Receiver Project Notes and Errata

Here’s a collection of all the notes I’ve gathered about the project, along with updated schematics:

JARC Receiver Sheet 1 of 4 (updated)

JARC Receiver Sheet 2 of 4 (updated)

JARC Receiver Sheet 3 of 4 (updated)

JARC Receiver Sheet 4 of 4 (updated)

The capacitors are all marked, but the text is 0.5mm high, so visors or magnifiers are needed to read them. LED lighting washes out so use incandescent when sorting. Visors are available around town, like Harbor Freight.

The little blue capacitors are all measured in picoFarads, and marked with 3 digits. The first two are significant digits and the third the number of zeros. For example: 271 = 270pF while 103 = 10000pF.

Resistor values can be verified by any ohmmeter (also available at Harbor Freight).

Varactor diodes D101 and D102 are reversed from what is shown on the board. I installed only one of them and it covered the entire 40m band with the potentiometer provided. I fully expect that the tuning will extend across the entire 40m band but resistors associated with tuning may need to be tweaked into the band.

If you have not applied the Q-dope to the toroid coils you can either stop by here (Jim’s shop) after they are wound, or make your own.

The blue resistors are 1% parts and are needed for the audio filter. Unlike the 5% (tan) resistors, they have an additional digit in the identification band. For example: 39.2 kOhm – Orange, White, Red, Red, Brown – 3 9 2 (00) 1% (the 2nd red = two zeros).

I recommend that you assemble the board in layers, starting with the lowest parts first.

Boards are through-hole plated, so you only need to solder on the back side.

Wire jumpers are placed across pins 1-2 on P6 P7 and P8.

See the PDF regarding the orientation of L102. The TAPPED winding terminal is near C105.

When the toroids are mounted and soldered, they need to be cemented down to eliminate vibration.

The orientation of SBL-1 MIXER is important. Pin 1 is denoted by a different color sealant (blue).

The ICs, U1 and U2 are marked by a dot or notch at the end where pin 1 resides. On the layout U1 and U2 show a notch.

The blue capacitor marked 4R7 is 4.7 pF and is a coupling capacitor in the oscillator circuit.

The rust colored capacitors are for bypassing and are marked 473 (0.047uF) and 104 (0.1uF).

When you are preparing to install your toroids, the copper wire is insulated. “Magnet wire” is copper wire with a thin coating of varnish on it for insulation. This is done so that you can maximize the number of turns in a small space (for magnetic coupling). The varnish gives the wire a darker color, some were even green. The coating must be removed before you can solder to the copper wire.

Simply heat up your iron (hotter) and apply solder to the tip and the wire. Slide the iron along the wire while applying some solder. Heat will darken and eventually cause the varnish to come off. You can also lightly scrape the wire to remove the varnish. In any case, be sure to tin the wire before inserting into the board for soldering. Having the solder on the wire makes it much easier.