Recent Posts

Multiple Feedback Band-Pass filter

Band-pass filters are filters that are designed to let only a certain set of frequencies pass through. Overtime a myriad of different topologies have been developed by some very creative designers. Passive vs active, RC-filters vs LC filters, combinations of low pass and high pass filters, with gain and without gain, etc. One of […]

40m DC-receiver – VFO

So the receiver is alive and kicking and I have received amateurs from The Netherlands, UK and Italy on a simple 10m wire antenna. However, the VFO is comprised of a Siglent SDG1032X function generator from work. Hardly a self-contained solution!After an article by Bill Merea in the GQRP Sprat magazine, I’ve decided to […]

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..

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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.

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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 […]

Sweep control oscillator

The purpose of this device is to help you sweep an audio or rf filter. It outputs a 0..10V sawtooth that can be used to control a sinus/ function generator or an rf generator. Together with a CRO oscilloscope, a millivolt meter and or power meter this can be used to accurately characterize a […]

LCR bridge

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L-meter

The usage of inductors in RF circuits is often intrinsic to its operation. Unfortunately, the measurement of small values of inductance is often difficult without specialized equipment. If, you have the ability to measure frequency, either directly with a frequency counter or indirect with an oscilloscope, this burden can easily be overcome.

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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 […]

GDO circuits bonanza !

The Gate Dip Oscillator (GDO) is one of the most useful tools for the radio amateur. You can use it to tune LC circuits, as test RF source, check antennas, etc. This GDO circuits bonanza features many previously unpublished GDO circuits from (primarily) Dutch magazines and books.

Bouwen en luisteren – IAN R. SINCLAIR

This […]