People making kit out of my circuit?

Ruud,

I thought he was a hobbyist. I asked him to use ugly bug method but he sent me a PCB of my ckt with metallic can 2n2222A. It only gave 150mW. I repaired the board and put PN2222A. It worked.

I found his website a few days ago. He's buying from China and reselling for $300 for a 5W 2sc1971 TX.

When I confronted him he said he was gonna take action against me for putting the picture of the PCB online, lol. Actually I have call recordings and he himself sent me the PCB. I am fine with ugly bug but for kits a PCB is used.

Told him not to use my designs. He said my designs were bogus, lol. More threats. Now he has blocked me. Problem is he knew nothing and I taught him the basics and shared almost all of my ckts including the 4W BS170 one.

In India the FM TX market is growing fast and most 2n3866 and 2sc1971 available are fakes. There's a big demand too for 1W to cover school & colleges. I'm not sure if anyone is interested in FM now except only when driving on the road for songs and music. People are so glued to their smartphones. I don't hear the sounds of TV anymore. Every one got DTH but internet is more interesting with Netflix and stuff.

To stop dependency on Chinese exported transmitter units I'm planning to use MRF101BN for 45W TX powered by 20V or 19.2V laptop SMPS supply.

Three mosfets cost $117 USD and free shipping.
65:1 vswr protection and rated for 115W at 50V.

I have never built a 45 - 60 watt VHF amplifier before.

It always happens!
I think it was in the 80's when a lot of satellite channels were scrambled. A colleague of mine asked me if I could make a decoder for the BBC world service, they used the 'SAVE' system.
(At the time I had no idea why he was so interested in this!)
I made a decoder for him, but to my surprise some time later I saw a commercial version of MY decoder! Even the non-critical resistor values were exactly the same.
It later turned out that there was another satellite channel that used the same encoding system and broadcasted "nature movies" at night.
The evil punished itself: a month after I delivered that decoder to my colleague, the coding system was changed, rendering all illegally produced decoders worthless!

Harry, good to see you. Which guy are you talking about? Did he copy your 150mW V7? It was my first introduction to a VHF transmitter. I don't know how you got only 15KHz of total drift in V7. The oscillator buffer caused significant drift during my test with osc + buffer only. I got 5mW but it drifted. It was solved by lowering greatly the power draw from the oscillator.

Ivan wrote:Hi Harry,
I stumbled across this RF amplifier. It remembers your 10W amplifier to me, with different transistors of course. Unfortunately they do not give its schematic.

VBR Ivan

Hello Ivan,
Yes, it is an amplifier of a similar circuit to my 10W HF amplifier, but there are major differences. That particular amplifier is "generic" in that something similar is used in may different types of equipment. They are all based on a text-book design dating back many decades.

Mine was unique at the time in that it used CB type transistors designed for 4 Watts AM/FM but I biased them in class-AB and used the design for SSB. I also had to stabilise the transistor bias current, and used "POT CORE" ferrites. Those ferrites manufactured RF transformers were not available at the time (or ridiculously expensive).

My design used a conventional resistive thermistor, which drove a fourth transistor to get a really low output impedance, for the bias of the output pair. That way could give good linearity over a wide temperature range and heavy loads.

They do not give the schematic, but you can get a lot of data from the photo, and make a pretty accurate guess from the component values.

But myself and Joy should be aware that there can be "similar designs" and "copied designs". The guy in India even left my callsign SM0VPO on the etched boards of his kits. If you remove the callsign then TR3 input matching falls, but that was by accident, not design  . I think my callsign changed both capacitance and inductance; the letter 0 for example is a shorted turn!!

Very best regards from Harry - SM0VPO

Hi,
the schematic you linked does not correspond with the kit linked by me. The kit has two transistors in the 2nd stage, with transformer power splitter and combiner.


KT922 and similar are Russian (originally Soviet) transistors, not Chinese ones. Marking 2T instead of KT is also possible and the types are the same. They are bipolar NPN RF power transistor intended up to 150 (maybe 170) MHz in a ceramic case (berylium oxide ceramic insulator is between the chip and the heatsink screw, aluminum oxide ceramic is on the outside). You favourite BS170 is a FET intended for low-power switching and data transfer.


