YooFab RFLEGO User manual

Kit Assembly instructions
RFLEGO Active Antenna Receiving Loop
Designed and produced by YOOFABTM
ASSEMBLY I STRUCTIO S
RFLEGO Active Antenna Receiving Loop
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 1 o 66

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
Copyright © 2018 - 2019 www.yoo ab.com G.D.COWNE - MØOOZ page 5 o 66

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