Tuesday, January 19, 2021

QSK once again how to make qsk ?

     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. 

THE CKT.

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

 HOW TO MAKE PCB BY HAND.

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.

https://www.youtube.com/watch?v=61WyLP8NHds


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. 

RESULT

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

https://www.youtube.com/watch?v=T7KEtFLjVts 

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

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.

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 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.

 

Saturday, January 2, 2021

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.

Friday, December 18, 2020

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