DIY WORKSHOP

Audio Signal Generator

A signal generater was one of the most needed or wanted appliance for a radio amateur.
Once there was an IC chip that could generate sine, triangular and rectangler waves.
I read an article in a magazine for hams and I actually built one for me. I was among those who jumped on such an article.
As for the digital display I got the indicator unit and the main parts from Mr. H.
As usual with me, I built one without enough understanding about the IC. That is, the shapes of waves generated were and are deformed in lower frequency. I haven't tried but there might be some measures to improve the phenomenon.

-1/4-

It may be hard to read but the chart is a scale-down copy of a kind of hand written user's manual.
The control panel is not well organized. Many functions were senselessly assinged to various switches and a double volume.
So it requires the user unless you use it often to have the manual at hand each time you use it.

-2/4-

The photo shows the display control boad on the bottom and the back side of the display panel on the front panel on the right side.
A smaller print board that is attached on to the back panel is the buffer amp.
Two power transformers are used the reason for which I can't remember. You can install two regulated power supply on a single transformer, of course.
I used to build things without well prepared designs.

-3/4-

The pnoto shows the oscillator unit.
The heat sink for the oscillator IC is made of a piece of copper sheet. It doesn't look smart at all.

-4/4-

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amp sp selector ss.jpg
Audio Selector

☆"Replacing Old Terminals With New Ones" is added
Preface
Among our radio amatures, three of us(Mr. L, Mr. H and me) are audio freaks. When someone of us completes an amp or a set of speakers, we have review meeting. At the meeting, a remote controlled selector of amps and speakers, which I didn't own long time though other two had their own, plays an active part. As I had made more amps and speakers, I began to feel I need one, too.
I had known Mr. H had principal parts and components for building another one. One day I asked him to help me build one. Naturally, he was cooperateive enough and finally I had one for my own.

-1/9-

It can select one set of amp and speakers from among three amps and two set of speakers either manually or by a remote controller.
The photo shows the first source and the second amp with the second set of speakers are selected.
A black spot between meters is the window for infrared rays with an optical pickup device behind.
One of five sources is selected manually by the switch next to the left meter.
VU meters are adjusted by sign waves to point 100% scale with 2 watts output. However, the needles point only around 20% even with a very loud music sound that would annoy neighbors. Setting must be changed.

-2/9-

The shassis model number is Takachi SL88-37-23SS.
They sell with needed holes cut to orders but I made them by my self to save cost.
Design of holes of panels printed on a paper was naturally very orderly but punching and drilling resulted in irregular holes, though within the permissible range.

-3/9-

In the shassis are
①DC12V switching power board
②VU meter amp board
③An infrared ray processing and program boards in one stack
④Amp & speaker relay board
⑤Source and amp input relay board

-4/9-

Postscript

I found all the more keenly the difference of wiring between the one for tube amps and that for digital circuit board.
The selector functions comfortably but it suffered a trouble. I surmised a mal function of a relay but it wasn't. The trouble was caused by bad contact within some old banana plugs. Have I used cheap banana plugs too long years?
It performed an important role in discerning the difference of sound of a bass reflex speaker and that of a back unloaded horn speaker. The most frequently used function in daily use is source selection.
Failure:
I made too big a hole for an AC inlet socket on the back panel. When finishing it with a file I did it too far. I had to make a small aluminum plate to aply in order to beautify the hole. Carelessness can spoil a whole work!

-5/9-

Postscript -2- (2017/03/21)

After using for a year it started to cause breaking off of sound.
I suspected mal-function of relays. But the actual cause was my imperfect soldering.
The initial trouble that happened soon after building might have been also related to the imperfect soldering.
The mal-function of the changer didn't happen always, nor longer enough for me to open it and find where it was caused. So it took many months to fix it.
I have experienced soldering for many many years and I didn't suspect my skill. Why such a mistake.
I learned that I have never used a double-sided circuit board that had large thermal dissipation areas. Such boards need more heat as you solder parts on them.

-6/9-

Photo：The Red circle indicates a spot of a typical imperfect soldering.
I've got a new eye and it found several suspected imperfect solderings.
I soldered them neatly again and the troubles stopped.

-7/9-

Magnified imperfect soldering spot.
The left leg-like pin is not perfectly soldered.

-8/9-

After re-soldering.
The pin is perfectly soldered.

-9/9-

Addition II
Replacing Old Terminals With New Ones
/Audio Selector
Installed on 2022/04/22

Banana jacks ans plugs on the rear panel became loose causing mal connection. These terminals were very low-priced. I found them at a net shop and I immediately bought them not doubting their poor quality. They were shining in golden color but they soon betrayed themselves. I had replaced a few of them later but recent mal connection decided me to replace them all with new reliable ones.

―Addition II 1/3―

I checked the price of some reliable ones and knew they were rather expensive, which drove me to handcraft them.
The photo shows the materials, a piece of bakelite board and hexagon brass studs with screws on one end, on which I installed a soldering tips while I enlarged screw holes of 3mm across to 3.8mm on the other ends. Their regular size is 4mm. The gap of 0.2mm is a measure for the weakening of the plug spring and keeps make the contact between a plug and a jack tight longer than my life.

