SDR (Software Defined Radio) with TX

In Stock:
BladeRF USD $420 – $650
USRP B200 USD $700?
LimeSDR USD $299

ADALM-PLUTO:
ADALM-PLUTO wikiUSD $99
ADALM-PLUTO: A New $149 TX Capable SDR with 325 – 3800 MHz Range, 12-Bit ADC and 20 MHz Bandwidth
Pre-Order:
LimeSDR Mini
up/down-convert 10 GHz
LMS8001 Companion
Hack:
Raspberry Pi + Rpitx + low pass filter as TX, RTL-SDR Dongle as RX
Transmitting FM, AM, SSB, SSTV and FSQ with just a Raspberry Pi

Digital Television Transmitter on Raspberry Pi:
GPIO -> QPSK (!)
Digital Television Transmitter on Raspberry Pi (GitHub)
DEMO

ideal power diode

Uses two more p-channel MOSFETs to eliminate cross conduction by forming back-to-back diodes with the body diodes of the MOSFETs.
The comparator (LM293) compares the battery voltage with the main power voltage. When the main voltage drops below the battery voltage, the MOSFET is turned on and the LED is lit.

answered Sep 27 ’14 at 8:28 CarpetPython

CarpetPython: Thank you!
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“Ideal” Power Diode
The protection circuit in the RPI model B+ functions as an ideal power diode.
Primer on PowerPath Controllers, Ideal Diodes & Prioritizers

High Side OR-ing FET Controller

smart bypass diode used in photovoltaic applications

How To: Battery powered Passive POE for Ubiquiti device

Ubiquiti device POE specifications: 10.5V ~ 25V DC

Network port pin out:
Pairs 4, 5 (+)
7, 8 (-)

For 100M device:
Use pin 4, 5 as +, pin 7, 8 as -.

For 1000M (1G) Device
We need transformers pass through data and inject power.

Plan A:
Li-ion battery x2 , 8.4V – 6V. DC-DC step-up to 14V (double volt)

Plan B:
Li-ion battery x3 , 12.6V – 9V. DC-DC step-up to 21V (double volt)

Plan C:
Lead battery x1 ,12V. DC-DC step-up to 24V (double volt)

24v passive POE power Injector:
Plan A:
ER-X SFP Gigabit POE port x5
Plan B:
千兆POE供电器 POE分离器 Gigabit Passive PoE PSI348G

P.S.
to do:
Protection?
ESD – Transient Voltage Suppression Diodes (TVS)
Lightning Surge
PTC Polyfuse 1.25A

gas tubes, reverse diodes and MOVs?
====================================================
2018 Aug 28 update:

802.3at/af :
TL-SG1005P 5 port 1000M switch (53.5V DC 1.13A input)
Single Port max 30W, Switch Max 57W.
$289 CNY

Link:
power over ethernet tutorial

DIY 1000M POE

Waterproof Ethernet Surge Protector High PoE+/ESD Gigabit 1000Mbs – Thunder/Lighting Outdoor Protection

Bourns Power over Ethernet (PoE) Surge Protection

Littelfuse : Circuit protection of IP-networked security camera systems

Protecting PoE Syste ms from Lightning and Other Electrical Hazards

RJ45 WITH INTEGRATED MAGNETICS for POE

Gigabit Passive PoE injector power over ethernet

千兆-POE供電模塊

Linux : decode APRS packet from RTL SDR

Flow:
SDR (rtl_fm) -> APRS Packet Decoder (multimon-ng) -> Network Sent APRS data (socat)
Rtl_fm Guide

multimon:
multimon-ng @ github
Command (copy from source code!)

Usage: %s [file] [file] [file] ...
If no [file] is given, input will be read from your default sound
hardware. A filename of \-\ denotes standard input.
-t : Input file type (any other type than raw requires sox)
-a : Add demodulator
-s : Subtract demodulator
-c : Remove all demodulators (must be added with -a )
-q : Quiet
-v : Level of verbosity (e.g. '-v 3')
For POCSAG and MORSE_CW '-v1' prints decoding statistics.
-h : This help
-A : APRS mode (TNC2 text output)
-m : Mute SoX warnings
-r : Call SoX in repeatable mode (e.g. fixed random seed for dithering)
-n : Don't flush stdout, increases performance.
-e : POCSAG: Hide empty messages.
-u : POCSAG: Heuristically prune unlikely decodes.
-i : POCSAG: Inverts the input samples. Try this if decoding fails.
-p : POCSAG: Show partially received messages.
-f : POCSAG: Disables auto-detection and forces decoding of data as
( can be 'numeric', 'alpha' and 'skyper')
-b : POCSAG: BCH bit error correction level. Set 0 to disable, default is 2.
Lower levels increase performance and lower false positives.
-o : CW: Set threshold for dit detection (default: 500)
-d : CW: Dit length in ms (default: 50)
-g : CW: Gap length in ms (default: 50)
-x : CW: Disable auto threshold detection
-y : CW: Disable auto timing detection
Raw input requires one channel, 16 bit, signed integer (platform-native)
samples at the demodulator's input sampling rate, which is
usually 22050 Hz. Raw input is assumed and required if piped input is used.;

socat:
socat

APRS iGate Expample:
APRS RX iGate z tunera DVB-T (RTLSDR) (Cubieboard , in Polish)

SDR Command (need test):
Decode to display in screen:

rtl_fm -f 144.64M -s 22050 - | multimon-ng -a AFSK1200 -a FSK9600 -A -t raw /dev/stdin

rtl_fm :
-f 144.64M //Frequency to tune to 144.64 mHz
-s 22050 //means to sample the radio at 22050 times/sec
multimon-ng:
-a AFSK1200 //add demodulator AFSK1200
-a FSK9600 //add demodulator FSK9600
-A //APRS mode (TNC2 text output)
-t raw /dev/stdin //Input file type raw from system stand input (?)