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.

cw transceivers

Problems:- 

I enjoy home brewing. When project  takes too much time in development , board is finished but i do not have other necessary technologies, to wrap up the things i box them up as it is. later on, when time comes ripe, i use these boxed-device after lots of changes. I am rejuvenating one of that transceiver project. That was made few years back. That was never tried on air nor their air worthiness checked.

Our ham station must have some air worthy transceiver.

On impulse of coming to air, few months back tried to make the 21168kc xtal based cwtx-dcrx transceiver but the xtal was 3rd harmonic one. It was not usable on 15 meter and did not liked to use it on the 7056, So i tried the 21096 in the same platform. RX was good sensitive but the irf 510 is not producing enough umphhhh.  Need to redesign the cw tx chain with 2n3866, 2n2078 etc a big work. not doing. abandoned the 15meter for now.

Then i remember in last to last lamington road electronic market, mumbai visit i had bought the 10 number of 3686 kc xtal.  I placed this 3686kc xtal in this modules and there  was RF ,light in the lamp load. WOW.  It might be producing more than 2 watt RF power. workable. This RF power can drive external linear. good. or it should be usable for local com. hope so.

I am becoming old without any contact. Story can be depicted " unused old stock but brand new in package". he he. Why we should re-invent new new platforms for each receiver and transceiver. I am really tired of making separate seperate receiver, transmitter, transceiver for different different bands. A thought was puzzling me, can't we make something that is workable, usable , reproduce-able and worth every cent of that dollar spent ? This  trx making is costly, time consuming, tedious task.

We need one unit with 3-4 bands, even if it is xtal based, DC receiver and CW / DSB transmitter. We must have at-least 2 to 5 watt. this can be put in small box ( samilar as MTR3-B ) and an external 20 watt linear for reliable communications.

Solutions:-

There must be some solutions. Then i searched my xtal storages boxes. i found this 6 xtal sets. All these are in ham-band. and does not fall into any popular crowded net.

meter band =  tx freq crystal = poliakov rx freq crystal
80 meter band = 3686kc = 1843kc
40 meter band  =7159kc= 3579kc
20 meter band= 14318kc=7159kc

So with one cw tx board, band switching and using the poliakov dc receiver using sub-harmonics oscillators i can make three band portable transceiver.

Good idea.When you are making new device, Plan it right as time is finite. Make airworthy, use whatever you have, operate on cw ,then modify for DSB fone. RX front end should have good band-pass filter. there should be wide/narrow AF filter. there must be RIT. Easy tx-rx change over. There should be RF-indicators. And VSWR antenna tuning. side-tones makes it perfect. just have a look at vk3ye.com and youtube for his work and idea in cw qrp.

So work is in progress when its finished will reveal here with a different write-up. 

And yes, i will be QRT with twitter, facebook social media . also not recharged the mobile-fones internet as no work no money due to corona epidemic.

Straight keying morse is a very tiring work so, i will make arduino automatic cq caller. cq cq cq de vu3inj vu3inj k. Please scan the band. you might catch me on 14315kc, 3686 kc calling cw. Send the SWL report and i will reply with handmade QSL card. i will reply very very short "ur rst 5nn bk hw cpy ? "
73
vu3inj
indrajit.
click here to see " 3686kc transceiver " on youtube.

how to do cw qso ?

here is a image i got from net.cw4u.org

have a look. and also visit at cw4u.org.
Enjoy 73
cu on 14.315 Mhz cw, 3686kc