Tagged: tutorial

Tutorial on Properly Positioning a Preamp (LNA) in a Radio System

Radio blogger Anthony Stirk has made a post on his blog explaining some critical concepts behind understanding why it is important to position a low noise amplifier (LNA) near the radio antenna, rather than near the radio. In the post Anthony explains how the Noise Figure (NF) and linearity (IP3) of a radio system affect reception.

Using the free AppCAD RF design assistant software, Anthony explains how the noise figure of a system increases with longer coax cable runs, and how it can be reduced by placing an LNA right next to the antenna. He also explains why the sensitivity of the radio won’t increase if the LNA is placed close to the radio instead.

In addition to this, he also explains why adding more LNA’s to a system decreases the linearity (IP3) of the system and that if the receiver has a built in LNA that the system linearity can be severely degraded by adding extra LNA’s, causing easy overloading and intermodulation. In conclusion Anthony writes the following:

In summary, a setup with a good antenna system connected to a receiver with a built in LNA:

  • May not benefit from having a preamp at the antenna.
  • The presence of a built in LNA is detrimental to the linearity and may degrade the signals.

So in conclusion:

  • Put the preamp as close to the antenna as possible.
  • Receivers with a built in LNA may not get the most out of an antenna system or preamp.
  • Proper gain distribution guarantees better performance than one-size-fits-all solutions, both in terms of sensitivity and strong signals handling.
Optimal Setup: Antenna -> LNA -> Coax -> Receiver
Optimal Setup: Antenna -> LNA -> Coax -> Receiver
NF and Linearity Calculations
NF and Linearity Calculations in AppCAD

Micheal Ossmann’s Software Defined Radio Course

Micheal Ossmann, creator of the HackRF is starting an online video course on the topic of software defined radio (SDR). His course will cover GNU Radio and will help you to learn the fundamentals of digital signal processing. The first video has been released and in this video Micheal shows how to set up a broadcast FM receiver in GNU Radio.

To do the exercises in the course you will need a HackRF or other similar SDR radio. Most exercises involving reception only should be compatible with the RTL-SDR with some small modifications relating to things like the changing sample rate.

New RTL-SDR Book for Beginners

Recently this year, Akos from the SDR for Mariners blog has put out a bunch of RTL-SDR tutorials aimed at complete beginners – that is people without any radio knowledge at all.

Akos has now gone ahead and created an ebook titled “Radio On A Tight Budget: RTL-SDR For Everyone”, which is purchasable from Amazon. Akos has mentioned that his book is not just his blog in book form, but something new. The blurb is as follows

Hands-on guide to hear to world using the 10-dollar RTL stick. Easy-to understand text covers software installation, antennas, noise reduction, guides from shortwave to airplane information reception – and many more. Diagrams and photos help the beginner, common tools and materials used: no soldering or expensive gear used. Useless tales, anecdotes, complicated theoretical explanations left out: only relevant information included.
If you ever had problems setting up the RTL stick, wish to significantly improve your reception or simply want to hear airplanes talk to tower, receive AIS information on a yacht or track airplanes, this book is for you.
Radio On A Tight Budget: RTL-SDR For Everyone
Radio On A Tight Budget: RTL-SDR For Everyone

SDRSharp Video Tutorial

If you’re new to the world of low cost software defined radio, and have just been through our Quickstart guide, this YouTube tutorial video by Clayton Smith on using the SDR# program may be useful to you.

In the video Clayton explains how to use SDR# and some of its many features, how to calibrate the RTL-SDR offset in the software,  and he also shows how to receive a few interesting signals in his area.