Down Load my Article Regarding the TR7

Bringing an Early Solid State
Transceiver into the 21st Century
Instead of replacing a basically sound transceiver, consider
adding the features found in new gear.
Marc van Stralen, DK4DDS
his article describes changes I made
to a Drake TR-7 transceiver to bring
it up to date. Many could be applied
equally well to other transceivers of the era.
The Drake TR-7, a solid state HF transceiver
manufactured by R. L Drake in Miamisburg,
Ohio in the late ’70s into the early ’80s, has
remarkably good performance specifications
compared to many more recent transceivers.
Its double conversion architecture and analog
circuitry lend itself to straightforward operation. The TR-7 is very simple to operate, has
no complex menus, and is easy to service and
to maintain.
I acquired some TR-7 transceivers, all
in working condition, via the Internet in
Germany and Holland for prices far lower
than current models.
front panel TUNE button nor a KEY jack.
 Displays suffer with an analog dial and
incandescent bulbs in the S-meter.
 Power output is not flat over the operating
range, 1.8-30 MHz.
This article will describe how I addressed
each of these deficiencies, while updating
the style of the equipment. I now have a
radio that can be favorably compared to
modern equipment. The modifications are
straightforward and incremental, so others
may select which are important to them. We
will take them one at a time in the sections
that follow.
But Wait — There’s More
There is far too much information related
to this upgrade to fit in a single QST article.
Some details are provided here, focusing on
the added circuitry that might be useful in
upgrading other transceivers. A more complete article as well as all PC board artwork,
additional schematics and photographs are
available on the QST binaries Web site.1
for the TR-7 is to use one that operates at
audio frequencies. I designed a dedicated
printed circuit board (PCB) that can be
mounted on the underside of the parent
board of the TR-7 with two small stand-off
insulators, the type normally used for PC
serial and USB ports. The filter is controlled
by a relay.
Only a small potentiometer has to be
installed at the front of the TR-7 to control
the notch filter. When the potentiometer is
turned fully counterclockwise, the notch
filter will be off. Table 1 lists the defined
specifications. The notch filter installed in
the TR-7 is shown in Figure 1 with the schematic and parts list in Figure 2.
DSP Noise Reduction
Most current transceivers offer digital
signal processing (DSP) noise reduction.
As with the notch filter, I chose an audio freWhile the basic TR-7 performance is
quency DSP to provide this function. I used
quite good, the 30 year old design does have
a modified NES-5 DSP board from BHI in
some disadvantages compared to modern
the UK (
uk). There are other products that could also
 The permeability tuned oscillator (PTO) Notch Filter
that controls the operating frequency drifts
The simplest way to create a notch filter be employed, however.
The NES-5 DSP noise reduction unit is
more than those of modern equipment.
intended to be connected to the loudspeaker
 The original power supply is very heavy 1
output of a receiver or
and has the same
Table 1
transceiver. It is built
dimensions as the
Specifications of
into a small enclosure
TR-7 itself.
Added Notch Filter
and includes a built in
 It has no notch
speaker amplifier IC.
I modified the unit
 The sensitivity on
300 Hz
30 dB
by opening the enclothe higher bands
500 Hz
35 dB
sure and removing
is too low for quiet
1000 Hz
42 dB
2000 Hz
45 dB
the PCB. I unsoldered
the LM380, the 12
 The TR-7 offers
V regulator IC, input
neither speech
Table 2
resistors R1and R2,
processor nor DSP
and also the output
noise reduction.
Component Changes
in TR-7 Exciter Section resistors R7 and R8. I
 The two VCOs of
replaced the resistors
the first oscillator
New Value
with two 10 turn/50
circuit generate
47 nF
220 nF
kΩ potentiometers
excessive phase
3300 Ω
as shown in Figure 3.
Figure 1 — Notch filter PCB assembled on to the parent
470 Ω
 There is neither a board of the TR-7.
Mount the DSP board
What’s Not to Like?
From April 2009 QST © ARRL
Figure 2 — Notch filter schematic diagram
and parts list.
C1 — 10 µF, 16 V electrolytic capacitor.
C2, C5-C7, C13 — 10 nF ceramic capacitor.
C3 — 10 µF, 16 V electrolytic capacitor.
C4 — 270 pF, 2% capacitor.
C8-C10 — 220 µF, 16 V, 3.5 mm electrolytic capacitor.
C11, C12 — 1 µF, 16 V electrolytic capacitor.
C14 — 680 pF ceramic capacitor.
D1-D3 — 1N4148 silicon diode.
L1, L2 — 4.7 µH SMMC RFC.
Q1 — BC 547 transistor.
R1 — 470 kΩ, 1⁄8 W resistor.
R2 — 15 kΩ, 1⁄8 W resistor.
R3 — 150 kΩ, 1⁄8 W resistor.
R4, R11, R12, R16 — 4.7 kΩ, 1⁄8 W resistor.
R5 — 15 kΩ, 1⁄8 W resistor.
R6, R7 — 4.7 MΩ, 1⁄8 W resistor.
R8, R10 — 100 kΩ, 1⁄8 W resistor.
R9 — 12 kΩ, 1⁄8 W resistor.
