40 Meter Receiver (7159kc)

Few days ago a friend asked me about the simple receiver to practise his CW Skills. Well, i have done few experiement with poliakov receiver and they have given a repeatable , proven results. I scanned indian products and could not find any thing for the small kids, new hams or something very basic minimalist, cheap devise. So, I filled in the space. Its better than pixie, tixies, foxx etc but less than well made DC receiver . Brainstorming started, I thought let's re-re-invent the wheel.....

here is the result

This requires minimum of time to make and its up and running within hours. It can be used to practise morse on air. It will certainly not bring the good dx nor it is frequency flexible.

See my previous posts, you will find many experients on this subharmonics receiver. It is still in development stage. You can have dip file from me. Just drop an email. I am making a suitable transmitter. In my mind is two way. One to use this LO and then use the doublers amplifiers to arrive at 40 meter so the hard to find find 7159kc xtal can be avoided and further 3560kc resonator can be used to give flexibility of freq. working on it. Tx might be three stage 3watt, along with relay change over etc.  Another tx will be using 7159kc xtal , class e two stage to arrive at 3watt.

Lets begin::: It all began with this ckt, have a good look. From this all other things are derived. First transistor is an RF amplifier. Two back to back diodes forms the sub-harmonics mixers. Second transistor is AF amplifier. The gain of This AF/RF amp depends on Rc/ Rb. If you find the gain is little low try experimenting with it. 470k/4k7 will give gain of 100.  The choice of transistor will determine the gain as well as noise. The RF transistor should have high ft ( gain bandwith product) that way it will produce good signal. In my experiments I found that bc547c, bc547b gave different gain. 

Small whip antenna works fine. For higher frequency please use some broad band transformer coupled RF amp. That will give good result in 20 meter. At present this ckt is good enough for 40 meter.

The diptrace schematics screen shot.





This is the diptrace pcb making software , This time I took time to make the schematics on this. EArliers I used make by hand and then scan. I realized to make a professional grade pcb, good quality image and parts making the pcb software is a must.

The ckt diagram

List of components

40 METER BAND RECEIVER

# RefDes Value
1 A1 whip antenna
2 C1
3 C2 100p
4 C3 100n
5 C4
6 C5 100n
7 C6 10 mfd
8 C7 10 mfd
9 C8 100p
10 C9 100p
11 C10 100p
12 C11 100n
13 C12 100  mfd
14 C13 1000 mfd
15 C14 33p
16 C15 10 mfd
17 C16
18 C17 100 mfd
19 C18 100 mfd
20 C19
21 C21 100n
22 D1 green LED
23 D2 1n4148
24 D3 1n4148
25 D4 1n4007
26 J1  speaker out put JACKPIN
27 J2 dc input JACKPIN
28 L2
29 L3 

34 Q1 BC549C rf AMP
35 Q2 BC547B af amp
36 Q3 BC547B Oscillator
37 R1 470k
38 R2 4k7
39 R3 470 ohm
40 R4 2K2
41 R5 120k
42 R6 2k2
43 R7 100 ohm
44 R8 120k
45 R9 2k7
46 R10 100 ohm
47 R11 47k
48 R12 470
49 R13 10 ohm
50 R14
51 T1
52 T2
53 U1 7805
54 U3 1/2 TDA2822m
55 Y1 3579kc
56 Y2 3579kc

Note of TDA2822m,

I always used LM386 but somehow I am finding difficult to get a good chip. All Chinese chips are faulty. So, tried TDA2822m  an 8 pin DIP ic. It is good one. It contains two amplifiers. This IC is a low voltage, low power  AF amp. So, use 4 to 5 volt maximum. When used with 12volt supply it starts heating up To reduce heating on IC, I used a ballast resistor of 200 ohm ( 100 ohm 2watt + 100 ohm 2watt) , so it stopped heating up. Remember this thing.  Only one part out of two is used.

Note on Antenna.

