Friday, July 31, 2015

15Watt Linear

Here is the schematics and PCB pattern for my 15watt linear.

15watt linear component placement

15watt linear pad placement

Descriptions, History :-

I had made this linear by accident. My 5watt cw tx/ DSB tx was not giving me signal reports. I was worried ! What is the  problem ? Then it occurred  to make a single device linear . One ckt was interesting . Put queries in the Indian Homebrewers forum at Facebook. And lots of reply came. VU2RON, VU2ESE, VU2DEV and lots more friend jumped in.

Finally tried it with IRF510 but it went burst with 25volt dc power supply. Then changed the IRF840/IRF640. Both worked fine. vu2ese had suggested me to put some 200pf at the drain. VU2DEV suggested making a Pi-LC matching. He even pointed out the calculations in the ARRL handbook , which he had gifted me. But, I settled for transformer & toroids. Ron hinted on impedance transformation of this broad band transformer.

Then made it. I used Small pig nose baluns bought from tpsonline Bhopal. Put 6 togather. 3x2, Glued with water pipe glue and it worked. It did not heat-up. The biggest problem with the ferrite is that it heats up and freq response depending on the size and material. So, we have to take care of this problem.

I used in the input a resistive 3db pad. This db-pad solved my problem for loading the exciter, proper match etc. It was happy happy solutions. With pad some fraction of input power is wasted in heat. Its okey.

I put LED to indicate power supply presence. I put a protective diode 1N4007. Not shown here. The VCC line is a big one.  Instead of deriving 12volt from the pcb I used the LM7805 voltage regulator. The simple preset is used on the pcb to bias the gate of IRF. At gate a small value resistor 5 ohm is used to stop parasitics. If you have ferrite bead please use that also. Now, a days we don't find ferrite bead esily.

Filter is classic bilateral 50 ohm three pole. Simplicity. Actually 7 pole filter should be used for more spectral purity.

The relays for changing over the antenna etc are not used here as it was meant to be a beacon / CW tx.

Components & Schematics:-

vu3inj linear

Setting up the linear:-

this requires some care & instruments.
Put Digital Multimeter into 10A range. Set the current to about 100mili amp. Now key the exciter. Make sure there is RF. This will increase the linear current to about 1.2 Amp. Use the dummy load or dipole antenna. VU2PTR digital VSWR meter will indicate the 15watt. So, this is the set-up. Nothing more. Mind you the preset tuning is little trickey. Slight increase in the bias and power jumps from 5 watt to 15watt. At one point of time you will feel that heatsink is too much hot but there is no power increase. buck down a little... don't set it for constant 1 amp. at max 300ma is also good. Do little experiments but just care for heat....

This linear has been never tested on SSB. If I ever do, will let you know.My approach was use whatever is on hand. Till date I have made two linears and both work wonderfully. One is with me and one is with VU2TOO.

Heat sink:-

It is one of the most important factor in this linear. You ought to use a biggest heatsink you can find. Old CPU heasink is okey. I also use the fan.

On Air test:-
On one two occasion I asked for listening service from VU3INK now (VU2JYX ), VU2DEV and two more hams. I am thankful to you Kishore for being with me. My signal was good. consistently 55 to 57. In this I had not tuned my antenna at all. SWR was around 2.5, So, the signal reports are not bad.

Will update few more fotos of linears and corrections within two days.

That's it folks the wheel has been re-invented.

Use it and don't forget to customize the bells and whistles ( relays, heatsink , box etc)


Tuesday, July 28, 2015

Signing Off - VU3INJ

Something is simmering within me. I am just closing my station, it seems due to one reasons or other reason I am not able to put myself on FONE. For me CW is okey. My journey had been a topsy turvey. Around 1994 is started ham radio, finding the forms, filling it up, giving the exams, finding books for exams, learning morce, waiting for exam dates, meeting hams, brewing , homebrewing, learning the soldering from the scratch, understanding the semiconductors, valve, EFY, for the result, police enquiry, missing of files at wpc, my MP,member of parliament putting my case and then the licenses. How much this all took time... lots and lots of years. Now a days the person who gives exam withing 3 months start enquiring when their license will come ? I waited , prayed, tried to figure out, many friend VU2MAU,VU2MKV, VU2Mukesh desai, VU2EXP, VU2JF(Jivanbhai-sk),VU2LB, VU2FQ and many many more,VU2DK,VU2HEG (Yep Old man hegde) and many more (whose name i am not writing here )really helped me in one way or others. Still I am stuck at the build the bitx paradigm, making of radio has become guardian knot. I don't know what to say. THANK YOU ALL. I am disheartened at the murphy looking me in each corner, each time I do something it breaks one vital element. May be this being on air is not for me. 15 years, this much efforts and still not on air.... I can say no more. Let it go indrajit... let it go

I had tried BUILDING, i tried BORROWING, i tried BUYING. But, found nothing that can put me on air. 25W decent can put anyone on air. So, the homebrew dream was wrong ? Some peoples are getting air with just 500mw (vu3pua) or 5watt. Why i am getting everything that has one or two minor fault. It never works for the fist time...I wished VU2OO had gifted me the Major havildar sing ( ?) RM96 for 20 meter. I wished had VU2ATN gifted me a working rig instead of coaxing me to build the bitx. Buying 50k rig is beyoung my budged. May be no -body understood the gravity of my situations and problem with murphy. But, thank you all.

