Wednesday, December 31, 2014

BITX Making part-0

Last year, during our brief one minute meeting VU2UPX gave me one packet. This packate contained a good selection of the PCB,PIC for DDS VFO, DVD.  I am thankful to Om Charudatt -ji for  this gift. He had specially commercially ordered those pcb.  Whatever my karmic problem, I was not able to assemble the DDS VFO ( see the previous post ). This costed me a years homebrewing time. Really appreciate and make further projects. Most of project were dependent on the DDS_VFO. I gave it a second chance.  Lastly from that package I made the R7 receiver successfully. ( see preious post)

Due to work, could not visit the HAMFEST INDIA 2014 at Banglore. They gave one BITX40 PCB to all the delegates. and there was arrangement for low cost kit components for Rs.500/-.

Well, I missed that bandwagon. I was felling little desperate. So requested for spare pcb In the HOMEBREW forum. Few promised, but arrived none. (piece be on them atleast they promised). . I wanted to brag about this bitx.  Seeing this, my neighbor and senior ham VU2BGH, Om Bhogibhai sent me his pcb.  Few days later , as a good gesture for participating in homebrew project in the HOMEBREW FORUM, Om Shinos sent me one PCB( also to 6 other friends).

Thus I got two BITX40 pcb , so I remarked that...
Now my time for bitx making has came.... all the bragging will be on vu3inj.blogspot...... pls bear with me.....  My friend @2UPX remarked the following to me.........all the best, but you already have your hands full, Oh humble peasant. He was right but I replied that, you know that commons and kings, never satisfied with their greed.... to make new things.., to acquire more get more beautiess.... he he he.... but actually i never had the cance to make the bitx & brag.......before bitx actually i wanted to make ararinha and one dsb tx......
This is the beginning part, all the bragging and other thing will be from the bitx40 making part-1
I will stat wit the pcb, components lists, links..... I am not giving any time frame..... I might need few 10mhz xtals and cores from some vendor....

so work in progress..... 2015...............

Friday, December 26, 2014

XOR gate mixer, vu2dev

The XOR gate pre-mixed oscillator mixer,
There are many mixer available for radio amateurs RF work i.e common diode mixers, transistor, IC, DBM, some specialized IC, they have their own advantage and dis-advantage. Sometimes you just need a single frequency devied out of two crystals...... a pre-mixed oscillator...                 
VU2DEV, (Dev Rama Prabhu) recently published this circuit by taming the nasty little XOR gates. He reasoned that PLL has xor gate why not try it as a mixer. He made it. I likes so requested for the circuit diagram. After two days, provided me a handdrawn schematic with a remark that he wanted to test it at least 2 - 3 times, so its repeatability, consistent results, characteristics can be predicted. (26dec2014)


Here on veroboard has two IC sockets. He tried it with two different set of xtals before giving me the ckt to test the repeatability. Only one IC is used for one mixer. LM7805 is used for voltage regulations. (A must.)
We need to put a tuned amplifier to filter out the  harmonics and unwanted spurious frequency products. Remember it is still a digital ckt (squar waves reach with harmonics). @2dev has put a LC tuned class-a amplifier. Not shown in the ckt diagram. See the second picture, the transistor Amplifier is on the copper plane.
My friend Om Jishnu has also made this ckt with success. I have to try this out. This digital gates will save me from ,using the hard to find little obselotte TA7358 mixer ic. see my previous post on this ta7358 mixer. They are good, but if you can do more with less component, in a simple way, why not give it a try... You will sure to love the result. Build process and other data will be updated later on....
When time permits, build it & update my own pictures giving my own twist...... till then ENJOY ( the wheel is running ,re-invented by 2dev)

7159kc beacon cw-tx

                This is my QRP project which was developed within a minute. This project can be made within an hour. During the testing of the R7 receiver needed on air signal. I did not wanted to test receiver with bench oscillators. 

