ESTRATEGIAS METODOLOGICAS Y MATERIAL DE APOYO PARA LA DISCAPACIDAD

signals, to produce an aural output that is differentially coupled to a LM386 audio IC. The audio amplifier IC is coupled to the headphone jack at J2 by capacitor C16. The receiver circuit is power from a single 9 volt transistor radio battery.

Let’s get started! Before we begin building the 80/40 meter receiver, you will need to locate a clean well lit and well ventilated work area. A large table or workbench would be a suitable work surface for your project. Next you will want to locate a small 27 to 33 watt pencil tipped soldering iron, as well as a roll of #22 gauge 60/40 tin/lead solder and a small jar of “Tip Tinner,” a soldering iron tip cleaner/dresser, from your local Radio Shack store. You will also want to secure a few hand tools for the project, such as a pair of small end-cutters, a pair of tweezers and a pair of needle-nose pliers. Locate a small Phillips and a small flat-blade screwdriver, as well as a magnifying glass to round out your tool list. Grab the schematic, parts layout

diagram as well as the resistor and capacitor identifier charts and we will begin our project. Place all the project components on the table in front of you. The 80/40 direct conversion radio is an RF or radio frequency project and it is best constructed on a printed circuit board with large ground plane areas covering the board for the best RF grounding techniques. Once you have all the parts and PC board in front of you, heat up the soldering iron and we’ll get started!

First, find your resistor identifier chart in Table 9-1, which will help you select the resistors from the parts pile. Resistors used in this project are mostly small

1_⁄

4watt carbon composition type resistors, which have

colored bands along the resistor body. The first color band should be closest to one end of the resistor body. This first color band represents the first digit of the resistor value. For example, resistor R2 has four color bands, the first one is a brown band followed by a green band followed by a black band. The fourth band is gold.

The first band is brown, which denotes a digit one (1), the second band is green, which represents a digit five (5), and the third band is black, which represents a multiplier of zero (0), so the resistor value is 15 ohms with a tolerance value of 5%. Identify the remaining resistors for the project and we can begin “populating” the PC board. Place a few resistors on the board at one time, so as not to confuse the process. Make sure that you place the correct resistor into the correct PC location before soldering it in place. Once you solder a few resistors in place on the PC board you can use your end-cutter to trim the excess component leads. Cut the excess leads flush to the edge of the circuit board. Then place a few more resistors on the PC board and solder them on to the board. Remember to trim the component leads as necessary.

Next we will locate the capacitors for the 80/40 meter receiver. Capacitors are listed as electrolytic and non- electrolytic types. The non-electrolytic types are generally smaller in value and size as compared with the electrolytic types. Non-electrolytic capacitors, in fact, can be so small that their actual value cannot be printed on them, so a special chart was devised as shown in Table 9-2. The chart illustrates the three digit codes which are often used to represent capacitors. For example, a .001 µF capacitor will have (102), while a .01 µF capacitor will have (103) marked on it to

represent its true value. Use the chart to identify the small capacitors in the project. Non-electrolytics have no polarity markings on them so they can be installed in either direction on the PC board.

Electrolytic capacitors are usually larger in size and value and they will have a white or black band on the side of the capacitor body or a plus (+) or minus (−) marking on the body of the capacitor near the leads. These markings are polarity markings and that indicate the direction in which the capacitor must be mounted on the PC board. Failure to observe polarity when

installing the capacitor may result in damage to the capacitor or to the circuit itself, so pay particular attention to capacitor polarity when placing the capacitors on the board. Note that the receiver can be built for either the 80 meter ham band or the 40 meter ham band. You will need to look at the parts list when deciding which band you want to receive. The inductors L1, L2 and L3 as well as capacitors C3, C4 and C5 determine the band selection.

Let’s go ahead and place some of the non-electrolytic capacitors on the PC board. Identify a few small capacitors at a time and place them on the PC board and solder them in place. Trim the component leads after. Go ahead and install the remaining non-electrolytic capacitors after choosing your desired band. Install the capacitors and solder them in place, remember to cut

Table 9-1

Resistor color code chart

Color Band 1st Digit 2nd Digit Multiplier Tolerance

Black 0 0 1 Brown 1 1 10 1% Red 2 2 100 2% Orange 3 3 1,000 (K) 3% Yellow 4 4 10,000 4% Green 5 5 100,000 Blue 6 6 1,000,000 (M) Violet 7 7 10,000,000 Gray 8 8 100,000,000 White 9 9 1,000,000,000 Gold 0.1 5% Silver 0.01 10% No color 20%

Chapter Nine: 80/40 Meter Code Practice Receiver

Table 9-2

Capacitance code information

This table provides the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, many are color coded and some have alphanumeric codes. The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

