When Aquarius project became more popular many QRP-ers asked me if I could develop simple ( means duplicable) SSB version of low cost QRP transceiver. Having very limited spare time for hobby I decided to do it anyway. Prototype phase launched on October 2004 then. The project was finished 20th of January 2005. For many reasons the project is divided into three parts: RX, TX and display. Schematics diagram is rather simple and some of ideas were taken from Luc F6BQU under his kind approval. Digital readout is a local manufacturer's kit.
Prototype of RX board.
I have used very covenient MC3362P chip again.
Final look of the RX part.
I removed one crystal from the filter finally and changed all circuit.
So Taurus is equipped both with Cohn's and Butterworth's variations of crystal ladder filters.
Prototype is ready to go.
Separate PA stage was not necessary as well as I could get 4 watts from 2SC2078 transistor
And the day has come. 1st QSO with M3THB on 2 of January 2005
|1||02 Jan 2005||12:42||M3THB||46||First contact ! What a day...Too much drift of VFO ( more than 100Hz during QSO). Modulation was O.K - Barry said...|
|2||02 Jan 2005||13:29||SQ1ST/mm||57||Short QSO, no problem to copy except above|
|3||09 Jan 2005||14:02||DL4TE||58||Changed VFO coil. T50-6 instead T50-2. Good move|
|4||10 Jan 2005||18:28||SP5COK||59||Last BFO and carrier oscillator alignment. Microphone level optimised for various types of microphones|
|5||17 Jan 2005||16:45||SP5HRX||59||Short skip QSO, very low drift of VFO, but...|
|6||23 Jan 2005||15:01||MJ/PA3GIO/p||59||First QSO after final alignment of VFO ( drift less than 50Hz during standard QSO) and packing into case.|
|7||23 Jan 2005||16:22||OO7JA||51-54||Jan said - In unstable conditions your signal is very clear and stable. Good for Taurus !|
|8-28||29 Jan 2005||13:00||UBA Contest||59s||Taurus performed fine during contest conditions. Could work even US station.|
Taurus logbook with comments and evaluation
RX schematics for 20 meter band.
AGC reacts for very strong signals intentionally.
TX schematics for 20 meter band.
Good linearity of driver and PA stages. Diode based voltage reference - simple ;-))
Taurus inside view.
Digital readout is in the right bottom corner of the picture
Tarus front view
Tarus rear view
Technical specifications (general):
1. Operating frequency band - 14,100MHz - 14,350MHz
2. Output power - 4W ( strong whistle)
3. Voltage supply - 13,8V
4 Microphones - dynamic or electret
5. Frequency stability - better than 50Hz after short warm-up
6. RX sensitivity - satisfactory ( not measured )
7. Overall cost - 5 weekends and approximately 50 Euros for parts
After succesful launch of Taurus 20, new version for popular 80m band was developed. No significant changes were done except IF which was chosen for 8MHz to remain VFO circuit unchanged. If you can read Polish you may download all files of Taurus project including 80m modifications from http://strony.aster.pl/sp5ddj in apropriate Taurus section.
Some photos of Taurus 80 are shown below.
Taurus 80m - general look
RF Gain added ( simple 1k potentiometer)
Taurus 80m - inside front look
Taurus 80m - inside rear look
Taurus 80m - RX side
Taurus 80m - TX side
Taurus 80m - RX side - power meter
Good quality PCB's are available on E-mail request
Finally Taurus 40 was built in February 2006. Still no significant changes were done except IF which was chosen for 11,059MHz to remain VFO circuit almost unchanged. The best impression is RX side, which seems to be very silent.
Taurus 40 front view
There is a new switch ( upper left corner) which enables tuning ( 2W of carrier)
Taurus 40 rear view
Selected gallery of completed Taurus projects
State of the art Taurus made recently by John PD7MAA
John intorduced very helpful modifications in order to improve
VFO stability and AGC performance - Many Thanks & 73'ss