JH8SST/7 FT8 dc receiver

JH8SST/7 FT8 dc receiver

In one social media one of my friend, living in JAPAN call sign  JH8SST/7 does lots of home brewing. I liked his design skills. His boards are cute, simple & working.  I saw & followed his design steps as he outlined on the twitter and asked one or two questions and he very courteously replied it. I am putting his work for my information and as a collected resource for inspirations for others. I hope my friend JH8SST will like this write-up. All copy right and credit is due to him. I just publish as it is.

Assembling a direct conversion receiver for 3.5MHz FT8 reception.  

The circuit diagram

First of all the circuit diagram. this ckt is based on VK3YE our all time favorite PETER from Australia.

JH8SST/7 DC receiver circuit

Now, i have a look at the pcb design and the text with them as translated from japanese to english by google translators. I will request JH8SST to look over this pages for any correction etc.

3.531 mhz xtal

design

PCB pattern

pcb pattern etched & ready

DC rx and other 28 Mhz SSB rx board etched togather

Hi patterned boards, do you want ferrocloride bath ?

xtal osc stage ready

Ahha finally completed board !!!

See 9v pp3 battery & board in plastic box.

with antenna tuner board is roaring.

another look of the board please.

Computer FT8 screen dump

beautiful japanese balcony with antennas.

QSL CARD.

JS8 & FT8 are slightly different thing. At present i know nothing about the JS8Call but have a look at its American inventor vedio https://youtu.be/G2kv41mVLPk    a 15 minutes vedio.Hope that will give enough information's about what is JS8Call , how to install software into computer, what should be interface between computer and transceivers and also do not forget to see the video of vk3ye channel. http://js8call.com/

Now the text as translated, you can understand  it as a build log.

1- Inspired by VK3YE's 3 Transistor's only FT8 Direct Conversion receiver, I designed and built the 3.5 MHz FT8 DC receiver. An RF stage was added to make it as RF-Ring Detector-AF, 1-V-1 configuration. I wonder if this simple receiver works for FT8 reception ? 

 

2- The Home Brewing in my winter vacation. I've completed all of the PCB's  as i planned. The 3.5MHz FT8 receiver has been tested and confirmed to work with no problem. It took a bit longer time to complete all of those PCB's. 

 

3- On the first and the second day in my winter vacation, I completed PCB etching. Unfortunately, the parts I ordered for those PCB's were not delivered during the vacation, but I managed to assemble them by using parts I have. The assembling procedure was started from the 4.630MHz Crystal Converter board, and then, 3.5MHz FT8 receiver board. 

 

4-  I ordered the 3.531MHz HC49 / U crystal for the FT8 DC receiver to the Arrow Electric with express surcharge. First, I assemble the crystal oscillator circuit portion and tested. It oscillated with no problem and the frequency was adjusted to 3.5310MHz by a TC/trimmer capacitor. 

 

5- The diode ring detector portion was assembled. 

 

6- The RF transformers were wound on the 10K coil-form, 2SK241 RF FET and related parts were soldered, and the RF stage was completed. The FT8 receiver board was completed. I wonder if this kind of simple receiver really works for FT8 reception ?

 

7- The Audio frequency amplifier portion was assembled. 

 

8-  Completed & put into Akizuki Electronic's plastic case. Does this simple DC receiver really work for receiving FT8 signals ? 

 

9- Testing, the 3.5MHz FT8 receiver. At around 20:00, many signals appeared on the waterfall. The signals from JA1, 2, 3, 6, 9, 0 areas were decoded. The antenna is a only 5m lenths wire + simple coupler. I was excited. 

 

10- My "Mini shack", comprising of Home made 3.5MHz CW receiver for practicing Japanese Characters CW reception and the very simple, RF-Detector-AF amplifier configuration 3.531 MHz FT8 DC receiver. The antenna of the 5m length wire + coupler is too simple, but by using those receivers, now I can enjoy the SWL/shortwave listening of FT8 in addition to the reception and practice of Japanese character CW .

