Bandpass Filters, TV & FM Filter and RF Amplifier


To learn about the Bandpass Filters, read the
Circuit Details - Varicap Tuned Bandpass Filters
before building this section.

Approximate time to complete 1:20 - Picture

SWL Modifications

The IR LED next to the 20 meter bandpass output relay is not installed. Removal of this IR LED is no problem as it is in parallel with the 20 meter bandpass switching LED and its removal increases the available current to the switching LED.

Preparation

This section uses all the T50-6 (Bag 4) cores in the kit. The wire length will give you plenty of extra on each end. Start with 1" of wire on the end you use to begin winding.

After winding, scrape the enamel off the wire on the ends as close to the toroid as possible and tin with solder.

Pre-tinning the wires must be done to get a good connection on the board.

Wind the coils as follows:

____2 - 8 Turns, wire length 7"
____2 - 15 Turns, wire length 13"
____2 - 29 Turns, wire length 24" - Wind the turns close together for the 29 turns will take up almost all the toroid.

Insert all the components that have their values inside the footprint. They are the following:

____9 - .01 capacitors
____1 - 100 ohm resistors (brown, black, brown)
____5 - 100K resistors (brown, black, yellow)

Solder

Resistors:

____2 - 1 meg (Bag 4), Next to the LEDs at the relays on the right side.
____2 - 1K (Bag 3), On both sides of the 100K pot.

Capacitors (Going left to right on the board):

____2 - .001 caps (Bag 5), Next to the 29 Turn toroids on each end of the 40/30 Filter. Orange, small square, marked "102".
____2 - 820pf Mica caps (Bag 5), Below the MV2115's on the 20/17 Filter. Bend the leads on the caps 90 degrees before putting on the board so you can get them to lay flat. These caps need to be laid flat on the board so they do not get in the way of the Infra-red light that activates the Photodiode. Brown colored, large size, marked "820 +/- 2%, 300V SAHA" or "CM06FD, 821J03" or "820 5%, 300V".

Ones with short leads, put in standing up as they have a slightly shorter profile. After soldering, bend down at a 45 degree angle.

____1 - 3.3pf NPO (Bag 4), Located at the text 20/17. Orange colored, small square, leads flared out, labeled "3R3 D", or short leads, grey with black top, labeled "3R3" (R looks like a P).
____1 - 10pf NPO (Bag 5), Located at the text 40/30. Small round capacitor, black top, labeled "10", or Orange colored, teardrop, labeled "100, A1J".

Solder

Other Parts:

____2 - 1N914 diodes (Bag 4), Black band, be sure to match the band on the diode to the band on the footprint, one on each end of the filters near the middle of the board.

Bend the leads about 1/8" away from the body of the diode for easy insertion into the PCB.

Picture

____2 - IR LEDs (Bag 4), Smoky colored, on a cardboard strip, do not cut the leads off the strip, tear the IR LEDs off the strip and clean the bottom of the leads. Mount as high as possible, then aim to the appropriate photo receiver.

Both IR LEDs are located to the right of the output relays on the left.

The IR LED located to the left of the output relay on the 20/17 Filter is not installed. Picture

Solder

____2 - MV2115 (Bag 5), Be sure to match the flat of the component to the flat on the footprint. Next to the 15 turn coils in the 20/17 filter. Flat of part is colored light blue, marked "MMV 2115".
____2 - MV1662 (Bag 5), Be sure to match the flat of the component to the flat on the footprint. Next to the 29 turn coils in the 40/30 filter. Flat of part has a red line on top and a white line on the bottom, no markings on part, two leads flared out halfway down.

