80 meter transmitters

In the early (around 96 to y2k) i had designed few transmitters.
 (later on will be  changing the writing in logical order its just mumbo jumbo at present...... )
My pirate Radio projects.

 Actually when i applied for amateur radio license, it took really long long years to get one license. I gave exams in 94 with vu2lex.

After it was boring  and nothing to do, so made this transmitters. two shown. there is one more. Its not original, but i have not exactly copied anyones ckt. different modules were taken from different sources and made compatible to work for me.

My first 'elmer' was vu2lex om faram khambhata, he allowed me to copy his amerikan book.it contained ckt of w1fb. his set up was all home made 1 watt cw tx diode dc rx, frequency counter using hct ic.cmos keyr with memory. atu, rf probes and a full 2foot by 2foot crate of various ckt modules he made.He never came on fone. After two visit i lost touch with him. he went somewhere for mqth and i also became busy.

Second guide 'elmer' was vu2atn ckt and few other articles copid from practical wireless etc. I made first receiver by duplicating vu2atn 20 meter cw tx. although it never worked on air, as there was no instruments. frequency counter, rf experience etc to tune it up.....when i fed mc1496 with QRO SIGNAL it gave audio note, i was happy, project successful, examinor happy, someone got the marks for engineering project. thanks. (i wish to have eyeball one day with vu2atn)

Then by chance, i made diode detectors and they worked for me. Those were my starting days. I did not know how to wind the coils, even how to solder ! but i learned everything. thats another story.

transmitter circuit description

This is a very low power xtal controlled AM transmitter capabale to provide one way reliable link over few hundred meters.

a sturdy metal cabinet.built in dc power supply, microfone (power supply),xtal oscillator, af amplifier, modulator, one stage rf amplifier. actual rf power is in the few milliwatt range.

few fotographs and ckt diagrams is given here for reference.If time permits will trace out components value  and make a list. Not used since a decade. I hope to revive it and gift ( i dont need money for it) to someone (if s/he wants to vu3hm* in rajkot city) for local (h)AM Experience.

As one transistor oscillator did not give me long range with small antenna i made this big ckt.

Antenna:- i used approximately 30feet long wire as antenna. No care was taken to measure rf or tune anything. I did not have ATU, simply connected the wire to the collector of pa and presto am signal came out very clearly. Litte tuning of pa core furtheer increased the clarity. I was able to receive the signals in portable am,fm radio plus cassette recorder ! This was placed into our second home and it was my bug, a private radio and a caretaker of intruders.

ONE TRANSISTOR transmitter

In facebook, my friend vu2uuu gave me a hand drawn sketch of one 80 meter tx from his own experiments.


Let me reproduce his ckt. I am thankful to OM Kaustava saha for taking out the time to hand draw , fotographa and publish it in facebook. that really reflects his love and care for fellow hams. Thanks OM Saha.

one transistor transmitter by VU2UUU

Considering your need for Local Ragchew on AM mode, I think the choice of 20m X-Tal is not a good one. You must use 40m X-Tal for Local Ragchew. Also, the Amateur 40m band is present (but not highlighted) in SW 41m band, and it will be available in any normal SW Radio. So you can use the SW radio as a Receiver. In case you use a 20m X-Tal then you need to make a AM receiver too,
I had seen a circuit on internet & it works very well. I am sharing my hand sketched circuit diagram for reference. On the antenna side, you can make a standard 40m antenna (prefered) or a random long-wire will also be OK. Take a 500pF variable capacitor & fix the L2 coil.
The L2 coil is made on a 0.6cm former using 10 turns of 22 SWG Cu wire, as shown, to form a tuner circuit in between the 2 section of the 500pF variable capacitor.
The L1 coils is made on a Ferrite Rod, with a 1.5cm dia former & 10 turns of 22 SWG Cu wire. Dont forget to use a good heat sink with the BFY50. The X-Tal needs to be 40m for better local activities, but you can use 20m X-Tal without changing any components. Use a 12v Battery Power supply, because a AC-DC adapter will generate considerable humm in your transmission.
Hope the circuit suits your requirement.
Best 73
de VU2UUU
Kaustav Saha


This all flooded nostalgia. I also had made similar looking ckt from "123 projects"- a book containing the 123 various projects related to the af, rf,digital  gates etc. .

Please dont reproduce my ckt i have dismantled it due to poor performance. but, i taught me lot. Instead use vu2uuu ckt it will works.

my version of one transistor tx (DONT COPY)

Carbon mic was hard to find. I requested a fone repair guy and he gifted one carbon mic for a free from a broken fone. wow !

