Thursday, July 15, 2021

20 meter cw transmitter reviving.

 I have one small around 2watt CW transmitter based on VU2ATN AND RM96 stages. It has one 80 meter VFO which feeds to quardrupler stage from it goes around to the tx stage and then driving the IRF510 LINEAR. those were my earlier days and i did not know nothing about the IRF510 and linear at all. But it heated the 2 watt 50ohm dummy load easily so left it as it was with hope that one fine day i will revive and make it air worthy.

There is one DC receiver strip lying around. My friend VU3INK now VU2JXL is avid cw lover and infact he has made one telegram group for CW only. it is time that i put this TX on air. Plan is to dismantle final IRF stage and put one stage which can bring me around 10 watts CW with 24 volts DC input.  i think it is doable. I also have 14.0 Mhz crystal . this will put me into 14.015 range these peoples are going around. Hope it works out.

Meanwhile enjoy the pictures, everything is hand made. first compartment is a VFO a very stable one. second contains TX cahins, quardrupler, then buffer amplifier, then another tuned amplifier then IRF510 in its rudimentary form. it works.

i doublt will i make a fresh new ones or i make this tx into another one ? will require lots of change. Still not decided what i will be using for the receivers ? POLIAKOV topology my favourite or the modules i have. Because the time is short and i need to make it fast.

the box. i have hand painted it. more thena decade old.

inside the black box. each stage has its own shields as they were talking to each others and putting out the self oscilaations.

VFO and tx chain.

another view.

ENJOY, as it is. wheel has not turned up !!!

Friday, May 7, 2021



I recently went to Mount girnar for the event SOTA  I have a good vedio materials and experience to share. But due to the suddent events of the life i could not put that wrtieup in Feb itself an/

it all started with this campaign. That my nearby hams were going to the HILL TOPS  and i should also join them, but that was conficting as i was not travelling due to physical debilities and no-vehicle at that remove place. i thought i also climb the mount girnar. I took my VHF/UHF baofeng handy and made a tour to my nearest hill top MOUNT GIRNAR. To had a sked plan on 145.500 to talk to them.

This journey had dual purpose. to propiate to my devi a very excellent shakti had not visited her since 2011. a 10 years time , i was living in that city. Anyway it was now due. i make a sankalp despite my ill healthy to climb and have darshan and possibly talk. But primary target was climbing up for religious reasons.

have look at the fotographs and vedios. (to be uploaded later on)

Tuesday, January 19, 2021

QSK once again how to make qsk ?


Once again i am making the QSK for the earlier made qrp  7.159 mhz vxo controlled cw transceiver. It had only simple switching and was good enough for doing tuing tuing carriers tones. but for the effective cw use you need FULL BREAK-IN QSK. 

I have found the problem why it did not work on air ? faulty dipole antenna coaxial wire. It had aluminium foil which does nto work , i should have used the copper one. dump it and will make a long wire or half-wave from that dipole install and remove the wire. let's see.

how i checked the dipole ? with the 40 meter receiver it was producing more noice then signal and with even a small house antenaa wire it produced less signal and ok volume. so that coaxial has been aproblem. sometimes it takes lots of time to find the true problem.

this time i will brew a linear for 80/40 also so that i can use the 3.686 kc system as well as 7.159 system. you need atleast 15 watts. and the 50 watts are good thing. the single FET IRF840 can produce it easily with 28 volt power supply.

before the linear is made atleast i should have the trx fully ready so this qsk. 


here is the circuit. its actuall and revised from the earlier version as i changed the components.

QSK revised
The components are placed on the veroboard. I like to use veroboard for this part as it is DC control section and veroboard holes provides easy to put components. Here we are taking the two output one is with delayed on/off control of the  relay. the delay is important. Two diodes are used to clamp the capacitor discharge voltage to a set minimum. It helps quick switching off the relay.
component placement !! work in progress

it will be finished and then uploaded the result.  

to be continued.....

Sunday, January 10, 2021

how to make pcb


pcb making by hand

This is a very very crude and old technique. it is wonderful for prototyping the small RF projects. This is a unique in a sense there is no through hole. the component is surface mounted but use normal components. It has maximum copper. It is more rigid and solid then sticking the copper-pads on the copper plain. Here component are also not hanging loose over the copper pad. the computer generated pcb are more efficient, accurate & repeatability. But, hand made pcb are designer, small kit builder, new hobbyist friendly. 

I have seen that these hand made PCB works wonderfully for the RF devices. I use it exlusively.

We need good copper clad boards. Better start with single sided glass epoxy based board. That is mechanically strong, copper is little thicker then the normal ply based copper board.
I use oil-paint to paint the tracks. My recommendation is to use two colors one for tracks, pads etc and one for plain copper ground. That way we do not mix-up while painting. 

