YooFab RFLEGO User manual
Table of Contents
Main Characteristics................................................................................................................ 4
Bill O Materials (Component List)...........................................................................................6
Circuit Diagram....................................................................................................................... 8
Circuit Operation..................................................................................................................... 8
Respect The Di erence!.....................................................................................................8
No Signal!......................................................................................................................... 10
Common Base Di erential Ampli ier..................................................................................11
The Output........................................................................................................................ 11
Connectors.......................................................................................................................12
Common Instructions or all RFLEGO kits.............................................................................13
What is an electronic kit?..................................................................................................13
YooFabTM Electronic Kits:................................................................................................13
How to build your kit.........................................................................................................13
About YooFabTM electronic kit PCBs...............................................................................14
About RFLEGO................................................................................................................. 16
Notes On Soldering Single Sided Sur ace Mount Boards.................................................17
Step By Step......................................................................................................................... 20
Printed Circuit Board.............................................................................................................21
Step 1............................................................................................................................... 21
Resistors R1 to R9................................................................................................................22
Step 2............................................................................................................................... 22
Step 3............................................................................................................................... 23
Step 4............................................................................................................................... 24
Step 5............................................................................................................................... 25
Capacitors C1, C2, C3, C4, C5, C6, C7................................................................................26
Step 6............................................................................................................................... 26
Step 7............................................................................................................................... 27
Transistors.............................................................................................................................29
Step 8............................................................................................................................... 29
How to identi y Base, Emitter and Collector on 2N2222 TO-92 transistor.....................30
WINDING THE TOROIDAL TRANSFORMER.......................................................................31
IMPORTANT..................................................................................................................... 31
Toroid winding step 1...................................................................................................32
Toroid winding step 2...................................................................................................33
Toroid winding step 3...................................................................................................34
Toroid winding step 4...................................................................................................35
Toroid winding step 5...................................................................................................36
Toroid winding step 6...................................................................................................37
Toroid winding step 7...................................................................................................38
Toroid winding step 8...................................................................................................39
Toroid winding step 9...................................................................................................40
Toroid winding step 10..................................................................................................41
Toroid winding step 11..................................................................................................42
Toroid winding step 12..................................................................................................43
Toroid winding step 13..................................................................................................44
Toroid winding step 14..................................................................................................45
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 2 o 66
Toroid winding step 15..................................................................................................46
Toroid winding step 16..................................................................................................47
Toroid winding step 17..................................................................................................48
Toroid winding step 18..................................................................................................49
Toroid winding step 19..................................................................................................50
Toroid winding step 20..................................................................................................51
Toroid winding step 21..................................................................................................52
Toroid winding step 22..................................................................................................53
Toroid winding step 23..................................................................................................54
Toroid winding step 24..................................................................................................55
Toroid winding step 25..................................................................................................56
Using the FT37-43....................................................................................................... 56
Step 9............................................................................................................................... 57
Soldering the trans ormer to the PCB...........................................................................57
Which wire? Which winding?........................................................................................59
Remember...................................................................................................................59
No excuses!.................................................................................................................59
So where are the leads soldered onto the PCB?..........................................................60
HARDWARE.........................................................................................................................61
Step 10............................................................................................................................. 61
Step 11............................................................................................................................. 63
Step 12............................................................................................................................. 64
Step 13............................................................................................................................. 65
Congratulations!.................................................................................................................... 65
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 3 o 66
Main Characteristics
The YooFab RFLEGO Active Antenna Receiving Loop Kit, once correctly built, will
provide a highly sensitive HF Antenna that should operate more in the magnetic domain
than it does in the electrical domain. It should be e ective across the whole HF
spectrum.
z
x
y
E
v
B
Electromagnetic wave
WAR I G: DO OT USE THIS A TE A TO TRA SMIT. This is strictly a receive
only antenna. If the Active Antenna Receiving Loop is connected to a transceiver,
remember this!
•This type of receiving antenna has a certain immunity to near-field
electrical QRM (noise), which is a distinct advantage or those that live in urban
areas and particularly to those who live in blocks o lats.
•This antenna permits stealth operation. Many radio enthusiasts live in places
which prohibit the installation o large antennas. This antenna provides excellent
results when used on a terrace, balcony or even near a window. It is also great
when used outdoors, as it is light and small yet provides great reception.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 4 o 66
•The differential amplifier design employed here has low impedance inputs to
which the 1-1.5 meter loop o wire is connected.