Value Type Code Value Type Code

1.5 pF Ceramic 1,000 pF /.001µF Ceramic / Mylar 102 3.3 pF Ceramic 1,500 pF /.0015µF Ceramic / Mylar 152 10 pF Ceramic 2,000 pF /.002µF Ceramic / Mylar 202 15 pF Ceramic 2,200 pF /.0022µF Ceramic / Mylar 222 20 pF Ceramic 4,700 pF /.0047µF Ceramic / Mylar 472 30 pF Ceramic 5,000 pF /.005µF Ceramic / Mylar 502 33 pF Ceramic 5,600 pF /.0056µF Ceramic / Mylar 562 47 pF Ceramic 6,800 pF /.0068µF Ceramic / Mylar 682 56 pF Ceramic .01 Ceramic / Mylar 103 68 pF Ceramic .015 Mylar 75 pF Ceramic .02 Mylar 203 82 pF Ceramic .022 Mylar 223 91 pF Ceramic .033 Mylar 333 100 pF Ceramic 101 .047 Mylar 473 120 pF Ceramic 121 .05 Mylar 503 130 pF Ceramic 131 .056 Mylar 563 150 pF Ceramic 151 .068 Mylar 683 180 pF Ceramic 181 .1 Mylar 104 220 pF Ceramic 221 .2 Mylar 204 330 pF Ceramic 331 .22 Mylar 224 470 pF Ceramic 471 .33 Mylar 334 560 pF Ceramic 561 .47 Mylar 474 680 pF Ceramic 681 .56 Mylar 564 750 pF Ceramic 751 1 Mylar 105 820 pF Ceramic 821 2 Mylar 205 1st Significant Figure 2nd Significant Figure Multiplier Tolerance CSGNetwork.Com 6/4/92 0.1µF 10% 104 k

the extra leads flush to the edge of the circuit board. Now, you can go ahead and install the electrolytic capacitors onto the circuit board. Go ahead and solder them in place and trim the leads as necessary.

This receiver project uses a number of small inductors. These small inductors will generally have color bands on them to help identify them. Molded chokes appear, at first glance, to be similar to resistors in both shape and band marking. However, a closer look will enable you to differentiate between the

two––chokes are generally larger in diameter and fatter at the ends than resistors. When doing your inventory, separate out any chokes and consult the parts list for specific color-code information. Note, that inductor L1 is an adjustable slug tuned type. Remember that specific chokes are used for each band: see parts list before mounting the chokes. Chokes do not have polarity so they can be mounted in either direction on the PC board.

The 80/40 meter receiver utilizes two integrated circuits and a regulator IC. Take a look at the diagram shown in Figure 9-3, which illustrates the

semiconductor pin-outs. When constructing the project it is best to use IC sockets as an insurance against a possible circuit failure down-the-road. Its much easier to unplug an IC rather than trying to un-solder it from the PC board. IC sockets will have a notch or cut-out at one end of the plastic socket. Pin one (1) of the IC socket will be just to the left of the notch or cut-out. Note that pin 1 of U1 connects to C1, while pin one (1) of U2 connects to C15. When inserting the IC into its

respective socket make sure you align pin one (1) of the IC with pin one (1) the socket. Failure to install the IC properly could result in damage to the IC as well as to the circuit when power is first applied.

Let’s finish the circuit board by mounting the volume control and the adjustable capacitors. The volume control potentiometer at R1 is a right angle PC board mounted type, which is placed at the edge of the PC board as is the main tuning capacitor.

Capacitor C18, which is connected at the junction of L3 and C1, is an 8.2 pF trimmer type; go ahead and solder it to the circuit board using two pieces of bare #22 ga. stiff single conductor wire.

Locate main-tuning capacitor C19, now locate the mounting location for main tuning capacitor C19. The tuning capacitor was mounted on its side using double- sided sticky tape. Remove the protective cover from the double-sided tape, and firmly press the body of

capacitor C19 to mount it to the PC board. Firmly press the double-sided tape over the silk-screened outline for the body of C19. You may decide to mount the tuning capacitor in a different way. At the rear of the capacitor: locate the four internal trimmer capacitors, and using a small jeweler’s screwdriver or alignment tool, fully open (unmesh) all four trimmers. Note: tuning shaft faces front of board. Bend the two rotor lugs so they are parallel to the front face of the capacitor as shown above. Connect the two rotor lugs to the PC board ground points as shown using scraps of lead wire trimmed from resistors as jumper wires. Cut a 6′′length of 24-AWG insulated hook-up wire in half. Remove about1_⁄

4′′of the insulation from each of the cut ends.