 

--- xxx ---

My note  

Now, i feel that FT8 reception will be achieved by a simple device and that will be inspirational for other to make their own. IMHO The Japanese transistors can  be substituted by any of our locale HF variety or even BC547 will work as used by VK3YE, 2N3819 FET, 1n4148 can be substituted for build. Will i ever try it ? do not know. I need to finish-up my long pending projects, box them up and then think on these digital technology.  

My dear friend JUN did look into the blog and corrected the google's Japanese to English translations. I am thankful for that. Now everything is OK enjoy the wheel.

PCB modules sketch

 This are my standard design for pcb making by hand.

In early days i made the pcb with a very crude way, painting the pcb copper side with oil paint. they dry it and then etch it , wash it then put holes. And polish it. Then populating it. 

It enhanced my RF circuits functions due to copper plains giving a good ground. Earlier i used to make circuits on general purpose 20x30 veroboards. They were good but due to the holes it very not useful in high frequency use. But, there are some uses which it is better to use vero-boards. 

In the plain copper PCB board the substrate are two types. Use epoxy-glass based one, Those are strong mechanically and electrically.

Here are my standard sketch

in first page you can see xtal oscillator , xtal filter, poliyakov diode detectors, RF amp stage with xtals used as IF or TRF . so this is a complete receiver.

 

In second page a simple RF or AF amplifier, common emitter format. that is also a standard building block.

one day i will build this into one and that will be the end of R&D in poliakov receiver. That will be available to all.

DDS VFO CONUNDRUM 2020

DDS VFO this little useful nasty things has always intrigued me from the start. My tick-toe started when i first met dear friend VU2UPX he gave me a pcb & IC to populate to make dds vfo. I procued the at that time famours AD9851 CHINESE module from banglor priya sloka arya ji. He was a very good gentle-men. he gifted the arduino nano. At that time tried to make one DDS VFO BUT could not due to the software skill-set was not enough. My friend from the EU helped me in my medical as well DDS VFO. He made a shield for me. I tried to test but somehow could not make it. As at that time My computer was old and i did not know how to programe ARDUINO etc. 

Time passed on. one fine day our beloved VU2DEV-SK also gave me a DDS VFO. even sasi bhusan of indian homebrewers forum gave a pcb but what i lacked was the ATMEGA328P a programmed IC but no one gave that to me that programmed. So, with time it went to dust.

Then few days back i saw on facebook one of my friend SHUDHINDRA  of banglore providing the VFO based on si5351. i liked his short introductory vedio. I needed something which is not power guzzling. gurudevs VFO was boxed well but it required 12v 1Amp power source of its own and did not understand its functions. ordered teh VFO. i chatted with him on whats-up. oHH now i have two working fones. hee hee. Then deposited money & he sent me via INDIA POST. it arrived. 

You can see its un-boxing vedio click here. I should appreciate his working skills are very good, nice packaging, boards are sweet may be specially custom made. I do not know from where this VFO+BFO is used. but anyway it is useful one. 

After unboxing it i tested it for VFO sections. I had made a superhet receiver board with 10 Mhz IF. it utilized teh xtals. i could not get on air signals with it there is some loss or gain mismatch. hard to probe it. I used it for testing the transmitters signals. I connected that receiver and this new VFO section. i did not connect wire for 10 mhz OSC of si531. The vedio of test is here. I find the DDS VFO very stable and well marked. the display is good. hardware part nothing to tinker for we end user. he has done it carefully. 

He has done everything. Software the arduino board has usb port so you can update if you have skills or simply replace it with y our own arduino. interesting. powered on and it started pumping the RF put to the diode mixer and it received my local Tx signal on 3686kc cw tx. interesting. single side reception is possible with superhet. It use the push button within rotary encoder for changing the resolution of 1 hz, 10 hz, 100 hz, 1k hz, 10 khz, 100 khz, 1 mhz in incremental step. With rotary you can increase or decrease the freq in step. 