Please note that this di erential ampli ier provides a certain immunity to common
mode signals. The circuit is based upon a di erential pair that has an unusual
common base low impedance input design which is an advantage here as the
input loop wire presents a low impedance. (Designed by M0OO )
•Gain: The amplifier has a voltage gain of approximately 20dB (10X). This is
more than su icient. I the gain proves to be too much or your receiver, do not
modi y the Di erential Ampli ier circuit. Instead, place an attenuation pad o 10dB
at the receiver end o the coaxial cable. Note: that 20dB gain will allow or very
small signals appearing on the loop to be ampli ied to a level suitable or a hal -
decent receiver.
•This antenna should operate across all HF bands and is a form of Low
oise Amplifier (L A)
•Its compact size makes possible a rapid setup. You may then receive HF
HAM radio signals with the much same ease as the use o a typical antenna
itted to a VHF consumer type radio.
•This antenna is great for almost any type of HF receiver. However, it is
especially use ul or direct conversion (DC) receivers, as it has a certain
immunity to emissions sourced rom the DC receiver's own Local Oscillator. Such
emissions may cause hum when received by a DC receiver on an end ed long
wire Antenna (Zeppelin).
•The LOOP connected to the two terminals is something that can be
experimented with. It should be between 1 meter and 1.5 meters in length. A
bigger loop will probably not help with better reception and instead may lead to
instability and reception o more unwanted signals.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
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Bill Of Materials (Component List)
The colour / style of some hardware components such as bolts or connectors may vary.
Attention: In the photo we see 3 transistors; there are two used in the circuit.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 6 o 66
ame Value Quantity otes
C1, C2, C3, C4, C5, C6,
C7
100nF 7 disk ceramic capacitor
C8 100uF 1 electrolytic capacitor more than 25 V
D1 led 1 red
FT37-43 10T BIFILAR 1 https://www.micrometals.com
Q1, Q2 2N2222 2 Transistor NPN
R1, R2 120Ω 2 Resistor
R3, R4, R9 1K 3 Resistor
R5, R8 4.7K 2 Resistor
R6, R7 270Ω 2 Resistor
Printed Circuit Board 1 Vinyl protected copper
35 mm stand-o 4 Black plastic
M3 bolt 4 Black plastic
washer 5 mm 2 Led inishing
RCA connector (Phono) 1 Gold Plated
Banana Connector 2
Power Connector 2.1 mm 1
Wire red and black 2
Galvanized wire 1 m length
Decal 1 To be placed on top o the PCB
Polystyrene piece 1 To organize your components while building
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 7 o 66
Circuit Diagram
Circuit Operation
The RF signal is induced across the wire loop, which is connected to the LOOP
terminals seen on the schematic. The signal is then coupled to the emitters of
the differential pair.
Respect The Difference!
The differential pair is largely immune to common-mode signals, such that when
the same injected signal appears on both inputs, it should be rejected.
Below we can see the circuit simulation o a 5uV (p-p) input signal rom the wire loop.
This signal is ampli ied because it appears to the di erential ampli ier's inputs, such that
as one side becomes positive, the other side becomes negative. The 5uV (p-p) signal
appears on the le t side o the ‘loop’ coloured Green and on the right side coloured Blue.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 8 o 66
YooFab Antenna Loop Differential pair amplifier
otes On Simulation:
Please note that in the above animated simulation, there are two 10 MΩ resistors that
go to ground. These are needed by the SPICE simulation and are not needed in reality.
The real world and the simulated world are different. Simulation is very useful. However,
necessarily it presents an artificially 'perfect' world where components behave as
idealists. In the real world no component is ideal, which results in differences in the
performance when compared to the simulated world.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 9 o 66
No Signal!
Compare the circuit simulation shown below with the above. The irst thing we
notice is there is no ampli ied output! The blue trace shows the input signal and the
orange trace shows the output.
In this simulation the signal has been injected into both di erential inputs. That is, the
signal appears to go negative and positive on both sides o the di erential ampli ier
(with respect to ground) at the same time. Ergo, there is no difference and so
nothing is amplified.
