led me to rtl_fm instead.
Also, when using rtl_tcp as a server, I found my signal strengths were weaker when connecting to the rtl_tcp server with GQRX. I changed gqrx back to use the USB dongle directly and then i click the hardware agc checkbox - which gives me better signal strength.
Is that not typical behavior? Maybe I'm not configuring something correctly?
Thanks :)
On Mon, Jan 7, 2019, 18:16 <tom@tswartz.net wrote:
Any reason that you couldn't use rtl_tcp instead?
It's pretty common to run rtl_tcp on a remote RPi server, then use a different, local computer to host GQRX. Squelch, frequency changing, and other features should be available via that protocol presently.
-- Tom Swartz
On Mon, Jan 07, 2019 at 05:01:37PM -0500, Mark Russell wrote:
Good evening - I am trying to make modifications to rtl_fm so that I can change frequencies, gains, modulation types, and squelch values on the fly (and thus avoiding a restart).
Its unclear to me what functions need to be called in order to apply changes to the sdr device so that I can do the above. The rtl_fm code
isnt
documented so I dont have much to go off of...
GQRX doesnt run reliably on any RPi3's I've tried so I hoping to use a modified rtl_fm in its place. Any help would be appreciated. Thanks :)
Hey Mark:
I'd happily be corrected, if it proves otherwise but I just gave it a shot locally.
My setup was: rtl_tcp streaming over ethernet to a LAN host running GQRX 2.11.5
Wide FM worked as expected, tuned up to a local broadcast FM station no issues. NFM also worked, and I received a local ham repeater on 2m band.
I did notice that the gain values were different in GQRX's GUI when switching between rtl_tcp and rtl_sdr drivers. Perhaps that subtle difference in gain values were what you had seen? I was not using Hardware AGC in either instance, but I set the values via the slider. rtl_tcp reported: `set gain 372` (and other values) when I adjusted the GQRX gain sliders.
Perhaps someone else with better knowledge of the agc/gain settings can speak to why you may have been seeing a difference with the AGC enabled.
-
Mark Russell -
tom＠tswartz.net