When i made one transistor ckt with 2N3053 (a very good rf transitor) , only 1 meter telescopic antenna was connected. 3.579 kc xtal did not worked, then changed freq to 27 mhz cb xtal it gave me a range of about 30 meter on 12v batery, but i did not realize that real problem is small antenna and very very low power. i used 100k for base bias. when you use 15k as base bias, the current increase so does the power.

And there is real antenna, tuner and ground. ATU and very long antenna. Now, i realized why i did not got the (range) a decade back !

ATU

When my dsb tx on 14318kc was not loading OM vu2kd told me to take a gang and wind a few turns air coil and put coil between it and tune it with diode two diode and led detector. He explained over fone in length but I could not grasp it ( beleive me please !). but vu2uuu drawing gave it clarity. I will certainly try this LC ATU. I am not yet understanding its theory but if practically it works who cares for theory !

Story of 80 meter:-

There is an interesting story. During my second transmitter testing with small wire antenna (may be 30feet) i was puting some morse code practise to nearby radio for learning and suddenly some reply was coming through. I could not understand it, but gave out my call sign (?)  and signed off. I never had intended to radiate more than 300 meters. Next time never heard him. poor fellow ! but i never received any rst report or any QSL card.  but that proved my second transmitter was working nice, pumping out few watts (!). but, i never tested it again with wire. beauty is that during this whole testing-time this transmitter was connected with dummy load and as a leak-wire / gimmick antenna was connected ! when this happened ! dont remeber the year. Dummy load had become very hot, it burned my finger so i remeber. I had used IRF510 as PA.

i had qsy to somewhere in pursuance of mqth.total about a decade years (2004 to 2012) So, when i started putting things back togather in 2012, that is the reason my tech is little old (10 years) and you find no digital things.... but, it is going to improve. only one aim is to be on air.

i  once heard the vu2pua from bhopal.might have audio recording also. he used just 300mw and tuned vertical.  i regularly hear vu2kd with just 5 watt bitx homebrew, i also hear regularly vu2seg with homebrew 15watt bitx. so, QRP is possible. my friend vu2isr also helped  in checking my signals on air as he is interested to show that even with qrp, west to south qso is possible.

someone has promised me to give an atu. lets see when i am able to get it............

80meter am transmitter

inside view of 80 meter tx

another transmitter based on similar to "two fer" tx

This is another transmitter. first i made mighty michigan and then added the pa stage consisting of bd139 and then found a small modulator transformer 1k to 8ohm used in small af amplifier. with help of lm741 and push pull transistor i drove it will success.

af amplifier, transformer as modulator,

My problem was not able to load the antenna. 

 Has anyone faced the similar problem. 

Various answere came, like , go to  a seniour hams, have atu, use swr analyzer etc etc. i dont have access to these tools ! do you have any idea ? it seem most of guys are using the commercial ones. okey.

 but i searched teh net and found something which is older than me. even i was not borrn at that time. Hams had faced similar problem for a "first time".loading the antenna .. we all face problems in the first encounter. have a look at 1959 popular electroncs . NOVICE 90. then there is endfed half wave ckt of recent origin not requiring the physical ground etc....

20 meter transmitter

The QRP transmitter.

 I was seeing through my old copy of the EFY. Found this. In year 96-y2k, Pradeep.G,   D.Prabhakaran,    vu3nsh etc had published very good work.

I have not made this. But made two tx on 80 meter using little different design and they had worked. All parts are easily available and can be substituted with others. It is a very straight forward transmitter.

If transistor SL100 is not available try 2n2219. Use crown heatsink.

Instead of BD139 try C1162 transistors with heatsink. Any metal slab with 5 cm by 5cm and 2 to 5mm thickness should work. Or try any heatsink you have. You can also try to use the cabinet chasis as heatsink but do care to use the mica washer (but dont use this last option). If you are feeling that transistor is making too much heat try a small fan, computer fan. Now a days computer fans cost very less !. Put it above the heatsink directly throwing air on it. fasten the fan tightly so it dont wobble the chasis or the ckt. Do, power the fan seperately as it requires 210ma ,12v dc.

Seperation of PA and other stage is not marked by dotten line, but i suggest to make the PA in different board, if using the general purpose pcb . Please also enclose the oscillator stage in a small aluminium box for xtra stabilty.

Minimum component and QRP does not mean we dont give it a big box. Of course ! cost will increase, but the metal box enhances the quality of your projects. In the end you will like the result.

May be we can switch the oscillator and buffer stage by a transistor switch. Try SK100, BD140 OR 2n3054 (?)  or a relay if its chattering is not annoying to you.

