Bandpass Filters, TV & FM Filter and RF Amplifier


Bandpass Filters
Blue Relays || Resistors || .01 Capacitors || .1 Capacitors || 1N914/VN0106N3/IRFU220 || Varicaps/LEDs || IREDs/Photodiodes
.01/1N914/SPDT Switch || 100K Potentiometer || 17/15/12/10 Coils || 40/30/20 Coils
TV & FM Filter and RF Amplifier
.01 Capacitors || Resistors || TV & FM Capacitors || TV & FM Coils || FT50-75 ferrite core || 2N5109 || Wire Loops
Double Checking Your Work

Section 3 - First Mixer and Crystal Filter


Board 1, Section 2


Bandpass Filters

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

Approximate time to complete 1:20

____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 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.

____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 resistor (Bag 3) (brown, black, brown)

____6 - .01 capacitors (Bag 3)

____4 - .1 caps (Bag 4) The "Lay flat on board" instruction on the board does not have to be done. Different .1's are used - small square labeled 8752T, J100V, 104K.

____1 - 1N914 diode (Bag 4), Black band, be sure to match the band on the diode to the band on the footprint.
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 on the part goes over the thick white line on the footprint. Marked "FU220, IR 625T,32 03"

____2 - MV2115 Varicap (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 "MV 2115".
____2 - MVAM115 Varicap (Bag 5), Be sure to match the flat of the component to the flat on the footprint. Marked MVAM 115
____2 - LEDs (Bag 3), Blue LEDs, 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: Sometimes it is difficult to push the LED through the plated through hole, it is OK to let the LED sit a little higher on the flattened wider points on the leads. Solder one lead, straighten the LED, then solder the other lead.

SWL AM Detector Modifications Click here

____2 - IREDs (Bag 4), Smoky colored, on a cardboard strip, do not cut the leads off the strip, tear the IREDs 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 - Photodiodes (PD410 IR Diode)(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.

Note: The SIPS shown installed in the following picture with the varicaps are not used in the SWL version.

____2 - .01 capacitors (Bag 3),
____2 - 1N914 diodes (Bag 4), Match black band to white band on footprint
____1 - SPDT slide switch (Bag 5) for Band Switch footprint. There are two hole patterns. Mount the switch in the holes that fit the switch in Bag 5.

Install 100K Potentiometer

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

Look at the following 4 pictures and instructions before installing the 100K pot.

____2 - 1K resistors (Bag 3), One on either side of the 100K pot.
____1 - Filter tune wire: 3/4" to 1" bare wire, can be a cut wire from a resistor

Push Pot through holes. Using a needle nose pliers, run the wires through the holes of the connections.

1. Bend down the connections of the pot to the bottom of the board.

2. Then bend the resistor wires over the connections to secure pot against the bottom of PCB.

3. The right connection will not go all the way to the board, it will be on top of the wire as it comes out of the board.

4. Lift up board to straighten pot vertically, recheck tightness of wires over the pot connections.

Solder and clip the leads.


The arrows in the pictures below show wires that are soldered to the pot. There are ground connections on each side of the pot on the board.

Since the case is not mounted in a metal case and naturally grounded, a ground wire is soldered to the case so that it does not pick up stray RF from the PCB or your hand.

Clean a small side section of the pot with a sharp razor, fine grit sandpaper, or a sharp knife and then tin the spots as shown below in the picture.

The wires also provide mechanical support.

17/15/12/10 Bandpass Filter

____4 - T50-6 Yellow cores, 14 Turns .9uH (Bag 4)
____3 - T37-6 Yellow Cores, 2 - 8 Turns .2uH, 1 - 2 Turns .02uH (Bag 4)
____Enameled wire (Bag 6)

40/30/20 Meter Bandpass Filter

____4 - T50-6 Yellow cores( Bag 4), 35 Turns 5uHy
____3 - T37-6 Yellow Cores (Bag 4), 2 - 11 Turns .41uH , 1 - 6 Turns .14uH
____Enameled Wire (Bag 6)

Winding the 35 Turn coils

Note: The first loop you make over the core is counted as turn 2!
The turns are counted by how many are inside the core.

Install 40/30/20 Coils and Aim the Photo Devices

The 35 turn and 6 turn coils in the middle of the 40 to 20 meter Filter will have to be bent over to allow the Shrink Tubing to run between the Photo Devices on the board. Allow extra lead length when soldering so they can be bent over slightly.

TV & FM Filter and RF Amplifier

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

To learn about the RF Amplifier, read the Circuit Details - High Level RF Amplifier.

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 2N5109 transistor
____1 - 470 ohm (Bag 4), Located above the 2N5109 transistor
____2 - 300 ohm (Bag 5),
____1 - 18 ohm (Bag 6),
____1 - 56 ohm (Bag 5), Located below the 2N5109 transistor
____1 - 5.6 ohm (Bag 5), Located below the 2N5109 transistor

____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.

____2 - T50-6 yellow cores (Bag 4)and enameled wire (Bag 6)

____1 - FT50-75 ferrite core (Bag 4) and wire (Bag 6)
____1 - One of the 8 3/4" Black/White wires

Notice below the end of the insulation of the wire overlaps the edge of the core about 1/4". This centers the wire so that both ends have the same amount of insulation over the edge of the core. Wind very tight.

____1 - 2N5109 Transistor and Heatsink (Bag 5), Put the heat sink on the transistor first before soldering to the PCB.

Install Bifilar core and Transistor

Making Connections

See Making Loops for Connections on the Boards for making easy connections to the board for testing and completing the board. Click 'Back' on your browser to return here.

Place two loops, one at the Antenna and one at the Ground connections.

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 MVAM 115.
____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.

Section 3 - First Mixer and Crystal Filter

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Last Update: 7/6/2019
Web Author: David White, WN5Y
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