Everything was smooth but i am here to find the faults. lets find first fault. This push-button is with rotary encoder, so its very tiring to push and sometimes i miss it as i have not pressed hard. menu also opens up with this. So, this is  software fault. One thing i noticed that push button increase the freq STEP resolutions it does not decrease the resolution steps say from 10 khz you can goto 100 khz step but can not goto 1 khz step. This is very annoying for rapidly changing the frequency. this is software flow. i need to ask him is it intentional where this ckt is originally used may be that will be the case.  up-down switch is highly recommend.

Second thing i find very very annoying is that in this beautiful device there is no provision for the BFO RIT. receiving side we need RIT. there must be a provision for changing BFO frequency, because our homebrew rigs xtals are not perfectly aligned and that is detrimental to receiving and transmitting on same frequency. If one pot is fixed for this that will be a nice thing.

So, this are two flows and it related to the SOFTWARE. it can be changed and i also humbly suggested. May be he will come up with solutions to my questions one day. But over-all it is WORTH HAVING THIS DDS VFO.

i recommend to procure this DDS VFO from him.

 

GDO AN PRM10

GDO AN PRM10 Recently my friend gave me his AN PRM10 grid dip oscillator. Well, in days of micro SDR and softwre DDS VFO who plays with this WW2 age devices ? 

It was a nostalgia for me. Cost was a bitter stip but he made it light due to his affection for me by sending me extra 2,5 kg power transformer, 50 watt dummy load and a meter. There were other buyers but he wanted to sell to actual users. My friend inquired why i did not home-brew anything or not on air for quite some time ? we had big chit-chat about me, my lifes updowns, homebrewing etc. he lowered price for me.He is my generous benefactors over the years. Earlier he had gifted me some RF boards, SPART hard compy a years magazine set. I just grabbed this GDO. I could have bought the microBITX but now a days i am detesting everything slamic. So, i wait for the xtian & pure hindu brewers to get me things. Well, that is my spiritual issue and nothing can be said or done on that. Well will finish later on.

He posted me the device through the couriers. it took strong 10 days to reach me. Then i did a first test of power on and blew the fuse. Then i reverted to him with my problem and tried to make my transformer using the reverse transformer idea but as the loading was pure resistivity, it required the current and voltage. So, once again i requested to send the transformer (as free fund). Very kind of him. its a bit heavy 2.5 kg piece. he specially found out from some radio junk. It was very dusty. dusted it used it. 

Then did the first test. with this new power supply. it dipped only 14 Mhz coils. i was thinking that other coils are 10 Mhz which it did not dip on 10-22 Mhz range nor in 5 to 10 Mhz range. Later on i ferefered my ckt diagram. Actually the If was a tunable 4 Mhz around. so, i said that it is success. hee hee. 

Then today did a oscillation check. injected the RF oscillations into the xtal controlled DC receiver. it produced good stable tone. Freq was very stable. good enough. the stray metal capacitance was not affecting the internal device. so that was the thing if you make a gdo it should be air tight. ok later one. 

on my you-tube channel there are videos. just google AN PRM10 and my videos come up on search. There are not many of these equipment surviving. I do not know whether how it dips or not as never used this type of instruments. thus test is going on, as i have to master this equipment. 

Yes, the equipment works but i will take time to learn.

110 volt AC conundrom.

 110 volt AC conundrom.

I needed some power supply of 110 volt ac for a valve device i recently acquired. Its need was 110 volt ac 20 watt. As all valve radio devices have pure resistive  loading part . So, they require more current capacity that required in start-up etc.

Well we in india have only 220 AC line. We find lots of auto-transformers for many nintendo and other consumer product. They work for them. i can also use them. My problem is i do not want to have live wire at any part of my instrument. That is because my small kids also loiter around my shack/office room/work room and they touch and help me also. when we are testing less worry we have more we concentrate on the work. 220 ac has very small thevenine resistance that means it can source lots of current.

I once had from junk an auto transformer having 220-110-0 . i did not like because when i put my device on it that ruined my fuze. thank god. you can see that in my vedio. link is here first vedio. part 1 

and second vedios is part 2 .