BTW, if you ever work with any parts containing beryllium oxide ceramics, be very careful. NEVER apply mechanical stress on the insulator. E.g. when tightening the heatsink screw, always hold its distant end (it is flattened for this purpose), not the transistor case. If the beryllium oxide breaks, it produces EXTREMELY TOXIC powder

VBR Ivan

Ivan wrote:Hi Harry,
I stumbled across this RF amplifier. It remembers your 10W amplifier to me, with different transistors of course. Unfortunately they do not give its schematic.

VBR Ivan

Hello Ivan,
I saw the transistor # and google returned this 15-30W VHF amplifier.

https://www.electroschematics.com/rf-15w-30w-power-amplifier-kt922-kt930-kt934/

Mine was 4.5W only with BS170 x 3 in PA.

I am thinking of adding two more for 7.5W and use two similar boards to combine RF Po in a piece of coax. Chinese parts in India are all fake.

I was quite surprised to see BS170 having 12dB gain at 100MHz. I did test it on a board, 25mW in 370mA out at 12V. That's how I know that LtSpice is very accurate.

Hi Harry,
I stumbled across this RF amplifier. It remembers your 10W amplifier to me, with different transistors of course. Unfortunately they do not give its schematic.

VBR Ivan

dare4444 wrote:One guy with whom I shared the 3904 & 2222 based 1W FM amp circuit  has now released a kit of my circuit at $100 per piece. The transistors cost just 5 cents a piece! My work was never meant for commercial purposes. Back then he was frustrated with fake 3866, c1971, etc flooding the Indian market. They had no idea that the solution was right in their junk box. I didn't have Spice in 2020 so the 2222 amp ckt took months of R&D, hours and hours of work especially the LC stability. No one was sure if 3904/2222 could output a watt at 100MHz.

It's a shame that people try to make money out of someone else's design. For such a simple ckt $100 price tag is too much. 

I've not seen even a single ckt of 3904/2222 1W 88-100MHz amp on google till date. It doesn't exist. Hobbyists leave the hobby due to the fake part problem. The 2222 ckt has opened up a new avenue for homebrewers.

I guided him step by stop even in this alternate design. Po is solid 1.4W @ 88MHz with 260mW dissipation in each 2222. With small clipped on heatsinks the Po stays constant.

Hello Joy,
I frequently found that many of my own projects have been copied and sold as kits by other people. One guy in India quoted my V5 bug as a "1W FM Bug". I received complaints from people who bought it, could not get the power, and didn't get any reply from the guy's e-mail.

I will see if I still have the contact information for a lawyer in the USA. I used to supply him with wireless microphones, ready built, that he was using in his trade. After a bit of e-mail banter the subject came up about doing exactly this that you describe. I gave the lawyer some copy-artist addresses in the USA and he said to leave it with him.

On several occasions he sent me money that he had "squeezed" out of the culprits if they did not want to go through the courts. The guy kept about 1/2 the proceeds for himself, but that is fair. I have not heard from the guy for a long time, probably about 20 years. If I can find his contact info I will give you a buzz. The only thing he needed was for me to have a disclaimer on the project or homepages, and some means of proving that the work was mine. I received around $200 on each occasion.

There were many cases he was not able to pursue.

So it is well worth locating the offenders and contacting a lawyer in that country, but it is best to meet a lawyer a hobby interest in radio. $200 for writing a couple of letters may not be much of an incentive for the average lawyer.

BR Harry - SM0VPO

No air care coils and trimmers between each stage.
Frequency stability was + or - 1KHz when I tested it in 2011 for 2 hours maybe. The BF199 chain made it work perfectly. Took me a week to perfect it.

Efficiency is only 37% at 220mW power out.
It can be directly connected to a 1T tapping of oscillator coil of a single transistor FM transmitter.

Ivan wrote:

dare4444 wrote:Spice is as good as building the real thing

IMHO it depends on the precision of part models used. The component library of the LTspice after installing is rather limited. It is necessary to either make your own models of all types (mainly of semiconductors) you want to use, which is quite time-consuming, or add some third-party library (-ies). If the numeric models are simplified too much, the simulation will be unreliable.

VBR Ivan

The inbuilt library works very well. For 2n2222 it shows 10.6V peak output, 10.3V in real life test across a 50ohm load. Super accurate.

dare4444 wrote:Spice is as good as building the real thing

IMHO it depends on the precision of part models used. The component library of the LTspice after installing is rather limited. It is necessary to either make your own models of all types (mainly of semiconductors) you want to use, which is quite time-consuming, or add some third-party library (-ies). If the numeric models are simplified too much, the simulation will be unreliable.