I see one further developement that we can modulelate the pa stage to make AM Transmitter for local use. It is worth a try.

JF01 ? getting old so forgetting his name also made three transistor 40 meter transmitter. Xtal is important. We will find this 14.318 xtal for some more years. its very cheap 10/-rs per piece. Dont try to port it for other band, you will end up frustrated. Use it as it is.

If i make then, will be sure to upload with my own version. But one last tip. Try one stage at a time. First make oscillator, then make the second stage use it. tweak it. box it. now make the cabinet put everything, fan etc and make the thrid stage. Some sort of atu and relay to switch ON off and QSK is needed. If some seniour hams with antenna analyzer makes some antenna then it will be our standard rig for lots of hams. By, the way 14.318kc xtal freq is very less populated so THE QRP ham can survive there. thanks enjoy de vu3inj

06april2014
please search the jf10zl.html and you will get lots of information regarding homebrew project using simple transistors and they work nice.

14318kc cw transmitter

 This is my hand drawing.

 This is how i put fan on the box , above the power transistor.

For the AM Modifications please search the pirate radio transmitter, they have excellent modulations method i.e heising modulations. Here a choke is used. Now a days there is no audio choke available, best ways is to wind yourself or order speciallly to local transformer manufecturer. You have to provide the data.

Another method is to use 12-0-12, 1Amp power transformers secondary. It work. There you will also need an audio amplifier.

I hope to make this one for  am local use .

In this project please look the blog from time to time. I will not disappoint you FRIENDS.....

coils winding direction

In the year Y2K i made few transmitter ckts. Only resources available to me was old analogue communications receiver with no digital dial (!), AM SW RADIO and simple-calculator, logaritham tables , formula book ( i collected the formulas and made  my own book ! ) on those days there was no internet. If we forget something, then we had to consult the engineering books. I had lots of books of theory, practicals and my own konsultations papers.

In one of the scrape-book i had drawn this ckt.

coil winding 

At that time alladin former was widely available in the form of SW,MW oscillator and antenna coils.

Another type of coils were the metal cans. KANK type, metal can type was only available for the 10.7MHZ fm radio if, 5.5mhz TV FM Sound if and 455KC if coil set, but those were very hard to make/change for other frequency. as they had internal capacitor. Coil wire size was very thin say SWG45, So, we used this alladin former for all experiemnts.

When i was replicating the VU2ATN  20 meter CW Transceiver,  I had to find out the hot and cold property . It was hard for me to understand at that time. I put RF probe on both secondary ends and was puzzled to find they both were showing RF. Hot. He he he. Log time After that experience and further reading got to know that Hot and cold means the  sinusoidal phase directions the rf is taken or given.

After that i made few more 20meter, 80 meter transmitters. valve transmitters. It was easy. In those days in the smae locality we had two big big homes. I had two radio room with big antennas on both houses ! So, whenever i did tx experiments i did not ask other hams to listen to it. I tuned up and do the listening test myself. gone were the days. I regret that on those hay-days i could have bought my own 50k transceiver. Anyway this is life.

On the marry note:- I should have married some  bhavangar girl, so on social visitation to her home, i might have found some communications receiver, tranmitter from ship-breaking yards. Fact is that beautiful womans uncle had one yard in alang. Year was 1992-94. Both were precious. Woman and com equip.

guarat earth quake

in the year 2k1 there was richter scale 5 to 6 magniture earth quack all over the saurashtra peninsula and kutch regions of the gujarat state. Its epicentre was near the bhuj city in kutch but after shock and effect was felt all over the regions. Even my home was also damaged in Junagadh. During this time i had only valve receiver and marine modified vhf which did not worked properly.

I did not go to the are but i did what i could. I monitored the signals and maintained the records.One of my friend when we had the eye-ball qso at my home and saw my logbook copied few entry. He remarked, we did only roughly maintained the log book at g'nagar control room, as it was very vital to keep communications going on. your book is correct based on this we will verify our own !. Thanks for compliments.

few pages

vu3inj

the copy  of license.

6meter tx and rx (ra3aae) experiments.

     Small transmitter

48mhz canned oscillator

local oscillator

pin details of can

Why this receiver

              There was a need to make  small RF oscillator for code practise and demo.  It was my deep desire to know far the small canned oscillator can work as some hams claims ! Is there any justificatins in the claims. Only way to know is test it yourself or beleive them.

             I had some 48Mhz canned xtal oscillator. Also i bought from metro, few 24Mhz fundamental xtals. This does not fall into the ham band but if you have the canned oscillator worth to try it.

     After initial successful testing 40 meter receiv er (PA2OHH design, see the march 2014 post) it was found that in the receiver, audio is bit noisy.

