--- Visited, Tsuchiura Radio Station(JOYL/1458 KHz) of Ibaraki Broadcast System(IBS) Co.,Ltd. ---
Tsukuba A3
From long time before, there is a radio set that needs without any power supply that called "crystal set", "germanium radio" or others.
It given the opportunities for examples to begin the electrical craft works and/or to stimulate the curiosity to radio technology due to it is a quite simple scheme that using only a few components.
However, currently, we can purchase much better sensitivity, selectivity and smaller radio set which costs only a few 1000 yen(around $10).
So maybe, seems like many people have forgot an existence of germanium radio no longer...
But nowadays, the latest design smart-phone has a capability of wireless battery charge system.
Or others, using RFID technology, like a Suica and PASMO etc. are based on the similar technology although it is very short-range(about a few cm).
So electric power is sent to these devices by the radio wave and use it for their systems.
In this time, going back to the principle, how does have a performance of germanium radio? No, how did?
So author tried to approach the radio station by bicycle, and re-confirmed it once again.
This is a Germanium Radio in this experiment
[Electric parts]
The box(maximum size：about W:50mm, D:90mm, T:25mm)was designed to fit the parts size by CAD software, and it was created by 3D-Printer.
Inside of this Germanium Radio
The list of electric parts：Purchased all parts at Sengoku Densho in Akihabara.
Parts
Parts# or
Function
Ferrite-Rod-Antenna
620 uH
For tuning inductance, and it also works as an antenna.
Variable-Capacitor(VC)
160 pF
For tuning capacitance that can be changed by rotation.
Dial for select frequency
Connects the VC rotator, and it shows the frequency.
Germanium Diode
1N34
Diode for detection(half-wave rectification).
Ear Receiver
Ceramic Ear Phone
For demodulation.
Medium-wave radio broadcast station has an amplitude modulation(AM: as shown in Fig.1) system that the carrier strength is modulated by the intensity of sound sources(voice and/or music).
And eventually, the modulated wave is transmitted from the antenna. Citizens-Band Radio(27 MHz), Air-Craft Radio(VHF/UHF) and etc. are same system.
Fig.1：A diagram of medium-wave broadcast station
As shown in Fig.2, the radio wave is being received by the resonant circuitry that consists of a ferrite-rod-antenna and a variable-capacitor(VC).
The ferrite-rod-antenna has 2 components, one is a coil that a long electric wire(litz wire) winds on about 1 cm diameter bobbin, and the other is about 8 cm length ferrite-rod.
That's inductance value is almost fixed, so the VC can be changed to tune the frequency of a target radio station.
The ferrite-rod-antenna is a kind of loop antenna as its name suggests. The longitudinal of ferrite-rod-antenna should be made a right angle with the radio wave direction because it has directivity.
And also, the ferrite-rod-antenna puts above from the ground horizontally because the medium-wave radio station are transmitting their programs by using a vertical polarization antenna.
The receiving radio wave is being detected(half-wave rectification) by this diode.
And eventually, the sound is demodulated(re-created) by using a ceramic-ear-phone that works as peak detection and wave-smoothing.
Fig.2：A schematic of Germanium Radio
At present time, a main stream of semi-conducter devices like FET, Bipolar-Transistor, Diode, ICs and LSIs are silicon base.
So the presence of germanium base device seems to be smaller than before.
But now, there seems to be still many germanium-diodes in market place.
And because the "band-gap" related to sensitivity is that the germanium(about 0.7eV) is narrower than the silicon(about 1.2eV).
So a germanium diode is mandatory device for it.
Long time before, crystal-ear-phone is a popular device for receiver that made by rochelle salt.
However, unfortunately, it seems to be very tough to purchase it now.
So as substitute, it is still possible to find a ceramic-ear-phone in the either of market place or internet web sites.
But not sure whether all of them will stay or not in the future.
[Functionality Check / Prepare for the experiment]
Although tried to catch a signal from the radio station after assembly of this germanium radio set, no signal was observed by adjusting its frequency dial.
So in order to confirm its functionality, about 5 meters length electric wire(works as antenna) connected to the anode of germanium diode.