Wish is a big if and not if. Wish is not a true reality... i could have wished god given me so much money that i might have been able to import the rig, I should have wished i never choosed the ham radio. I could have wished Niar Hyderabad had given me club rig. I wished i should not have wasted 15 years on a dream. I wish i should not have written signing off note.... wish is a never ending thing.....

WISH IS NOT A TRUE REALITY. Many peoples are really not understanding my words, meaning and more.... this is the real signing off note.


My jinx is simple........... I am not able to be on air. And once on air with brewed, borrowed, bought or begged rig, home brew or commercial, then murphy will let me go. Jinx will be broken and then even 500milliwatt signal will give me good mileage.... thats it folks.....
Listening for final finale...

You peoples had been a good company. will miss you.


Wednesday, July 22, 2015

BITX, Single Frequency Receiver-2

Peter VK3YE  made a wonderful signel freq transceiver based on the BITX. My previous experiment is here. write up looks similar.

Frequency is 14315kc , ( 20 meter band )

 I had one 14315kc transmitter and made two three single frequency receiver. Those receivers work for Testing my local signal only. I wanted something air worthy. Which can receive other hams signal. So, made this...

Lets start from back-wards.

1.AF Amplifier stage:-
LM386 In standard form with BC549C af preamplifier.

2.Product detector:-
Using subharmonics detector... he he... I don't have third 14.318kc xtals. So used the available 7.159xtal. Also did not had the balun core. If you have balun cores use them please. Another option is to use  differential 3 transistor Single balanced demodulator.

3.IF Amplifiers:-
 As given in bitx. As frequency is higher the gain will be low. Ohh this is the reason for Rx being so much deaf. Need to add one amplifier in Front end. { Read last para, finally found out the true reason, the xtal  had moved a little and loose connection happened. It works fine. No need of extra gain }

4. Front end band pass filters.
Even after making this working receiver I did not put the filter. Could not find the RFC nor a IFT. Was lazy to wind it up. One day legendary VU2DEV suggested to me K&R Filters. Here the tap is taken from the capacitor instead of the L.  My problem with filter was that I could not find suitable component for L and taped L does not work as receiver BPF. You can see VU2DEV use this type of filter for his JOTA, S7 trx, GR40, ISDR etc. Somehow I managed to make a suitable filter.

Have a look at his blog

5.Cabinet and Speakers.
All standard things.... I really homebrew cabinet.  In our kitchen we buy 15Kg oil in metal pack. So, when it is used up, I cut the metal box which is 2foot x1 footx1foot. So, it give a good one box for my projects. I buy paint from local store. Generally black paint . It is a thin metal, so I can do most of the mechanical work without any problem and it last more than 10 years.  After that give a pint job and it look new. He he. this tech is 15 years old.

The schematics and pictures will be updated. With full details.

PCB Sketching:-
I sometimes make the pcb very very old style. Using the oil paint, paint brush and Feric Cloride as etchant. It is no hole , surface mount type pcb. Of course for normal components. This is the process to make a quick prototype. Draw it, etch it, make it and test it. The prototype is ready within a day.

 Here AF amplifier stage pcb patter before it is etched. In the blank right hand side I have put the detector using manhattan style.
Af Pre amp + LM386 audio amp. 
RF amplifier, Second stage is cascade.
RF Amplifier with Xtal filter.

If I make further project then will integrate all the ckt in single board with replaceable filter assembly.

You will often see the similar ckt. reason is simple. The modules have given me time proven performance. So, they are innovated and used.

AF pre amp, LO,detector, IF2,xtal filter, IF1 Amp.

The last write-ups and this write-up looks similar. It should be as it is one and the same thing.
I intend to put up a BPF and do some on air test for my beacon. From one QTH to another QTH and measure its performance.


I  finally boxed up with last screw.  I want to make it as a black box. Literally its painted black. The VXO does not deviate much... I need to make some components change in VXO... add one rfc.

It is quite sensitive. There was one glitch. signal was intermittent. Did the screw driver test. I put screw drive at the second IF amp. It did sound loud. Then put at antenna side. No signal. so somewhere is dry solder. Pressed one xtal. Presto the signal boomed in. Did heat up all joints. Then suddenly once again signal went down. So, I looked minutely. Oh the real culprit was second leg of xtal. It was loose. So soldered it. And all is well.

Now.....Installing the bandpass filter. Installed and working fine. Will do some field test ..........

