AM Radio Receivers
Figure 1.
Authors: James Talmich
Richard Velasco
JC van der Schans
March 14, 2008
“AM Radio Receivers”
Authors: James Talmich, Richard Velasco, JC van der Schans
The AM Radio Receiver project consisted of learning how radios work and to then design and
build our own radio. Through the beginning research we learned about the four main receiver
designs: crystal, regenerative, reflex, and superheterodyne. Once agreeing on which type of
design would work well with what we had we were able to begin the construction process.
While components are relatively cheap, there were some problems with availability and ability to
buy single pieces. Building our own Printed circuit board proved to be quite the challenge, yet
satisfying once completed. Once we had built our radio and placed it in an enclosure it was easy
to see that our radio would not be able to compete with radios on the market today. With costs
that were much larger than retail radios today our radio has no place in retail stores, but does
have applications that are better suited for our process.
Table of Contents
Illustration List------------------------------------------------------P.4
Introduction----------------------------------------------------------P.5
AM/FM---------------------------------------------------------------P.5
Edwin Armstrong---------------------------------------------------P.6
Crystal Radio Receiver--------------------------------------------P.7
Regenerative Radio Receiver-------------------------------------P.8
Reflex Receiver-----------------------------------------------------P.9
PCB Design and Build---------------------------------------------P.10
Superheterodyne Radio Receiver--------------------------------P.11
Hybrid Digital/Digital---------------------------------------------P.12
Testing--------------------------------------------------------------P.12
Economic-----------------------------------------------------------P.13
Manufacturability-------------------------------------------------P.13
Applications-------------------------------------------------------P.13
Conclusion---------------------------------------------------------P. 14
Illustration List
Figure 1. – “Old Time Radio Programs.” Entrepreneur.com. <http://www.entrepreneur.com/
businessideas/514.html>.
Figure 2. - “Frequency Modulation.” 2 March 2008. <http://en.wikipedia.org/wiki/
Frequency_modulation>.
Figure 3. – Peterson, George. “The 2005 Technology Hall of Fame.” 1 September 2005.
<mixonline.com/mag/audio_tecnology_hall_fame/>.
Figure 4. – “Crystal Radio.” 9 March 2008. <http://en.wikipedia.org/wiki/
Crystal_radio_receiver>.
Figure 5. – “Crystal Radio Set.” 27 April 2001. <http://www.electronics-tutorials.com/receivers/
crystal-radio-set.htm>.
Figure 6. – “Twin Triode Regenerative Radio Receiver.” PV Scientific Instruments. <http://
www.arcsandsparks.com/twinregenerative.html>.
Figure 7. – Kitchin, Charles. “A Short Wave Regenerative Receiver Project.” 16 December 2007.
<http://www.electronics-tutorials.com/receivers/regen-radio-receiver.htm>.
Figure 8. - “Reflex Radio Instruction Manual.” Ocean Electronics. Purchased January 12th,
2008
Figure 9 - Personal Product Photos
Figure 10. – “Superheterodyne Receivers.” Introduction to Naval Weapons Engineering
Figure 11. - Excel Sheet Containing Personally Obtained Data
Introduction
During the 2007-2008 school year James Talmich, Richard Velasco, and JC van der Schans took
up a project proposed by Professor Ender Ayanoglu for their senior design project to fulfill the
requirements for EECS 189A/B. The project focused on AM radio receivers. The main portions
of the project were to learn about the different AM radio receiver designs, fully understand how
they work, and design and build our own radio using discrete components. During the research
process they learned much about the differences between the AM and FM band, and perhaps the
most influential man in the advancement of the radio, Edwin Armstrong. Edwin Armstrong is
widely considered the inventor of the FM radio and also some AM radio receivers, however,
during his life he was embattled in several patent wars. While there are several different AM
radio receiver designs, they focused on four different ones: Crystal, Regenerative, Reflex, and
Superheterodyne. Once understanding of those four designs was complete they were able to
move on to the next, and perhaps most important, part of our project, the design and construction
of their radios.
AM/FM
AM radio broadcasting makes use of amplitude modulation. During the first eighty or so years
of the 20th century AM broadcasting was the most dominant method of broadcasting [1].