7,159kc beacon/ cw transmitter, (40 meter band)

Bifiliar transformer wound on the ferrite balun core is a non critical but a very essential part. You can use any other toroid. Use 30swg, enameled copper wire . Give 8 twist per inch with small hand drill or by hand.( don't use power drill).

Had bunch of the BC549c. It is important to use this transistor, particularly c variety. It is also okey to use BC547/BC548 etc but all the c variety has high gain so can be used for 10 meter and have litte more umphhhhh.

First made the collpit oscillator. don't forget to ground the xtals metal case with wire. Sturdy mechanical fabrication is a must. I made it on the Veroboard.  ( will upload the picture). DC input to Q2  is about 180 milli watt. By putting two extra stage of a small linear the power output can reach to comfortable 500mw to 5 watt.

Well box it and use it as a small beacon around my QTH for testing the on air signals.

I had another idea, put a direct conversion receiver strip, shown elsewhere on this blog to make a simple qrp transceiver.

It will be a really big challenge to get a few contacts with this......

Saturday, December 13, 2014


During the eyeballs visit with vu2upx had gifted me one SSB RX pcb along with other pcb and DDS VFO board , IC.

It seems to be R7 receiver. It is the simplest ssb receiver. I have plenty of the ta7358, 10mhz xtals and tools. Why I did not noticed it earlier. Anyway lets catch up with true things.....
here is the pcb & ckt diagram

Top side view the board::-

Componet side


Showing the links of the R7
The circuit diagram for the above pcb. The PCB is courtesy  OM Charudatt, VU2UPX. Thanks boss

Only components I don't have is the bf245. May be I will use 2n3819 which is on hand. For the varactor have to think or do some  juggad....instead of MV2109 I have BB139. Another bottle neck is the can used in oscillator and filter. I have plenty but not this one. need to modify it. All other parts are simple and one weekends project.

On the 13 dec started this project. lets hope I finish it and brag about it........
on 14-12-2014 done all the big parts i.e ICsockets, I cut 18 pin DIL ic-socket into half and got two 9pin SIL, On the rough edge, please file gently to make it smooth. As this sunday writing down the parts list to shop.
here is the list with my note. Click it on to make big.

1.Print the ckts. Study the ckt and pcb. See that you have all the necessary critical components. There is also help in the form of three pdf files at the fuji qrp website. Read it please. If possible characterize the filters, make LC tuned tanks before doing anything. These are the hardest element of this kit.

2.Ask the elmers, original builder or someone who built it for some insight. In every design there is always some silent points which needs to be adhered. My dear friend 2upx who gave me this pcb remined me to start from the back. Thats the way we all do ! Frankly this will be my first "RF KIT" build. I have always done my own design on perf boards, copper boards with giving some twist to the originals.

3. Study it again. see that you have all the tools instruments. Mulitmeter, 12vdc power supply, cutter, twizer,LC meter. See that y our soldering iron is very clean, if using ordinary iron then file it shining. As tracks are very close there is possibility of accidental shorting. Use MAGINFYING LENSE to do visual inspection. Before placing the components see that you are placing the right values, measure /check it( with mutlimeter, LC meter etc ). Once the components are soldered there is no way to know what it was and the trouble shooting will be very hard.

Lets begin solderig.

4.I first soldered the IC sockets, connectors. As a good practice you should use sockets , connectors.

5. Then Soldered the power supply module. LM7805, 1N4007, LED indicator.due to 1000mfd there should be good filtering. Important for smooth audio.

6. Then the audio stage. LM386. Mounted all the components. I wonder why there is no by pass capacitor (0.01mfd) at the intput pin3. Anyway i am not doing my own change. Try to stick to its original values. As it is the superhet design audio stage is not critical but it seems to have low gain.

Connect the Volume pot and 12v dc. Don't forget to put LS. See that there is voltage on pin6 of LM386. LED light is ON. Normally there should be only murmur/slight noice in speaker, But it should be not loud one. otherwise halt and investigate. Now do the finger touch test. There should be loud noise. All well, then proceed to TA7358stage.

