1W FM RF Amplifier Circuit (Boost Low Power Transmitters)

[@EyesOnReality]

Very good job on this RF amp. Just a note: Can also use small PCB pads cut from PCB board and glue each pad in each place for each component on any surface (even medal for best ground plane) and then solder on components. In other words, using small PCB pads a custom layout can be made when actual PCB board is not possible.

[@electronicsNmore]

Yeah I know. That works great too. Thanks For Watching!

[@RiaRadioFMHD773]

careful around 108 - 110MHz because that band is reserved for aircraft RF traffic communications.

[@Dazzwidd]

The balun you have used is a good idea as it is also a 4:1 impedance transformer. The folded dipole is a good antenna if you want lower voltages at the ends of the antenna and a wider SWR bandwidth than a conventional half wave dipole of the non folded variety. However the impedance of a folded dipole is around 288 ohms, a bad match for low impedance coaxial cables, be it a 50 or a 75 ohm line, it is also a balanced load for your transmission line (feeder cable). The half wave bal-un you used is not only a bal anced to un balanced transmission line converter, but it is also an impedance transformer with a 4:1 impedance transformation ratio. So if you're using 50 ohm coaxial transmission line for the balun feeding the antenna as well as for the line to your transmitter, then it present a 200 ohm source impedance to antenna. If you use 75 ohm coaxial transmission line for the balun and for the line to the transmitter then the antenna will be presented with a 300 ohm impedance. This is a very close match to a folded dipole (almost perfect). For your low powered experimental purposes I would use 75 ohm line and use a field strength meter to peak your amplifier for field intensity :)

[@electronicsNmore]

Very simple. Go to Google and enter "single layer air coil calculator". All you have to do is enter the uH value you need, the diameter of the enamel wire your using, and the diameter of the drill bit you will be using to wind the coil on.

[@stanmeyer9770]

I remember a few years ago messing around with a 3 transistor FM mic transmitter and replaced the 3rd transistor ie the output amplifier BC 547, or 2N 2222 etc with a medium power transistor BD 139 etc and increased the voltage to this output stage 15 to 20volts or so and using nothing more than a lengh of wire 1 to 2m long. The range achieved was at least 3 to 5km this was in the valley surrounded by mountains so could be that the range tested outside of the valley could be further. In fact if I recall correctly I also experimented with just adding the BD 139 after the 3rd transistor in the origional circuit and just loading it with a 6turn coil and 100ohm load resistor with the antenna coupled to the collector. There was no noticeable harmonics generated so never added any further filtering or refinements. It was just an experiment to see what could be achieved with a minimum parts count.

[@electronicsNmore]

The power circuit can be any well regulated and filtered 9-12vDC power supply.

[@electronicsNmore]

100mhz = L1>.82uH(18ga enamel wire-10T-7/16" drill bit as form) L2> .47uH(18ga enamel wire-10T-5/16" drill bit as form) RFC> 10uH is very common in a lot of electronics, If you do not find one, do not buy one, then you need an inductance meter to make your own. You will need to wrap enamel wire around a ferrite core until the value reads 10uH on your meter.

[@MyProjectsTV]

I can only count 8 windings for L1 in your video.

[@iksdk]

MyProjectsTV LOL, I think you should try cleaning out your ears dude. It’s 10t for a 100mhz but in the video I heard him saying that he used it for 109mhz. Maybe that’s why the amount of turns isn’t the same 🤪😂

[@southernexposure123]

Thanks for the video. Although the parts are very close together, you still might reverse engineer your transmit power circuit to draw and post the schematic.

[@electronicsNmore]

Your English is not too bad. Go to Google and do a search for "single layer inductor coil calculator". Yes the RFC does effect the frequency. I did not design the circuit, so I cannot answer what your looking for.

[@tomwold8269]

The 2N3866 is made for 28 volt use. It might be better to replace the 2N3866 with a 2N4427 or a 2N5913 or MRF607 which are designed for 12-14 volt use

[@electronicsNmore]

No, but I have another video using a 2sc1971.

[@electronicsNmore]

Go to Ebay and enter, "to-39 heatsink". You will see them.

[@herbertsusmann986]

Your two coils ideally should be at right angles to each other so they don't couple. These form the output matching network as well as the output low pass filter network. With the coils in line and fairly close as you have them you will not get the desired properties of this network.

