Old Style Simple Transmitters

QST Sep. 2013. In Technical Correspondence, there is a short article "Fun With Old Style Simple Transmitters" by Larry, WR1B. The basic idea is to build the 1946 style transmitter in current technologies. It uses the 74AC540 logic chip to put out 1W of power (with 6V). Clever.

Homebrew 50W linear amp for QRP transmitter

I found an interesting article on building a linear amp with MOSFETs: Homebrew Challenge II Co-Winner, The Lowest Cost Entry (David W. Cripe, NM0S), QST October 2010.

It uses two IRF520 MOSFETs that operate in Class E mode. The technique called Envelope Elimination and Restoration (EER) is used to make this a linear amplifier. As MOSFETs are relatively cheap and the efficiency of Class E amplifiers are very good (around 90%), this is something I am interested in and I would want to experiment with sometime.

Monitoring ADS-B System

I found an interesting article from TCA July/August issue.

In All Things Digital, Robert(VA3ROM) presents an article Monitor and track aircraft using the automatic dependent surveillance -broadcast (ADS-B) system.

I may have a necessary dongle so I would try when I have a chance but these are the summaries.
- Frequency : 1090mHz/1030 mHz
- RTL2832U dongle with R8207 or E4000 tuner (for DVB-T and DAB signal reception)
- adsbSCOPE software (free)

With the stock antenna (designed for lower frequency range), the reception range is about 75kM.
There are also Internet tracking sites.
- flightradar24.com
- planefinder.net
- planetracker.net

GNU Radio & RAC Canada Day contest

It is a long weekend. I am trying to do something useful during this weekend.

One of them is to start experimenting GNU Radio as I have been interested in the software defined radio(SDR) technology and its development. I have not been so passionate though. I installed something called UHD and GNURadio as per the instruction on the website. Unfortunately, it does not seem to work. It complains my computer is missing some DLL file. I will investigate this error later.

Monday, July 1st, is a contest day. I have been participating at the RAC Canada Day contest almost every year. I have won the contest twice on the single band (28Mhz) category. The reason for choosing 28Mhz band is because it is relaxing as there are not many contacts to make on this band. Maybe I am thinking to work on 21Mhz band this year to be a bit busy. The 21mhz band is more widely open apparently and the situation would be a lot different from 28Mhz, especially considering we are at the solar maximum this year even though a clumsy one.