Milton Keynes Amateur Radio Society... |
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The MKARS80 transceiver, available from radio-kits.co.uk in association with MKARS |
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Significant interest has been shown in the construction of Pic-A-Star transceivers (see Pic-A-Star pages) by members of MKARS, but for most the Pic-A-Star is either too complex or too expensive project to take on. The MKARS 80 was designed for those who would like to build and use the radio they constructed themselves; in the design of this radio I have tried to balance complexity, functionality and cost - most of all the radio must be usable. (Click on pictures to see a larger image, where available) |
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 Pictures of the first prototype and components for 25 kits |
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| Prototype (track side) |
Prototype (component side) |
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| Brief Specifications | Completed Project |
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Frequency - whole 80M band by VFO |  |
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Modulation - lower sideband SSB | |
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Power output - >5W PEP into 50 Ohm load | |
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Sensitivity - <1uV | |
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Audio output - > 0.5W | |
| Basic Description | |
The transceiver is based on a super-hetrodyne architecture using an IF frequency of approximately 10MHz. The circuit is developed from the BITX20 designed by Asshar Farhan, however significant changes had to be made to achieve the required performance on 80M. |
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| To meet the cost target the radio has various "novel" features, these include: | |
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Use of a low cost "polyvaricon" type variable capacitor for the VFO and a large 10cm knob in lieu of a slow motion drive . |
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Frequency lock circuit - this is internal and consists of a PIC micro which measures the VFO frequency and compensates for moderate drift, frequency range is approximately 1.5kHz which is sufficient to keep the radio on tune indefinitely if operating conditions (temperature etc.) remain stable. |
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Standard discreet 10MHz crystals in the 4 pole IF filter. |
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Single board construction without the need for inter-stage screening. |
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Low cost IRF510 MOSFET transistor as the RF output device. |
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Reverse polarity protection. |
| Construction | |
| The kit of parts contains the PCB, the display and all components to be mounted on it, not included are case, knobs etc. The price is £40 including the display and £45 including case, with a £5 discount for MKARS members. To keep costs down the latest printed construction manual and revision notes are available for download via the internet. It may be possible to supply paper copies for those without access to the internet but a charge will apply for this extra service. | |
Construction has been made easier and more pleasurable by having when built in its simplest form a completely "wireless" design, though the extra options mentioned below will require a small amount of wiring as will an on / off switch if thought necessary. |
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Full support will be given to any club member building the transceiver; as most problems can be traced to poor soldering and wrongly identified components a short lesson on correct soldering techniques and component identification will no doubt be provided before construction commences. |
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 Introduction the MKARS80 at the Club |
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| Options | |
| There are several option planned some will be "built in" and others are simply plugged in to the speaker and microphone sockets. | |
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The standard kit comes complete with frequency display module if this feature is not required the display and associated components can be removed from the kit and price adjusted accordingly. |
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Future option will be an upgraded micro giving the feature of a battery voltage readout and owners call sign / message on the display at start up. The additional cost of this is estimated at £5 |
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LCD frequency and lock display - this is wired to the frequency lock micro and shows frequency to the nearest 25Hz on the top row and amount of frequency compensation applied on the bottom row. |
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PC audio interface - Plugged into the microphone and speaker sockets this module allows the PC to control transmit and receive switching and also provides the required audio level change to enable PC driven modes; SSTV, PSK31 etc. |
| More Information: | |
You can purchase the MKARS kit from Steve Drury G6ALU |
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Download the latest manuals, templates and overlays from www.radio-kits.co.uk |
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MKARS80 Yahoo group, useful information source: http://uk.groups.yahoo.com/group/mkars80/ |
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v1.25 Updated 5th October 2009
