September 2015


In the previous article, I described the features I want in this transceiver, and sketched out some ideas of how its user interface might accomodate these features. In this article, I start the construction.

[See the full list of articles in this series HERE]

The transceiver is powered from a single 12 (13.8)v source, such as a sealed lead-acid battery, bank of rechargeable cells or power supply. Protection is provided to prevent swapping the input leads, then the power is smoothed and converted into additional 9v and 5v supplies. Several connectors are provided for the various modules that comprise the complete system.

The original Easibuild’s power supply was a little simpler, with 12v being protected by fuse and ‘idiot diode’, and a little smoothing. 5v regulation was only needed by the VFO/buffer, and so was done in that unit. The receiver also converts the 12v into 8v for the NE612 mixer – I’ve retained this scheme.

In this revised power supply, I’ve added 7809 and 7805 regulation with smoothing electrolytics, and changed the idiot diode to a transient voltage suppressor. The use of transient suppression diodes, and idiot diodes generally was covered in an article in Practical Wireless, June 2015, by the Rev. George Dobbs G3RJV. Joe N2CX also has a useful article at his blog in which he recommends using a transient suppressor diode. For more on why series idiot diodes are a bad idea, see this article.

Input to the transceiver is via a Kobiconn 163-4304 power jack, available from Mouser, but Maplin’s JK09K, or Proto-pic’s PPADA610 are suitable. The matching plug for this is a Mouser 1710-2131, or Maplin HH60Q. The positive power then passes through a 1A fuse, in a 5x20mm Schurter fuse holder, and then to the switch on the volume potentiometer. From there it – and the negative from the input socket – are connected to the 12v connection on the power board.

The output power connections are 4-pin 2.54mm pin headers, which I’m using throughout the project for various interconnections.

Schematic

The schematic for the supply is shown below (click diagram for a larger version):

Construction

I’m using prototype board for many of the modules in this project, for no other reason that it’s really cheap. I bought 20pcs of the board below from an Amazon seller in China, called Hielec, for £3.30.

This prototype board is a little thinner than the Veroboard I’m used to, and the solder pads are not perfectly aligned with the holes, but it’s good enough. There are 18×24 holes per board.

The board layout I used is shown below (click diagram for a larger version):

This is the view from the component side; I mirrored the above bitmap horizontally in GIMP and printed it to ensure I got the wiring on the underside right.

It could be smaller: the layout leaves some space around the voltage regulators, so that any heat they generate is away from the nearby smoothing capacitors. Don’t want them drying out! The transient voltage suppressor is quite large, so needs the space allocated. The capacitors are around 6mm diameter. All wiring on the bottom of the board used 1/0.6mm wire, stripped as necessary. Although the circuit only takes up a few columns of a prototype board, I haven’t cut it down yet: I might need some extra board space for patching/fixups later.

Parts list

All parts were obtained from Amazon sellers, Mouser electronics, RS components, Hobbytronics, CPC, or Maplin. Some I had anyway. For detail on cost as of mid-2015, vendor website URLs of each component and where I obtained it, see the Excel parts list spreadsheet [Excel 2011 For Mac .xlsx format].

Part Value
12V_IN 2-pin male 2.54mm header
12V_IN_PLUG 2-pin female 2.54mm plug
D1 1.5KE18A transient voltage suppressor
C1, C2, C3 10μF 50V electrolytic
IC1 LM7805
IC2 LM7809
PWR1-6 4-pin male 2.54mm header
… not shown on this schematic; part of the case/front panel …
VR1 100kΩ log pot & switch
J1 Power socket; Kobiconn 163-4304
F1 1A 5x20mm fuse
FH1 5x20mm Schurter fuse holder

Testing

I assembled the board, checked for shorts with a magnifying glass, checked continuity of the main traces to the output pin header cluster, then wired it into my prototype breadboard, connecting the power jack, fuse, and on/off switch. Applying power from a pack of 10 1.2v Ni-Mh rechargeable AA cells, I measured voltages in the correct ranges on all of the pin headers.

Conclusion

This board is general-purpose, and I expect to reuse it for future Arduino Micro-based amateur projects.
In the next article, I’ll describe the Arduino digital control board….

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In the previous article, I gave an overview of the transceiver design and construction approach. In this article, I’ll consider the features I want to offer from a user/operator perspective, and how these might be achieved.

[See the full list of articles in this series HERE]

The controls of the transceiver are minimal: straight key or paddle, single rotary encoder with button, volume and on/off control, and a 16×2 LCD. I initially wanted to add a couple of other buttons to give a fancier user interface, but did not have the digital input pins available – I could extend the Arduino Micro, or use a more powerful Arduino model such as the Mega, but this would increase the cost, and anyway, minimalism and constraints often foster creativity – so, how can I offer a simple set of controls with a system that’s less expressive than early click-wheel iPods?

I am not using the key or paddle for the user interface, that’s just for transmit / keyer control.