Although it is still widely used today, FM broadcasting has overtaken it as the most dominant
method of broadcasting. The beginnings of AM radio go back to 1906, and the demonstrations
of Reginald Fessenden of the first radio broadcast. AM works by varying the strength of the
signal being transmitted in relation to the information being sent [2]. It then amplifies the
variations in the signal to drive a loudspeaker or earphones. Amplitude modulation is inefficient,
in terms of power usage, because much of the power it uses is wasted. Most of the power it uses
is in the carrier signal which contains no useful information [1]. It is also important to note that
some signals act differently during the day and during the night. During the day, AM signals
tend to travel by groundwave, diffracting around the curve of the earth. However, during the
night AM signals tend to travel by skywave caused by changes in the ionosphere [2]. Skywaves
enable the AM radio station to be heard from much farther away from the transmitter than would
be possible during the day. As a result many stations are required to reduce their broadcasting
power slightly during the night hours, some stations even stop broadcasting during the night.
AM signals can be disrupted in large urban centers due to the abundance of large metal
structures, tall buildings, sources of radio frequency interference, and countless sources of
electrical noise, such as electrical motors, and lights [2]. Because of AM radio’s susceptibility to
both atmospheric and electrical interference, it is mostly reserved to broadcasting talk radio, such
as news, sports, religious, and political stations. Music radio has now mostly shifted to FM
broadcasting.
FM radio was invented by Edwin Armstrong in 1933, and uses frequency modulation to provide
high-fidelity sound over broadcast radio [3]. FM sends information over a carrier wave by using
variations in its frequency, this is in contrast to amplitude modulation where the amplitude of the
carrier wave is varied and the frequency in held constant as can be seen in Figure 2 [3].
Figure 2.
Armstrong was driven to eliminate the biggest problem with radio at the time, static. AM radios
carry sound patterns by modulating the amplitude of the carrier wave at a fixed frequency.
However, this system was often disturbed by such things as electrical storms [3]. Armstrong
created a wideband FM system that in tests showed could handle the worst electrical storms and
would still provide the highest quality sound heard by radio at the time. Wideband FM does
require a wider bandwidth than AM would at an equivalent modulating signal, but this allows the
signal to more robust against any type of noise or interference. FM is also able to withstand
phenomena such as signal amplitude fading, which is why today FM is more widely used than
AM radio.
Edwin Armstrong
Figure 3.
As stated above Edwin Armstrong is perhaps the most influential man in the advancement of
radios. Edwin Armstrong, electrical engineer and inventor, was born on December 18, 1890 in
New York City [4]. He studied at Columbia and later became a professor there. In 1912, while
studying and Columbia University, he had his first big invention, the regenerative circuit. The
regenerative circuit revolutionized wireless radio communication at the time [5]. Filed for a
patent in 1913, and received the patent for the regenerative circuit in 1914. In 1915 Lee de
Forest, another inventor, filed for a patent on the same regenerative circuit, which he sold the
right to AT&T [4]. With the radio business booming AT&T filed a lawsuit to overturn
Armstrong’s patent in favor of de Forest’s. Their patent battle went through a dozen courts
between the years of 1922 and 1934 [4]. In what most experts agree was a wrong decision,
Armstrong, backed by Westinghouse and Radio Corporation of America (RCA), eventually lost
through a judicial misunderstanding of the technical facts [4]. While serving in the military in
1917, during World War I, Armstrong invented the superheterodyne circuit and patented it in
1918 [5]. The superheterodyne circuit allowed for greater selectivity and amplification. He was
called “The Major”, his rank in the military, by his friends. In the late 1920s Armstrong
experimented with an entirely new system, where the wave frequency would be modulated, but
the amplitude would be held constant. In 1933 Armstrong created FM broadcasting [5].
However, with the country in a state of depression during the 1930s the radio industry was
unwilling to move toward a new FM system. Changing toward a new FM system would require
basic changes to both transmitters and receivers. In 1940 Armstrong was able to get a permit for
his own FM station; however he obtained it at his own expense [4]. After World War II, in the
mid-1940s, FM broadcasting began to flourish, however that came to a screeching halt when the
FCC, ordered FM into a new frequency, very much limiting the capabilities of FM broadcasting.
At the same time he was being challenged by a multitude of corporations on the rights to his
inventions. Facing another long legal battle, worn down by money problems, and frustrated with
the failure of the public to recognize the importance of FM Armstrong committed suicide in
January of 1954, by jumping from his 13th floor apartment window [4]. After his death his
widow, Marion MacInnes, continued the lawsuits and ultimately won 10 million in damages [4].
