MOSFET AMP IRF510, a little discussions-2

 A friend was discussing the IRF510 with the homebrew group.

"Any friend with Bitx linear original version success build are most welcome... I completed linear of bitx20 last day and found that the Transformer T1 at the drain of IRF510 getting very Hot just after switching the linear ON... core i used is FT37-43 with 2 turns bifiler my current bias is 50mA @ 19V DC.. any suggestions are most welcome..."

             Well I had made the first version linear by the VU2ESE. He sent his linears foto. (thanks friend)  I feel it is not  is not the first, version but the version 3.

             Important difference between the version1 and version3 are the linear amplifier. In the first version 2ESE  has tried the plastic former and balun core. Now a days foreign hams / Indian hams use the TOROIDs which comes along with KIT.

            During my quest with taming the linear ,VU2ESE had hinted me of using the tap washer reason it was not possible to find the suitable toroids/balun cores.... I gave it (tap washer) a try and it worked.... thanks Farhan.. The tapwashers many turns absorbs the capacitance of the FET. Which makes it more efficient... 2ESE has always multiple use for a part.

              At present My friend just want to using only two turns on the power amplifiers transformer. IMHO this is not right. There has to be more turns to increase the inductance.  May be the innocent looking balun core is a big culprit. The turns depends on the material, how much RF flux it can handle, operating frequency.   This RF amp fault  has burnt power supply IC and there is lots of frustration.... He will be happy if the linear gives him more than 2watt, enough to drive a big linear....

bitx ver.1--- linear

the top view of the linear.

          Well what I can say... Here is the actual linear ...Have a look. IMHO the culprit is two fold. big leads causing the self oscillations/vhf parasites. Core is not handling the power level........ he should try putting the negative feed back network (100k+0.1mfd) betweed drain and gate. At gate he should also put a 10 ohm resistor coming from the bias to the gate. Cut short the length of the gate. Try different heat sink. If ckt is on a plain copper plate, then try to make it sleep behind the pcb..... In the nut shell there is positive feed back.....

      Most probably his FET oscillated and gone QRT. There is no way to test it. Just replace the FET. make the Leads short and It should work. First try with 12v DC unregulated. with 1 amp fuse. That way can save the power supply and LM317 voltage regulator.

Here is my version of the above linear on veroboard. I have made two prototype with success.  Just keep the lead short whatever method/pcb you use....

VU3INJ, linear

    
 (Lets wait for his response......  This my own musing / hypothetical solutions I have omitted others comments-views and nothing to do with him or his skills personally.)
 

CW TX 14316kc

RF Linear

Last year made a CW transmitter. Power was very low. So decided to make a linear, then  after a year my cw tx is perfectly working with this  homebrew linear.

Here is the picture.

All details will updated later on. Atleast this is working......( updated as on 27jan)

Main power supply is the 24-0-24 @5amp with 0-12 @1amp . The cheap computer fan is used to cool it. The bottom plat is a thick metal one. Used as a heat sink.

One 12v dc @1amp, white box is used to supply the power to swr meter and keyer. Here the SWR meter requires the reverse polarity power supply.


The open box is exciter with having its own power supply on right had extreme. Well I can drive the exciter from the main transformers... will do that.... one friend said this much power sources.... well its on the assembly bench so I took liberty of using more....

Here is the ckt diagram.





linear amp after modification



(with input 50ohm resistor exciter can not drive amp
so removed the resisotors )

The RF Power Amp is used to drive the inv-v dipole antenna. Antenna is on the roof top....


Inverted-V antenna

On first test, i tried to load the dipole only 12feet from ground. But could not get the report. Well on suggestions, I made another antenna on the top of building. It was not cut to exact freq. Bought 20swg copper wire. 100 gram at rs.60/-. ... Used common dish wire to connect with TX. The plastic tube used as end insulator. Antenna was done in clear hurry..... but it worked well....

Used 20watt RF power. The SWR meter shows me the 3.0 reading. Then 2DEV gave me hint to put the antenna away from rooftop about 10feet with some plastic pole. I used a bamboo. then SWR reduced to 2.6 ok. One important thing I learned that for the receiving you can put dipole anywhere but for transmitting you must put your dipole/inv-v ver high and without any obstructions ( metal building) tree might be not that much trouble....  Put antenna atleast 30feet and up and you can punch a hole with 20watt north to south. For 5watt I got about 55 report. for 20watt about 57 report.