(Gain is distributed all over the receiver. Still i feel that AF preamp for LM386 is needed.. I had to remove the 1k restor between pin1 and 8 of the LM386 to increase audio.)

7.When we do something in india we have to idianize it. in europe & america there are many local hams with strong signals. I dont have hams around me in 100km straight. So i have to make it more sensitive and need not worry for local strong signal.

8. At this time i had to choose the IF frequency. I had 10 pieces of the 5Mhz xtals and 10 pices of the half size 11.059 Mhz xtals. For matching the xtal i built a small oscillator. See the " filter making 1.html ". Noted the readings. Asked the seniour OM over internet for choosing the 4 xtals and one oscilator xtal. They unanimously chose. I put those xtals.

9. BFO was moving from 4999.8 to 5001.8 kc. Okey. At this time i should measure the bandwidth to put the BFO at right frequency. But, still i went on. This stage passed the finger touch test. Moved to the Front end mixer.

10. I just got the 4 pieces of the 680 pf of white styroflex variety. These are good for making a a very stable VFO. Used here. I could not find the 4.7micro henry coils for pin3 load. Can find only 100 micro henry and 3.9 micro henry. Got them. resontaed 3.9 micro henry with a capacitor in my LC Test Oscillator. with 68pf this coils resontates at the 6.9 mhz. I did not like a non-moving resonant tank , will replace it with 100 micro henry coil.

11. Went again to shop to purchase the few more henry coils and few pf values. Found the some old IFT like coils. Wound one IF with one turn. It showed teh 0.1 micro henry. So 11 turns were wound on the internal dumbell and it should be 1 micro henry. As was pushing it into the pcb for knowing whether it can fit or not. The pcb holes were very tight. So with small hard nail tried to winden it. But, still it stuck. As these coils very very old one leg broken during pushing & pulling. I said this will create a mesh. So, soldered it anyway and resonated to HF. it gave me about 22pf+68pf at around 12 mhz. Okey with me. With a varactor i can tune it. for entire 40 mete band. For the varactor i could not find the MV2109. I have BB139 but will try 33v zener diode or normal 1N4007 rectifier diode.

12. till now the luck was favouring me. I have spent atleast 1 hours per day for this little project and at the finale it is giving me trouble....

13. Need a resonant ckt at the front ends. Will have to wind the IFTs for 7 Mhz resonance. I don't have the BF245 FET. Well i can substitue the 2n3819 which is on hand Its not critical but it should be a FAT so that the tapping of the coils can be avoided. This stage is a must othewise the gain will suffer. All the RF selectivity is here. Hope gain of this stage migh make the receiver roarding.

14. I will Tune it with some xtal oscilator (7.159Mhz) and then conect antena & on air test. Hope i get the on air signals.

( Work in will be rewriting this soon24 DEC 2014)

xtal filter making 2

Crystal filter making :- Part Two

In the first part we explored the theoretical part of the filter. Now, at this time we will actually try to find the suitable xtals for the bitx transceivers. Then try to measure the  bandwidth, frequencies of the xtal so that we can put the BFO accordingly.

First thing :- The oscillators to measure the series frequencies...

xtal series frequency test oscillator

As discussed on the part -1, measured the xtals series frequency with & without 33pf. All the data is given below.

I used the PIC frequency meter. all readings are in Khz. the minimum reading is 10hz if you get more accurate reading it will be better to use it. All  xtals are standard HC49.

{ Please be aware  11059kc halfsize xtals did not oscillated in this ckt ....No.8 is not the typo it was actually 10mhz mixed-up in the 5mhz bag. }

(wire open-with 33pf,)  ( wire close-direct , shorted the 33p)

xtal no.--- Open---- --------Close

1.        4999.38       4998.39

2.       4999.37       4998.38

3.       4999.38       4998.41

4.       4999.39       4998.46

5.       4999.36       4998.36

6.       4999.34       4998.33

7.       4999.33      4998.35

8.        ---------      --------

9.       4999.36      4998.34

10.     4999.40      4998.40

11.     4999.37      4998.37

Now, what 3 or 4 xtals should i choose for 5mhz ladder filter. ?