VBR Ivan

dare4444 wrote:So if I start a website in my name and put up all my circuits there with a copyright message that without  written permission from me my circuits cannot be used and sold as commercial kits for profit, would that  be enough to deter people?

I expect some yes, some not. I am no author's law expert. But such message gives you a better possibility to start law enforcement against those who violate your copyright. Without it they may say that they "thought the schematic was released for free use".

VBR from Ivan

I made many prototypes and accuracy of LtSpice was confirmed. S12 or reverse isolation was -58dB from buffer 2n3904 to final PN2222A x 2 delivering 300mW only as the driver was biased in common base mode.

In this attached circuit I've not measured the S12 on spice but I've measured changes in oscillator Vpeak by connecting 1, 50, 75 ohm load and even a 100K. Vpeak changed by < 2mV .

It was quite a surprise for me as I was trying for days. Spice is as good as building the real thing, lol.

This is the best oscillator to load isolation I've ever tested on spice. The impedance seen by the oscillator remains constant no matter what the output is terminated into. Po was 20mW, not bad. Notice the 10nH oscillator coil (sorry it's now 70nH). On Spice 10nH only worked with BC547. Why?

Large tuning capacitor value = cuts down on ambient temperature related drift. Ideally it should be between 1-3KHz total in 24 hours given NP0 caps are used. Even a varactor diode introduces a few KHz drift so it's not used here. A 2n2222 works with 70nH coil.

So if I start a website in my name and put up all my circuits there with a copyright message that without written permission from me my circuits cannot be used and sold as commercial kits for profit, would that be enough to deter people?

Ivan wrote:

dare4444 wrote:He was rude to me after I told him not to make my circuits for commercial use and not replying to my msgs anymore even though I gave him hours everyday with my shoulder and back problems.

We have a proverb: "do a favour to a devil, he will take you to the hell".

VBR from Ivan

Got it, Ivan. So true.

dare4444 wrote:He was rude to me after I told him not to make my circuits for commercial use and not replying to my msgs anymore even though I gave him hours everyday with my shoulder and back problems.

We have a proverb: "do a favour to a devil, he will take you to the hell".

VBR from Ivan

MRF101 AN/BN RF POWER MOSFET rated for 50V 115W in a TO220 package. Proposed 45W FM TX  ckt.

BS170 Vds is 60V

2N2219A Vce is 40V

BS170 parallel is better for the driver stage than using two 2n2219.

If we use a 1:4 25ohm coax at the output then max Po is 15W & broadband. I don't have a 25ohm cable so two parallel RG316 should do.

Use 1:16 or two cascaded coaxial 1:4 transformer for 50W max output at 20V. RG316 length = 17.6cm

Add LPF & BNC connector. I would be happy with 45W between 88-100 MHz. A L+C matching may be needed between drain and coaxial transformer. Bw would then be limited to around 4 - 8 MHz given my past experience with a 5W amp.

Chinese 15W units put out around 12.5W.
This amp is about 4 times as powerful. Range should be somewhat better with more signal
strength and less dead spots in the coverage area.

75 square kms coverage is easy provided its a flat terrain and antenna is 40 to 100 feet high on a pole. I want to put a simple 45W amplifier circuit out there. 75W is the max power out at 20V provided standing Id is 500ma for the final stage.

75W is a bit more attractive. It's a lot of power for hobby use & small radio station. Rural areas and villages in India have their own low power FM broadcasting started by private individuals. It's not exactly rural anymore as we now have better roads and so much of car traffic in rural India. Big FM stations already cover small village towns that are in a radius of 30-40 kms around a city. They now have access to cheap 4G too, 1.5GB of data a day for $4 a month. Only the people travelling in cars listen to FM mainly for entertainment. 4G data is way cheaper here. 25 years ago only rich people could afford mobile phones. Chinese Redmi Mi brand is best seller in India. Check out their Redmi 10S Note vs iPhone 11 or 12 comparison on YouTube. Note 10s costs 6 times less than iPhone 11.

I was thinking to have BS170 x 5 at each side and input fed out of phase drive via a grey ferrite transformer. The output of the two sections are then combined in a 17.6cm long RG316 coaxial cable for 15W out. If we shrink the coil size, 2mm 26SWG for example, then it could all fit on a single PCB the size of a notebook.

MRF101bn with free shipping is $115 for 3 mosfets or $39 USD each, not bad. At 24V it's possible to derive 80W if we increase the standing current to 500ma. No matching between 2n2219 driver and its gate is needed and it still works without failing. VSWR immune to 65:1 at 115W!