―Addition II 2/3―

The photo shows the new rear panel with new terminals(jacks). They liberated me from the unkind mal contact that suffered me long time.

―Addition II 3/3―
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5V Power Supply For USB

I usually listen to music at home by way of a DAC connected to a personal computer.
There are not a few articles on web pages that say the power on a usb line supplied by a computer is of a bad quality and it's not suitable for a DAC to be driben with. Whether it's true or not, I made 5V DC power supplies for my DACs in order to clear the misgivings concerning the quality of the power.

-1/6-

The photo shows the inside of a power supply unit. I used a toroidal coil transformer, which I bought at Kyohritsu Electronic Industry Co., Ltd. Some say toroidal coils are less noisy.
The primary voltage is regulated to the final 5VDC in two steps. That is, 15VAC from the toroidal transformer is reguralte into 9VDC first, then it is again regulated into the final 5VDC.

-2/6-

I made an adapter to incert between an usb terminal and an usb DAC. It substitudes the outer power for the original usb power. The original power line is cut and the outer power line is connected instead.
You can find connectors at AKIZUKI DENSHI TSUSHO CO.,LTD. The connecting barts of cords and socket are covered with hishi(ganpishi) tube.

-3/6-

For your information, the usb pin assignment is as follows.
1 Red Vcc(5V)
2 White D-
3 Green D+
4 Black GND

-4/6-

I prepared anoter adapter, too, converting a two-outlet usb hub into a kind of a combination hub with an original and an outer power supply.
The conversion process is similar to the first one above. You had better mark which outlet is original, for our memory is easy to disapear.
Usb hubs are not made to be remodeled. You have to be careful not to break one. They are easy to break and you have to be ready for breaking one, too, in disassembling.

-5/6-

Postscript

Some say the power provided by computors is of a bad quality while others say it brings no bad consequences in musical playback. It seems very hard to judge which is true.
However, I found one thing myself that the capacity of an usb power supply is limited and to supply enogh current needed in any usb equipment, you need an outer power supply. It is not only the case with an usb DAC. I once experienced a mal function of a disc player, which was solved by an outer power supply.
So, my conclusion is that it is worth using an outer power supply for driving an usb DAC in listening to music.

-6/6-

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encased booster sss.jpg
FM Booster Dedicated To 83.6MHz

Preface Skip Preface

Building an fm booster was one of the measures to kill noises. For an FM receiver has a function of eliminating noises of amplitude characteristics when signals are strong enough.
Incidentally, we had a typhoon a few days before the booster was completed. When it had gone the noises were also gone with the wind.
I was glad but the purpose of making the booster suddenly disappeared. Did I stop making it? No. I didn't think the situation was eternal. So I completed and installed it into my fm receiver for the future noises.
The result was totally unexpected one. The sound I heard was quite different, wonderful sound！ It made me write about this filter equipped booster.

-1/10-

The chart shows the circuit of the filter equipped booster.
Surfing over the internet I happened to find a page which was written by JF1DIR and knew there was 2SK211Y, an FET for amplifying VHF waves.
I ordered a few of them. Luckily, there was a test circuit for 100MHz on a manual sheet enclosed with the FET.
The FM station I listen to is on 83.6MHz. I added one 83.6MHz LC filter at the top and tuned the two original LC filters to 83.6MHz too.
Unfortunatly I can't know the specification of the filtered booster but it gave me a wonderful result.

-2/10-

The photo shows how it looks.
The coils are of 0.8mm enameled wire which were made winding 4 and a half times on a pencil. The trimmer condensers are 60pF, which were adjusted neatly after they were assembled on the board.
The circuit board was made with a piece of copper foil tape, peeling off unnecessary parts. My first experience.

The board is equipped with a DC 9-volt power supply too. The power source is DC 13V taken from the tuner.

-3/10-

This mention is out of order but I calibrated the dip meter before making LC filters using my FM tuner.
The photo shows the meter is set on 83.6MHz. I handled a dip meter after more than forty years.
A dip meter was a must tool for hams. The meter on the photo was not mine. I borrowed it from a radio friend of mine. Unfortunately I have lost mine.
P.S. To my great delight！I found mine later in an attic. It was a model LDM-810 by Leader Electronics which was kept in a corrugated cardboard box clean and safe with a few other ham devices. Only a few bit of expanded polystyrene pieces stuck on the power cable.

-4/10-

The photo shows the cupper foil adhesive tape I pasted on the punched board. The sizes are 0.08mm×38mm×5m.
It was the only item I could find in the store in the line of goods.

-5/10-

I encased the booster in a aluminum case (Takachi MB-1). Later I rewired inside with 1.5D2V coax cable.

-6/10-

The photo behind the antenna terminals.
The coil was wound on a plastic bobbin on the legs of which I attached a trimmer condenser. I wrapped the whole filter with a piece of heat shrinkable tubing.

-7/10-

The photo shows how the booster and the filter were installed in the tuner.
I covered the filter with copper foil and grounded it. I took off the pre-amplifier I installed before, for it turned out that the sound volume was enough without it.