One  ham  VU3YFD, informed, he had also made the transceiver for single freq. But, I have not seen his ckt  nor the picture of that project.
VK3YE , Peter had made it and worked successfully. He has put it website. Both hams done transceiver in 40 meter, mine is just single receiver.
 I have tested and found working. Will try to design the pcb and offer kit also so that  others do not have struggle.
The wheel is re-invented  Worth try it.

Friday, July 10, 2015

On air , part-5

Tale of two transceivers:-

I have promise of the SSB transceivers on 20 meter an another on 40 meter. I have all types of wire antennas, dipoles etc, power supply for QRP and one or two liners.

Licence is valid for next years.  And upto next year will be in and around at my present QTH. After that it's possible I will not operate, not renew my license ! Who knows.....

I have plan to print the QSL CARDS. Will send it for one months QSO. Then 100% on demand only. Will be regular on band and will finish up my bitx and other transceivers and will gift them. Will print card without call sign so other friends SWL can also use it.

If this does not realise or there is some problem, then what ? Nothing. My region, district is a ham desert. There is no one around me. I have know how to teach. I can initiate/encourage some new guys into becoming hams. For that, I require a working Transceiver  to give demo. I could not give them the feel of being on air with a sinleband xtal CW TRX.

As a seed some trx was needed, I have nothing to test my home brew stuff. Loss of digital marine receiver was serious loss. It's not just money, I lost a friend also. I dislike loosing the friendship, for me friendship is more important , as its hard commodity to get by easily.

May be I will be getting the JOTA transceiver 40 meter and BITX-20.


Wheel has moved.....

Ha Ha Ha ........ where is the wheel ?

As of 15 july :-
May be in this week I will be getting this JOTA transceiver at my shack... But, somehow my desire to be on air has been killed by "build the bitx dialogue by many senior/juniour hams...".  But, for me this is it. I am not buying any HF transceiver after I receive above Jota Trx and BITX transceiver.....

23 July 2015:-
I have received the Jota transceiver. Its modulations is nice. vu2dev has specifically made for me. And for making it he made another rig also to test this rig. The metal body is good. VFO is quite stable. Very kind of 2dev. He has gifted the mic-handset of ahuja make. Also, did not charge any curier. Thank you Dev Ramaprabhu sir. 

25 July 2015:-  
I did test with long wire and power meter. It seems its a real QRP of 2watt. Today bought the 12 volt relays each costing rs70/- (about 1 dollar).  I asked the shopkeeper give me 8 terminal relays. He  smiled at hearing this. I should have said, give me two c/o relay. We are in this business since last 15 years.... he he. Ya, i said, this is the layman's language..... 

I am not using the existing 20 meter PA by output changing LPF coils, I will make another 40 meter Linear  based on IRF840. Let's  make and see that it gives me the contacts. With long wire antenna i was able to listen only. Will erect the dipole tomorrow. If  this set-up does not give me anything then i am QRT and will be running the beacons only ( pirate)  or CW on xtal based transceiver.

Peoples using smallest efforts, little money and easily come on air. What is problem with me ? Spending this much time , effort, resources, still not able to put myself on SSB fone. Many peoples have helped me. Still this problem ! VU2KD, VU2DEV, VU2UPX VU2PTR, with pcb, materials, instruments, books, tech support. They are the masters of the masters.
May be my ham-karma is bad. and frankly I don't know how to balance it !!!!!

I have no local support. My support is from DX places. Time and time, again its proved that the QRP never works for me. I need atleast 15watt to 20watt pure RF power, just to be heard at some nearby stations.

26july 2015:-
Opened up the JOTA TRX top lead. A very professional approach. The metal body is a very strong one. May be 16 SWG sheet metal. Which can be very hard to bend. Inside there is big relay. There is one copper plane in middle. Which shields the VFO as well as the modulator. The PIC counter is neatly placed behind the LCD panel so it does not occupy too much space.  It smells fresh. No smell of anything burning. There is no loose connections. Everything seems to be in order. But the 13watt linear is not producing the power ? I have run CW tx in those its a continuous power, in the SSB its peak power.  OK ? OM Sunil  TT also has the similar trx, but he has dds vfo. May be there is no problem at all. I just need to put a big antenna and a very big linear due to my living in the dry western part..... ok
27 july 2015:-
I opened the top lead and staring at the linear. Trying to figure out the connections. I am tired of the "miss murphy". Requested for the ckt diagram. If possible will start trouble shooting. Most probably I will remove that linear card and put  my own "2watt linear" into the box.

I wished that VU2OO had gifted me that RM96, which he promised three years ago. Anyway sometimes you have to let it go.....

I AM NOT ON AIR-40 METER as of 28july2015.

there is no wheel !  the wheel has not moved. End of searching the wheel.

(Each time I say I am QRT and still try to mess with Miss Murphy, hope one day she will yield to me and she will give birth to the child called success ! )