YooFab Differential amplifier for loop antenna No amplified signal
Remember This When Testing: We must remember the di erential nature o this
ampli ier when testing. I we orget this and connect a signal generator to both sides o
the di erential ampli ier, then at best nothing will appear at the output. In practice the
amplifier is not completely immune to common mode signals and so instead of
there being no signal we should see a comparatively small signal at the output.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 10 o 66
Common Base Differential mplifier
On both sides o the ampli ier circuit, we see two NPN transistors with the bases biased
at just below 2V (assuming a supply o 12V. At 6V supply, the bias is just above 1V)
Each transistor has approximately 11 mA current passing at quiescent state. This, in
addition to the low impedance inputs, provides some headroom or dealing with large
signals i they are present. Bear in mind that ideally, we want to be able to ampli y
signals o 1uV or less on our wire loop. However, every signal rom ELF to upper HF
may arrive at the loop, and so it is that we need to allow or this probability together with
the possibility o large variance in signal strength. In other words we need the
amplifier to have a relatively large dynamic range.
The Output
The output is taken from the transformer which is used to convert the balanced
output to an unbalanced output suitable for feeding along 50Ω coaxial cable. Here
we must note that there is a DC path to ground through the output winding o the
trans ormer. o capacitor coupling is used as it is assumed that the input o our
receiver will have a capacitor.
We may choose to add a capacitor if DC coupling is not desired. If this is done,
we should use a value of 100nF, which is placed between the output post of the
CA socket and the pad.
The other side o the trans ormer is coupled to both the collector load resistors o the
di erential ampli ier via 100nF capacitors and thus removes the DC component which is
present and stops the two sides o the di erential pair being shorted together!
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 11 o 66
Connectors
1. Power supply - The circuit is powered using a 6 - 16 Volt DC supply. This is
connected to the circuit using a standard 2.1mm Power jack, with the centre pin
as ++. The supply must be clean (free from noise or ripple from the mains).
Indeed, you should probably use a 9V battery to test the antenna loop.
2. RF output - The Active Antenna Loop output uses an RCA socket. This makes
the loop ampli ier compatible with YooFab RFLEGO. However, you may need to
use an adaptor or make your own cable i you need to connect this to BNC or
UHF type connectors.
3. Wire Loop A and B - Two Banana sockets allow the connection of a 1 - 1.5
meter length of wire. Your kit includes a length of galvanized wire, which
may be fashioned into a loop. This is thin wire, yet has enough rigidity to
maintain a orm. Note that the orm does not have to be circular. Indeed you may
experiment with di erent shapes and the use o other types o wire.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 12 o 66
Common Instructions for all RFLEGO kits
What is an electronic kit?
Generally, kits are composed o electronic components, a circuit diagram (schematic),
assembly instructions and o ten a printed circuit board (PCB) or another type o
prototyping board.
YooFabTM Electronic Kits:
•Easy to build
•Serve a use that is market driven
•Provide valuable hands-on experience in electronics
•Feature well-written instruction books
•Feature a ull description o how the circuit works
•All YooFabTM kits require soldering skills
•The PDF instructions document describes the steps necessary to completely
build the kit.
How to build your kit
1. Read the instructions twice, even i you have much experience with electronics.
2. Veri y the contents o the kit; use the piece o polystyrene supplied to place the
components prior to building.
3. Prepare your work area; keep it clean and organized.
4. Follow all instructions in the prescribed sequence.
5. Visually check the inished kit. Check that the soldered joints are bright and that
there are no obvious errors.
6. Continuity check. Using a digital voltmeter, check the entire circuit.
7. In case the kit does not work, take photos and send us an email.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 13 o 66
bout YooFabTM electronic kit PCBs
•Your printed circuit board is hand-produced using a high quality reliable method.
The copper is protected by a layer o vinyl that prevents oxidation which protects
the copper sur ace until it is ready to solder.
•Remove all vinyl, as though it were a sticker. Please do not scratch or polish the
sur ace.
•Optionally, and be ore starting to solder you can apply a ew layers o lacquer
(hairspray) on top o the copper sur ace. Apply each coat o lacquer about 25 cm
away rom the board and let dry or about 10 minutes. Apply the second coat
ollowing the same procedure. And a third. This lacquer will protect the copper
rom ingerprint stains, during the construction process, and it will also protect it
rom uture oxidation. This lacquer will vaporize with the heat rom the soldering
iron.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 14 o 66
•When component soldering is complete, the module's front panel is the
non-copper side of the board. For this reason, there is a decal sticker that
must be attached to the side without copper just before soldering the
connectors and any other through-hole element onto the board. You should
cut some crosses using a kni e in the indicated locations. For ease o assembly,
cut all excess pieces as shown below with a side cutter. Care ully a ix the decal
to the non-copper side o the PCB. Take care to align the drilled holes with those
o the decal sticker. Proceed to place the connectors and other through-hole
elements through both the board and decal and inally proceed with the
assembly.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 15 o 66
bout RFLEGO
1. All RFLEGO modules are compatible with each other and make use o standard
Banana connectors or power (except where speci ied), while signal lines use
RCA connectors.