-8/10-

Postscript

The sound of the tuner was good even before installing the booster but the effect of the filter-equiped booster was amazing. I wanted to know why and gathered descriptions about FM receivers.
What I learned was that FM receivers were required to take the measures against jamming, interference and multi-paths.
I surmised the booster I made this time had three LC filters and they worked to improve the quality of the sound. The feeder used to the tuner carried all range of VHF to UHF radio waves and the lower VHF signals for FM radio were being buried among them suffering intermodulation distortion.(to be continued)

-9/10-

Postscript (continued)

I have also learned that analog tuners that were produced during 70's and 80's were much superior than those later digital tuners. I wished I had known it much earlier.
I found a description about how to adjust an FM receiver without dedicated equipment, too. It's my next challenge.

-10/10-

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FM Booster Dedicated To 83.6MHz (II)

Having tasted the delight of sucessful installment of an FM booster into my old FM tuner I made another booster. A portable one this time equipped with five BPFs.
Followings are the manufacturing processes.
The photo shows an outlook of the booster. I omitted installing a power switch but an LED pilot lamp. It has an input and an output sockets for F-type plugs for a wide use.

-1/10-

As I have been usually doing I made a reversed plan of the case in order to mark the positions of holes.

-2/10-

The photo shows the coils of filters.
Each filter is tuned to 83.6MHz.
I planned the pattern so that it makes like a stripline wishing its conduction be effective.
The fifth filter is placed at the outlet.

-3/10-

Trimmer condensers are placed on the other side at the foot of each coil.

-4/10-

An assembled look of the amp and the filter boards.
At first I installed an GaAs wide range amp which I bought at Akizuki Denshi Tsusho but unfortunately it bore noises. The gain of the amp seemed to be too high to the signal that was already boosed. So I replaced it with an 2SK211Y amp.

-5/10-

Photo shows the booster amp with an 2SK211Y with one filter at the outlet.
Copper foil was also pasted over the other side.

-6/10-

A look of inside of the case(TAKACHI MB-2）with the transformer.
The transformer is big but it was what I had at hand. I gave it a short ring with copper foil.

-7/10-

A look of the inside of the completed booster.
Like the former booster to the Pioneer TX-6300, the specifications are unknown.
The booster, when applied to the TRIO KT-8300, moved the needle of the signal indicator upper by a half of its width when it was already pointing almost full scale.
Luckily it didn't bear any noise.

-8/10-

Postscript

We had rain the day before I completed the booster and there wasn't any noise that day on FM.
My TRIO KT-8300 was delivered on the following day. I immediately checked how it worked. It was a perfect tuner and the sound so charmed me that I decided to replace TX-6300 with it putting my old tuner in storage. It was totally an unexpected luck. My original idea for buying the Trio tuner was to keep it as a spare. I lost the opportunity to try the booster on the Pioneer tuner, which I don't care.
Unusually rainy days are continuing as I'm writing this and I haven't had chances to check how the booster works against noises. As for the effect on the sound, I haven't found any changes so far.
The performance of Trio tuner is obviously superior to that of Pioneer TX-6300. It seems tougher against noises as well as for producing hi-fi sound being equipped with the pulse counting detector on top of five variable capacitors. That is, there wouldn't be a chance for the new booster to work for the Trio tuner. (to be continued)

-9/10-

Postscript（continued）

I now surmise that that the effect of the first booster I installed into TX-6300 was superb was because the naked performance of the tuner was poor.
TX-6300, which I bought new when I was much younger was put on sale in 1975 for the labeled price of 24,800 yen, was equipped with two variable capacitors while TRIO KT-8300, which was put on sale in 1978 for the labeled price of 63,000yen, was equipped with five variable capacitors plus the pulse counting detector, a forefront technology of that time.
The distortion free sound of the Trio tuner is in excellent health even now. It is almost moving. Only the outlook is deteriorated. It seems the tuner wasn't used much and the owner kept it in a good place. Lucky I really was to be able to have obtained such a tuner.

-10/10-

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fm antenna installed sss.jpg
FM Antenna (Built In Order To Suppress Noise)

Preface

Noises on NHK FM began stronger and persistent. They were only apparent after a few dry windy days before.
The alternative way of listening to the same programs was by Rajiru Rajiru on the internet. It is completely free from noise but its sound is ACC cordec processed, against which I have a prejudice that it is less Hi-Fi. That is, I couldn't give up broadcast FM music. So, I built an antenna for better FM receiving.

-1/15-

Alternative Antenna

I had been receiving an NHK FM broadcast without a dedicated antenna because the needed signals through UHF TV antenna were strong enough until recently.
So I presumed any metal rod could serve as an enough antenna. I connected a cable to the antenna pole as you see it in the photo. Unfortunately, it didn't work.
I realized the situation and set about making a decicated antenna for FM receiving.

-2/15-

The first antenna

The pnoto shows a part of one of the elements of the antenna(TA33Jr) I used for ham radio. I decided to use it for making a new FM antenna. It had been left years on the roof.

