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


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 begin winding.

After winding, scrape the enamel off the wire as close to the toroid as possible and tin with solder. Pre-tinned wires make 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.

____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.

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

After tinning, remove any excess solder. Wipe the excess solder to the top of the pin so the pins will fit in the holes. When soldering on the board, the heat will melt the excess solder and the relay will fall against the board.

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.

____5 - 100K resistors (Bag 3) (brown, black, yellow)
____2 - 1 meg (Bag 4), Next to the LEDs at the relays on the right side.
____1 - 100 ohm (Bag 3), (brown, black, brown)

____9 - .01 capacitors (Bag 3)

Note: There is one capacitor next to the text "40/30" that is marked "10". Do not put a .01 in that spot by mistake.

____2 - .001 caps (Bag 5)
____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".

____3 - 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.
____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 - IRFU220 (Bag 2), Note thick white line on footprint, the heat sink of the part goes over the thick white line on the footprint. Marked "FU220, IR 625T,32 03"

____2 - IREDs (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. They are located to the right of the output relays on the left.
____2 - MV2115 (Bag 5), Be sure to match the flat of the component to the flat on the footprint. 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. 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.
____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 - Photodiodes (Phototransistors) (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.

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

____2 - 1K (Bag 3), On both sides of the Filter Tune pot. Do not solder at this time.

Push the Filter Tune Pot through the holes, bend the end tabs over, pull the resistor almost out of their holes, and run the leads through the hole in the tabs. Then bend the resistor wires over to secure pot against the bottom of PCB.

Solder and clip the leads. On the left hand tab, solder will flow into the hole of the tab, but not so much that it flows onto the ground plane. Then clip the end of the tab to prevent a short to ground. Solder other 1K resistor leads.

Install Filter Tune Wire from Filter Tune Pot to Filter Tune Circle and 12 Volt Wire to Tune Pot

____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.
____2 - .01 capacitors (Bag 3)

Install BPF Wire from switch to BPF Tune

The wire can be run either below the board or on top the Board. Shown in the next picture is how the run the wire below the board.

Running the wire on top of the Board is shown in the following two pictures.

Installing the Bandpass Coils

Make sure that the wires of the coils are clean of insulation where they are soldered underneath the board. If not, raise the coil enough to get clean wire for a good solder connection.

Aim the Photo Devices

When bending the Photodiodes forward, as shown in the picture, keep the face (with the bubble) vertical.
Bend the 820pf capacitors down slightly.

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

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.

____6 - .01 capacitors (Bag 3)

____1 - 100 ohm resistors (brown, black, brown) (Bag 3)
____1 - 1K (Bag 3), Located above the 2N3019 transistor
____1 - 470 ohm (Bag 4), Located above the 2N3019 transistor
____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 - 56 ohm (Bag 6), Located below the 2N3019 transistor
____1 - 5.6 ohm (Bag 6), Located below the 2N3019 transistor

____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.
____2 - 120pf NPO (Bag 5), Next to the 8 turn coils. Orange colored, teardrop, labeled "121".

____1 - 2N5109 Transistor and Heatsink (Bag 6), Put the heat sink on the transistor first before soldering to the PCB.
____1 - T4-6T Transformer (Bag 4), Note dot on top and match the dot on the silkscreen.

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 tab on the 2N5109 transistor.
____Check the flats on the LEDs and make sure they fit the flat on the footprint.
____Check the flats on the MV2115s and the MV1662's.
____Check the black bands on the three 1N914 diodes.
____Use a Volt-Ohm Meter (VOM or DVM) 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 white 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: 4/22/15
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