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. -- Tom Swartz On Mon, Jan 07, 2019 at 06:55:13PM -0500, Mark Russell wrote:

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 :)