Then i did thought well 110 volt is just half of our line voltage why not put two transformer back to back and get. I thought i got the solution and rushed to the shop. bought two 12-0 , 5 Amp and 12-0-12, 5 amp transformer. With mischievous smile that i conquered my problem urgently wired and the transformer. it cost me 170+170 =340 Rs approximately 5 us$. i said ok as could not get the 110 volt ac transformer. Then made it it gave me around 116 volt ac. i said ok now lets test my American soldering iron of 30 watt. If that work then sure my device with 20 watt power will work. Put my soldering iron and it loaded started to slowly heating up. i said ok, test the voltage and it was around 72 volts.

See my notes. putting here as pictures. Then, i thought that my device is not getting enough source current due to the inherent high resistance. So , i need more current to push. So, on next day i bought another 12-0 , 5 Amp transformer. paralleled it with 6 ohm combiner. Thinking was that it should see small resistance going toward the output 110 volt ac transformers and high resistance path towards other transformer. see 6+6 ohm path and zero to output transformer. 

Then i parallel 12 ohm to get 6 ohm as could not get 4.7 ohm. i think this idea is good but you need some small 1 ohm resistance that will be enough.

well what happened, first i said compare my result with only one transformer, 12 ohm. it gave me No-load 93 volt. good enough. Then with 6 ohm resistor i got 107 volts ok. but on loading 30 watt soldering iron it turned down to 43 volt ac. Why this happening because we have finite VA that wattage and we have internal resistance of the transformer so when you need more current then voltage reduces and you do not have enough umphhh. EMF.

Then i paralled two transformer. See the diagram. 

i tested and it gave 113 volt ac no load and 57 volt with 30 watt load. As last try removed the resistor by bypassing it. so it hold me around 77 volts and the iron was immediately becoming hot. which means it is getting enough current.

Despite having this 3 transformers i am not getting my result. Why why why. i did everything to reduce the thevenine resistance to get more current ?

i paused, if i had asked someone to make me a transformer then in 510/- that person might have made me a brand new transformer. what i will require is 110 volt act with 500 ma to 1 amp current capacity. it might be big. 

I knew that my thinking is right, my problem is thevenine resistance. i do nto want to use 0-18 volt ac in output transformer. As it will increase the no-load voltage and then reduce it to working one still it will be not constant 90 volt, the required minimum. What a conundrum.

What i have not tried. Looked at the setup. Not finding solutions. i gave up. solutions is simple i have more then enought VA as input. Why i am not getting the enough current and voltage as per plan.

Paused. let it go. Then in the night time when i was closing down my room then looked at other transformer. Ohh, the 12-0-12 volt ac has thinner wire compared to my other jumbo 12-0-12 5 amp transformer from different company. Ohh, it seems i found the solutions. I need to replace that big transformer with this tiny transformer.

RULE OF THUMB is that output transformer should be thicker wire then input transformer. 

Lets see.

I tried one of my old very meaty transformer having thick wire. it produced me 120 volt ac. No voltage drop. Then on loading 30 watt iron it got me around 82 volts. That means i am nearing the range of 90 volts. I am going on right directions. If i use these two big beefy with large dia-meter wire i am sure that will work out. as 20 volts loads less. and minimum voltage of 90 volts i am near about. If my shop had those tranformers i might have solutions with less cost. Anyway i will be using these power transformers also in other projects. It is not wastage.

Meanwhile, the original source, the friend who got me this GDO has promised that he has a spare power supply transformer and that will work. waiting for it.

I can say it was partial success because, theoretically i was right in getting the voltage, testing it. But, practically i invested 3 tranformers but my choice of half voltage was wrong i should have chosen 18 volt combinations, 0-18 & 18-0-18 vac with thick wire. lower voltage we go the wire gets thinner.

RULE OF THUMB  choose higher voltage transformers. Less loss in flux, hysterisis, less internal copper resistance.

RULE OF THUMB Second thing, use both transformer with thicker wire, that will reduce voltage droppings. If you are planning learn from my experience. VA ratings should be atleast 4 times of the load.

problem solved. hope this helps you out. It is possible to use this configurations for low power use. Please always avoid auto-transformers. It has shock hazard as its directly connected to the mains AC line. It can source large current so device if not fuze protected or voltage current sensitive, it will be hard to it.

so, wheel is re-invented but it has puncture. so, waiting for the spare wheel.