(1,2,5,7,11 would be my selection dear Rathorejee! replied VU2DEV and all concluded on 1257 for filte and 4 for oscillator)

filter from the  xtal no.........1,2,5,7
and for oscillator use the xtal no.,,,,,,4

In the selection we have to see that the xtal frequency should not deviate from each other about 50hz.

THUS this part concludes with success.........
The xtal filter as brewed :: How to test it.How to describe a filter ?Measuring other parameters. i.e Xtal activities, frequency will write on these later on...pls..... meanwhile........
One friend popped up the question "what shoud be the position of bfo freq. if the IF is 4 MHz and VFO is 11 MHz... to tune 40m LSB... should the BFO be below ladder filter central freq. or above the ladder filter freq. ..." .. i checked your blog first.. ... din found the topic... so can you brefly let me know...
Interesting question actually i made a little write up and forgot to upload here. Well answere is simple but somewhat lengthy.... consisting three parts.

First part::- consider filter as a gate. This gate has a centre frequency, actually a band of frequency between those frequency it allows to pass and for others there is steep rejection. These frequecies can be measured by feeding it a RF Signal from DDS_VFO and measuring the voltage at the output. At some freq it peaks then at some freq it drops down. now is the interestng part we have to find this steepness. at one point filter has 3db bandwidth these are two important frequency. It can be represented by the Voltage (y-axis) -----> Frequency(x-axis)... a flat dumpbell shape.

Every xtal-filter has different characteristics as it is not a commercially made filter for a fixed frequency. In our homemade ladder filter we accept whatever frequency band-pass our filter gives. so each fitler differes from other homemade filter.Bandwidh can be increased / decreased by ckt topology and components emperically.

Second part:: - Amplitude Modulation is the basis for all the analogue modulations. In the Amplitude modulations there is carriers and two sideband containing acutal informations. (about 66% rf power is at useless carrer. In the DSB signal we suppressed teh carrier by balanced modulations. Now our signal contains only informations in two sideband. But by using the DSB singal we still waste our RF power in another sideband. As both sideband contains same informations. Is there any way to remove this another side band. Well we have to trim the sideband by some filtering. And here the role of the filter comes.

In DSB modulations ,now our information is on the two side bands. USB is the signal where the information is on upper side band. in the LSB the information is In the lower side band. Another concept clerance this side band is related to the carriers frequency.

where should the bfo need to be put..... Now, there is steep dumpbell like shape of the filter and the dsb signal is without the carrier unlike the AM signal. We have to play with it.

Now, we have the steep ness of the filter. Our signal with two side bands. We have to fix the signals carrier frequency so that it collides with its steepness and let pass only the single side band of our choice out of two side bands.

Third part::-
For LSB The carrier frequency should be high i.e high side of the filter steepness

For USB the carrier should collide with lower side of carrier steepness that is its frrequency should be lower.

To lower the oscilattor frequency use the choke and to increase the xtal osc freuq use the capacitor. Well using the LC in xtal oscillator will give you good tuning range, as we don't know where our filters freuqncy is exactly ? Xtal filters generally shift little down from their xtals marked frequency. To shift the freq down we need L in osc.

hope you got it. some time i also get confused, so i draw it on the paper.... will upload it with full diagrams Actually these all are the practical things once you understand the theory afterwards it has be done practically.

graphical presentation of AM signal & xtal filter

After passing through filter we got LSB signal

After passing through filter we got USB signal

Query and answere ends here.

Chat Conversation End

It will be ALSO interesting to read the PY2OHH. he has published god work on farhans BITX. I HAVE FOLLOWED THE 2ESE in xtal making. As many people have successfully made xtal filter following him. Why re-invent the wheel ? Lets use it, as invented by the VU2ESE.