Solder the jumpers to the capacitor rotor lugs, and to the ground foil run on the bottom of the PC board. Since the tuning capacitor has four sections, you can increase the tuning ranges by paralleling different sections to give a greater tuning range: see Table 9-3. If you used just the 140 pF section, your tuning range would be 190 kHz, but if you combined the 140 pF section with the 40 pF section your tuning range would become 180 pF and so forth. Capacitor jumpers: 180 pF =use 140-pF and 40-pF sections paralleled; 222 pF =use 140-pF and 82-pF sections paralleled; 262 pF =use 140-pF, 82-pF and a 40-pF sections paralleled; 302 pF =use all four capacitor sections in parallel.

The 80/40 meter code practice receiver can be built for either of your favorite ham bands. First you will need to decide which band you are interested in. Then you will have to select the proper components from the chart in Table 9-4, for the band of interest. Note that you will have to select three capacitors and three coils for each band.

1 2 3 4 8 7 6 5 1 2 3 4 8 7 6 5 Input 00774433 SA602 78L05 LM386 Bottom view GND Output (TO-92) Plastic package (z)

Figure 9-3 _{Semiconductor pin-outs}

Chapter Nine: 80/40 Meter Code Practice Receiver

Let’s take a few minutes for a short well-deserved break, and when we return we will look over the circuit board for any possible “cold” solder joints or “short” circuits. Pick up the circuit board with the foil side facing upwards toward you. First, we will examine the circuit board for “cold” solder joints. Take a look at all of the solder joints on the board, they should look clean, bright and shiny. If you see any solder joints which look dark, dull or “blobby,” then you should remove the solder with a solder-sucker and then reapply more solder and re-solder the joint all over again so that it

looks good. Next, we will look the board over for any possible “short” circuits which are often caused by “stray” component leads cut from the board or from small solder blobs which may have bridged between circuit traces. Rosin core solder can often leave a sticky residue which will collect component leads and solder blobs, so look the PC board over carefully for any foreign objects on the foil side of the board.

The 80/40 meter receiver radio prototype was mounted in a metal chassis box on plastic standoffs. The PC board was aligned in the enclosure so that the volume control, and main tuning control and power switch were all mounted at one side of the case. Alight the PC board along the edge of the chassis box, so that you drill holes in the chassis for the volume and tuning controls. The 1_⁄

8′′switched headphone jack at J2 was

mounted on the front of the chassis, while the antenna input jack at J1 was mounted on the rear of the case. The 9 volt transistor radio battery was mounted in a battery holder which was fastened to the bottom panel of the chassis box.

Your new 80/40 meter direct conversion receiver project is almost completed. Apply the battery clip to the 9 volt battery. Connect up an antenna to the antenna jack, a dipole antenna cut for the band of interest would be the best type of antenna. For test purposes, you could connect a long piece of wire to the antenna jack for a temporary antenna. Plug in an 8 ohm headphone and then, turn on the power switch to the “On” position. Now, adjust the volume control to the mid-position and then turn the main tuning control. If all-goes-well, you should begin to hear some radio stations. You may want to test the radio in the early morning or evening when these two bands are most active for best results. Hopefully you will hear some stations while you tune across the band.

If for some reason, your receiver is DEAD, then you will want to turn off the receiver and remove the battery clip and do another inspection of the circuit board. This inspection is best done by another pair of eyes, someone who is skilled at electronics might be your best choice for inspection. You will want to make sure that you installed the electrolytic capacitors correctly with respect to their polarity. You will also want to make sure that the integrated circuits are aligned correctly in their respective sockets: it’s easy to make a mistake. Check to make sure that the regulator IC at U2 was correctly

Table 9-3

Band tuning range 80 Meter Tuning 302 pF 350 kHz 262 pF 310 kHz 222 pF 270 kHz 180 pF 230 kHz 140 pF 190 kHz 82 pF 110 kHz 40 pF 55 kHz

40 Meter Tuning Range

302 pF N/A 262 pF N/A 222 pF N/A 180 pF 310 kHz 140 pF 250 kHz 82 pF 150 kHz 40 pF 75 kHz

Table 9-4

80/40 Band change components

40-Meter Components 80-Meter Components

C3 - 470 pF capacitor C3 - 470 pF capacitor C4 - not used C4 - not used C5 - 680 pF capacitor C5 - 470 pF capacitor L1 - 1.5 µH molded coil L1 - 6.8 µH molded coil L2 - 1 µH molded coil L2 - 3.3 µH molded coil L3 - 10 µH molded coil L3 - 33 µH molded coil

installed with the input of the regulator going to capacitor C12, and the output of the regulator going to capacitor C11. Finally, make sure that you have the battery clip polarity wired correctly. Once you have examined the circuit board once more, you can go ahead and reconnect the battery and antenna and try the receiver again to see if it works now.

If your receiver is now working correctly, we can move on to the alignment of your new receiver. There are two primary methods of aligning the receiver’s local oscillator.

Receiver alignment