Armstrong would never see his dream of FM clearly being established as the superior system in
the 1960s.
Crystal Radio Receiver
Figure 4.
Crystal radio receivers are probably the simplest kind of radio receiver devised for the reception
of AM signals. It requires no power other than the power received from radio waves by a long
wire antenna [6]. Figure 3. contains a schematic for a basic crystal radio set.
Figure 5.
The circuit consists of an inductor, a variable capacitor, a germanium diode (crystal), a filtering
capacitor, and very high impedance headphones [5]. The inductor has taps on it to connect the
antenna and one to connect the germanium diode to it. The variable capacitor is often connected
across the whole of the inductor to form a tuned circuit. How the crystal radio receiver works is
that the long wire antenna will pick up the thousands of radio signals from the air [5]. The
setting of the variable capacitor determines the amount of capacitance and this in conjunction
with the fixed inductance of the coil will make a resonant circuit. The capacitance in conjunction
with the fixed inductance will resonate at a certain frequency [5]. This is how a particular
frequency is chosen from among the thousands of signals collected by the antenna. Once the
signal is chosen it is passed through the germanium diode, where half of the signal is used. The
0.001 uF fixed capacitor then sends the signal to ground leaving a tiny audio frequency, which
should be the exact same as the audio frequencies that came from the radio station [5]. This tiny
audio signal drives the high impedance earphones so we are able to hear the music or words.
Regenerative Radio Receiver
Figure 6.
Edwin Armstrong invented and patented the regenerative circuit while at Columbia University.
This is the invention in which he would go into the long patent war with Lee de Forest [7]. With
vacuum tubes being expensive and consuming much power, the regenerative receiver was a
blessing during its time. The design got the most gain out of one vacuum tube, thus filling a
need of the radio community and instantly thrived [7]. The regenerative radio receiver makes the
most out of few parts. Figure 6. is a schematic of one kind of regenerative radio receiver.
Figure 7.
As we can see in Figure 6. the receiver is separated into three parts: radio frequency (RF) stage,
regenerative detector, and the audio amplifier [8]. A bipolar transistor is utilized in the RF stage,
while the JFET, in the regenerative detector, and the audio amplifier use low cost integrated
circuits. In the RF stage of this circuit, Q1 amplifies the signals from the antenna and prevents
the radio’s oscillations from causing any interference to other receivers [8]. In the regenerative
detector section of the schematic JFET Q2 uses positive feedback to increase the sensitivity and
selectivity of the receiver [8]. The positive feedback builds the input signal to very high levels.
In the audio amplifier portion of the circuit IC1 amplifies the audio signal and is able to provide
ample output to drive the small speakers or headphones [8].
Reflex Receiver
Reflex radios were popular many years ago, when transistors were very expensive. These radio
receivers required the least amount of components when compared to other radio receivers; they
can be made with one or two transistors. This in turn made them cheaper for the consumer and
makes the battery last longer, which obviously attracted consumers. The way the reflex receiver
saves on components Is that it makes the amplifier do twice the work, by amplifying the Radio
Frequency (RF) signal and the Audio Frequency (AF) signal at the same time. This is very
ingenious and because of this makes the design a bit more complicated.
Fig. 8
For our project we ordered an AM reflex radio kit seen in Figure 8. The radio signal comes in
through terminals 5, 6, and 7 and gets amplified by the transistor. The 800uH choke coil doesn’t
let any of the radio signal pass and it sends it back and it gets demodulated by the diode and
capacitor. The demodulated audio signal then gets amplified by the same transistor that amplified
the radio signal, and the choke coil lets the audio signal pass to the audio amplifier and then to
the earphone.
PCB Design and Build
There are a couple of methods for etching PCB’s, the main difference being the way the ink
traces are put on the copper board. There is the photofabrication method, which is literally the
way they develop photos. Then there is the brute method of ironing on a laser jet printing of the
PCB artwork on the copper board. And of course there is always the option of sending it out to a
vendor that prints circuit boards. However, before any of this is done, one has to get the PCB
artwork that is going to be transferred on the copper board. This can be done by using free
software available on the internet, or by purchasing a professional software like Cadence
Allegro.
(Left) PCB Artwork on PCBArtist (Middle) Etching Copper (Right) After copper was etched
Figure 9.
