This construction article describes a single band all solid state SSB-CW Transceiver. The complete transceiver is assembled on a single side Glass Epoxy PCB measuring 25.5 c.m. X 16.5 c.m.(10" X 6.5"). The intended output power is around 15 watts but many HAMS have managed to get around 30 watts RF output on 20 meter band.
All electronic components used in ATS-1 are available in Indian market.
Several prototypes with some variation here and there were developed and one of them is described in this article. The original set of PCB's for this version were procured from Amateur Radio Association Delhi, and PCB's are now available with VU3CAV (OM Rajani Mohan) who has dedicated this project of ATS 1 home brew in memory of his fundamental, SK OM VU2MMP. VU3AKW (OM Ashok) has been instrumental in getting the required hardware purchased from various stores in Chandni Chowk in New Delhi - and no amounts of words can describe the efforts put together by OM Rajani and OM Ashok to make this project a success. On the construction front VU2ASB OM Ashok - is leading the front with meticulous planning and construction(check download section for his inputs), with assistance from OM Rakesh VU2RAK - who has matched down the circuit and PCB print and published his finding in the public forum on this site. Back to Construction of ATS 1.
All electronic components used in ATS-1 are available in Indian market.
Several prototypes with some variation here and there were developed and one of them is described in this article. The original set of PCB's for this version were procured from Amateur Radio Association Delhi, and PCB's are now available with VU3CAV (OM Rajani Mohan) who has dedicated this project of ATS 1 home brew in memory of his fundamental, SK OM VU2MMP. VU3AKW (OM Ashok) has been instrumental in getting the required hardware purchased from various stores in Chandni Chowk in New Delhi - and no amounts of words can describe the efforts put together by OM Rajani and OM Ashok to make this project a success. On the construction front VU2ASB OM Ashok - is leading the front with meticulous planning and construction(check download section for his inputs), with assistance from OM Rakesh VU2RAK - who has matched down the circuit and PCB print and published his finding in the public forum on this site. Back to Construction of ATS 1.
The PCB contains all the sections of the transceiver : RX mixer, 9 MHz crystal filter, post filter amplifier, IF amplifier, product detector, noise limiter, AGC, audio pre and power amplifier, variable frequency oscillator (VFO), Beat Frequency Oscillator (BFO), Mic amplifier, balanced modulator, Transmit mixer, driver and power MOSFET RF power amplifier, output power sampler and complete power supply.
Since the complete TRX is on a single PCB, it may look complicated at first sight but everything being on the same PCB makes it more compact and easy to assemble. On carefully checking the PCB you will find space for more number of components and more holes drilled than required. This is because the PCB is designed to accommodate different sizes of components with the idea "if this is not available you can use that".
The only thing unique in the circuit is the use of CA7611 (an IC primarily designed for the video section of colour TV receiver), as the receiver IF amplifier, product detector, noise blanker, and audio pre amplifier. Except the audio derived AGC and the use of 761 1, rest of the circuit blocks have been taken for various HAM publications and application notes.
The lack of switching of VFO and BFO signals during TX RX change over in ATS-1 is not, what an electronic engineer would recommend, but has been used nevertheless for simplifying and minimizing the number of components.
The ATS-1 is a single conversion transceiver with intermediate frequency of 9 MHz. A 9 MHz crystal filter manufactured by Bharat Electronics Limited (BEL) is used. The carrier generating crystals are also from BEL. Crystal filter and Crystals used in BFO are available as part of the kit - that has been made available by VU3CAV.
Since the complete TRX is on a single PCB, it may look complicated at first sight but everything being on the same PCB makes it more compact and easy to assemble. On carefully checking the PCB you will find space for more number of components and more holes drilled than required. This is because the PCB is designed to accommodate different sizes of components with the idea "if this is not available you can use that".
The only thing unique in the circuit is the use of CA7611 (an IC primarily designed for the video section of colour TV receiver), as the receiver IF amplifier, product detector, noise blanker, and audio pre amplifier. Except the audio derived AGC and the use of 761 1, rest of the circuit blocks have been taken for various HAM publications and application notes.
The lack of switching of VFO and BFO signals during TX RX change over in ATS-1 is not, what an electronic engineer would recommend, but has been used nevertheless for simplifying and minimizing the number of components.
The ATS-1 is a single conversion transceiver with intermediate frequency of 9 MHz. A 9 MHz crystal filter manufactured by Bharat Electronics Limited (BEL) is used. The carrier generating crystals are also from BEL. Crystal filter and Crystals used in BFO are available as part of the kit - that has been made available by VU3CAV.
About VFO
For 20 meter band a Variactor tuned VFO with a range of 5 to 5.35 MHz is used.
By simply tuning the receiver band pass filter, transmit band pass filter for 3.5 to 4 MHz and assembling the harmonic filter at the output of power stage for 80 meter band, ATS-1 can be made for 80 meter operation without any other change. The VFO will however tune the other way round.
For use on 40 meter with 9 MHz IF frequency, the VFO will have to tune from 1.9 to 2 MHz to cover the 7 to 7.1 MHz range, the RX and TX band pass filter and the harmonic filter at the output of the power stage will have to be made for 40 meter operation. The VFO will tune the other way round in this case also.