Solder

____2 - VN0106N3 (Bag 2), static sensitive part, touch a ground wire before removing from the bag. Match the flat of the component to the flat on the footprint. Spread the outside leads slightly to fit the footprint. Marked "SI N, 0106, 8302".
____2 - LEDs (Bag 3), Red color, at the left side of the relays on the right. Match flat of the LED to the footprint. The short lead is on the same side as the flat. Note: If you ordered the Super Bright LEDs, they can replace these LEDs. Use different colors so band identification will be easy. See Modifying the LEDs.
____2 - IRFU220 (Bag 2), Note thick black line on footprint, the heat sink on the part goes over the thick black line on the footprint. Marked "FU220, IR 625T,32 03"

Solder

____2 - Photodiodes (Bag 4), Small square part with a tiny bubble on one side. Be sure to match the bubble on the part to the bubble on the footprint. Mount as high as possible straight up.

Solder

____4 - Blue Relays (Bag 4), Be very careful with the part as the pins are fragile. Do not bend the pins when mounting/soldering to the PCB. Orientation does not matter, inner pins are the coil, outer pins are the relay.

Important Blue Relay mounting information!

1. Clean and tin the pins with solder before mounting on board to ensure a good solder joint. The pins can be difficult to solder without pre-tinning.

2. Be sure to mount the relays flush with the board. If mounted slightly off the board, the relay will flex back and forth while handling the board, and break the pins between the relay and PCB.

Solder one pin to the PCB, then hold the relay against the top side of the PCB and remelt the soldered pin to set the relay against the board. Then solder the other pins.

Solder

____2 - 15 Turn Toroids, mount on the 20/17 filter.

Bandpass 40/30 Coils

____2 - 29 Turn Toroids, mount on the 40/30 filter. The coil on the left of the filter is used to block stray IR energy from hitting the 40/30 photodiode. With the board in the same orientation as the picture above, turn both coils on the 40/30 filter horizontally. Picture

Solder

____1 - SPDT Miniature PC Mount switch (Bag 5), There is a switch footprint in front of the Bandpass Filter. There are two hole patterns. Mount the switch in the holes that fit the switch in Bag 5. Picture

Solder

____Bandpass Filters (Picture) - Between the VN0106N3's, there is a BOLD circle that is labeled "Gnd for 20/17" and marked "BPF". Solder a 4" length of wire to the circle and to the left side of the "Band Switch" labeled "To BPF".

Solder

____1 - 100K Panel Mount Potentiometer (Bag 6) (Picture), The three holes labeled "Filter Tune" should accept the pins of the potentiometer supplied with the kit.

____Bend the outside solder lugs inward slightly and crimp the solder lugs with a pair of needle nose pliers a little bit so they slip through the holes. Picture

____With a knife, fine grit sandpaper, or a screwdriver tip scrape two spots on the upper sides and tin with solder. These are used to solder ground leads from the PCB. Picture

____After inserting the pot, bend the outside solder lugs backwards onto the solder joints of the resistors. Solder the lugs onto the leads of the resistors. Make sure the lugs are not touching the ground plane just above the solder pads. The lugs will be extending over the ground plane. Picture

____To help secure the pot and ground the case (the case can pick up unwanted RF), run wires from the ground holes on both sides of the pot to the case of the pot.

Then solder the ground leads to the pot and to the ground plane underneath the board. Picture

____Piece of Hook-up wire 2 3/4" long. One end goes to the FILTER TUNE circle in the middle of the bandpass filters and the other end to the center pin of the pot. Place and solder the wire underneath the board. Picture

Solder

____Piece of Hook-up wire 4" long. One end goes to the "To 12V" hole at the 1K resistor to the left of the Filter Tune pot and the other end goes to the "12 Volt" box above the text "First Mixer". Place and solder the wire underneath the board. Picture

Note: The two connected arrows at the bottom left side where the wire is attached indicates where a short will occur if a spacer is placed in the hole noted by one of the arrows. If you put a spacer in this hole, the trace indicated by the other arrow will have to be trimmed to prevent a short to 12 Volts.

Solder

TV & FM Filter and RF Amplifier

To learn about the TV and FM Filters, read the
Circuit Details - TV & FM, Broadcast Filters
before building this section.

To learn about the RF Amplifier, read the
Circuit Details - High Level RF Amplifier
before building this section.