(work in progress ,,,, )


Tuesday, December 9, 2014

xtal filter making 1

Little History:::

This is the one of the building block which was never mastered to brag about. Years ago I hade made one xtal filter, without any matching and see the way I put the pcb, aluminum shield. After a decade I look and smile at it. It was never used, just soldered it.

After the free gift of BITX40 PCB & cheap/low cost kit supply at the HFI2014 many peoples are making the BITX. from the facebook group it seems that VU3JOJ and VU2SWX are making and uploading the process/fotos on facebook. Few others were also making the bitx.  (As I did not attend HFI2014 at hydrabad, so I did not get the kit or free pcb) I requested for the a gift of pcb if any other ham have spare or not building it. But this gift  did not arrive as of  9dec2014(!) , Then asked a friendly person to make one pcb, not coming. then asked another friend to make one ( which he will at his leisure), meanwhile someone suggested to make Dual bander for coming onto the air.  Asked the kit supplier of HFI2014 but peoples were not giving good opinions. What I can say about it. But if you are reading and want a kit then buy from the VU2SUA. Only he gives the matched xtals.

Whether I make the bitx is not sure but mastering the filter is a must to make my many dc receiver into superhet and DSB TX into the fullfledged SSB transmitters. Lets see.

Designing the Xtal filter :: ( little theory first)

bitx smd version crystal filter testing.html
bitx.htm by py2ohh
TT's Jotting Blog of VU2SWX ... Building Bitx Part2-The crystal filter. html


First stag is choosing the IF of the receiver. The BFO should not be harmonically related to input RF freq,  for 14mhz band 10 MHz IF is okey. so VFO becomes 4.000mhz and IF is far from one and half of the vfo.

Second stage is you need many xtals so it must be easily available. Higher the frequency greater the VXO shift. Generally Ladder filter does its work (filtering) little lower than xtal marked freuqency.

Third stage is matching its frequencies and make the ladder filter. This musing ends here.

Fourth stage is measuring the bandwidth and other parameters of the xtals. For this I don't have any access to instruments i.e. CRO, RF mili voltmeter , DDS VFO, Compute programs
links are on the scanned page please read it .....

Please see part two for practical selection procedure for crystal and other details


Monday, December 8, 2014

RF-AMP designing problems

On the Indian Homebrewers facebook groups posted this Indrajit Sinh
I want to try this ckt, as it does not need toroids. hope simple balun cores will work. i have 36volts power supply ready. dsb,cw tx produces about 2-4 watts. From your view points am i missing anything ? or suggestions please. ckt is on workbench.....thanks.
I want to try this ckt, as it does not need toroids. hope simple balun cores will work. i have 36volts power supply ready. dsb,cw tx produces about 2-4 watts. From your view points am i missing anything ? or suggestions please. ckt is on workbench.... I NEED MORE THAN 20watt.thanks.


  • I also added that how much power should i expect ? i have big heatsink with fan. what will be tune up proceedure of gang capacitor. this is rough sketch, yellow lines shows my intended modifications. i am soldering it. Not finished yet,...

    Ashhar Farhan the output circuit is a series trap connected to the ground! thats a terrible thing to do (it passes the rf to ground at the operating frequency! i would suggest that you could use a tv balun or even an tap washer. this will also need a low pass filter in the output. it not only clears the output harmonics, it absorbs the stray capacitances of the bifilar output transformer.

    Indrajit Sinh Thanks Ashhar Farhan May be i will try put PI or LC filter. Yes, sir tap washer i have tried in 5watt amplifier. It works. due to 30 swg wire it becomes very hot. This time i wanted the more than 20watt and did not know whether tap washer will work at these power level !