First draw the ckt on plain paper. correct it for all mistakes. put the circuits in small small portions/modules. That will help finding the faults or isolating the RF stages.
Then have actual transistors, resitors, inductors, capacitor, connectors etc you want to use for their dimentions.

Once again see how this components will be placed on board, what will be their size, orientations, shieldings etc. Signal flow directions. Vcc lines. Controls, indicators etc.
Oscillators always need to be shielded even if it is xtal controlled.  xtal filters needs more ground plane. 

Be it RF amp or AF amp using a single transistors you need atleast minimum3-5 pads for placing components around transistors. IC needs atleast whatever its pin counts, so on and on.
After placing components with minimum distance & not crowding them you can create the copper islands on papers. check it with components size. See your whole project in simple modules say input RF band pass filter, Rf amplifier, filter, diode detector, xtal oscillator, Af amplifiers, IC amplifier , power supply, connectors. Thus ckt are understood as a modules unit. then giving transistor ic parts number makes easy for us to loacte them in PCB & ckt and for future discussions. Thats it !!! we compartmentalized our pcb into module after module. When you are placing the components see your circuit diagram. refer to it. check you are not missing any components. Visualize it. Thus finally on paper your board is visualized and drawn. use 1 inch graph paper that will increase accuracy.

Now take the pcb. measure it cut according to the size you realized on paper. wash it, clean for dirt thumb prints, greece etc. file the edges clean smooth it.

Generally i use 3 inch by 5 inch size boards. Not hard and fast but this size is ok. On this draw one inch greed lines. These boards are not small nor big. Enough for a small project. 

Sometimes we have to cut the board according to our box or the project in which we already want to add & fit into. there we can use 3-4 small sized boards and put them on vertical stack. usable. imagine. when you use the sealed can/ shieldings then signals do not see others and do not interfere. That's good enough. Sometimes  for shielding put 1-2 cm high copper board that also works good. 

When designing see that you have maximum copper ground area. It should not be broken between two module that  create complications & earth loop. You have connectors at edges, there is round holes for the pcb. if these holes needs to be isolated then plan it early. 

Before etching do not drill holes. That part do not cover with color and it will etch-out and drill hole. So that nut-bold/screw used for that hole will not touch our pcb ground.

After pcb is drawn checked i let is sleep for 12 hours/ over night. Next day i check for any mistakes or things i remember to put at hindsight. 

If there is any variations, just rub the boards with ink-erasur/ alcohol that part of whole pcb board and wash with water dry and do once again with pencil & markers.
Use ruler for straight lines. go slow do not make mistake. Now foto graph that for future reference.

pcb coloring/painting is simple. use the finest knibbed edge / paint brush. dip and brush fir island, tracks. let it be straight lines boxes do not let it blot & spread out etc.
let is dry. 

Then use the different colour paint and paint the copper ground that you do not want to etch. At this time, mistakes are done/happens as colours touches already painted tracks. so be careful. if you make mistake, note it down on paper and move on. when the colour dry at that time remove that colour with small kife very carefully. 

So, the board will start drying within a hour but do not touch it. let it dry over-night. next day these board is ready.
If oil stains your hand wash it with soap.


Next day when the board is dry see that it is clearly dry paint is not soggy. if need arise let it dry for another day. After then put that pcb into fecl3 ferric clride solution/ or HCl hydro-cloric acide and add h2o2 hydrogen paroxide ( available from medical store) and about half hour one hours it will etch. time to time stirr it. is it bubling or not, then add more h2o2 and it will start bubbling. When the pcb is etched take it out and see are you able to see track from back side. then its done.

wash your pcb with simple water, soap. have little bit of scratch-papers, i use from kitchen. and remove oil paints. Do a visual check. have continuity check with mutlimeter, if needed  cut the track with knife. Now you can not put pcb into etching solutions.

here is the vedio of painting the pcb full 12 minutes process. click here.

After this you should wrap etched copper pcb in dry cloth or paper till you use it.

For tools i used, marker pen, knife, ruler, paint brush, paper drawings. 

to be continued... etching fotos and end result. 


the pcb was etched successfully. here is the part2 vedio of pcb making. it looks nice. 

use fresh acid, fresh hydrogen peroxide. add the hydrogen peroxide generously and it will bubble up. wait wait  then it will etch fast. never used the acid used earlier. do not use more acid then dippin the pcb. keep the tray as small as possible, more acid more hydrogen peroxide needed. so use small container that dips the pcb and thats it.

always keep water and cloth to wash acid if it touches your body. use the goggles , white glass for eye protections.

(by the way i have populated the board and DC receiver based on poliyakov design is ready here see the fotograph and write up will be here and vedio will be here :- link to be included later on )

3686kc  poliyakov receiver.

the wheel is successfully invented use it.

Thursday, January 7, 2021

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


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.


JS8 & FT8 are slightly different thing. At present i know nothing about the JS8Call but have a look at its American inventor vedio    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.

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

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.

Wednesday, January 6, 2021

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 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.