The following list is from Glen Leinweber. He has graciously compiled a list of all the components in the SW-40+ and included a description.

 

A dictionary of SW-40+ components: the purpose and function
by part number, alphabetically. Assumes 40 Meter band.


Capacitors , Diodes , Transistors , Resistors , Inductors

Transformers , Integrated Circuits , Crystals


 

 

Capacitors


C1...150pf RF tuning capacitor for T1, setting resonant frequency to
7 Mhz. to attenuate RF outside 40-Meter band.


C2...47pf Capacitive voltage divider, in combination with C3. Reduces
the RF amplitude of the VFO signal injected into U1 mixer
while providing DC isolation.


C3...10pf See C2 above. C2 and C3 also affect the VFO's frequency.


C4...2700pf Part of Q2 Colpitts VFO oscillator.


C5...2700pf Part of Q2 Colpitts VFO oscillator.


C6...3300pf Couples resonant RF energy from L1 into oscillator transistor
while blocking Q2's DC base bias voltage.


C7...68pf Resonant tuning trim capacitor. Tweak to get the VFO into
the correct frequency range to cover subsection of 40M band.


C8...82pf Bandspread capacitor. Sets the span of VFO tuning range.


C9...10pf Capacitive voltage divider, in combination with C10. Reduce
the RF amplitude of the VFO signal injected into U5 mixer.


C10...270pf See C9 above. C9 and C10 also affect the VFO's frequency.


C11...47pf Part of an L-network (with RFC1) to convert U1's 1500-ohm
output impedance down to be compatible with the IF filter.


C12...150pf Increases Y1's series resonant frequency to give the proper
(symmetrical) I.F. filter response shape.


C13...150pf Provides proper RF coupling between Y1 and Y2.


C14...150pf Provides proper RF coupling between Y2 and Y3.


C15...150pf Increases Y3's series resonant frequency to give the proper
(symmetrical) I.F. filter response shape.


C16...68pf Increases Y4's series resonant frequency above the I.F.
filter's center frequency to give about a 800 Hz offset.


C17...47pf Part of the internal Colpitts BFO oscillator in U3.


C18...47pf Part of the internal Colpitts BFO oscillator in U3.


C19...33nf Filters out RF mixing components (mostly 8MHz.), leaving
audio frequencies below 1.6 Khz. unattenuated.


C20...0.1uf Audio coupling capacitor - blocks DC output of U3.


C21...0.1uf Audio coupling capacitor - blocks DC output of U3.


C22...150pf Low-pass filter for U4 - attenuates audio above 2Khz.


C23...150pf Low-pass filter for U4 - attenuates audio above 2Khz.


C24...0.1uf Delays receiver audio turn-on after transmitting to avoid
clicks, in combination with R8, D6.


C25...820pf Part of U4b's audio bandpass filter (800 Hz).


C26...2.2nf Part of U4b's bandpass filter (800 Hz).


C27...47uf Couples audio to headphones, blocks U4's +8v D.C. output
voltage from headphones too.


C28...47pf Part of U5's internal Colpitts transmit-mixer oscillator


C29...150pf Part of U5's internal Colpitts transmit-mixer oscillator


C30...47pf Tunes T2 primary to 7 Mhz. resonance.


C31...220pf Couples RF from T1 to T2, to give nice bandpass frequency
response.

C32...47pf Tunes T3 to 7 Mhz. resonance.

C33...10nf Couples RF into Q4 buffer and blocks DC base bias voltage.

C34...10nf Couples RF from Q4 into Q5 and blocks DC voltages.

C35...10nf Couples RF into gate of Q6 and blocks base bias voltage.

C36...0.1uf Couples RF into PI-filter and blocks Q6's DC output voltage.

C37...470pf Part of PI-low-pass filter.

C38...1nf Part of PI-low-pass filter.

C39...470pf Part of PI-low-pass filter.

C40...47pf Connects receiver to antenna, resonates with RFC3 at 7 Mhz.

C101..0.1uf Supply bypass capacitor keeps stray RF out of U1.

C102..10nf Bypass capacitor to keep RF out of U2.

C103..10nf Keeps noise and RF from modulating the VFO...only DC allowed.