After that, JOAK(594 KHz), JOAB(693 KHz), JOQR(1134 KHz) and JOYL(1458 KHz) were heard very weakly.
In spite of like a simple scheme and also without any power supply, catching the sound is feel like a "wonder" whenever make it every time.
Of course, there is no power switch, and besides the sound is free-flowing as long as existing the broadcast signal.
Originally, the germanium radio set should have a nice effective height large size antenna(ex: inv-L-type antenna of vertical 10 m, horizontally 10 m) to obtain as much as a lof of power.
But in this experiment, tried to confirm how much does it catch the signal by using just only a ferrite-rod-antenna intentionally.
Medium-wave stations available in Tsukuba-city(Distance:calculated from doho-koen park/Receiver:ICF-SW100S of SONY)
Freq(KHz)
Station Name
Call Sign
Power(KW)
Place
Distance(Km)
Signal?
594
NHK-1
JOAK
300
Saitama, Kuki
44.3
Very Strong
693
NHK-2
JOAB
500
Saitama, Kuki
44.3
Very Strong
810
AFN
50
Saitama, Wako
55.5
Good
954
TBS Radio
JOKR
100
Saitama, Toda
50.5
Good
1134
Bunka Housou
JOQR
100
Saitama, Kawaguchi
42.1
Strong
1197
IBS
JOYF
5
Ibaraki, Mito
50.3
Very Weak
1242
Nippon Housou
JOLF
100
Chiba, Kisarazu
74.8
Good
1422
Radio Nippon
JORF
50
Kanagawa, Kawasaki
68.5
Weak
1458
IBS
JOYL
1
Ibaraki, Tsuchiura
5.1
Strong
1458
IBS
1
Ibaraki, Chikusei
27.2
Unknown
1530
CRT
JOXF
5
Tochigi, Kanuma
59.2
Very Weak
[Experiment by bicycle]
Due to found out that hear nothing by using a ferrite-rod-antenna only, and vice versa, approaching the radio station by bicycle.
And tried to find out where can be caught the signal.
In this experiment, the target radio station is Ibaraki Broadcast System(IBS) Tsuchiura Radio Station(1458 KHz/JOYL/1 KW) in Kamitakatsu, Tsuchiura because it locates the nearest medium-wave radio station from Tsukuba-city.
Except for NHK-FM(Mito), each relay TV stations and community-FM stations, IBS is the only radio station in Ibaraki prefecture.
And it is rare among all 47 prefectures of Japan, Ibaraki is an only prefecture that there is no local TV station.
Unexpectedly, and it might be lucky that there is the "precious" radio station near here.
An entrance of doho-koen park(Ninomiya, Tsukuba)
Doho-koen park of Ninomiya, Tsukuba that was chosen as the start point of this experiment.
Under the entrance sign-board is a bench-mark, and it locates about 5.1 Km almost west from the target radio station.
This park is along the nishi-odori road that passes through Tsukuba Science City from north to south.
And there is Meteorological Research Institute on the south side.
The park has a heated swimming pool, gymnasium, and some tennis courts, etc. And there is a large pond(Doho-ike) in the center.
So adjusted the both of antenna direction and frequency dial around this pond but did not hear anything after all.
The doho-ike pond(Ninomiya, Tsukuba: about 5.0 Km point)
Next, there is a route from nishi-odori road to higashi-odori road(pass through parallel) on the north side of the park.
And travel about 1.2 km to the east, and after passing between JAXA and AIST, exit to the intersection of Namiki 1-chome.
In this intersection, there is an overpass over the higashi-odori road, and adjusted it while watching the car traffic from the top of this bridge, but could not hear anything.
The namikikita-bashi bridge(intersection of Namiki 1-chome, Tsukuba: about 3.9 Km point)
Next, after running about 1.0km south-east on the cycling road that is along the higashi-odori road, there is a similar overpass in front of the intersection of Umezono 2-chome.
Climbed the overpass and tried to catch the sound but there was no signal as well.
An entrance of namiki-shopping-center(intersection of Umezono 2-chome, Tsukuba: about 3.3 Km point)
And more, there is the sasagi-bashi bridge about 1.2km north-east from an entrance of Namiki-SC.
