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?
Features
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Full 80M LSB coverage (3.5 - 3.8MHz)
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~ 5 Watts output power
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Single conversion superhet with 4 pole crystal filter
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Frequency display with "Huff and Puff" circuit for stabilisation
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Modulation monitor - helps stop over modulation
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Volt meter - useful for battery operation
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Reverse polarity protection (fuse protected)
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
Latest version for currently supplied kits.
MKARS80
construction manual version 1.3 in Spanish
Thanks to Jon EA2SN for the translation
Drilling
template
Printout with Adobe Acrobat
reader, set paper size set to A4 and page scaling set to "none". Stick
onto case as described in construction manual and use as a drilling template
for the holes and cutout.
Panel
overlay (Use for undrilled box only)
Print and laminate as a front panel, alternatively use the mirrored overlay
below.
Mirrored
overlay (Use for undrilled box only)
Print on acetate and use as a front panel, the print will then be on the
reverse side so it doesn't become scratched
Panel
overlay for use with ready drilled box
Print and laminate as a front panel.
Hires
Schematic (JPEG)
Bold
Text Schematic (PDF)
Two different formats of schematic which will be easier to read than that
in the manual
MKARS80 PIC firmware
Download and modify for your own use, perhaps the easiest modification
is to change the startup screen to include your own callsign. This will
require the installation of MPLAB, download from the Microchip
website free of charge.
VFO
stability modification
Makes a significant improvement to the VFO stability on early transceivers,
this was incorporated into the kit from Dec 2008
Old data
MKARS80
construction manual V1.0
Only for use with kit version V1.0, this has minor component differences
so don't use with other versions
MKARS80
construction manual V1.2
For kit version V1.1 and V1.2
MKARS80
construction manual version 1.3
For kits supplied prior to 20-03-2016
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