-3/15-

The photo shows trap coils installed in a piece of thicker pipe.
A coil is installed on each end of the thinner pipes so that they are connected each other by way of the case pipe. The thinner pipes thus connected form one long element that works as a multi band element which can be electrically lengthened on a certain frequency or shortened on a certain other frequency. They are beautifully made.
The coils, which are not necessary this time, I took off. I only needed the insulation. A luxurious usage.

-4/15-

Here are the parts ready to be assembled.
They are from up to bottom and left to right:
1. Two elements
2. Screws, U-bolt, Balun
3. Stainless angle stay, U-bolt collar
4. Element holder, wire
Pipes are polished. The balun is a 300Ωto75Ω device for TV.

-5/15-

I tied the balun on to an element, which I cauked with waterproof material.

-6/15-

I didn't make the cable detachable with the first antenna.

-7/15-

The painted antenna being dried.
As the cable is not detachable, it is to be cut to the needed length on the spot.

-8/15-

Second Antenna (Improved Version)

I thought the antenna was perfect but its gain wasn't enough for the limiter of the receiver to completely suppress the noise. So I decided to make an improved version.
I designed a longer holding tube at the center so that it can contain the insulaters of thinner elements on both sides as well as the balun.

-9/15-

The first antenna shared one insulator and the balun was fastened outside the holding tube on an element as it is shown on a previous photo.
With the improved one the feeder is taken out from inside at the center of the holding tube within which is contained the balun.

-10/15-

This time the coax cable is attachable(detachable). The balun is attached on to the short feeder. The needed coax cable to be connected to the balun is already set at the site when the first antenna was installed.

-11/15-

I made use of an old distributor for an mixer.
The device in the red circle in the photo is the distributor(for indoor use).
I used it in reverse as a mixer. The UHF cable and the FM cable are merged into one cable which leads to another mixer for merging with BS cable.
A new mixer like the one next to the red circle was too expensive. Somehow the shops I visited didn't sell one for indoor use.

-12/15-

A close-up and a whole views of the antennas
The FM element is facing the transmitting tower to the north.
Noise levels became very low with the improved antenna but not quite enough. There must be something more to be done in order to reduce the noise?

-13/15-

Review

I suppose the noise comes from those double stack insulators used for high-tension power lines(of 6600V). Their couplings bear sparks breaking over a thin sulfide layer on the surface. The layer is formed and get thicker as insulators get older.
I can try to ask for improvement to the power company. Would they respond to such requirement?
I'd rather try for a time to improve the situation by making a signal booster dedicated to the frequency of the staion I listen to.

-14/15-

Postscript

About one and a half years ago I started listening to NHK FM music programs. Since then the programs became my indispensable source of music.
I have a lot of music saved in my pc but they lose freshness.
NHK has a mass of live music recording and it is growing daily. The quality of the sound is much better than those of usual CDs. Some CDs I have found are noticeably poor in their sound quality.

-15/15-

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Full Digital FM Tuner

Developed by Teruhiko Hayashi

(Installed on 2019/07/6)

● 'Digital FM Tuner:A Wi-Fi donguru Installed' is added. (2024/07/20)here

● 'Installation of a power selective switch' is added. (2022/03/05)here
● 'Installation of a Raspi' is added. (2022/02/14)here
● 'A new repair description' is added. (2021/10/01)here

***********************************************
The photo　above shows my first digital FM tuner I have just built.
About a month ago my Trio KT-8300 FM tuner broke. It really wasn't but I judged so at that time. While surfing for a new tuner I came upon a fpga FM tuner developed by Teruhiko Hayashi. I bought one from him and encased it in an old broken dvd player as shown in the photo above.
Encasing wasn't smooth. Only with his kind advices, for which I'm greatly thankful, could I finish the work.

―1/13―

The case I used is of an old dvd player I bought for 540 yen at a HARD OFF as a junk. My project was to make use of the case, a power unit, terminals and the power switch. The project has proved successful.
At the cash desk of the shop a young lady kindly told me "the player doesn't work." I might have looked very old to her. I know I am.

―2/13―

The photo shows the inside of the player. The disc tray can be operated in and out very smoothly. The power capacity was enough as the voltage was 4.96V with 625mA load. The front display was perfect too. Nice machine it was and hard for me to dismantle it. But I had to do it.

―3/13―

I removed the tray and the case had a good space for the fpga board to be installed.

―4/13―

As the original control board and the display are killed I made a power indicating LED lamp.
The photo shows it. It's made of a high brightness white color LED and a red tip of an old LED lamp. I made this because the former consumes only 0.3 mA while the latter consumes more than 100 times as much power.

―5/13―

The photo shows how the lamp is installed inside the front panel.

―6/13―

The photos show how the pilot lamp works.

―7/13―

The tuner is equiped with a multi-path canceller(MPC) the action of which can be monitored with a small LCD display as well as managed with stop and go buttons.
In order to watch this display inside the case I cut a small opening on the case top.

―8/13―

Installing the display needed a device too. The most reasonable place for installing seemed the place over the provitional four holes for an additional microcomputer.
Unfortunately the hole positions didn't meet and I devised flexible joints with tin wire as shown in the photo above.

―9/13―

The display was mounted as shown in the photo.

