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 .

 

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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.