Approximate time to complete 0:35 - Picture

The 4.5 MHz High Pass Filter is optional. The parts for the High Pass Filter are not included in the kit. If you live in a large metropolitan area where several high power AM stations or nearby amateur radio stations are present, you might consider installing the parts. Check out TV & FM, Broadcast Filters for information.

Insert all the components that have their values inside the footprint. They are the following:

____6 - .01 capacitors (Bag 3)
____1 - 100 ohm resistors (brown, black, brown) (Bag 3)
____1 - RF choke (Bag 3), On the 12 Volt trace at the lower right hand side. Footprint on PCB is a rectangle with square edges, "RF" inside the rectangle. Choke is about the size of a 1 watt resistor with rounded edges.

Resistors:

____2 - 300 ohm (Bag 5), Located at the 50 ohm pad above the Minicircuits T4-6T 1:4 transformer.
____1 - 18 ohm (Bag 6), Located at the 50 ohm pad above the Minicircuits T4-6T 1:4 transformer between two .01 capacitors.
____1 - 1K (Bag 3), Located above the 2N3019 transistor
____1 - 470 ohm (Bag 4), Located above the 2N3019 transistor
____1 - 56 ohm (Bag 6), Located below the 2N3019 transistor
____1 - 5.6 ohm (Bag 6), Located below the 2N3019 transistor

Solder

Capacitors (Going left to right on the board):

____2 - 120pf NPO (Bag 5), Next to the 8 turn coils. Orange colored, teardrop, labeled "121".
____2 - 100pf NPO (Bag 3), Next to the 8 turn coils. Orange color, short leads flared out, labeled "101".
____1 - 330mfd Electrolytic (Bag 4), Note - (Minus) is marked on the part, and the + (Positive) is marked on the board. Located at the upper right corner of the section.
____1 - 10mfd tantalum, 3 pin (Bag 4), Located below the relays, next to the "12 Volts" box. Orange colored, with three short pins.

Solder

Other Parts:

____1 - Minicircuits T4-6T transformer (Bag 4), Match the dot on the part to the dot on the silkscreen. The dot on the outside of the footprint will let you double check to make sure the dot is in the correct place after it is mounted.
____1 - 2N3019 Transistor and Heatsink (Bag 6), Put the heat sink on the transistor first before soldering to the PCB.

Place the gap of the heat sink directly over the tab of the transistor. The tab will be clearly seen through the gap in the heat sink.

The heatsink will be a tight fit on the transistor, so be careful, a small screwdriver may be needed to spread the heatsink in difficult cases.

Note the tab on the transistor and match it to the tab on the footprint. Position the bottom of the heat sink even with the top of the T4-6T transformer. Do not mount the transistor flush on the board.

Solder

____2 - 8 Turn coils on T50-6 toroid, mount in the TV & FM Filter.

Solder

Double Checking Your Work

____Place the PCB in front of a bright light. If you see light shining through any of the soldering holes, you missed a solder connection.
____Check the dot on the Minicircuits T4-6T transformer.
____Check the tab on the 2N3019 transistor.
____Did you put the Heat Sink on the 2N3019 transistor?
____Check the flats on the LEDs and make sure they fit the flat on the footprint.
____The flats on the MV2115s and the MV1662's should be facing to the left.
____Check the black bands on the two 1N914 diodes.
____Use a VOM in resistance mode and check that there is zero resistance through the coils. Place the probes away from the soldering holes to check for cold solder joints at the coils. ____Check the IRFU220s, make sure the heat sink of the part is directly above the thick black line on the footprint.
____Check the flats on the VN0106N3's, they should be facing away from each other.
____Use a Volt-Ohm Meter (VOM or DVM) in resistance mode and measure between each outside solder lug (underneath the board) of the Bandpass Tuning potentiometer, labeled "Filter Tune", and the ground plane and make sure the measured resistance is no lower than 1K. If either outside lug shows zero resistance, it is shorted to ground. Fix the solder bridge so it is not grounded.

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Last Update: 1/4/10
Web Author: David White, WN5Y