On my request 2KD also suggested few things. Well as the rooftop renovation work is going on will assemble/modify the antenna next week and try to have cw/dsb toway contact.

My test signals could be heard all Gujarat, sought india. But, the central india and Northern india I could not get the report....

What I feel:::   In the secondary school you get your first kiss..... (its different matter I have never got a kiss).

But atlast I have become the transmitting ham. Will modify it to DSB and hook up a receiver.

There are many hams to thanks. They helped me in varous stages of deveoplement by moral supprts, pcb, guidance, critical reports, critical words and above all kept my company....... 2TOO,2KD,2DEV,2UPX, 2PTR,3YFD,OM Ashok khachar, OM Vagishetty, Om Gurudata, 3HMM,3HML,3JOJ,3JOG, Om Mehta- Jamnagar, ( Last year during cwtx exciter time 2RAK, 2ATN,2UUU & 2ESE,3SXT,3SXN,2ORO....) also land lots more..... THANKS.....

DSB Modulator,20 Mb

The Modulator,
               After perfecting my system with the 14318kc transmitters, cw. dsb and linear amplifier , push pull amplifier and wasting so much time and energy on making, learning,teaching things it is my time to be on air finally or forget the dream forever.

DSB Exciter

             So making it with my time proven modules. I have previously made the single ic modulator and mixers. Now giving it a little twist making on the copper plane. I call the copper board as a magic carpet. Better than pcb. It gives me the creative edge how to shape the project.

             For working on the copper board you need small hacksaw, big hacksaw, triangular file, round file, sharp knife, marker pen, steel ruler or straight bar, some crocodile clips, little vice. one sharp steel pin, de-soldering pump & good Magnifying lence,

As for 04jan2015 see the foto

I soldered the transistors. Used BC549c. Tried to use same components so that inventory can be good.

06jan2015:- soldered all the wires, jumpers, extra capacitors.

07jan2015:- At the modulator state fixed/measured the LC valued in the Test oscillator with the frequency counter.
Soldered it.
15jan2015:- finished up.



27jan2015:- Tested OK, slight careers leakage is there, but which need  to be reduced...
01feb2015:-uploaded the ckt diagram.

MY write-up for the contest.

14,194kc, 20 meter DSB MODULATOR by Indrajitsinh, VU3INJ,

For 20 meter only xtals widely available is 14318kc . Sometime we also get the 14166kc but not always. But this is far from the crowd. Most of the excitement is around 14200kc fone part. So this idea was born.

The DSB modulator using the two simple cheap easily available xtals and two TA7358AP, the 9pin SIL, FM mixer IC. Its widely available it contains one RF amp, Gilbert cell mixer and oscillator. It also cheaper than NE612 . Using two ta7358ap is a little bit over kill for a single frequency dsb exciter. Only advantage is simplicity, no critical tuning. When you are using the QRP the stability of signal is utmost important. Due to use of the DDS VFO and narrow xtal filters even 100hz deviation go dutch for some operators. This will give us a good solid stable signal and our friend will know where to find us.

            First IC is TA7358ap which modulates the signal. Internal coll-pitt oscillator between pin7& pin8 is used. Xtal here is 4.194kc. not pulled much. One stage bc549c used as MIC AF amp with 4k7 preset as crude af level control. Another af amplifier stage used is within ic. The DSB signal is taken out from pin6 by resistor to make it simple. So it does not effect the mixing/modulating much. But, a tuned amplifier is used to clean the signal, filter out harmonics & amplify. Common BC549c is used will give enough gain here. No need of RF transistor.

           After that the signal is given to a mixer second IC TA7358AP. Here 10.000 mhz xtal is little pulled up higher / to change the frequency few kc upwards, trimmer capacitor is used. But a small panel mount 50pf will be good. You can try also the varactor diode. Single stage tuned amplifier using BC549c follows the mixer ic to select the sum product i.e 14.194kc. Our goal is to arrive near 14200kc.