―10/13―

The photo shows how you can monitor the work of MPC.

―11/13―

The fpga fm tuner board was installed as in the photo.
The power board is partly enclosed with aluminum plate the inside of which is lined with copper foil. The button on the extreme left on the front panel is assigned for starting MPC training, the next button for stopping training and holding the result.

―12/13―

It took about a month before I was able to listen to FM music again. On account of the tuner developed by Teruhiko Hayashi I can now enjoy FM music with better sound. He suggested the sound can still be improved by improving the receiving antenna, which I'm planning.
The adoption of the full digital tuner was a case of good coming out of evil. For my diagnosis that the Trio KT-8300 broke was wrong. It wasn't. The distorted sound also happened with the new tuner. The solution, after all, was to change the tuned stations from NHK-FM in Gifu to NHK-FM in Nagoya. The cause is unknown!

―13/13―

★Repair Of The Tuner★　　as of 2021-10-01
swollen capacity with arrows.jpg

The red warning lamp of the monitor inside the tuner had started blinking when starting, then a few days later the tuner stopped working. Opening the case I found the chemical condenser pointed with the red arrow in the photo was swollen. The output voltage was almost none either. It should be replaced I judged. Lucky it was the trouble was visible. I changed the power cords which are pointed with the green arrow too in this occasion (see 3/3 below).
Incidentally, I had modified an old DVD player to encase the tuner board utilizing the case and the power unit, that is they are very old.

―repair 1/2―

The smaller capacitor in the photo is the one taken off the power unit whereas the bigger one on the right is the new one which I found in my parts box and fit for the old one.

―repair 2/2―

The voltage check revealed the power cords to the tuner unit were not thick enough. They caused about 0.3V drop by 20cm. So I replaced them with the thicker ones as shown in the photo. Naturally, the tuner revived vigorously(?).
P.S. I listened to an NHK fm program in the evening after repairing and found the sound had changed. I gloated over the sound. My wife, passing by the room, mentioned the sound was good. It's an objective evaluation. Stupidly I hadn't paid attention to the power cord. I knew the importance of the regulated power to be supplied to the audio equipment but it was the empty knowledge. Now the digital FM tuner is showing its real ability.

―repair 3/3―

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★Installation Of A Raspi★　　as of 2022-02-14
added2_1raspi installed.jpg

Drastically renovating inside I installed a frisc sized computer Raspberry Pi 0w for I2S recording (I2S＝Inter-IC Sound). The red arrow in the photo above points at it. I2S recording can minimize the deterioration of sound signals as they don't need outer USB and DAC processes. You can tell the difference by hearing. 　

―raspi 1/2―

You operate the raspi from your pc. On finishing recording the raspi immediately sends the file to your nas. Raspi has a wifi antenna at the place pointed by the deep-blue arrow. The tuner case shields out wifi waves. In order to let in/out the needed wifi waves for the raspi I installed antennas(≒1/4λ whips) as shown in the photo. The inside one in the red circle comes just at the place pointed by the deep-blue arrow. It has been working effectively enough. I had prepared an usb wifi donguru only to keep so far.

―raspi 2/2―
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★Installation Of A Selective Switch★ as of 2022-03-05 raspi bypass power sw.jpg

I installed a selective switch as shown in the yelleow circle in the photo above. This switch selects which way the power to be forwarded, either to the tuner only or to the tuner and the raspi. The tuner board is equipped with such two power inlets. I devised a green led pilot lamp and installed it too. It lights when the power is forwarded to the latter.
The lower part of the photo shows how the switch, the led and the terminal are fit inside the case. Thanks to this new switch you can save unnecessary booting up of the raspi, and thus you can save its shutdown procedure either.

―new sw 1/1―
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★Digital FM Tuner:A Wi-Fi Donguru Installed★　as of 2024-07-20
1_wi-fi donguru out of its hole.jpg

Belatedly I replaced my very old Wi-Fi router with a newer one that can manage WPA3 protocol. Consequently however the recorded music file had often been lost not beeing sent to the NAS. The raspi installed onto the digital FM receiver board takes charge of recording and sending the recorded file with its built-in antenna.
I was possessed with the idea that the raspi OS was wrong and I repeated formatting SD cards onto which I wrote back the OS image uselessly. The situation didn't improve.
Then I learned that the recording of FM music had been normally done. What was wrong was communication between raspi and the NAS. The 1/4λ whip antenna which showed no trouble before working with the old router seemed to have become incapable of communicating with the new router.
The Wi-Fi donguru I had bought and kept since I introcuced raspai to the receiver saved the situation. The trial use showed the raspi OS was normal. The file was perfectly sent and saved in the NAS.
Thus I fitted the donguru to the raspi (at the place where the antenna was) as shown in the photo. It took about two months before I can resume and enjoy recording again.

―addition 4：wi-fi donguru 2/1―

While testing the donguru I placed it by the tuner carelessly. However as the trial use was successful I had to decide where to put it. The best place was where the whip antenna was. I enlarged the hole and let the donguru thrust its body upward through the hole.
Now I enjoy its blue flicker. It makes me feel assured that the file is beeing sent.