For making pcb from schematics , I put a two tank band pass filter, otherwise single tank with whip antenna is sufficient for all purpose.

Note on the Xtal Oscialltor- 3579kc

we need very small Rf injection to the diodes so single transitor osc is used. There is shown two coils and two xtals. I put it there only reason if someone wants to modify experiment , the same pcb will be useful. F6GQB. So, I can get 60k shift , more than enough for this set-up.  Except this two square I have not hidden anything. Only this squares have few extra empty parts.  Only single xtal is used, No RFC used.

If anything is missing please let me know.

You can make it, but remember its still in development stage. When I first put it on facebook there was two errors. one transistor part was wrongly labeled. And 12 volt and 5volt lines mixed up at 2822m. So, ckt on this blog should be final.

THE RECEIVER CKT IS FINAL. there will be no modifications. but revision of write-up , addendum will be added later on.

Input Band Pass Filter modifications. As of 17 may 2016 Modified the input filter system. Put fixed inductor 2.2 micro hentry with 215 pf =( 100p || 100p) + 180pf , tap taken from junction of both 100pf. The RFC of 2.2 micro henry can be used ready made or  made one 9 to 10 milli-meter dia plastic tube, I used felt pen, 30swg around 22 to 24 turns close wound, length will be 10 to 12 milli-meter.  Measure it with LC meter.  Plastic tubing former was around 3 cm long.  Will upload close-up fotos soon.

Receiver sounds good. Housed in the home made box. Other modifications like painting, putting nut-bolts that will happen as per need but electrical ckt is finale.  Am breakthrough is very minimal. AF filter might be a good idea. But the simplicity beats all. Make this receiver and please wait for compatible transmitter.



BPF

so, till then enjoy, the wheel has been re-re-invented, take a ride.
de vu3inj.
 here is a link to my youtube chanel. on similar design made the 20 meter one. have a look at https://www.youtube.com/watch?v=G4LTTf-waVc please
NB;- you may write down few words please.

Mobile Expedition

Here is write-up for my short expedtion on HF 14.315kc.
The following "image" inspired me to make my own experiments, which I was post-poning for sometimes.

vu2mau_7388_Small_Emergency Mobile

After hearing from the GJ1-CD-7388 mobile of VU2MAU. I was inspired. Why I also don't put the receiver on my bike.

As I did not want to be big eye-catcher and explain to the public and police what and why I have put antenna on my bike ??? he he. But, first time I took my original license with me to make them understood in case I find some idiots.....

So I took a 1 meter telescoping antenna, put it onto the small direct conversion receiver. See my blog for xtal controlled ra3aae poliakov 20 meter receiver. I used three 4.4 volt battery to arrive at 12 volt. So receiver was ready,concealed into a cloths carry bag I checked signal upto 6 km. It clearly gives me the beep beep on 14.315kc. Wow ! tx was pumping 20 watts, antenna was dipole, I did not care for SWR. It should be around 2.7 to 3.0 a very high but okey for me. It was a very nice experience. Almost at all places the signal report I gave was 55 to increasing into 59 at one heigh place and near my qth... So, good experience. I will make proper quarter wave antenna and another direct conversion receiver with good gain.... will see how far my ground wave goes. This auto-beep for testing is the penalty for being lonely and only hams....

If I make the 40 meter transmitter 7059kc and test them, its possible that I might reach my friend at 100km with 20 watts.. Waiting to hear from other friends what is their experience with vertical antennas for mobile use.....

10 December 2015
I find this article very useful... have a look for portable antenna.... http://www.zerobeat.net/g3ycc/yccwhip.htm 

BITX, Single Frequency Receiver-2

Peter VK3YE  made a wonderful signel freq transceiver based on the BITX. My previous experiment is here. http://vu3inj.blogspot.in/2015/06/bitx-singlefrequency-receiver.html 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.

Schematics 
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.

Testing:-

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.

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....