          Afterward this signal is filtered and given to the linear amplifier. Whole strip is driven from the 5volt regulator. Current consumption is about 45ma.... Signal is clean. There is not much tuning or testing. Except setting 4k7 trimmer for good sounding audio in receiver. Use whatever mic you have and accordingly modify the mic bias resistor. All the tanks are pre-tuned. i.e means the LC components were used as a tank in the collpitt ocillator. By adding standard capacitors values to arrive empirically at the given freq. The freq was measured by the counter. Now, this same components were soldered on the board. This is emperical and quick method of putting the fixed frequency coil for BPF work. To simplify 2.2 micro henry ready made rfc used as first tank. For second tank I could not find suitable candidate in commercially made RFC. Its 22swg wire,1/8 inch dia ( a metal dril bit used as a former) to wind it. 12 turns, tight wound. Then with the adhesive it was made rock solid.

         I had made two prototypes. First one a year ago on vero-board and another this time on copper board. This second prototype was mechanically more challenging than the veroboard. I had to cut groves on the copper plane , solder the copper pad with adhesive on copper board. But happy in the end that it worked. To solder/brew it took me three days But, testing required little more time as my receiver was not working....

        Components details, values and ckt diagrams follows. Please also see the PY2OHH & various TA7358 design on the web.

(x)indrajitsinh, vu3inj. Copy right. If you find this ckt useful please enjoy and pass it on with your refinement and above all enjoy the brewing.

Block diagram

Ckt diagram:-


DSB MODULATOR 14194KC



 

Two prototypes:-

Bill of Material:-

Resistor	Value	Note	Capacitors	Value	Note
R1	1M		C1	0.1
R2,R5,R8	100		C2	1000pf
R3,R6	470		C3,C6,C14,C21,C22, C23, C24,C25	0.1
R4,R7	47K		C4	100MFD
R9	10K ---100K	Choose as per MIC	C5	10 MFD
R10	100		C7	0.1 / 10 MFD
R11	10K		C8	NIL
			C9,C10,C16,C17	100 PF
			C11,C13	47PF
			C12,C19	* TEXT
			C15	33PF	TRIMMER
			C18
			C20	10PF
			C26	470 MFD, 25V
			C27	1000 MFD, 16V

Transistor	Value	Note	Diodes	Value	Note
Q1,Q2,Q3,Q4	BC549C	NPN transistor	D-	LED
IC-1,IC-2	TA7358AP	FM Front-end IC	D-	1N4007	reverse polarity protection
IC-3	LM7805	Voltage regulator

Other items & hardware...

Mic & PTT switch, Relays.

Copper wire,20swg or similar for connecting the stages.

Copper islands cut for placing the components

Adhesive tube used in plumbing to join the water piples.10gm.

Fone pins, plugs,

Aluminium sheets to cover the entire units. Some paper for insulation.

Special note:-

Please make sure the Vcc is 5Volt dc .

How many contacts I have made with this ? None,

Is there any AM signal ? Yes there might some leakage of carrier due to the gain stages and absence of the xtal filters.

What development I can make ? well nothing much, in this one. if you don't like the tuned stage, please use the resistor as load but then there will be no harmonics filtering. This is just a simple DSB modulator. Take it as a basis for your own design.

Can I use the external VFO, DDS:- No need .its made for simplicity. If you want to use vfo/dds then it will be more rewarding to make a complete trx set of bitx.

 

BITX Making part-1

BITX making will start this 1st week of the 2015.

Actually I wanted to finish my DSB transceiver and a linear project. But due to persistent request from a friend I have to make the bitx-20/bitx-40. I have all the materials, components, tools, and friends with expertize. But there is shortage of quality time due to MQTH and work.

I am also supposed to find the fault with my own bitx--20 and a friends bitx-40. There has been a classical mistake. All the components are soldered with big lead. All the coils are wobbly. There are dry solders. Did not write its making. there is no documenting the process and components changes etc. Thanks ,it has landed on my lab. Nothing to worry my friend i will find the fault. Some time I also do same type of mistake, every body has some ENTROPY. Well, I am 100%committed to solve and send it back.

Well as  promised I am starting with printing the bitx schematics and other hams write-ups...