[@electronicsNmore]

Hello. If you notice the 2 coils on the right side are positioned at right angles. I was told by the designer to make sure those are 90 deg apart. He said the other coil is fine. Thanks For Watching!

[@craftymulligar]

Next you could try to use a PLL and stereo encoder. Maybe a modded car fm transmitter.

[@jay7264]

Awesome engineering now I can make public service announcements telling every body to bring 50$ bills to an address saying their counterfeit bills #PROFIT THEN I SHARE MY NEW FOUNF WEALTH WITH THE HOMELESS. Merry Christmas electronic man

[@hotbikerguywithscar]

Nice job. Have you run it into that 2sc1971 amp yet?

[@kamaloddinsayyad3305]

HI ! Guys I have built this RF FM amplifier, but the transistor 2N3866 doesn't ON, because the diode FD700 (in the base) doesn't work and the circuit never on. If you want to operate this RF amplifier, replace the diode FD700 with a coil (AWG 23/4-5 turns) wound on small ferrite bead. And click the base of transistor 2N3866 with metal screw driver, your RF amplifier circuit will certainly work. But before this you have to solder a 100 ohm resistor in the o/p of amplifier as a load. Beside this, this is a class C RF amplifier, so the dynamic rage of fm reception will certainly reduced i.e. very short ( approximately 100 to150 meters). Thanks !

[@kamaloddinsayyad3305]

Correction: (AWG 26 /4-5 turns)

[@dm.2023]

The 2N3866 will yield you about 500mW Try using a 2N4427 or a MRF237 to get a full 1 Watt output as the video advertises.

[@electronicsNmore]

According to the datasheet, 1W. rtellason.com/transdata/2n3866.pdf

[@jballen9889]

The FD700 diode is quickly becoming 'un-obtanium' and has no clear substitute. I used a 1N4148 and it seems to be working in my application (10mW input). I used a 2N2219 (a heavy-duty 2N2222) to see if the circuit would work. It did and I left it in. A decent heat sink is a must. Be wary of 2N3866 fakes. It is very simple for a pirate manufacturer to put a 2N2222 die into a TO-5 package. Who is going to pay return shipping for that? The 10 uH choke is built on a magnetic core. I would use a 43 material toroid (FT37-43...FT50-43). Don't use the green axial inductors. The choke is critical. An incorrect choke can result in an awful hum or a red-hot transistor.

[@libervolucion]

Hey, really nice video. Do you have the class C circuit? The Techlib file is not working anymore

[@electronicsNmore]

You might want to contact Charles at Techlib. Thanks for watching!

[@e.a297]

I have a push-pull no coil just linestrips FM which is also so powerful, almost 5km with simple antenna

[@ReedSwitchTube]

electronicsNmore nice video, I like it! Do you know where would you find all the capacitors and resistors?

[@electronicsNmore]

banggood4less.com or ebay

[@billybonewhacker]

Whats the purpose of the 2 coils in the amp. Since its .."I'm assuming" not tuning. And the original transmitter is .thanks for all your work

[@electronicsNmore]

This RF amplifier needs to be tuned "closely" to the frequency that is being amplified. The coils are part of that tuning.

[@abdul-alimbalarabedawud9628]

Hi, i love your video, well done. I was hoping if it will be possible for you to make another video on how to make a coil for a particular frequency including the formulas and the necessary considerations. Also, the antenna you design is also very cool. will appreciate a lot if the process of achieving it is also explained. thanks

[@electronicsNmore]

Glad you enjoyed the video! I supplied a link in the video description area to the person's website that designed the FM RF amplifier. Unfortunately there's not enough interest to spend hours making a video. I'll be losing money. Thanks for watching

[@crackahcrackah]

Can you recommend a good Tx circuit for a beginner? I've done many other soldering and circuit projects, but never a Tx circuit. I would like to make one that I could scale with such an amplifier, or that would broadcast well at say ~4W with crisp audio and no harmonics.

[@antonispsomas7210]

very good video

[@electronicsNmore]

+antonis psomas Thank you Antonis! Please be sure to share my channel with others, check out my video playlists, and rate thumbs up. Thank You

[@TheManeliss]

Thanks!! I'm blind!!

[@andrewandrosow4797]

It`s very nice device!But I don`t understand: for what is the resistor (10 Ohm) in output?

[@electronicsNmore]

I didn't design it, a buddy of mine that owns a big electronics company designed it. He deals with RF devices.

