Tag Archives: electronics

Hard-to-find faults and other homebrew ‘Gumption traps’

I recently cut this small piece Veroboard to hold two vertically aligned miniature potentiometers on a receiver front panel. The three soldered tracks to the right allow connection of the audio signal to the volume control using shielded twin conductor cable. Very standard stuff, I’ve been wiring up audio amplifiers to volume controls like this for about four decades. But this one wouldn’t work. It has a fault — it’s there, in the picture above, right in front of your eyes… can you see it?

Continue reading

Advertisements
Tagged , , , ,

Veroboard at radio frequencies

Charlie ZL2CTM has been pushing out a series of excellent videos on his YouTube channel that take you through the circuit design, making and testing of superhet SSB transceiver modules.  Yesterday my eyebrow involuntarily raised ever so slightly at his use of Veroboard as the substrate for his latest 8MHz crystal filter.  Veroboard? At radio frequencies?  Veroboard et les fréquences radio ne sont pas compatibles!

Continue reading

Tagged , , , , , ,

VK3YE’s ‘non-invasive’ LED-LDR AGC add-on

When I saw the AGC circuit by Peter Parker VK3YE, I realised it solved a problem common to many simple homebrew receivers.  You cannot automatically control the gain of a receiver with fixed gain stages. Most simple receivers do not have IF stages, let alone variable gain IFs. And the LM386 has no gain control. So it’s easy enough to sample the audio at the volume potentiometer, amplify it, rectify it for a source of AGC. But then you need a voltage controlled gain stage ( a Voltage Controlled Amplifier  or VCA).  If your receiver doesn’t have one, AGC won’t work, and you with have to either add a VCA in the receiver somewhere or replace one of the fixed gain stages with a VCA.  Until now.

Continue reading

Tagged , , ,

Saving an Arduino-controlled Digital VFO frequency over a power cycle

Following the success of My First DDS VFO, complete with Arduino script programming, I found myself interested in mimicking more of the features of the digital dials in ‘real’ rigs. Like dynamic incremental speed-tuning, where the tuning rate increases or decreases dynamically depending on how fast you spin the dial. More on this later. A more achievable feature is to have the band, mode and VFO come up on the frequency where you left it at the last power-down. This involves writing these parameters into the Arduino’s EEPROM, using the EEPROM library.

Continue reading

Tagged , , , , ,

More power to the activator (choosing a new LiFePO4 pack)

When the time came recently for a new battery, I jumped onto HobbyKing and was bewildered by the range of options, even after limiting the search to a particular current capacity, in my case 4-5AH, and 4S (4 cells). Wishing to leverage the ‘wisdom of the SOTA crowd’, and at risk of reopening the “whats the best battery for SOTA” chestnut, I posted to the yahoo SOTA_Australia group:

I’m buying another LiPo from HobbyKing. This battery will be for general purpose 5 watt txcvr use, but will also be used to power an afterburner of the W6JL type, using a pair of IRF2Z24N hexFETs, for up to 50 watts. My question is, what do I make of the discharge figure on the LiPo packs, which varies from 10c to 35c? I presume this is the rate at which the battery can supply current under load, the higher the better. A higher discharge figure might be important when powering an afterburner, which might draw current peaks of many amps on voice peaks. Prices seem to correspond with higher discharge figures, from as low as $25 (10c) up to $55 (35c) for packs around the 4AH rating.

My only current Li-XXX asset.  

Continue reading

Tagged , , , , , ,

Artisan Printed Circuit Boards

I have been hand-making printed circuit boards since I was a teenager.  In the late 1970s I started with ‘proper’ PCBs, hand-drawn, hand-drilled, then painted with resist (bituminous paint) thinned with turpentine and applied with a tiny brush to form the copper traces, drilled holes on the copper side, etched in Ferric Chloride, cleaned and sprayed with a clear enamel to stop tarnish.  This was the way all circuit boards looked at that time, including commercially made ones in kits, and those inside transistor radios, digital clocks, televisions and ham radio transceivers.

Sometime in the 1980s I tried a ‘copper side up’ board, dispensing with the drilled holes, free-hand drawing on the copper side, painting and etching, then soldering the components directly to the copper pads. I’ve been making them this way ever since.

Continue reading

Tagged , , ,
Advertisements
Homebrew Amateur Radio

Homebrew Amateur Radio and Electronics.

W3JDR Bright Ideas

For Ham Radio Experimenters

ZL4SAE

Amateur Radio and Stuff

WB8NBS

My Projects

The Dragon and The Phoenix

Bard's Journey into the Collective Subconscious and How It Shapes Our World

Bryce Dombrowski's Projects

electronics engineering and more!

VK1 SOTA on 1.2 and 2.4 GHz

Andrew VK1AD | Amateur Radio | 23cm 1296 MHz | 13cm 2.4 GHz | Summits on the Air

designerlythinking

Design thinking, enterprise architecture, systems thinking, theory and practice.

Ripples in the Ether

Emanations from Amateur Radio Station NT7S

Hackaday

Fresh hacks every day