First will be the bill of materials... as per  BITX-40......HFI2014.
BLOCK DIAGRAM

BITX

 Now bill of materials...

03jan2015
prepared the list of resistors

Bitx bill of materials. Bitx-20 or bitx-40

Component number	Value	Module	Transistor
R1	2k2	RF Rx input amp	q1
R2	1k
R3	10
R4	220
R5	220
R6	100
R7	2k2	Rf TX output amp	q2
R8	220
R9	100
R10	220
R11	10
R12	1k	Rx, If amp-1	q3
R13	2k2
R14	1k
R15	10
R16	220
R17	220
R18	100
R19	2k2	Tx, if amp-2	q4
R20	220
R21	100
R22	220
R23	10
R24	1k
R25	100	Rx, if amp-2	q5
R26	220
R27	2k2
R28	1k
R29	1k
R30	470
R31	2k2	Tx, if amp-1	q6
R32	1k
R33	4r7
R34	470
R35	100
R36	220
R37	2k2	Rf tx output amp	q7
R38	1k
R39	10
R40	100
R41	100
R42	2k2	Vfo amp	q8
R43	1k
R44	10
R45	220
R46	100
R47	100k	Xtal vxo	Q9,10
R48	1k
R49	1k
R50	1k
R51	100
R52	220	Mod/demod	pad
R53	22r
R54	220
R55	4k7	vfo	Q11
R56	220k
R57	10k
R58	10k
R59	100
R60	4k7		Q12
R61	2K2
R62	1K
R63	10	Audio amp	LM386
R64	100
R65	220
R66	4K7	Af pre amp	Q14
R67	120k
R68	2k2	Tx af amp	q14
R69		Not needed
R70	10k
R71	220
R72	2k2
R73	4k7
preset

 and capacitors. ...

Capacitor

Component number	Value	Module	Transistor
C1	*text	BPF
C2	22pf trimmer
C3	*text
C4	100n
C5	22pf trimmer
C6	100p
C7	10p
C8	22pf trimmer
C9	100p
C10	68p
C11	0.1	Rx, RF input amp	q1
C12	0.1		q2
C13	0.1		q1
C14	0.1		q1
C15	100n*/0.1		q1
C16	0.1	TX, RF output amp	q2
C17	0.1
C18	0.1
C19	0.1		q3
C20	0.1		q4
C21	0.1	Rx,If amp-1	q3
C22	0.1		q3
C23	0.1		q3
C24	0.1	TX, If amp-2	q4
C25	0.1		q4
C26	0.1		q4
C27	100p	Xtal filter
C28,28a	100p,100p	Xtal filter
C29	100n/0.1	Rx, IF amp-2	q5
C30	100n/0.1		q5
C31	0.1	TX, IF amp-1	q6
C32	0.1* not needed
C33	0.1		q5
C34	0.1		q6
C35	0.1		q6
C36	0.1		q6
C37	0.1		q6
C38	0.1	Tx, RF PA	q7
C39	0.1		q7
C40	0.1		q7
C41	0.1		q7
C42	0.1	VFO driver amp
C43	0.1
C44	0.1
C45	22pf trimmer	Xtal OSC	q9
C46	47p		q9
C47	220p		q9
C48	220p		q9
C49	0.1		q9
C50	0.1		q10
C51	50micro henry
C52	22pf trimmer	Mod/demod	d12
C53	10p	Mod/demod	d11
C54	0.1	VFO	q11
C55	0.1		q11
C56	10p		q11
C57	22pf trimmer		q11
C58	47p		q11
C59	220p		q11
C60	220p		q11
C61	220 micro H,25v		q11
C62	1 micro H, 25v
C63	0.1	Af amp LM386
C64	220 micro H,25v
C65	0.1
C66	1 micro H,25v	Af pre amp	q13
C67	50 micro,25v	Tx, AF amp	q14
C68,68a	1 micro H,25v, 100p		q14
C69	1 micro H,25v		q14
C70	50 micro H, 25v		q14
C71	50 micro H, 25v		q14
C72	0.001 / 1000pf		q14

One thing I noticed , total R-73 total C-72, nice combinations. wow !

Now other components
Transistors :-2N3904 / BC549c
IC:- LM386
DIODES:- 1N4148
balun cores,