[@julianmetallica161]

Sir, I need an antenna, can I use a coaxial cable TV? my tester says 1 ohm, and also I have a guitar cable, my tester mark 32 ohms ¿?

[@notvalidcharacters]

Actually a *folded* dipole has a characteristic impedance of 300 ohms, six times that of your output port. A *single* element dipole would be 73 ohms, a much closer match. Just send single elements out, terminated on the ends, instead of folding them back.

[@electronicsNmore]

Been a while, but I think I used a balun. Thanks for watching!

[@electronicsNmore]

This circuit is too powerful for that. You first need to find out what frequency the transmitter uses. Once you find that out, then you have to look for a RF amplifier circuit that can be used for that particular frequency. I would imagine that you could use a 200mW to 500mW RF amplifier with very good range.

[@Starbuckin]

Nice job!

[@alirezaniknejad8395]

Hi what is the size of pcb and the diameter of each coil and the wire??

[@arricat5e311]

Do you think it will work with the Raspberry Pi?

[@blockcamp]

what exactly do you want to do with it?

[@pattymoreira4510]

Friend salute you good afternoon from Manta Ecuador and would like to know what are the values ​​of the other components of the amplifier and if suddenly you have the schematic diagram of the amplifier printed circuit because I realize that the transistor is a 2N4427 and if I have here at home and I need to know what are the values ​​of the other components, ie complete Liata need the materials to start with the design. Greetings from Manta Ecuador.

[@seyedmarashi]

Good job, thanks

[@electronicsNmore]

Glad you enjoyed it. Be sure to check out my extensive video playlists, rate thumbs up., and share. Thanks!

[@lleaves]

Is your transmitter an AM or FM transmitter? I am guessing it is an AM transmitter. If on the other hand you are using an FM transmitter what is the frequency deviation. I would think very small since the amp is class-C. Do you have a link to a schematic for your transmitter? Thanks for the video.

[@electronicsNmore]

FM. The link is in the video description area. Thanks For Watching!

[@CouvertureMagazine]

I realize that this question is non-related but is it possible to build an circuit kit that will convert RF from surrounding areas and convert that to 5 volts to power say a mobile device?

[@electronicsNmore]

Yes, you harvest RF energy. www.mouser.com/applications/rf_energy_harvesting/

[@mhmdibrhimmstfa]

thanx a lot 4 such an informative video

[@electronicsNmore]

+Mohamed Ismail You're welcome! Please share, rate thumbs up, and subscribe.

[@mhmdibrhimmstfa]

allredy done :)

[@ReedSwitchTube]

does 2sc1971 works? I only got that type of transistor.

[@electronicsNmore]

2sc1971 is good up to 175 MHZ, so it should work, but it's overkill at 6 Watts.

[@davidkerl1431]

109 MHz??? The aviation band. Whu did you chose that frequency????

[@ДаниелСпасовски-ъ4к]

Im interested about this amplfier :) I will run it on 100MhZ FM :) Can you give me the specifations of the coils about that frequency ? How much turns , which diameter of wire , on what diameter of body to wind it ? and something more about RFC :) Thanks :)

[@aspergerhellasbn]

These fm amplifiers can work to a fm transmitter for a rc boat? I think its the same thing.also this amplifier goes to transmitter not to the receiver right?

[@electronicsNmore]

The frequency of the RC boat transmitter must be VHF. The transmitter output would be boosted.

[@aspergerhellasbn]

@@electronicsNmore i am refering to remote control bait boat. In greece old transmitters use Fm/Am bands while the new uses 2,4ghz and 5ghz. As far as i know those VHf bands are used to military,for police and at real boats:)

[@kipgynn]

Hi, Nice design! Is there a formula(s) to determine the values of c1,c3,L1,L2, and RFC if the carrier frequency is 73.600MHZ?

[@electronicsNmore]

Not positive, but if you send an email to techlib.com, he will be able to tell you. I would think C1 would be around 100pf, C2 around 12pf, C3 around 10pf-12pf, L1 around 1.0-1.1uH, L2 around .7uH, RFC 18uH. Just my guess based on the chart.

[@daretodream25]

You can use a air core inductor from collector and two trimmer capacitors to match the output. Stretch the coil and adjust the trimmers for max output

[@yoayo]

TRANSMITER IS GOOD!!

[@faseonepk2002]

I keep searching the net for a heatsink that will work on this or any round transistor...I'm totally stumped. Could you provide a part number/source for these? Thanks!

