BITX20 by Hendricks Kits
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This little board should have been a ‘work first time’ too…but it isn’t.
The BITX20 was originally designed by Ashar Farhan VU3ICQ, and the aim was to use common, low cost parts. This would mean that radio amateurs in poorer countries could build a working SSB transceiver and work the world on 20m. His website is here.
Sunil Lakhani VU3SUA, made available some PCB’s, so those who didn’t want to build ‘dead bug’ style or make their own boards, didn’t need to. Here is Sunil’s website, but he sometimes sells on eBay too.
I opted for the version by Hendricks QRP Kits in the states; details here. At that time you could buy just the PCB and components kit for about $60…now, you have to buy a complete kit including case and frequency counter; $180 before carriage and UK import taxes.
Hendricks BITX20
I found the board quite fiddly to assemble…I don’t really know why, it just was. Some of the semiconductors supplied did not match the manual and I had to look up which one was the equivalent; not a major hardship but they could have listed the options in the manual.
As it is now, I have the receiver working but deaf as a post with the bandpass filter in circuit; thankfully my spectrum analyser will help with that. There are no incorrect parts or bad joints…so who knows.
The transmitter PA also takes off when you try to set the bias current…apparently there’s a mod for this. Would I build another? No, I’d go for the ILER-20 which is cheaper and almost certainly a ‘work first time’.
MKARS80 Transceiver kit | |||||||||||||||||||
The MAKRS80 is a QRP transceiver designed for use for use on the 80M band, the circuit was developed from the BITX20 designed by Ashhar Farhan. Although simple in design perceived performance is as good as a commercial transceiver. Main changes from Ashhar's original design are the inclusion of a frequency counter and a Huff and Puff frequency stabiliser; this circuit will help keep the VFO tuned to the same frequency for long periods without any 'drift'. As seen in the photo to the left, all components are mounted on to a single high quality PCB making construction relatively straight forward. The only 'wiring' needed is short pieces of wire to connect the potentiometers to the PCB. To assist with construction there is a comprehensive manual that can be downloaded from this page, also available for download are a drilling template and front panel overlay. Why not joint the MKARS80 support group? | |||||||||||||||||||
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Photo showing a typical finished MKARS80, note that the knobs supplied as an option are all black without the aluminium inserts. | |||||||||||||||||||
Downloads MKARS80 construction manual version 1.4 MKARS80 construction manual version 1.3 in Spanish Drilling template Panel overlay (Use for undrilled box only) Mirrored overlay (Use for undrilled box only) Panel overlay for use with ready drilled box Hires Schematic (JPEG) | MKARS80 PIC firmware VFO stability modification
MKARS80 construction manual V1.0 MKARS80 construction manual V1.2 MKARS80 construction manual version 1.3 NOTE: Kit version can be found on component listing in all component bags. | ||||||||||||||||||
Kit Contents The kit contains all PCB mounted components including display, connectors and a ready programmed micro. The builder will need to provide a loudspeaker (3-32 Ohms) and an electret microphone; a dynamic type can be used if the bias resistor (R17) is removed or a series capacitor is installed between microphone and transceiver. Knobs are supplied with the boxed kit as standard, they may be ordered as an option for the kit sold without a box. Neither kit comes with an overlay, you can either design a personal version or print off one of the options above. | |||||||||||||||||||
Availability Unfortunately some key parts (10MHz crystals, variable capacitor) have become obsolete, I have a small stock of variable capacitors and in order to use these up and produce a small batch of kits I'm trying to find a source of crystals, until I can do this the MKARS80 will be unavailable. Steve G6ALU | |||||||||||||||||||