With a cheap 20V 90W adapter it could push 40-45W at 100MHz. This MOSFET is here to stay.

Harry, you really should build a 80W FM amplifier and put up the details in your website. There are so many homebrewers looking for obsolete transistors to build high power FM amplifier. Most leave the idea and experiment with a watt or so of maximum power. MRF101BN is a neat little MOSFET.

T5 delivers 250mW to drive a power stage. DIP switches and NP0 caps set the frequency. Oscillator sees a 2.2K load on its collector. Benefits are no coil tapping and stable frequency. The 5.1V zener trick eliminated any remaining drift. The DIP switches are not mandatory. 

1.5MHz tuning with the pot. This is a 200-250mW LC based 88-100MHz exciter. T5 is driven with 20mW via two cascaded emitter followers. 

No RF transistors are used here.

40mW in and 1.3W out @100MHz with 85% efficiency. 12V supply. The driver should be replaced with a 2n2219A.

Asked him not to sell this BS170 design. 5.5W DC in and 4.5W RF out from three parallel mosfets costing 15 cens each. All unwanted signals are -45dBc down. 85nH is 3T 20SWG 8mm. The complete 4W amplifier should cost less than $10 eliminating the need of transistors like 2sc1971. It's powered by 19.2V laptop charger and 7812. The 250mW exciter is able to drive it. 

Pin = 96MHz 360mW
Pout = 96MHz 4.5W

Another simple amp ckt as proposed by me. It cuts back on parts. It's a no brainer but shouldn't be sold as kits for generating profits.

John_1981 wrote:Please don't let it put you off sharing your circuits with us on this forum. Anyone who is daft enough to pay that for a handful of cheap components must be mad. I get a lot from studying other peoples circuits, even if I don't make up the circuit there is always lots to learn and it often leads to new ideas. I get more from sticking parts into a breadboard and testing/experimenting than building a kit anyway.

 Yeah. Here's his circut prototype. It wasn't working so as per my directions there are two separate base matching networks now. He has hired someone else to build the prototype. He also got a channel on YouTube. People would buy the kit for $100 when it took less than $5 to build it. Rural village FM radio stations are popping up everywhere and they make $2000 a month generating revenues from radio ads. I am guiding him for a year now letting him know all the secrets of RF homebrew. He was rude to me after I told him not to make my circuits for commercial use and not replying to my msgs anymore even though I gave him hours everyday with my shoulder and back problems. Output is a constant 1.4W and it ran for a week. Everything works fine. Without my inputs this circuit wouldn't have been possible. I'm going through financial difficulties and if I wanted I could have sold kits. No 1W FM TX is available in India which costs $5 to build. 

It's very stable into a folded dipole antenna. Frequency drift is limited to + or - 3KHz I believe. 

Hi, maybe we should emphasize one fact in the headers of this forum and also Harry's pages: all circuits published here are free for personal and educational use, but a written permission of their author is required for any form of commercial use. It is a real shame that certain individuals try to make profit from other's work.

VBR from Ivan

Please don't let it put you off sharing your circuits with us on this forum. Anyone who is daft enough to pay that for a handful of cheap components must be mad. I get a lot from studying other peoples circuits, even if I don't make up the circuit there is always lots to learn and it often leads to new ideas. I get more from sticking parts into a breadboard and testing/experimenting than building a kit anyway.

One guy with whom I shared the 3904 & 2222 based 1W FM amp circuit  has now released a kit of my circuit at $100 per piece. The transistors cost just 5 cents a piece! My work was never meant for commercial purposes. Back then he was frustrated with fake 3866, c1971, etc flooding the Indian market. They had no idea that the solution was right in their junk box. I didn't have Spice in 2020 so the 2222 amp ckt took months of R&D, hours and hours of work especially the LC stability. No one was sure if 3904/2222 could output a watt at 100MHz.

It's a shame that people try to make money out of someone else's design. For such a simple ckt $100 price tag is too much. 

I've not seen even a single ckt of 3904/2222 1W 88-100MHz amp on google till date. It doesn't exist. Hobbyists leave the hobby due to the fake part problem. The 2222 ckt has opened up a new avenue for homebrewers.

I guided him step by stop even in this alternate design. Po is solid 1.4W @ 88MHz with 260mW dissipation in each 2222. With small clipped on heatsinks the Po stays constant.