―addition 4：wi-fi donguru 2/2―
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An HB9CV Dedicated To NHK-FM On 82.5MHz

I built a new antenna in order to improve gain and directivity. It has replaced the old dipole mounted at the lowest posidion on the mast shown in the photo below. The antenna added stabilty to the superb sound of the FPGA tuner.
(Installed on 2019/08/02)

During the last June my old Trio tuner started to distort the sound at its peaks. I thought the tuner got out of order and I bought a new full digital tuner. It was very expensive for me and the purchase was like a leap in the dark. It turned out later that the tuner was okay. The distortion was caused by the radio wave that was not strong enough by some reason unknown. The new tuner is equiped with a LCD monitor of receiving radio waves which told me I need a new better antenna. That's why I built the one.
Incidentally, HB9CV was the call sign of an ex Swiss ham who devised the antenna which is now called by his call sign.

―1/8―

I designed that the boom contains feeders inside. The photo shows the process of one of the ends of the boom. I made full use of materials on hand. The photo shows a process of one of the ends of the boom. The plug I found luckily in the waste can for metal materials. They were a little too small but I mended the size by applying an aluminum belt I cut out from a beer can.

―2/8―

The photo shows some parts of gamma matching. Materials are crimp terminals and pieces of brass pipe. I couldn't get the terminal and pipe in just matching sizes. So I processed the terminal hole with a 6.5mm drill. They were a bit loose but after soldering they got tightly joined.

―3/8―

The photo shows the feeder connecting component. From right to left, they are a condenser fixing washer, a condenser on a insulating sheet, a nut and a joint connector with a washer. When installing, the condenser fixing washer comes first inside the boom in order to fix the condenser with the wire lastly.

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The photo shows the component being installed inside the boom. Before the installation you wire coaxial cables first, then insert the joint connector to start assembling. The assembling is finished by soldering the fixing wire to the washer.

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The gamma matching on the radiator.

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The core wire is taken out through the brass pipe which is installed at the boom end and soldered on to the crimp terminal. The outside washer on the joint connector is connected to the center of the element pipe.

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The antenna with all components assembled.
At this stage I tried to measure the resonant frequency with a dip meter. Unfortunately, there wasn't a dipping aroung 82.5MHz. There were dippings around 65MHz and 100MHz. I adjusted the radiator length but the dipping points didn't change.
There seemed to be needed to adjust the length of the gamma matching stubs and the capacity of the condenser. However, I was running out my energy then. I was working outside under the temparature of 36-degree C. I winded up the work by measuring the directivity and the gain of the antenna.
Connecting the FPGA tuner I turned around the antenna which I temporarily fixed on the mast on the ground. The monitor showed 5db maximum gap of radio wave reception, a satisfying valu to me.
Review: The rf reception improved from around 75db to over 80db range with more stability. However, the signal levels tend to change worse toward evening. It seemed the receiving circumstances were very poor at my place. Causes unknown. What can be the measure?
My conculusion was to make an 82.5MHz channel filter expecting it to function as an attenuator as well that I continue working to build the filter.

―8/8―
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Dedicated Filter For 82.5MHz

In order to clean the receiving radio wave for NHK-FM Nagoya I made a dedicated filter for 82.5MHz.
(Installed on 2019/08/11)

The little box inside the white circle contains the filter.

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The following is the plan of cavity boxes.

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Marerials of the cavity boxes are a piece of cardboard and copper foil tape. The manufacturing processes are cutting out needed pieces of cardboard and covering them with copper foil. To finish each part you solder the pasted joints.

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Cavities are made as in the photo.

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Before fixing coils and condensers you need to fix pieces of little print board on the two pieces of copper wire( 0.9mm) which are put through cavities. The photo shows how the coils are fixed. The two plates over the cavity box are the pedestal and the lid of the box. You need, of course, to have prepared the coils and condensers that are resonant to 82.5MHz ready before.

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The condensers on the other side.

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The cavity box, which is soldered and closed up, is encased as in the photo. In finishing the cavity you need to readjust trimmers in order that the filter as one is resonant with 82.5MHz.
Review:The total sensitivity turned out to be some 75db, which is 6db to 7db minus. There seemed to be no sound difference before and after installing the filter. A big loss of sensitivity, however, the reception became very stable, plus the input overflow red lamp on the tuner board stopped warnig ever. It's good for my mental health. I keep on using it trying to find anything more in the long run.

―7/7―
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Gauging The Resonant Frequency Of A Pipe Element

Making a dedicated coil(probe) for a pipe element.
(Installed on 2019/09/02)

A few months ago I made an antenna for receiving an NHK-FM station but I finshed building it without gauging the frequency of the elements. I tried but my dip meter didn't respond and so I have been using it off the frequency. I read about a dip meter written by Satoru Ibaragi and learned how to qauge the resonant frequency of an antenna element. Unfortunately his method didn't work for a pipe element. As I wanted to improve the antenna I sought after the method of linking the meter and a pipe element. It took a few weeks but fortunately I came to a solution by making the black coil (or probe) shown in the photo.