2. YooFab RCA 50Ω patch leads may be used directly to connect RFLEGO
modules together.
3. Adapters are available to convert RCA to BNC, SMA or PL-259 SO-239.
4. High quality components are sourced rom trusted suppliers. All components are
mounted on a single sided, predrilled printed circuit board. The board is
supplied with a vinyl protection, no legend, solder resist or other markings.
5. The PCB style used is popular among RF design engineers.
6. RFLEGO is a term used to convey the modular and connective nature o an
educational and unctional system that is the intellectual property o YooFab™.
7. The PCBs are hand crafted at the YooFab™ workshop.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 16 o 66
Notes On Soldering Single Sided Surface Mount Boards
1. Sur ace-mount construction method construction method is avoured by many RF
design engineers.
2. This Printed Circuit Board is designed with care using RF design principals and
should permit somebody with soldering skills to success ully complete the board.
3. You are strongly advised to use a high quality, low voltage temperature controlled
iron. This will help ensure success by allowing you to select the correct
temperature or the job.
4. You are also strongly advised to use 60/40 solder and not Silver solder, which
requires more heat.
5. This style o design is related to both 'messy or ugly' styles and to 'dead-bug'
style. However, unlike the a orementioned prototyping methods, this is a Printed
Circuit Board with ample ground plane and wide tracks.
6. The layout o this PCB permits assembly o a great-looking inished circuit with a
high build quality, where the guess-work is removed and which is durable.
7. When compared to a through-hole board with vias and tented thermals, soldering
is somewhat easier, as nothing is hidden. However, we need to be aware that
components will only tolerate heat or a short time. Indeed, time is probably more
signi icant here than is temperature, up to a point.
8. We will solder component leads directly onto the copper tracks and ground
plane of the printed circuit board.
9. 60/40 solder melts at 188 C. This is a plastic state and makes a poor
connection, dull in appearance. This is o ten re erred to as a 'cold joint'. We must
use a temperature above 188 C.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 17 o 66
10.60/40 liquefies at 260 C. This is the ideal soldering state, which allows the
solder to low to the component and copper substrate layer. This state leaves a
smooth, shiny connection.
11. 60/40 flux vaporizes at about 370 C. This is also to be avoided as it will leave a
dull looking and uneven connection.
12.Use a hot iron. In order to solder sur ace-mounted boards such as this, we need
a hot iron, where the temperature is below 370 C. We want to make sure that
there is enough heat to heat an area within the large copper tracks, or ground
plane, while also lique ying the solder rapidly. We do not want to apply heat to the
component lead or more than 3 seconds. So, we do want to heat up the copper
track and component lead rapidly and then apply the solder to the point in the
track where we want the joint.
13. A temperature setting between 260 C and 350 C is optimal assuming that you
are using either a chisel (2) or a bevel (3) bit.
This picture shows 1 Conical (pencil) bit, 2 Chisel bit, 3 Bevel bit
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 18 o 66
14.Make sure that your soldering iron bit is new, tinned and is kept clean by wiping it
with a wet sponge be ore and a ter each joint.
15.Cut the excess component lead at each step. Unlike a through-hole board, we
will be cutting away the excess component lead a ter each joint is made. We do
this because the components are mounted only on the copper side o the board
and the excess component lead will get in the way o working on the board. On
this board, only the connectors pass through drilled holes to the other side.
16.Inspect soldered joints and cables. Make sure that component leads or wires do
not touch the board in any place other than the designated positions marked in
the illustrations.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 19 o 66
Step By Step
We are going to build this kit, using a step by step method, which irrespective of
your skill, you are strongly advised to follow.
We will start by soldering components on the copper side o the board. However, when
completed, the module's ront panel is the non copper side o the board.
Where possible, an illustration and a photograph are shown. The photographs show a
prototype board with the same design.
In most cases, the photographs in the instructions below show soldering by a
novice at the YooFab Lab. Despite this, the modules worked perfectly first time.
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 20 o 66
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