    Dev Rama Prabhu Rathorejee, there is one QRP boots circuit in your Handbook which also does not need Toroid's! By replacing his RF transistor with IRF510 we can easily get up to 35 watts with 24 volts supply, except that it is only 40 MTR band! I have tried that circuit and shall post a foto tomorrow! Need to take care of capacitors, higher voltage better!

    Indrajit Sinh I am amazed at the whealth of much needed information available with this group. Thanks VU2DEV sir, looking for it. 40 meter is also okey. I need something consistent which when fired give me an assured contact with friends.

    Nidhi Rajeeve Buying some good toroids and following standard proven circuits will avoid wastage of time and money. Moreover proven circuits will work like a charm. Its high time,that we should junk PVC gang caps and go for reproducible home-brewing.

    Aravind Balasubramanian This is where kits make life easy Try joining the Siars Chennai VUSDR Kit group assembly which also has seperate PA board with Lowpass filters covering all the HF bands

    Indrajit Sinh Aravind Balasubramanian digital is out of reach for me. This is my desperate attempt to get a few cw/ssb/dsb contacts before i once again go QRT. It seems there are very few peoples, who build make RF PA.
    3 hrs · Like · 1

  • Indrajit Sinh Nidhi Rajeeve, i dont have any fobia or toroid fobia or dislike for digital, as simple brewer i want something which can be reproduced by anyone. I make and if it does not work then tell the crital report in a clear impartial words.... may be what i do is a re-produceable one . is it not so ? TAHIR we have see the path of signal , from where RF is coming and where RF is going. FARHANS comment is right. At the series LC the impedance will be minimum and rf will follow the minimum losss path i.e ground instead of going to hi-z the antenna connected at the tap. In the filter rf is experiencing the impedance and only way out easily is the antenna. So , i doubt there is little drawing mistake or 2vkc might have modified but not cared publish it. To put end to our discussion only the 2vks or 3nsh can correct our doubts. Thanks to all. PY2OHH, ararinha, first version has the solutions. It used the simple coil for impedance transformations. Once again thanks all. de vu3inj.

    Ron Mallik This will not work: the output is a grounded series resonant network! RFC from drain to Vdd and then a l or gamma network, followed by a 5 pole lpf, can be managed with air core coils on discarded white board marker pens as former. In your case: load impedance is higher than drain output use netowrk 3 or 5...or whatever: here:

  • Ron Mallik Use Drain impedance as Z0 = Vdd square / 2 Po....ignore drain capacitance for now....
  •  Finally this ckt was found to work for me....
    RF Linear
    here it is ...... writeup is on next blogpost.


For the 40 meter, 20 meter what type of rf pre-amp stage should be used. ,,,,

any design guidelines, examples , i have made one but i need some practical insight please..... it will be driven to the diode pdm ( product detector module).... de vu3inj...

    Dev Rama Prabhu A small 13 dB gain amp would do because of the diode DBM which is lossy!
    Normally the loss of diode DBM is around 7dB to 9dBso excess gain should not be used!
    Happy home brewing!
    By the by 12 dB gain = 4 times voltage gain!

    Kalyanasundaram Ramachandaran Around 10db will ideal.

    Indrajit Sinh should i use high ft transistor c2750 or common bc547 for 40/20 meter front end , calls A,wideband 3:1 balun transformer as load , secondary connected to dbm......

    Dev Rama Prabhu Better to go for 2N3866 as it is strong signal low noise amplifier!

    Ron Mallik 2SC3355 will easily work with 30mA of current at 9-10V Vce. Amazing noise and IP3.....2N3866 very dubious these days..."printing maal" as per local trusted dealer

    Ron Mallik Indrajit Sinh and others: IMHO the electronics is not the main problem. How skilfully you wind your magnetics, will play a big role. For example, the original designer may have carefully wound the bifilar coil with say uniform 8 twists per turn and spacing them evenly on the toroid. The novice did everything, but wound the coils randomly (anything but broadband ) and did not check for phasing: same electronics, but it doesnt work in the latter case! Designer gets bad name but HOW designer will document his skill and experience

    Ron Mallik For 40/20m BC549C is great.....10mA Ic is enough! We should not also ignore the C9018 transistor. It is a brilliant but cheap device. The vendor will make a BIG difference though.....Better to locate Fairchild/Onsemi 2N3904 instead. Atmospheric and antenna noise is much higher so do not bother about noise figure at these frequencies!