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I had tried various methods but they all ended in vain. One day after having tried for longer than a week the dip meter responded with the linkage as shown in the photo. The black clip on the outer mesh wire of the link adapter is directly connected to the center of the element while the yellow lead is indirectly contacted to the pipe. The electric link seemed to have been formed through a stray capacitance between the two leads at this particular place. I saw at last the silver lining in the dark cloud. However, it turned out that the dip point which was unstayble was hard to be regarded to identify the resonant frequency of the element.

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Looking for any overlooked clue I continued web surfing and luckily came to an illustration as shown above. The point was the shape of a link coil. It was a coil as a whole but the shape wasn't circular nor helical. It seemed really a promising clue.

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The next day I lost no time in trying the idea. I made a link coil as shown in the photo. It made the dip meter respond to the pipe. My long grope in the dark came to the end. The next step was to refine on it that it can replace the original coil which works corresponding to the printed frequency on the dail. I enjoyed the building work calibrating it with the original coil hereafter.

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These in the photo are the newly made coil and materials of the coil. They are tin wire, plug tips, a plastic fragment for the spacer and heat shrnking tubes.

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I took the photo above in order to show that their shapes indicate their inductances are the same. The left one (the original) is about 1.5 times taller than the other but has one three-turn helical coil while the other (doesn't it look nice?) has two 1.5 turn coils with a straight line inbetween. Thus the dip meter circuit oscillates the same frequency with either one of them.

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The items in the photo are a part of the adapters and attachments I tried. The white one is a 1:4 balun built-in plug for TV with which I was sure it worked. Actually it didn't. The problem I was facing was too hard a nut to crack for me.

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The photo is a scene of an actual use of the coil. With a much wider coil the link will become stronger making easier reading of the dipped frequency but I gave the direct reading of frequences with the dial the highest priority.

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FM Antenna HB9CV Reformed

The element size was decided so that it becomes resonant with 82.5MHz. The two elements are identical in length. Also, I applied it the theory of HB9CV antenna fully thanks to the article by JA1CPA.
(Installed on 2019/10/09)

The reformation, which had started with devising a dedicated probe for gauging the resonant frequency of a straight pipe, was finally completed.
The phase gap between the radiator and the reflector is being set to 225°.

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Another feature of the reformation is a vinyl chloride boom, which I applied in order to avoid any mal influence of a metal boom to the elements, idiosyncratic without data, though. It looks stout enough.

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The feeder, the mesh and the core of which are connected, between the elements is installed as shown in the photo. It's kept in the center inside the boom by heat insulator, which also keep a constant space between the ground wire (in dark blue) and the feeder by pressing it to the pipe wall. Details (in Japanese) about the feeder is here.

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The photo of the finished boom component.

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The feeding connector is installed on to the boom by screws. The ground wires connected here link the centers of the elements.

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The photo shows how I had gauged the resonant frequency of an aluminum pipe. The pipe I used for finding the wavelength shortening rate is 1500mm long and 17mm across. The rate turned out 0.89. For the former HB9CV I had applied 0.92 only hoping it right. The elements were a little too long.

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The photo shows how I gauged the resonant frequency as well as the best feeding points on the elements. The dip meter responded well to the one-turn link at the end of the coax cable connected to the antenna. The finalized feeding points on the elements were almost the same with calculated ones.

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The view of the finalized HB9CV-II with two identical elements in length. Their sizes look different only because the photo is taken from above a little slantwise. They are both 1635mm long.

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The closed up photo of the feeding point on the reflector.

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The link wires which are beeing connected to the outer side of the socket creep inside the boom and are taken out of it near the cramps at the end and connected to their centers.

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Painting done and ready to be launched.

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REVIEW
HB9CV I-II initialize.jpg

The monitoring pictures of HB9CV-I(left) and HB9CV-II(right). In comparison the peak in the middle in the right picture is lower. Ideally it should be flat as it shows no multi-paths. Wishfully the result is better but actually the gain as well as DU value is lower. Plus, without the channel filter the red right lights. The results are dissapointing. However, the sound being good as before I accept the results.

―12/12―
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A New FM Antenna HB9CV-III

I built another FM antenna(HB9CV-III) on the veranda.
(Installed on 2019/11/05)

'The antenna has been moved' is added here.
'I renovated HB9CV-III again.' is added here.

The former one(HB9CV-II), which is still in use, is not resonant with 82.5MHz but with 80.5MHz. I persuaded myself that the gap is within acceptance. However, the notion that I shouldn't do that incessantly recurred to me. Besides, its place is on the third-story housetop, high but closer to a utility pole. It was a big suspect of noise, especially as it starts raining.
So I built a new one on the veranda adjusting its resonance accurately with 82.5MHz. The place is lower but away from the utility pole and power lines.

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I set up the stainless mast on to a pole of the veranda. The section of which required some special washers for the mast to be fixed tight. The photo shows the mast with the washers.

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The mast was fixed to the pole sturdily with two 5mm stainless bolts.

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The photo shows the device with which I adjusted the length of the element. I notched the ends of elements in units of 5mm in order to read the increased length with sleeves. I carried out adjusting while reading the resonant frequency with a dip meter. The sleeves were fixed with bolts after completing adjustment. Details about building HB9CV-III is here.

