40m DC receiver – “It’s alive!”

With a three day Pentecost weekend and my wife away on a camping trip with my son, I had some time to look into the receiver again. With the previous series of tests, I’ve found that product detector was working fine and featured good conversion gain. The LO oscillator injection was flawed because the […]

Double-balanced cross-coupled product detector

The double-balanced cross-coupled product detector had a brief stint of popularity in the 70s and 80s. It’s popularity quickly faded once integrated product detectors like the Plessey SL640, Motorola MC1496/1596 and the CA3028A came on the market. Offering ease of use and further integration. My attention was first drawn to the cross-coupled product, when […]

Brickwall audio filter

For my 40mDC receiver, i was looking for a good audio filter that I might reuse for multiple receivers. While browsing in old magazines I came across a filter designed by Robert Penfold. It was featured in an article in Ham Radio Today March 1986 (see download section).

The brickwall audio filter […]

40m DC receiver (2)

After my previous attempt at building a 40m DC receiver failed (I received nothing but noise while at my Kenwood HF receiver, plenty of signals were heard), I made some changes to improve the sensitivity and to add some features that were desperately needed..


40m DC receiver (1)

The design for this receiver is based on an earlier design by Steve KD1JV. it is build around two analog switches TS5A3157. These switches have on resistance of ca. 5.5 Ohm 10 times smaller as the often used 74HCT4053 switches.


Gain distribution in DC receivers

For an upcoming 40m (7Mhz) DC receiver that I am working on, I wanted to know the necessary gain. After building the first prototype, the output was kind of quit. So the question came up, how much gain do I really need for a DC receiver? Back of the envelope calculation : to get […]

Walkie talkie (2) transmitter

Below you see the block diagram for the walkie talkie transmitter.

Transmitter block diagram

The carrier oscillator is crystal controlled to guarantee sufficient stability. It is much easier to create a frequency stable carrier by means of a crystal than with an ordinary LC oscillator. The latter would require carefull selection of components and […]

Walkie-talkie (1)

Lately my 6 year old son has gotten interested in walkie-talkies. Now, I could go to the nearest toy-store and buy something but where is the fun in that? Since, he is getting more interested in technology it would be nice to design something that he can, at least to some extend, help me […]