            In the KE3IJ (160 meter/40meter receiver design) there is one Common-Base amp stage. His callsign also contains 3IJ , my callsign is 3INJ ,what a remarkable co-incidence ! we both are brewer.
 

Transmitter

              Now, soldered the oscillator-transmitter and RA3AAE receiver. Will test it for range, antenna and all. 

Testing

          Powered up the tx. Switched on the rx and no tone. On increasing the volume it breaks into the oscillations. There is less noice unlike the common emmiter configurations but it breaks into the oscillations due to the  high gain of common base amplifier stage ! solutions- decouplings. or once again use noicy CE stage.  Ok. This receivers AF stage works. switched on off the QRPp tx (!). but there is no CW tone. RF probe shows tiny lights as it is very low power ( may be 10 miliwatt its not an issue).  Are they on right frequency ?

        Measured the freq. 

        48Mhz canned oscillator. reading shows stable 48.000.30 . thats OK.

        24mhz xtal oscillator shows some what like 24.020.5x

 OK. That means 24.020Mhz after the 24mhz it is up by 20k and on doubling it result into the 40k. No human being can hear it ! only BAT can hear hello cq. 

solutions, due to the VC (trimmer) freq is up,  Try to pull it down with L- a small inductor. But, this 24mhz osc is little wobbly in 100hz range. Put a little filter rc in the +vcc of osc.done not much improvement.

25march2014

         I am writing this on, day by day but will publish after all process is successfull. As one of my friend remarked is it working or not ?

28march2014

the thing which started out as the fun and simple is turning to be a major challenge. Reasons are two. Oscillations very-low freq motor boating due to high gain, and xtal oscillator (LO) is not coming down to even 24.001mhz. I need only 1k to 2k audio tone. Very strange. Tried lots of L and C combinations. It took my whole 3 hours. But, could not bring it down to the 24.005 Mhz. 

So, i will be leaving it and try to cure the audio motor boating first. Then test with the vfo 24mhz instead of the xtal. I think will make it in a bigger board with good audio stage utilizing the LF411, a pin compatible but better than LM741 op-amp ic.

(31march2014)

Deoupler circut :-

I saw this type of decupler in the ARRL dc radio R2 and Farhans(VU2ESE). Well now a days, i am seriously looking into the farhans fone stock website. What he has used and how its used. then look from my collections of the ckt compiled over the years (4 years) from the net. And then at-last the web. But, generally i find the answere from the compilations.

de-coupler

 This decoupler simply reduces the hums, noice going into the low noice pre-amp. It prevents noice coming from line to get into the input and amplified. Its design in not critcal, but use is higly recomended in the direct conversion receivers af pre-amplifiers. You will feel the difference.

VXO

vxo

I did not use the oscillator with two xtals as Low side shif was needed. An inductor was put to pull the frequency down toward 24.000Mhz but i can only manage to get the 24.005 Mhz with inductor -(10 turns,22swg, with ferrite core). So, it is not zerobeating the 48.000Mhz xtal QRPp tx. 

This will be ok with the sound cards-i.e. software radio but for humans ear s  up to 4k  tone is needed. 

So,it will be replaced with normal coil for 24Mhz and beat heard and the project will be declared success. in the front will put a cb rf amp with small whip.

Problem with this type of detectors are when a longish antenna is connected overloading is present and short antenna is not good enough. 

1april2014

It has become april, and project is taking time due to the morning QTH & other activity. I also have to do my share of chores....

Most probably, as shown in the G-QRP magazine SPRATs Mouse Trap receiver, will put a 1k pot in the input for the test.

8april2014 once again got the courage and put it on the table. heated up the soldering iron for an hour. changed few things.Lastly measured the voltages. Hmmm on the collector is less voltages then the base i.e first af stage is not amplifying. needs to change the bias net work. second discouragement was that 24mhz oscillator was not coming down to less than 24,005kc. so, still i will be not able to hear the audio note (10kc) for the test. Tried everything i knew on oscillator includin super oscllator style but no way.... Atlast removed the oscillator and will try it once again. If the compuer was used as receiver i might be able to see the 48kc wide spectrum. Hmm  from that wspr i had taken the ckt ! any way tx stage is okey. rx stage is also ok but they are not matching..... so, project ends here will try to put 20mhz can and with small antenna and batery will test the range. actually this was what i wanted to see.

(to be conitued........................)

