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.

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....

40 meter cq

At last i have made the vu2vwn qrp tx running about 3 watt. It is very stable due to the crystals. Freq 7060 Khz. Keying is also good. Only problem is that it is for cw (A1A). Either it needs to be run into AM (A2A) or DSB (J3A) for voice communications. 

After putting it in a box will try a small linear using  mosfets or may be design a new DSB tx from the scratch.

my cw call will be

cq cq cq de vu3inj vu3inj vu3inj  AR.

vu3inj  de vu 2/3 ???  vu2/3 ? ? ? k

vu2/3 ???  ur rst rst 559 559 de vu3inj  qsl k

vu3inj ur rst ----- ------ tnx.

cq cq cq de vu3inj vu3inj vu3inj AR

If i use morce-code this is the conversations i can understand at most. I have not practised code for 7 years. Straight key. Seperate tx and receiver .NO full break. There is no NO QSK. Inverted-V dipole.  Timings about 7.30 to 8.30 mornings. QRS slow speed code. Please bear with me. If you hear me please reply in SSB or DSB.

Also requesting for a sked.

73

vu3inj

indrajitsinh 

LL9033, 6955- 03 , Anyone giving me SWL report will sure to get a qsl card.

20 Meter CW
As of 27Jan2015 will start working on the 20 meter with 15/20watt CW power. xtal freq 14315kc plus minus 1kc. I have no RIT so don't zerobeat me. My receiver is a very wide one. No filter just tuned ckts. Will be happy to work with you here also.