C104..10nf Keeps one of the two inputs of U3 at RF ground potential.

C105..10nf Supply bypass capacitor keeps stray RF out of U3.

C106..47uf Keeps RF and audio noise out of U5's DC supply.

C107..0.1uf Keeps RF and audio noise out of U5's DC bias point.

C108..10nf Keeps one of the two inputs of U5 at RF ground potential.

C109..10nf Keeps RF out of U5's DC supply.

C110..3.3uf Keyclick transmit waveform shaping capacitor.

C111..10nf Keeps driver's RF from coupling to 7.5v DC supply line.

C112..220uf Big current reservoir on 12V DC input supply.

C113..0.1uf Keeps Q6's large RF output off DC supply line.

C114..0.1uf Emitter sees 10 ohms-to-ground for RF, but 61 ohms-to-ground
for DC.

 

Diodes



D1...MV1662 A diode whose capacitance varies with applied D.C. voltage.
Used as a small variable capacitor to tune VFO frequency.

D2...1N4148 The full 8v is too close to maximum acceptable for SE612 chip:

D2 drops 8v to 7.4v. Also adds a little RF isolation for U1, U3.

D3...1N4148 During receive, clips large +ve-going noise spikes. During
transmit, limits gain of U4 by clipping.

D4...1N4148 During receive, clips large -ve-going noise spikes. During
transmit, limits gain of U4 by clipping.

D5...1N4148 Engages mute gate very quickly, by discharging C24. When the
key goes up, C24 charges slowly through R8, not D5.

D6... Negative clamp for Q6. Keeps the R.F. drive generally positive
for Q6: it stays "on" for a larger part of the cycle.

D7...1N4148 transmit signal clamp. Keeps excessively large RF voltage
out of U1 during transmit. D7 and D8 clamp +ve-going RF peaks.

D8...1N4148 see D7 above. Two diodes are used in series to allow very
large receive signals in without generating distortion.

D9...1N4148 transmit signal clamp. See D7. This one's for -ve-going RF
peaks.

D10..1N4148 see D7, D8, D9 above...this one's for -ve-going RF peaks.

D11... Avalanche diode sets supply voltage to 7.5 volts DC for U5.

D12... Avalanche diode clamps excessive RF peaks that might occur
with strange antenna loads, protecting Q6.

D13...1N4001 DC supply protection diode, prevents damage should input
DC supply be connected with wrong polarity.

Transistors


Q1..MPF102 Analog switch: OFF during transmit, ON during receive.

Q2..2N4401 VFO Colpitts 3MHz. oscillator. Tunes about 40 Khz via D1.

Q3..2N3906 PNP transistor switch: ON during transmit, OFF for receive.
It pulls the transmit mixer, driver up to 12v during TX.

Q4..2N4401 Linear buffer, loads T2,T3 filter very little, but provides
low-impedance drive for Q5. Has voltage gain of 1.

Q5..2N4401 RF amplifier. A linear amplifier to boost RF power to drive
the final amplifier.

Q6..2SC2078 Final (Class C, D?) amplifier. Boosts transmit RF power
up to 1.5 W. Non-sinusoid output requires filtering to ant.

Resistors


R1...470 I.F. filter termination resistor presents the proper load
impedance to the crystal filter along with 1500 ohms of U3.

R2...10k Input gain-setting resistor for U4a differential amplifier.
Gain is determined by R7/R2. It is large enough to prevent
loading down U3's output resistance of 1500 ohm.

R3...10k Part of U4a differential amplifier: required to present a
balanced load to U3, and give good common-mode rejection.

R4...510k Sets the D.C. bias point for U4a. Also required to give
good common-mode rejection for the differential amplifier.

R5... Not designated

R6...10 Supply isolation resistor for U4

R7...510k Sets the gain of differential amplifier, with R2 (see R2).

R8...1MEG Gate bias resistor: Pulls Q1's gate up to source voltage
while key is up (receive). Its time-constant, (with C24)
keeps the receiver muted for a short time after TX.

R9...4.7M This resistor leaks a little audio past the mute gate during
transmit, to provide a sidetone.

R10...22k Bandpass filter input resistor. Sets the bandpass response
of U4b amplifier, in combination with C25, C26 and R13.