RA3AAE detector

 ra3aae

ra3aae subharmonics detector

DIRECT CONVERSION RECEIVERS.

when making the 14316kc cw and dsb transmitters one receiver was needed for monitoring the local signals. i have tried few projects with the direct conversion receivers.  I had tried successfully the ring diode mixers but now a days dont have the ferrites. What a problem.  due to this despite the  caution of a good brewer (VU2ESE). I tried the ic based receiver.He suggested to use DC-40 receiver (ARRL origin) and re-produced world over.

 TA7358AP. a 9PIN sil package fm front end ic as used by py2ohh   it worked but there was problem heavy am breakthroug could work as the local monitor but  junked it. later on i found that py2ohh also used it as building block for his rigs IF stage. i should have taken the words of OM very seriously.

This TA7358 will work within the superhet receiver  as a second detector very fabulously. This ic also gives good performance as the mixers, frequency converters and A very very good DSB modulators. So, i love this ic but not worth for a dc receiver.

So, back again looking for a good receiver to monitor all the signal from homebrew transmitters. LRR40 never worked. My main SAIT Marine is failing me on 40 meter in fact less than 10mhz it is becoming insensitive.a serious problem. I was upset.

Then as a last try, there were two options 1.to work with the digital switches (4066) or 2. these un-conventional looking diode sub-harmonics detecktor. infact russian hams are very fond of this detectors.

RA3AAE sub-harmonics detector

saw few ckts on net but finally decided to go with PA2OHH ( HE IS DIFFERENT FROM A BRAZINLIAN HAM-PY2OHH. PY2OHH has made  the ararinha). This european hams has done a good work on this sub-harmonics detector. he has extensively used it in his rigs. 

back-side of pd

You would not beleive that, withing 10 minutes of the brewing it started working. I did not expected the performance to be so good. so i will stay with this detectors.

beauty is that for 40 meter your oscillator needs to be on 80 meter. i can make the 80 meter oscillator using the ceramic resonators. it has  half the signal frequency. so can be used as QSK signal monitor. will develope it further to a fullfledged receiver for 40 meter.  

CLOSE UP VIEW RA3AAE DETECTOR

Working test :-

For af amplifications a lm386 bases complete audio amp box was used. (see singal tracer post). a small 1 meter wire was used a s antenna.

test set up

 from left, wire-antenna,(tuned ckt is back of first board), ra3aae detector, oscillator. in the back-ground sketches of the the various ckt using this detektor.

test-setup

I dont understand the preset (p1) but when put into the exact half position quality of sound is okey , volume is low. May be it is used to balance-cancel the AM breakthrough....

How to choose diodes:-

there was no guidelines. but, i understand that it is a balanced ckt so, measured the 1n4148 diodes forward resitance in the digital multimeter in 2k range. the two diodes which gave me the same reading were choosed.may be one or two ohm difference will work !

Circuit ( presently used as on 22march2014):- 

my ra3aae experimenta ckt

I am using this ckt. But would like to go for a commond base rf input amp and an common base AF AMP. the hiss of common emmiter in af amp stage is untolerable. My purpose of listening to the cw beacons is solved. so, its okey for me. will box it and if i make further refinements will inform. there need to taken care of the low impedance. p1 has to be low 220 ohm .... when i connected it with big antenna there was problem of complete am blanket so i have to redisign and make a good rf front end taking above issues.

CONCLUSION

:: THIS DETECTOR CIRCUIT WORKS ::

 

Further:-

there are lots of the pair of xtals available ie. (24mhz-12mhz), (20mhz-10mhz,) (10mhz&5mhz),  ( 8.866 mhz & 4.433 mhz) etc. so they can be used to test this detector and possibly use it in some-way or others. these detectors are better than other diode detectors in practical use. try it yourself !

Please dont use it as the front end mixer. I have never encountered ckt for using it as the frequency changer. However, it works good as the product detector. why ? i dont know. It requires very low oscillator power In fact there is needs to reduce the power. I tried to put lesser value capacitor for taking the output from the oscillators. I have not heard the 40 meter signal on air as i am using it as a very simple signal monitor receiver for vwn tx on 40 meter. will update more if i find up anything useful...  (19march2014)

This is one of my project which was realized within half hours including all the r&d. I am surprized why in VU, hams are not using this ckt ? i dont find any problem with it.

Reading sources:- 

I have taken the help of two sites.

First is above mentioned PA2OHH. for  taking the design. further-

Second helpful reading is the http:// www.ke3ij.com /  please aslo visit it. there is a beautiful explanations and his own experiments is shown. worth see his site.

g3bxm has used it in WSPR applications. worth to see his blog also. Roger G3XBM's Amateur Radio Blog:  Roger G3XBM's Amateur Radio Blog:

thats is folk. use this strange wheel. it was always there. but we were not beleiving it....