For our project we used a free software called PCB Artist. It is not difficult to get the artwork
done, one simply draws the schematic and the program will automatically route all the
components together with traces. We decided to use the brute force method of ironing on the
artwork on the copper board, which proved to be very difficult. Once that is done you peel the
paper off and hope the ink is stays on the copper. If there places where there is no ink, you can
fill it in with a sharpie. When it’s ready you can drop it in a plastic container with enough Ferric
Chloride to submerge the copper board. The acid will start etching away the copper that is not
covered by the ink. This works faster if the acid is warm so it’s a good idea to keep a lamp on it.
Superheterodyne Receiver
Heterodyning is the mixing of two frequencies. Superheterodyning is taking the difference
between an incoming signal and a generated signal resulting in a signal with a lower beat
frequency than the original incoming signal. This is not for the purpose “encoding information
for transmission. What superheterodyning does is to purposely mix in another frequency in the
receiver, so as to reduce the signal frequency prior to processing.”[9]
For AM reception, the receiver is tuned to the carrier frequency between 570 and 1700 kHz. The
signal is amplified and then mixed with a signal generated by the receiver. The generated signal
is an intermediate frequency (IF), and is always the same, regardless of the frequency of the
incoming carrier signal. This is done by a variable oscillator that is tied to the tuner. The IF,
typically 450 kHz, can then be amplified, demodulated, passed through an audio amplifier, and
then the speaker.
Figure[10]: Stages of superheterodyne receiver.
There are three main advantages to use of a superheterodyne, the latter two pertaining to the AM
receiver. First, it reduces the signal from very high signal sources. As noted, this is not an issue
for the am receiver, but for frequencies that are high enough to cause damage to components, this
is a way to get around that problem. Second, receivers can be built much more inexpensively. As
most of the components need only operate at a fixed frequency, it is much easier to optimize and
build them. Third, superheterodyning can “improve signal isolation by arithmetic isolation.”[9]
Simply stated, if there is a 2% spread in the signal. That 2% will be a smaller value at the IF than
the incoming signal. These qualities of the superheterodyne make it a cheaper and more robust
receiver.
Hybrid Digital/Digital
Hybrid digital or “HD Radio, is the trademake for in-band on channel (IBOC) selected for
terrestrial audio broadcasting.”[10] This technology was developed by iBiquity Digital
Corporation. The application is more prevalent with FM stations, as AM stations have been slow
to adopt the technology. Hybrid digital works, as the name implies, in both analog and digital
modes. First the receiver locks onto an analog signal. and then tries to find a digital signal. The
AM signal is usually transmitted at 40 kbits/s., while the FM signal is transmitted at 100 to 150
kbits/s. Some of the main problems with hybrid technology are the expense and the lack of
coverage. Receivers for the car are around $100, while tuners for the home cost in the range of
$75. Coverage is a problem because up to now, the HD signal was 1% of the power of most
stations analog signal. Because of the weak signal, the receiver often reverts back to analog
mode.
An example of digital available on the market is satellite radio. There are two providers of
satellite radio. They are XM Radio and Sirius Radio. Each system has three satellites with backup ground transmitters and transmits at 2.3 GHz.
Testing
To conduct some testing on which radio design worked better and to what extent it worked better
we obtained some radios from Professor Ender Ayanoglu and did some testing on what signals
and the clarity of the different radios. There were four radios used in the tests: reflex,
regenerative, superheterodyne (with IF), and superheterodyne (without IF). The tests were
conducted at two different times of the day, one at night and one during the day. We also
conducted the tests in two different counties, Orange County and San Diego County. The results
of our tests can be seen in Figure 11. attached to the end of the paper. Based on the results, the
all radios seemed to work better during the day. This can be attributed to there being more
signals being transmitted during the day because some stations stop broadcasting during the
night. We can also see that there are more weak signals during the day due to more interference
caused by other signals during the day. Though there are less signals during the night the signals
are clearer because signals are stronger during the night travel on skywaves, as stated above,
which allow for signals to travel further. Both San Diego County and Orange County produced
nearly identical results in terms of number of station being received, though they were not
necessarily picking up the same stations in both counties. The reflex and regenerative radio
performed similarly in our testing, both picking up somewhere in the range of 5-11 signals. They
were both always within two, in number of stations, of each other. It could be argued that reflex
did did slightly better, but not by much. The big winner in the testing was the superheterodyne
receivers which performed above and beyond the capabilities of the reflex and regenerative
receivers. The superheterodyne receivers were picking up anywhere from 2X to 4X the amount
of the reflex and regenerative receivers. There were two superheterodynes being tested. One
with an IF and one without. The superheterodyne receiver with the IF performed the best
picking up a low of 27 signals and maxing out at 37 signals received. The superheterodyne
without IF did not perform as well, yet was much better than the reflex and regenerative. The
superheterodyne picked up a low of 16 signals and peaking at 22 signals. Based on this testing
conducted it is very easily seen that the superheterodyne with IF was the best type of receiver.