Third vedio of working power supply ok here is the first working https://www.youtube.com/watch?v=jLmvUZ_2dTo

morse code radiotalks 2

In this page , we will start our journey to understand the morse code.
how it is made, why it is made, what is science behind this code.
how code is actually made and from this code how coding and decoding of inforamtions is done.

So, the vedio is the direct introductions to the morse code.  key words are
 https://www.youtube.com/watch?v=zHzNP72n5vM
morse code
dot, dash, space,
alfabets, numerals, punctuations, pro-signs, short forms, grammatical symbols.
coding and decoding.  morse key. hear it write down pen paper.

By listening to this short durations 9 minutes vedio you enable yourself the above concepts. why and how code is created is given in the end part.

So, now what ? is it end ??? no, it is beginning. morse code is sound. have a good start. easy regular and everything will be fine.

Next vedio we will learn each alfabets of these codes. till then 73. by the way this blog is always under construtions. whenever new nice words things comes i put them, re-arrange it.

Lets learn,
first vedio is  ET IM AN link is https://www.youtube.com/watch?v=Be8wy9iGU-I
 second vedio is So DU GW KR link is https://www.youtube.com/watch?v=TfGxzy8F52w
third vedio is H BVJ C  FLYQ PX Z link is https://www.youtube.com/watch?v=JnNB6jd1mjM
Fourth vedio is
Fifth vedio is about practising the character so far we learned. https://www.youtube.com/watch?v=TnTcp6gmqTQ . Download the software. practise listening to it daily 10 minutes morning evening at your convenient. That will be a good help.

MORSE CODE CHART

1, E T
2, I M    AN
3, SO  DUGW KR
4, H BVJC FL YQ PX Z

MORSE KEY

INSIDE MORSE KEY

familiarize.

radio talks 1

https://www.youtube.com/watch?v=8aZuB5DK7zy

click here  for vedios https://www.youtube.com/watch?v=8aZuB5DK7zY

Here is the transcript of the talk.

My name is indrajit, i live at the foothill of mount girnar. i am farmer, advocate and i am radio amateur with call sign VU3INJ. i also write a blog. you can find link in the discription. vu3inj.blogspot.com.

For me the inspirations of making this small vedio tutorial is the KE0OG, Dave Castler. he remind me our elmer vu2dev, guru dev.

There are many information's, vedios, books, talks inspiring us to be radio amateur. there are many vedios on how they enjoy their radio hobby and their achievement or special technical subject of expertize.

From my experience, the radio amateur journey can be classified in the follwoing time-line segments.

First is ---> inspiration to be ham / radio amateur and then actually contacting a real  ham. Getting a demo in club stations etc. First step is inspriations, many peoples are doing great work on it.

Second is :---> getting ready for the asoc , ham radio examinations.
fill the forms,apply for radio examinations,get the study materials, preparation for exam, giving exam and finally declaration of the result.

after this i call a
Third stage is :---> If successful, waiting for the license this can be month or years. There will be anciliary process of police verifications, fee and other correspondence.

Forth stage is ---> Actually getting the licenses in your own hand.

And fifth stage is :---> procuring the instruments.radio equipments. the biggest pitfall is here. You need to decide. What choices ?  make your own radio instruments, buy cheap chines ones , american kits, or japanese commercial equipment. this is a big thing.

Advice from my experience is go for commercial equipment. over the time save your money over the years when you get around 35k-50k look for fresh rigs which suits this budget ft817 and many mores etc.

Do not fall into the traps of homebrewing. although i am a big homebrewer and learned at great cost of money and time.

Whole point of all these talks is getting into the air and communicate.

in india due to red tap and securities issues the license issuing process is very very slow. nothing can be done about it. bear it.

Be on air. that is true ham radio. being on the air should be our motto. All other steps are necessary evil of the system.

be on air day after day and then you will really enjoy the friendship and comradary of radio amateurs.

73, see you on AIR.