R11...510k Keeps U4b properly biased while transmitting, otherwise
U4b would thump during T/R switching.

R12...1M Sets the DC bias point for U4b.

R13...1M Sets U4b's gain, and bandpass response in combination with
R10, C25, and C26. Also required for DC biasing U4b.

R14...10 Buffer for low-Z phones - U4b may not like to see strange
reactive loads.

R15...47k D.C. base biasing resistor for Q2 VFO oscillator.

R16...22k D.C. base biasing resistor for Q2 VFO oscillator.

R17...2.2k D.C. emitter biasing resistor for Q2 VFO oscillator.

R18...1M Varactor diode biasing resistor - applies the D.C. tuning
voltage to D1, with minimum R.F. loading.

R19...1k D.C. dropping resistor sets D11's zener operating current
to about 2.5 ma.

R20...22k ensures that Q3 turns off quickly when key goes up.

R21...10k T/R switch base biasing resistor. Provides base current for
Q3 when the KEY connects to ground, turning it ON hard.

R22...10k D.C. base biasing resistor for Q4 emitter follower.

R23...22k D.C. base biasing resistor for Q4 emitter follower.

R24...500 Emitter biasing for Q4. It is a trimpot that varies the input
RF level going into Q5 RF driver.

R25...2.2k D.C. base bias resistor for Q5.

R26...470 D.C. base bias resistor for Q5.

R27...10 limits the gain of Q5, and keeps it amplifying linearly.

R28...51 D.C. emitter bias resistor for Q5.

R29...100 Base swamping resistor for Q6 final - damps transients and
helps to supply T4 secondary with a somewhat linear load.

Inductors


RFC1..22uH A L-network to match U1's 1500-ohm output resistance to the
I.F. filters lower input resistance, with C11.

RFC2..22uH Lower's Y5's series resonant frequency to give 800Hz TX/RX
frequency offset.

RFC3..10uH Resonates with C40 to 7 Mhz, coupling antenna to receiver's
input.

L1... VFO tuning inductor. Resonates with (C3+C4) (C4+C5), C6, C7,
C8+varactor diode, (C9+C10), at about 3 Mhz.

L2... A choke that provides a DC path to the supply for Q6, but
presents a large impedance to 7Mhz RF output.

L3... Part of PI-low-pass output filter.

L4... Part of PI-low-pass output filter.

Transformers


T1... 7 MHz. tuned transformer provides input selectivity and matches
low impedance input to U1's 1500-ohm input resistance.

T2... 7 Mhz. transmit filter rejects other mixer output frequencies.


T3... 7 MHz. transmit filter rejects other mixer output frequencies.

T4... Broadband transformer allows Q5 to have high gain, while
providing low-impedance drive to Q6.

Integrated Circuits


U1...SE612 A mixer/oscillator chip used here to convert 7 MHz. receiver
RF down to 4 Mhz. I.F. frequency. The oscillator is unused -
the local oscillator is coupled in from Q2 (VFO).

U2...78L08 Three-pin low-current voltage regulator outputs +8v DC.

U3...SE612 A mixer/oscillator chip used here to convert 4 Mhz. I.F. signals
down to audio. A 4 Mhz. crystal oscillator is included.

U4...NE5532 A dual op-amp. Two low-noise amplifiers are used to amplify
audio linearly and to drive headphones.

U5...SE612 A mixer/oscillator chip used here to convert 3 Mhz. VFO RF
up to 7 Mhz. for the transmit amplifier. A 4 Mhz. crystal
oscillator is included.

Crystals


Y1...4MHz. Used in combination with Y2, Y3 to make a narrow bandpass
Cohn filter to provide signal selectivity.

Y2...4MHz. See Y1.

Y3...4MHz. See Y1.

Y4...4MHz. U3 contains a transistor(s) arranged as a Colpitts oscillator
using Y4 to provide 4 MHz. RF to convert IF frequencies to audio.

Y5...4MHz. U5 contains a transistor(s) arranged as a Colpitts oscillator
using Y5 to provide 4 MHz. RF to up-convert the 3 MHz. VFO to the
7 MHz. band.

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