Economic
We built two radios, a reflex and a superheterodyne. We spent in total about $100 to the reflex
radio. While it was relatively cheap to find components for this radio, the bulk of the money
spent on this radio went towards material to be used to make the printed circuit board. The ferric
chloride and the copper board used in the printed circuit board process cost roughly $50. The
enclosure cost about $10. When we take into account the costs to build this radio, this radio was
very expensive to build. The superheterodyne radio built cost a little over $100. Most of the
cost was caused by difficulty to find components and the necessity of having to buy components
in bulk. The components included: resistors, capacitors, transistors, and inductors. Components
alone cost about $80. There was also the need for somewhere to place the components. This is
where the cost of $25 for a breadboard was. This was the extent to which that radio was taken,
and would have obviously cost much more if we were to change the circuit into a printed circuit
board and enclose it in some kind of surrounding.
Manufacturability
Under no circumstance should the radios we built be sold in retail stores. AM radios today are
priced anywhere from $14.99 - $29.99. These radios are of much higher quality than our radios.
Their signal is much clearer and stronger. They are also placed in a nicer protective case. They
also have other functions that our radios are not capable of, such as: FM radio, alarm, and clock.
We were able to build two radios, with some degree of success. The reflex radio was by far the
best radio that we built. However, for the amount we spent it does not come close to competing
in the market of multi-function radios. There would have to be major changes to our design and
the costs if there were ever going to be any possibility of being manufactured.
Applications
As was shown above, there is little to no possibility of the radios we constructed to be sold in
retail stores. However, there are a few possibilities that our radios can be used for. Applications
include educational use, and use by hobbyists. There is a market for people who wish to learn
more about how a radio works and how to construct their own printed circuit board. As can
easily be seen on the internet there are numerous websites with step-by-step processes on how to
construct a radio with detailed descriptions on how these radios work. These types of websites
are very educational because they allow users the opportunity to learn by the hands-on-approach.
Users of the website will need to gather their own components, place, and solder those
components onto some sort of board. From there they will move on to creating a printed circuit
board, where as shown above has many steps of its own. This first-hand experience will give the
user in depth knowledge on steps to be taken in building a working radio. If we were looking to
make some money from our design we would look to sell a kit to build our radio to hobbyists.
There are dozens if not hundreds of websites and listings online that sell kits with step-by-step
instructions on how to build their radios. There are a number of people out there who take great
joy in building their own radio and listening to the radio they built.
Conclusion
Despite the low cost of simple radios in stores, it was quite expensive in our process to build our
radios. The construction of a single radio, that is not as efficient as those in stores, was well over
five times the cost of radios sold in retail stores. Optimization of a design is very difficult and
tedious work, requiring countless hours of testing and correction. It is safe to say that of the four
radio receiver designs we studied: crystal, regenerative, reflex, and superheterodyne, that
superheterodyne was by far the beset design. However, it is also a much harder design to
implement. As we look at radios today it is easy to see that we are in a new era of HD and digital
radio that will very well push the radios of yesterday further back into the past.
Works Cited
[1] – “AM Broadcasting.” 13 March 2008. <http://en.wikipedia.org/wiki/AM_broadcasting>.
[2] – “Amplitude Modulation.” 13 March 2008. <http://en.wikipedia.org/wiki/
Amplitude_modulation>.
[3] – “Frequency Modulation.” 2 March 2008. <http://en.wikipedia.org/wiki/
Frequency_modulation>.
[4] – Lessing, Lawrence. “Edwin H. Armstrong.” Dictionary of American Biography.
Supplement Five p. 21-23. <http://users.erols.com/oldradio/ehabio.htm>.
[5] – Halper, Donna. “Major Edwin Howard Armstrong.” Old Radio.com. 1998. <http://
www.oldradio.com/archives/people/armstrong.htm>.
[6] – “Crystal Radio.” 9 March 2008. <http://en.wikipedia.org/wiki/Crystal_radio_receiver>.
