From GNU Radio
Revision as of 06:59, 19 March 2017 by Wgebers (talk | contribs)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search
The printable version is no longer supported and may have rendering errors. Please update your browser bookmarks and please use the default browser print function instead.


This page concerns the hardware issues for a transceiver. The software design is explained by existing documentation about receiver and transmitter flow graphs.

Half or full duplex

It is necessary to decide whether you want half-duplex or full-duplex

Full-duplex is more complicated, especially if using a single antenna on the same band for transmit and receive.

Transmitter activation (PTT switches, etc)

When building a transmitter or transceiver, there are various ways to start and stop transmission.

  • always on - as long as the application is running, transmission occurs continuously.
  • widget - using the mouse or keyboard to control a widget on the user interface
  • USB microphone with PTT switch - this may be linked to a widget on the UI - example some USB microphones have a "mute" button, which is not the same as a PTT button: press once to mute and press again to unmute. Others have a true PTT button - hold it down to unmute/transmit, release it to mute/stop transmission
  • USB foot-switch - this may be linked to a widget on the UI - example
  • VOX (voice detection)

-- Hamlib --

Many commercial transceivers have some sort of serial/USB/network control interface. The hamlib project collects the low-level protocol details and provides a high level abstraction layer. In addition to PTT logic, hamlib handles frequency and mode control, and received signal strength reports. HID-PTT

The modified USB sound card interfaces are popular with the AllStar network (Using Asterisk to add VOIP linking to repeaters). Recent hamlib should know about HID-PTT too. DIY , or buy a URI from DMK Engineering

Connecting power amplifier and antenna

Based on these comments

  1. use an RX/TX path switch (only for half-duplex)
    • USRP example: control it using the USRP device's GPIO pins
  2. use a circulator (more expensive solution, suitable for full-duplex though)

Amplifier vendors:

  • Kuhne make some interesting power amplifiers that can take the low power signal from an SDR (typically 100mW or less) up to the desired level.