OFDM vs OFDMA

OFDM vs OFDMA

The 4th video in the series of the 802.11ax training videos. In this video I explain the difference between OFDM and OFDMA and introduce the concept of RUs in the 802.11ax standard

Dual Band ANT performance in The 6GHz Band

Dual Band ANT performance in The 6GHz Band

Looking at the S11 and S21 parameters of dual band ANTs shows acceptable performance up to 6.7GHz. In the photos below 4 markers on the S21 parameter graph can be seen. MK1 was set to the beginning of the 2.4GHz band, MK2 was set at the beginning of the 5GHz band, MK3 was set at the last frequency in the 6GHz where the dual ANTs still gave acceptable levels of performance and finally MK4 was set at the end of the 6GHz band (7.2GHz) where the performance degraded by a factor of 6dB below the performance measured in the 5GHz band.

Note: For more info on the S-Parameters and what do they mean you. this page https://www.antenna-theory.com/definitions/sparameters.php gives a simple and clear explanation of the concept.

The Setup
Measuring the S11 (Reflect Coefficient)
Measuring the S21 (Transfer Coefficient)

A New Milestone Achieved !

A New Milestone Achieved !

On the 23/02/2021 at around 10:00am I took on a 4 hours exam an attempt to achieve the iNARTE Spectrum Management Certification. The exam was challenging, I wouldn’t say it was difficult but, definitely it wasn’t an easy one. For anyone who might be interested in taking on the exam a good background in Electrical Engineering principles and a fair knowledge of HAM radio rules regulations and best practices will definitely be a big a help to clear this exam. Finally, you can check my certification by clicking on the link below.

Experimenting with the Hackrf

Experimenting with the Hackrf

The Hackrf is a small affordable SDR (software Defined Radio) that can operate in frequencies up to 6GHz with a channel bandwidth of 20MHz. This makes it an excellent choice when it comes to experimenting with WiFi. One of the few drawback of a Hckrf is the lack of amplification on the Tx side. In this experiment I was successful in amplifying the transmit signal of a Hackrf by 30dB using a Skyworks FEM ( Front-End Module).

GNU radio is used to generate an 64 tone OFDM signal which is forwarded to the Hackrf. I will be writing a detailed post on how to replicate this experiment in the future. For now I would like to share with my readers short videos showing the difference in Tx power with and without the a FEM.

Without a FEM, received signal level from the Hackrf is around -60dBm

With a FEM, received signal level from the Hackrf is around -30dBm