R13 — 47 kΩ, 1⁄8 W resistor.
R14 — 39 kΩ, 1⁄8 W resistor.
R15 — 27 kΩ, 1⁄8 W resistor.
R17 — 10 kΩ linear potentiometer.
U1 — HEF 4046.
U2 — HEF 4069.
U3 — MF 10.
Figure 3 — Schematic of modified DSP including control circuitry.
Figure 4 —
DSP mounted
on the
of the TR-7
parent board.
Figure 5 — Added
speech processor board.
From April 2009 QST © ARRL
Figure 6 — Schematic diagram and parts list of speech processor board.
C19 — 330 pF ceramic capacitor.
C1 — 1 nF ceramic capacitor.
C22 — 22 µF, 16 V electrolytic capacitor.
C2 — 100 µF, 16 V electrolytic capacitor.
C23 — 10 nF ceramic capacitor.
C3, C13 — 100 nF ceramic capacitor.
D1 — 1N4148 silicon diode.
C4, C18 — 1 nF ceramic capacitor.
L1-L4 — 100 µH SMMC RFC.
C6 — 470 pF ceramic capacitor.
Q1 — 2N2907 PNP transistor.
C5, C7, C17, C20 — 1 µF foil capacitor.
Q2 — 2N2222 NPN transistor.
C8 — 470 pF ceramic capacitor.
Q3 — 78L05 voltage regulator IC.
C9, C15 — 3.3 nF ceramic capacitor.
R1-R4, R7 — 10 kΩ, 1⁄8 W resistor.
C10 — 220 nF ceramic capacitor.
R5, R6, R10, R18 — 100 kΩ, 1⁄8 W resistor.
C11 — 1.8 nF ceramic capacitor.
R8 — 56 kΩ, 1⁄8 W resistor.
C12 — 220 nF ceramic capacitor.
R9 — 150 kΩ, 1⁄8 W resistor.
C14, C16, C21 — 10 µF, 16 V electrolytic
R11 — 330 kΩ, 1⁄8 W resistor.
R12 — 47 kΩ, 1⁄8 W resistor.
R13 — 33 kΩ, 1⁄8 W resistor.
R14, R17 — 1 kΩ, 1⁄8 W resistor.
R15 — 18 kΩ, 1⁄8 W resistor.
R16 — 1 MΩ, 1⁄8 W resistor.
R19 — 10 kΩ trimming potentiometer.
R20 — 220 kΩ trimming potentiometer.
R21 — 50 kΩ trimming potentiometer.
U1 — 4066.
U2 — SSM2166.
Figure 8 — TR-7 with rear extension installed.
Figure 7 — Installed front panel extension, as seen from the
From April 2009 QST © ARRL
Figure 9 — LED
built into base
of dial light
provide much space to integrate additional
electronics or circuit boards. The only places
are on the underside on the parent board and a
little space in the high pass filter compartment.
There is also very little additional front panel
real estate for additional switches or controls.
I decided to increase the transceiver and front
panel height by about 5⁄8 inch to accommodate
additional jacks and control functions. The
changes are shown in Figures 7 and 8.
in Figure 5 with the schematic and parts list
provided in Figure 6.
The additions and changes to the TR-7
that I have described add the modern conveniences we have come to expect to a radio
that has been around for more than a quarter
century (see Figure 10). The result is a radio
that is fun to operate and a good performer in
any time period.
Marc van Stralen, DK4DDS, has been
licensed since 1970 at age 18 first as PAØMJY,
later as PA1HFO. He received his present call
letters on his move to Germany in 2004.
and a small 10 V reed relay on an empty
Marc has studied electronics and telecommu­
piece of PCB board material so that the whole
nications and had his own business refurbish­
assembly can be mounted on the underside of
ing and selling used electronic manufacturing
the parent board as shown in Figure 4.
equipment such as soldering machines and
placement equipment. Marc retired in 2008.
Speech Processor
His interest in electricity and electronics
Bulbs Replaced by LEDs
The speech processor is a design of
started early and when he was 3 years old he
The bulbs of the S-meter, all indicator could screw connectors on to electrical wire. At
Ulrich Graf, DK4SX, who also used it for
lights and the analog dial light are replaced 12 he made his first attempt at building radios,
his modified TR-7. The processor is based
on the SSM2166 IC from Analog Devices by high intensity LEDs. I used simple defec- starting with a germanium diode crystal set.
His first Amateur Radio project was the con­
( I designed a dedicated tive bulbs, removed the glass and internal
struction of fully transistorized (solid state)
single sided PCB for the speech processor,
10 W, 2 meter SSB transceiver. After earning
to allow it to fit on the underside of the par- the bulb base as shown in Figure 9. By using his A license, he focused on HF homebrew
ent board. Some small modifications of the
and kit radios.
exciter board are needed to switch the pro- sockets in the transceiver.
You can reach Marc at Schulstrasse 21,
cessor on or off. The whole unit was built in
D-48455, Bad Bentheim, Germany or at
a complete enclosed metal box, as shown Conclusions
Mechanical Changes
The original TR-7 envelope does not
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Figure 10 — Bottom view of the TR-7 showing modifications installed.
From April 2009 QST © ARRL