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The feeding receptacle is installed at the middle of the boom. The feeders which are installed inside the boom are kept in its center position with plastic material and taken out from the ends to be connected on to each element.

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I made stouter cramps this time by folding their ends and let solder permiate into the folds. I could tighten them stronger.

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The photo shwos how the boom, an element and a feeder are joined or connected.

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Here is the monitor of the reception. It shows one simple peak. With HB9CV-II there were three peaks. The one peak shape is kept the same even when it starts raining. Three month work finally came to its end providing me with noise free and less multi-path FM reception. Banzai!

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Supplement-1：HB9CV-III has been moved. hb9cv-III moved.jpg

Mr. Hahashi, the developer of the tuner kindly advised me to probe a better antenna position for my DU value was too poor for the MPC to function effectively. So I moved the antenna to the other end of the veranda. It worked! DU value improved from less than 14db to more than 20db.
I had to install the mast again and install a longer cable too. However, the trouble was rewarded with much improved sound. It evolved more to a higher stage of hi-fi sound.

― supplement-1 ―

Supplement-2：I renovated HB9CV-III again. hb9cv-III moved.jpg

I renovated the antenna again in order to improve its gain. The gain resulted in 59db improving by 2db. Incidentally, a dipole gain for comparison is 46db.
This improving was suggested again by Mr. Hahashi, the developer of the tuner, who surmised that considering the distance to the transmitting tower and the natural features in between, the gain by an hb9cv should be at least 65db.
I probed carefully and neatly the best space between elements as well as the best feeding points. The former settled on 620mm (from 412mm) and the latter on 195mm from the center of the boom on both elements.
Unfortunately, the work ended with 59db, 6db less the target gain. However, I have been enjoying listening to NHK-FM music more than ever without boosting the signal sice then.

― Supplement-2 ―

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Condenser Discharging Igniter

I have the habit of trying to improve the performance of things.
When young, the general ignition system of cars were Kettering ignition. An essential constituent element of the system was a mechanical contact called 'pointo' (here in Japan). The contact point had to be maintained regularly as it corrodes easily by sparking.
The appliance in the photo is one of the last version of my condenser discharge igniters (hereafter cited as CDI). It was the one I installed to my SUBARU LEONE.

-1/2-

I read an article of CDI in the magazine I was subscribing and I wanted to install the system to my car in order to improve the performance of ignition.
At first, I made a coil by myself for DC-DC converter. Later, I bought products. I followed up CDI articles in the magazine and employed an improved circuit to avoid a voltage drop which disturbs the oscillation when starting the engine.
Years passed and cars stopped using mechanical contact switches. Cars today are full of black boxes and refuse the owner's additional improvement.

-2/2-

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installed sss.jpg
Man Sensing Timer Switch

Preface

I suppose not a few families are using heaters of some kind in their rest rooms. We are using electric fan heaters. They are requisite in winter.
However, an equipment must be turned off as you leave the place. If you don't, it keeps on heating untill some one turns it off. You are to suffer a great frustrating regret consequent upon your failure. To get rid of such a problem, I installed an infrared sensor that triggars a timer switch.
I could buy necessary parts at AKIZUKI DENSHI TSUSHO CO.,LTD.

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The photo shows the inside of an aluminum case in which are assembled a sensor and timer switch board, a transformer, a 15A semiconductor switch, a fuse, a DC power unit and an outlet. The board in the center is the sensor and timer switch board.
I made two units as there are two lavatories in our house.

-2/4-

The unit is fixed on the wall as shown in the photo. It is screwed on to metal bars which were grued on tiles with double-sided adhesive tape.
I worried if the semiconductor switch could withstand switching the apparatus of 1200 watts fan heater. The rush current is very big. The result was "No problem!" They have been working for more than two years without a trouble.

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Postscript

It seems a characteristic of an infrared sensor that it becomes dull in hot summer.
Timer is set for about 100 seconds. That is, you have to move a little to be sensed every 100 seconds. You may think it's a nuisance but actually, it's not. The length is decided from the view point that an electric apparatus is switched off as shortly as possible when no one is there.
I tried a board with a program that keeps it 'ON' while the sensor repeats sensing but the board was too dull for me to adopt.

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Underfloor Ventilator

One day, we happened to know that under floor space was very damp and musty. There were vents here and there but they seemed not working enough. We were too ignorant for a long time.
I bought three Panasonic under floor ventilators. I bought them with a 24-hour timer, too.
I installed them at the original vents on the northern side. But installing was not easy as the ventilators were too big for the original vents. I had to gouge concrete to enlarge the vents.
I didn't have an impact drill at that time and I did the work with a normal drill. Consequently, I suffered a sharp pain on my right arm for about six months after the work. I knew later that the pain was a sympton of aging. Pity!
The ventilators, becaming noisier a little though, are still working during the daytime every day.

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Tandem Communicator

When young, I was riding a motor bike. I used this device to communicate with my wife behind, setting microphones and earphones in our helmets.
The device is simple with only one IC amplifier, which amplified the voices of the two at all times. The volume is set at the level that your voice doesn't bother your ear while you talk.

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