    2SC9018, 2SC9018 Datasheet, 2SC9018 AM/FM IF Amplifier, buy 2SC9018

    Indrajit Sinh i fully agree with Ron Mallik on the toroids winding. infact i have written on it in my blog. pahsing and twist no problem. will go for bc549c yes C variety.... as the rx is just for checking the local signal during the testing phase of the transitter... it will be use will similar to FSM. i will be listening on my tic tic and adjust the tx.... as for 2n3866 its a good one but in the market they sell two variety one cheap and one guranteed so not buying any2n3866
    Indrajit Sinh for the bad name :: designer has to really write two type of writings. one as a normal they are doing and one very extensive one ( like i do with writing down even a trivial thing, the process, what i thougt and what went wrong and how i got it corrected etc ). second type of writing we dont see any... that was the reason for me to re-invent wheel dialogues.... lets hope by doing thought churning something good will come out... ( i am not a designer just a reproducer, jugadu...)

Sunday, December 7, 2014

14318kc , ra3aae dc receiver

I had made the linear (25w) using the IRF510 for pumping the radio waves into the ethers. At present only 20 meter antenna was known to work. The 40 meter dipole has the possible coax problem. I have long wire also. But I thought to test this linear on 20 meter due to constant traffic on that band.

I had the ra3aae receiver prototype receiver to test tx on the 40 meter but nothin on the 20. I also wanted to  modified original PA2OHH design for the INDIAN conditions. So made this receiver for the 14318kc cw/dsb tx using the 7159kc crystal.
Will house it in a neat sleek box so look like a walkey talkey.

Hope to monitor it for long range.

building blo
RA3AAE, Poliakov sub-harmonics mixer. by VU3INJ, Indrajit sinh 04dec2014

Diode mixer for amateur :: At the first glance we thing that how the lowly doiode will help us ? But, fact is that they are easily available, very simple to make, gives a very good result, they have high dynamic ranges... can process small signal as strong signals.

In this particular detector, i have made atleast 3 prototypes on the three different frequencies. Now, it is safe to say that its a reproduceable design.

Block diagram:::

First stage is the BPF + RF amp, Detector, AF Preamp, AF Amp. Xtal VXO, ( power supply, antenna and speaker switching, casing etc Hardware).

List of components:::

Ckt Diagram of the first version as derived from the PA2OHH.

This latest Working Version. :::

Tips for building it on copper boards. :::

Problems and solutions.:::

I did not encounter the problems. As most of the problems were solved at the first prototype. Be symmetrical and dont hesitate to use liberal adhesive to solder the copper pads on the copper boards. You will need crocodile clips to hold the components and pads togather. Use wood for giving support during cutting. Please cut the copper carefully so that its straight & clear. Carefull during toroid making so wire does not get shorted.

From this where ?

Its a serious toy. Can impress with childrens. As a gift to new local swl for listeing your signals or as a single frequency local net receiver. field-fone... 

This receiver is  housed in the metal box but i think you should place it in a plastic box. works okey in monitoring my own tx signal i.e 14316.04kc beep beep beep.........


 14318kc receiver


For some time I was not able to post into the blog due to some minor technical problems of the cookies and something else but hope will be able to post here some more experiments done during this times.

During that time I had created a facebook page to upload my images here is the link
I have seen that when you upload the images to facebook its very faster than blogger and the software at the websites makes your images light so it becomes easy to upload on this blog.

If hand drawn image please use black pen to sketch JPEG formet is ok.

I am maintaining this blog as well as the facebook page.

ON AIR 14315KC,  will be installing the single frequency set-up....



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