[7] – “Crystal Radio Set.” 27 April 2001. <http://www.electronics-tutorials.com/receivers/
crystal-radio-set.htm>.
[7] – “Regenerative Circuit.” 12 February 2008. <http://en.wikipedia.org/wiki/
Regenerative_circuit>.
[8] – Kitchin, Charles. “A Short Wave Regenerative Receiver Project.” 16 December 2007.
<http://www.electronics-tutorials.com/receivers/regen-radio-receiver.htm>.
[9] – “Superheterodyne Receivers.” Introduction to Naval Weapons Engineering
[10] – <http://fjallfos.fcc.gov/edocs_public/attachment/FCC-02-286A1.txt>.
Addendum
Figure 11.
Midnight in San
Diego
Regenerativ
Superheterodyne (with
Superheterodyne (without
ReflexTotal=6
e
Total=8 IF)
Total=29 IF)
Total=16
600clear
600clear
540clear
600clear
760clear
690weak
600weak
620clear
900weak but clear
750clear
620clear
660weak
1090weak
1090clear
640clear
690clear
1340weak
1130weak
660weak
760clear
1360clear
1230clear
690clear
900clear
1360clear
710weak
950clear
1470clear
760clear
1090clear
800clear
1130clear
810weak
1170weak
860clear
1210weak
900clear
1220clear
930weak
1360clear
950clear
1420clear
1040weak
1470clear
1070clear
1700clear
1090clear
1130clear
1170clear
1230clear
1270clear
1310weak
1360clear
1420weak
1470clear
1530clear
1550weak
1580weak
1630weak
Midday in San
Diego
ReflexTotal=9
570weak
600clear
640clear
Regenerativ
Superheterodyne (with
Superheterodyne (without
e
Total=11 IF)
Total=33 IF)
Total=19
600clear
540clear
600clear
640clear
570weak
620clear
690weak
600clear
640clear
760clear
800weak
900clear
1090clear
1340weak
1360clear
750clear
790weak
1090clear
1130clear
1170w eak
1230clear
1360clear
1470weak
620clear
640clear
660weak
690clear
710weak
750weak
760clear
790clear
800clear
810weak
860clear
900clear
930weak
950clear
1040clear
1070clear
1090clear
1130clear
1170clear
1210clear
1230clear
1270clear
1310weak
1360clear
1420weak
1470clear
1530clear
1550weak
1580weak
1630weak
690clear
760clear
790clear
800clear
900clear
950clear
1090clear
1130clear
1070clear
1210weak
1220clear
1310weak
1360clear
1420clear
1470clear
1700clear
Midnight in Irvine
ReflexTotal=7
570clear
640clear
690clear
740clear
830clear
1090clear
1190clear
Regenerativ
Superheterodyne (with
Superheterodyne (without
e
Total=5 IF)
Total=27 IF)
Total=16
830clear
570clear
550weak
1090clear
640clear
570clear
1190clear
690weak
590clear
1480clear
710weak
620clear
1530clear
720clear
640weak
740clear
660clear
760clear
740weak
790clear
770weak
810weak
830clear
830clear
840weak
930weak
950weak
960weak
980clear
1020weak
1030weak
1070clear
1090clear
1190weak
1370clear
1480clear
1510weak
1530clear
1540weak
1580weak
1600clear
950weak
1020clear
1090clear
1190weak
1370weak
1480clear
1580weak
Midday in Irvine
ReflexTotal=10
570clear
640clear
690clear
740clear
790clear
830clear
1070clear
1090clear
1110clear
1190clear
Regenerativ
Superheterodyne (with
Superheterodyne (without
e
Total=11 IF)
Total=37 IF)
Total=22
570weak
540clear
570clear
640clear
570clear
600clear
690weak
600weak
640clear
740clear
640clear
690clear
790weak
690clear
710clear
830clear
710clear
740clear
1070clear
740clear
790clear
1090clear
790clear
830clear
1110weak
830clear
870weak
1190clear
860clear
930weak
1480clear
870clear
950weak
930weak
980clear
950weak
1020weak
980clear
1070clear
1020clear
1090clear
1070clear
1110weak
1090clear
1190clear
1110clear
1390weak
1150clear
1480clear
1190clear
1580weak
1240weak
1600clear
1280clear
1650weak
1300clear
1350weak
1370weak
1390weak
1410weak
1430clear
1440weak
1480clear
1510clear
1540weak
1550weak
1580weak
1600clear
1640weak
1650weak