Boot Key Cruisers Net on the Net

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Boot Key Cruisers Net on the Net

Postby couillon » June 5th, 2016, 8:48 pm

Good morning all. and thank you in advance for your interest and assistance. Let me apologize for the length of this first post, but trying to get most all the info on hardware / software / configuration / etc in the initial post rather than taking up the thread posting them later...

The Project:
The Boot Key Harbor Cruisers Net is a marine vhf net that meets every morning at 0900 in support of the local community of cruising boats here in Marathon. In the winter "season" we can have as many as 300+ boats in the harbor and surrounding area. After discussions with some of the other net-controllers, we decided it would be good to push the broadcast onto the internet so folks not able to participate on the live VHF net due to moving outside the local area or time constraints like a job, can still listen

Goals and Requirements:
Eventually, we would like to be able to record and push the mp3 encoded files to the internet server unattended. Currently the recordings are started and stopped manualy using the hardware/software listed below. If we can get the physical footprint small enough and operate "headless" we may be able to convince the Marathon City Marina (one of our sponsors) to allow us to hang the system off their tower with an ethernet connection to the public wifi router. To this end, my logic dictates a RasPi2 or 3 running linux and arm compatible software. The low power requirements of the Pi would allow it to run 24/7 with recording and SFTP functions controlled by simple bash scripts. Therefor, we are looking at linux only software that also can be run from the command line only (No gui).

Hardware: (Current)

Standrd 1/4 wave loaded VHF whip antenna. Elevation aprox 15'.
Rtl-Sdr usb dongle (RTL2832U with 1ppm TCXO). Coupled direct to antenna with PL-259/SMA male adaptor.
15' usb cable (no balun)
IBM t42 laptop running linux OS

Software: (Installed)
Navigatrix OS (Debian/Ubuntu 14.04)
RTL-SDR (current latest)
GnuRadio (current latest)
Gqrx (current latest)

History, Issues, Current Status:
Initial setup using rtl_fm tested on VHF WX2 (162.4M)with good results. 1Kw station with tall tower located about 25 miles distant. rtl_fm test on Cruisers Net VHF 68 (156.425M) very poor quality do to interfering signal at about 156.125M (See gqrx waterfall screen shot below). Testing using gqrx usuable to good quality despite strong nearby signal. Encoded udp stream as mp3 using | sox and pushed to server via sftp (manual). Usuable gqrx settings as follow:

Filter: Wide
Mode: Narrow FM
AGC: Fast
Squelch: -58.5 dBFS
LNB LO: 0Mhz
Gain: 10
Freq Correction: 0ppm
Stream as UDP
Freq 156.425M

Have been unable to duplicate gqrx settings in rtl_fm after numerous tries despite going over the rtl_fm documentation numerous times. While gqrx works as long as I am here to interact with the gui, it is not command line happy as far as scheduled control via bash. Rtl_fm also has another issue with how it handles squelch. When squelch kicks in, it stops output and busts the sox recording pipe. Found a modified version that is supposed to address this issue, plus another that includes outputing a udp stream rather than a raw file, but until I can get the command line switches set up to match the working gqrx config, its kinda a moot point... One thing at a time.

Specific Questions:
Can anyone help us configure the rtl_fm command line to the same config as gqrx listed above? Any suggestions as to software we have not tried yet that will meet the requirements of command line operation? Have not tried RTLSharp yet... know it will run on linux under mono, but not sure on raspian.

If you have read this far, thanks for your patience. You can listen to test recordings on our partial website at Screen shot of typical gqrx waterfall below (no traffic on target freq).

Looking forward to your replies

Posts: 1
Joined: June 5th, 2016, 8:31 pm

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