Although this point is just only about 2.5km from the radio station, it could not be heard anything completely.
The prospec is very fine because it is a river-side, but it may also be affected by the low altitude.
The sasagi-bashi bridge(Hanamuro river, Sasagi, Tsukuba: about 2.5 Km point)
Moved about 2.5km along the Hanamuro river to down-stream direction from the bridge, crossed the Jyoban-highway road, and passed on a dirt road of the river-side.
On the left side, there is a slope that towards Nagakunidai Tsuchiura-city, and ran about 400m on the slope, found a small park in the right hand.
Decided to take a rest here and sit down on the bench to tune the frequency dial for a while.
Then I could hear some sounds but could not read what it is...
The sound itself seems to be distorted rather than the sound being too small, so it could not be read exactly.
Finally, caught the signal of IBS here.
The hidamari-koen park(Nagakunidai, Tsuchiura: about 1.2 Km point)
After the break time, go up a slope of Nagakunidai and entering Amakawa area.
And then, after passing a way along the golf course and entering the road along Tsuchiura-Yosui river, and the large radio tower appeared there.
Going further and searching for the dial near the entrance of the underground tunnel of Tsuchiura-Yosui, IBS was begun to be heard.
Then, when tried to move and search, suddenly the sound became loud, so investigated the cause, it seems that the metal frame of bicycle became an antenna,
and the radio waves induced from here that were picked it up by the germanium-radio.
Moreover, found out that the same effect can be obtained by approaching a can of canned coffee.
The effective height of the ferrite-rod-antenna seems to be too low...
And have noticed one more thing. Before the experiment, I was expecting if it is approaching, the receiving sound is going to be louder?
However, it is difficult to hear unless the "threshold value" is exceeded.
Germanium-radio had a very "analog" impression but it seems that the behavior is like a "digital" when the signal is very weak.
Probably because of the "raw" characteristics of the diode was shown.
Looking back on the situation at Nagakunidai, it may be a characteristic of ceramic-ear-phone but it felt like a digital-radio that the error could not be corrected sufficiently.
Such discoveries may not be noticed by using a complex and sensitive radio set.
Near the tunnel of Tsuchiura-Yosui(Amakawa, Tsuchiura: about 400 m point)
In front of the radio station, it can be received without any problems at all. There is a bulletin board that written "about Tsuchiura-Radio-Station",
established since Jan-20, 1965, the broadcasting frequency "1460 KHz" still uncorrected after 9 KHz step(Nov, 1978).
Because it seems like an output power was increased from 100 W to 1 KW as shown in this board(Dec, 1972).
So this board seems to be built during that time.
Generally, medium-wave radio stations are using "capacity-hat" at the top of antenna. However, this station does not use it.
It seems to have enough length because the antenna height is 88.5 meters as shown in the board, so it might not be necessary to add.
Possibly, this antenna works as a half-wave length dipole antenna, so it maybe an end-fed type antenna?(if so, it is Danger! High-Voltage)
The bulletin board is rusting as you can see. It seems like a guide plate to old temple or ancient ruins.
At present time, this station seems to play a part as a relay station. But long time before, the original programs sometimes broadcasted from here independently(as shown below) that separated from JOYF(Mito).
Recently, it can be listened to via internet, and also IBS has begun to service some VHF-FM radios(94.6MHz/88.1MHz).
And therefore, the presence of medium-wave station is being smaller and smaller.
But hopefully, they will survive for the future because it is important role as the news sources whenever disasters were happened.
Tsuchiura Radio Station(Kamitakatsu, Tsuchiura: about "ZERO" point)
From 12:55 for 5 min、★YF（Mito）and ★YL（Tsuchiura）have broadcated independently.
IBS Time Table(Source: IBS Co.,Ltd. / Provided by Kyoto YM39)
[Conclusion]
Summarized this experiment as shown below,
Place
Distance(km)
Signal?