I have the following features in mind:
Three main modes of control:

  • Normal operating mode, showing the current band/frequency. (e.g. 14.060.00) The rotary encoder allows the user to tune up/down the band, within the limits set for the band (according to your country’s allocation). One of the digits of the frequency display is underlined. This digit is increased/decreased when tuning. Tap the rotary encoder quickly to change the underline to the next digit, to allow fast tuning. (e.g. 14.060.00, 14.060.00, 14.060.00, 14.060.00, 14.060.00, then back to 14.060.00) If the underline is under the MHz (14.060.00), then the rotary encoder will switch between the configured bands. Operating the key/paddle will switch to transmit, and key the PA directly if a straight key is configured, or cause the keyer to generate the appropriate automatic keying if a paddle is configured. After the last keying signal, and the chosen break-in delay time has passed, the transceiver will switch back to receive.
  • Immediate menu, allowing access to a menu to configure the settings most likely to be used when operating. Press the rotary encoder for 0.5sec to switch to this menu, and again for 0.5sec to return to operating. The menu shows the name of a setting, and its current value. The rotary encoder allows you to scroll through the names of all the settings, showing their value. Tap the button to allow you to change the setting by scrolling through the range of possible values. Tap the button again to set the value, or hold for 0.5sec to cancel changing the value and return to operating mode. After tapping the button, you can continue to scroll through the names of the settings, or hold for 0.5sec to return to operating. This sounds more complex to describe than it actually is – there will be a > symbol next to the name or value that you are changing so show you whether you are choosing a setting, or changing it.
  • Setup menu, same as the immediate menu, but hold button for 2sec to enter this menu. Contains settings you’re likely to change less frequently.

For inspiration on the ranges of the various settings, I’ve used the same ranges I find on my Yaesu FT-857D.
The available features are (I => Immediate menu; S => Setup menu):

  • Bandpass filter 1 (S): from { RECEIVE, 160m/1.8MHz, 80m/3.5MHz, 60m/5MHz, 40m/7MHz, 30m/10MHz, 20m/14MHz, 17m/18MHz, 15m/21MHz, 12m/24MHz, 10m/28MHz } – this tells the transceiver which filters you have installed, in which socket, so the appropriate one is enabled when you switch band. RECEIVE is general HF coverage, possibly a ‘straight through’ with no filter components, with transmit disabled.
  • Bandpass filter 2 (S): as for 1
  • Bandpass filter 3 (S): as for 1
  • CW delay (S) from FULL, 0.03-3.0 seconds. This is the delay after the last keying signal that the transceiver will stay in transmit mode for, before switching back to receive.
  • CW filter frequency (S) from 400-800Hz – this is set to the fixed frequency chosen for the Hi-Per-Mite filter’s passband, and is used as the receive offset frequency. When operating, the display shows the frequency you are transmitting on, but the receiver will actually be tuned to the TX frequency +/- this CW filter frequency. It’ll be TX+ on bands > 10MHz, and TX- on bands <= 10MHz, as per convention. You don't need to do anything to switch between +/-. (Not sure what I can do about reducing confusion of listening to an image on the opposite sideband…)
  • CW input (S): straight key/single padddle/iambic A/iambic B (I have no idea about iambic modes, double paddles: I’m a straight/single paddle guy!)
  • CW Farnsworth speed (S): from 4-60wpm
  • CW keyer speed (S) from 4-60wpm. (Dit/Dah ratio is fixed: I see no need to change from the standard.)
  • CW paddle reversal (S): normal/reversed
  • Frequency lock (I): on/off (since you’ll be using the rotary encoder’s button to enter menus, change settings, etc., you may want to lock the TX/RX frequency.) Lock status will be shown on the screen when operating.
  • Macro 1 edit (S): use rotary encoder and button to edit text. Current character is underlined. Button to change it; button again to return to character choice. Choice of typical CW characters and prosigns {A-Z, 0-9, ‘.’, ‘,’, ‘+’, ‘?’, ‘/’, ‘=’, AR, AS, BT, HH, KA, KN, NR, SK, VE, ENDOFMACRO/DEL/INS}… not really sure how I’ll edit macros with only one button and a dial…I need to research 80’s video game high score table editing…
  • Macro 2 edit (S): as for 1
  • Macro 3 edit (S): as for 1
  • Macro 4 edit (S): as for 1
  • Macro 5 edit (S): as for 1
  • Macro 1 send (I): keys the text of macro 1
  • Macro 2 send (I): keys the text of macro 2
  • Macro 3 send (I): keys the text of macro 3
  • Macro 4 send (I): keys the text of macro 4
  • Macro 5 send (I): keys the text of macro 5
  • Receiver Incremental Tuning (RIT) (I): from -9.99kHz to -9.99kHz that’s added to the receive frequency (in addition to the CW filter frequency above), relative to your transmit frequency. Any nonzero RIT frequency will be shown in operating mode.
  • Reset (S): reset to default settings, with confirmation
  • Sidetone pitch (S) from 400-800Hz
  • Sidetone volume (S) from 1-10
  • Tune (I): transmit continuously until rotary encoder button pressed, for adjusting an antenna matcher (don’t overstress your PA!) – with a 20 sec timeout?
  • Version (S) shows the firmware version
  • In the menus, the key/paddle and transmit is disabled (except when setting the speed and sidetone pitch/volume, when keying will generate a sidetone and mute the receiver, with no transmit.)

    A tall order, given the limited facilities of the Arduino. I’ll have to recall all the space-saving techniques I used back in the 80s as an assembler programmer!

    In the next article, I start on the construction, one module at a time.