15 and 10 meter: With 9MHz IF this ATS-1 can not be directly used for 15 or higher band because it will require a higher frequency VFO which may not be stable. If you can make a stable VFO from 12 to 12.5 MHz (for 15 meter operation) or 19 to 20 MHz (for 10 meter operation) then you can make ATSI for 15 or 10 meter operation. However a premixed VFO isrecommended for these bands. It will require addition xtal oscillator, balanced mixer and a suitable band pass filter for the premixed VFO output. There is no provision for these additional stages on the PCB. But because of improving propagation condition on the higher bands as the sunspots climb the next solar cycle; we are soon going to offer an add-on board for premixed VFO. The board will fix vertically near the VFO and will have all the necessary stages.
The ready made coils available as part of this kit are for 20 meter operation with 9 MHz I.F. The 9 MHz IF coils can however be tuned for 10.7 MHz I.F. by decreasing the value of the tuning capacitors. Therefore a 10.7 MHz SSB filters can also be used without much change.
By simply tuning the receiver band pass filter, transmit band pass filter for 3.5 to 4 MHz and assembling the harmonic filter at the output of power stage for 80 meter band, ATS-1 can be made for 80 meter operation without any other change. The VFO will however tune the other way round.
For use on 40 meter with 9 MHz IF frequency, the VFO will have to tune from 1.9 to 2 MHz to cover the 7 to 7.1 MHz range, the RX and TX band pass filter and the harmonic filter at the output of the power stage will have to be made for 40 meter operation. The VFO will tune the other way round in this case also.
15 and 10 meter: With 9MHz IF this ATS-1 can not be directly used for 15 or higher band because it will require a higher frequency VFO which may not be stable. If you can make a stable VFO from 12 to 12.5 MHz (for 15 meter operation) or 19 to 20 MHz (for 10 meter operation) then you can make ATSI for 15 or 10 meter operation. However a premixed VFO isrecommended for these bands. It will require addition xtal oscillator, balanced mixer and a suitable band pass filter for the premixed VFO output. There is no provision for these additional stages on the PCB. But because of improving propagation condition on the higher bands as the sunspots climb the next solar cycle; we are soon going to offer an add-on board for premixed VFO. The board will fix vertically near the VFO and will have all the necessary stages.
The ready made coils available as part of this kit are for 20 meter operation with 9 MHz I.F. The 9 MHz IF coils can however be tuned for 10.7 MHz I.F. by decreasing the value of the tuning capacitors. Therefore a 10.7 MHz SSB filters can also be used without much change.
Please Note
- This project is recommended for hams who have previous experience of assembling and testing of Variable frequency oscillators, crystal controlled oscillators, etc. and are otherwise familiar with testing and adjustments of RF circuits. It is recommended for those who have already made and operated on air at least a simple CW or AM transceiver.
- Following equipment are required for proper alignment of ATS-1:
- Multimeter.
- 2-30 MHz GDO (Grid or Gate Dip Oscillator).
- R.F. millivoltmeter.
- R.F. power meter -30 Watt.
- High Frequency Cathode Ray Oscilloscope (optional)
- LCR or Inductance bridge (optional)
- Other than the capacitor marked with + sign on one of their terminal i.e. electrolytic capacitors, capacitor C39, C40 and C37, and the trimmers; all other capacitors are ceramic disc type. Do not use any other type of Capacitors.
- C39, C40 and C37 are Polystyrene capacitors. They are the capacitors which are transparent and you can clearly see the wound aluminum foil inside the capacitor. If you are unable to get Polystyrene capacitors, use NPO (NP zero) type of ceramic disc capacitors instead. Ceramic disc capacitors with zero thermal coefficient are some time marked with black color strip on the top end of the capacitors.
- Before attempting to make ATS-1, make yourself familiar with the functioning of the circuit. Consult some good book on Amateur Radio electronics.
- First get the receiver portion working perfectly only then begin work on the transmitter section.
- First fix four 4mm X 25mm (or nearby size) screws in the four, mounting holes in the four corners of the PCB so that when tne PCB is placed on the Hat table, its Jrack and solder side is about 25mm (1 ") above the table surface. This is done so that when you apply power to the PCB for testing during assembling, there is no danger of any short circuit because of any lose wire pieces or components which might be lying on the table surface.
- Fix all the wire links on the PCB using about 18 SWG good quality insulated copper wire. All wire links on the PCB are marked with thin white continuous lines. First cut a peace of wire about 2.5 c.m. longer than the link length, solder one end of the wire, then pass the wire through the hole at the other end of the link then lightly pull the wire tight with a nose plier and solder in place. Do not stretch the wire to much otherwise it may break, stretch just sufficient to remove slack and kinks if any.
- Solder the four power rectifier diodes D29 to 032. Be careful about the polarity of the diodes.
- Solder all IN4148 diodes. Be careful about the polarity of the diodes.
- Starting from R1 solder all the resistances but check all the resistance with a multimeter before soldering.
- Solder all the variable preset resistances. Check all the variable presets with a multimeter before soldering.
- Solder all the non polar capacitors starting form C1, i.e. all the disc ceramic and Polystyrene capacitors.
- Solder all the trimmers.
- Solder the two PCB Relays.
- Solder PCB pins an all the terminal point on the PCB on which inter connecting wires or coaxial cables are to be soldered.
- Solder all the electrolytic capacitors, be careful about polarity.
- Solder all the IFTs, RFchocks, and inductors in the receiver portion.
Note: After soldering each components, carefully check the soldered joints for short circuits, solder bridges or dry solders. Correct if defective.
Before soldering any resistances on the PCB, first check it with a multimeter. Sometimes good looking resistances have breaks in the thin resistance film. Similarly check all the diodes and
capacitors etc. before soldering.
The chocks and ferrite transformers of the TX section will be soldered after the receiver is functional.
The active components are to be soldered section by section and each section has to be made functional one by one.
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