Doho-ike pond in Doho-koen park(Ninomiya, Tsukuba)
5.0
nothing
Namikikita-bashi bridge(Intersection of Namiki 1-chome, Tsukuba)
3.9
nothing
Namiki ＳＣ entrance(Intersection of Umezono 2-chome, Tsukuba)
3.3
nothing
Sasagi-bashi bridge(Hanamuro river, Sasagi, Tsukuba)
2.5
nothing
Hidamari-koen park(Nagakunidai, Tsuchiura)
1.2
heard something?
Near the tunnel of Tsuchiura-yosui river(Amakawa, Tsuchiura)
0.4
good
Tsuchiura Radio Station(Kamitakatsu, Tsuchiura)
0.0
strong
【How about the performance of latest design radio set?】
Regardless of electrically noisy environment in the central of Kyoto-city(Distance: about 400 Km), according to "Kyoto YM39",
the JOYL can be listened during evening time by using his "pocket radio" (PJ-35 of Olympus) itself that without any special equipment!
Below sound file recorded that the traffic information from IBS(JOYL) and some programs from other stations(NBC Radio Saga, or?).
Those radio stations were cross-talking each other under QSB(fading) condition because they are using same frequency(1458 KHz).
a sound from IBS (March-14, 2019 around 6PM in Kameoka-city, Kyoto: Tuned by Kyoto YM39)
From the above example, assuming that the farthest receiving point from JOYL(1458 KHz /1 KW) is about 400 Km, ignore the effects of ionosphere, and just think about the distance only.
There seems to be at least more than 1000x(60 dB) sensitivity difference between the latest design radio tuner and germanium radio because the experiment result was about 400 m.
In other words, even though a large antenna(realistic size) is used for a germanium radio, it is far from the sensitivity of commercially available radio tuners. So the benefits of vacuum tube and transistor inventions are immeasurable...
[Consideration]
Due to ferrite-rod-antenna is a kind of loop-antenna, the effective height of antenna can be roughly calculated by below (1).
Effective Height: H = (Q * ２π * T * S * μe) / λ (m) ... (1)
Output voltage from loop-antenna R(V) is that multiplied H(m) by E(V/m) as below (2).
Receiving Voltage: R = H * E (V) ... (2)
E-Field Intensity: E was introdued before, it can be roughly calculated by below (3).
*Note that; it is a bit difference from actual because medium-wave mainly propagates on the ground surface.
E = 7 * (√Pr * √Gr) / d (V/m) ... (3)
Assumes that each variables are as shown below,(Antenna:ferrite-rod-antenna, Station:JOYL/1458 KHz)
Variables
Contents
Value
Q
Quality Factor
100.00
2π
Two-Pi
6.28
T
Turns of coil
100.00
S
(㎡)
4.00E-5
μe
Relative Permeability
20.00
λ
Wave length(m)
205.76
Pr
RF Power(W)
1000.00
Gr
Antenna Gain
1.00
Assumes that a germanium diode can be worked from R = 100 (mV), try to estimate distance d(m) that is the farthest point(outdoor) from the radio station by utilizing (1), (2), (3).
ｄ = 540.49 (m)
In accordance with the result of this experiment, there seems to be the farthest point at between 400 (m) and 1200 (m).
So it almost corresponds with this roughly calculation.
In case of other stations(Radius < 100 Km: Daytime), it may catch the sound by using a germanium radio set if it could be estimated enough effective-height based on RF Power(W) and Distance(m).
[Further experiments]
IBS owns the other 2 medium-wave radio facilites in Shimokuniicho, Mito(1197 KHz/JOYF/5 KW) and in Tsuji, Chikusei(1458 KHz/1 KW).
So I am going to report it after receiving those waves by using this germanium radio.
[Acknowledgements]
Author would like to thank "Kyoto YM39", he has been provided me a precious material(time table of Dec/1991) and a real sound for writing this article.
[Referrences]
ぼくらの鉱石ラジオ（筑摩書房：小林健二 著）
ゲルマラジオ製作徹底ガイド（誠文堂新光社：初歩のラジオ編集部 編） Lucky FM 茨城放送ＨＰ（株式会社 茨城放送）
[CAUTION]
Please note that the author(s) do not take any responsibilities for that occur any problems for using this article.