[@quantum5170]

Nice video, but as usefull as an ashtray on a motor bike without the specs & cct diagram.

[@electronicsNmore]

Video description area......

[@ocayaro]

Nice!

[@harrybugallon3516]

B+ main supply of the circuit?

[@simonemastroianni1985]

I have a low power fm transmitter. I want to amplify my signal to 20 meters. Can I use only a small transformer?

[@electronicsNmore]

If you only need 20 meters distance, then you don't need this RF amp. Th circuit you have should be able to transmit 20 meters.

[@Betty19ch]

Hello Thanks for good video first And can 2N4427 work too? or only 2N3866? Thanks!

[@electronicsNmore]

Both work

[@roytan7962]

2N3866 is a very good transistor for RF circuits 👽👍I build transmitter mostly use 2N3866, I have bought a lot and keep it.

[@pratwurschtgulasch6662]

That transistor (2N3866) is no longer for sale except ebay and it costs a lot. Does anybody know of a suitable replacement?

[@klausbrandt5064]

2N4427

[@manuelvillanueva3753]

I built one but it won't work... I wonder why?

[@artmatthew1]

Would this circuit work to amplify a 10mW signal which is 74.7 MHz? Could anyone help me figure out what size the coils would need to be for 72-75MHz range? Would any other elements need to be changed to accommodate that freq.? Thanks!

[@electronicsNmore]

Yes. Refer to the link posted in the video description area. Thanks for watching!

[@skyline3delectronics]

Nice

[@electronicsNmore]

Glad you enjoyed the video! Be sure to check out my extensive video playlists for other great videos of interest to you and share.

[@electronics3992]

I have 1w fm transmitter and I want more power (

[@electronicsNmore]

No, you'd need to make changes to everything.

[@electronics3992]

electronicsNmore Ok

[@poorvikasharma4211]

Can I connect my KT0803K Ic based small car fm stereo transmitter....?

[@electronicsNmore]

Yes, but if the power output isn't too much, you won't get the full output of the RF amp.

[@papastalinlenin1108]

Can this also work for shortwave transmitters?

[@electronicsNmore]

It's only designed for the FM band.

[@reza.babakan]

I was wondering if it is possible to boost car FM players using this circuit ?

[@electronicsNmore]

If you have a small FM transmitter, yes.

[@thomasrjansen8626]

how increasing the transmit power ?

[@danhess547]

can I buy a prewired transmitter (TV) from you and how do I go about doing that? thanks in advance..!

[@elitehaxor7]

+Dan Hess You can buy them online pretty much anywhere, but it's going to cost you a pretty penny

[@hosseinrf1004]

Did work with I pod very very low power FM transmitters??

[@electronicsNmore]

+‫حسین یزدانی‬‎ As long as the power level is not too low.

[@buildkhawari3787]

please add my videos to end screen

[@peaps]

Do you have any information on the mini transmitter that feeds the input to this amp?

[@electronicsNmore]

No, but I do have several other FM transmitter videos. You need to look through my FM transmitter playlist. There are a few good ones you can use.

[@jballen9889]

I realize this is quite old, but it would be helpful to know the approximate mW output of the transmitter. There is pretty much no documentation on this circuit on the internet. I would not attempt to drive this circuit with much more than 10 mW, unless an attenuator is used.

[@momi5656]

can you tell me how can i make the RFC ? and can remplace FD700 with another diod ? and thank you :-)

[@electronicsNmore]

Take the RFC value(uH) from the schematic link in the video description area and use the link below to figure out how it should be made. Use the same diode. www.daycounter.com/Calculators/Air-Core-Inductor-Calculator.phtml

[@philgritsr2]

do you have specs on the coils

[@LucaVornheder]

Is there any way, to calculate how many power a transmitter have?

[@electronicsNmore]

Hi there. Normally you would use a meter inline with the FM transmitter output. Some people like to get a rough idea by measuring the total input current and taking a percentage of that amount to determine how much was used for RF. Thanks For Watching

[@user-fk5bt6xl3v]

Good luck

[@letitrotfuckit]

Alright thats a problem because i already have 25 watts, i need to amplify it to at least 100 watts but the power i dream of is 1000 watts. I think this can do 100 watts if i give it a lot of amps and volts and a huge mosfet.

[@electronicsNmore]

Make this instead for 100W power output: www.electroschematics.com/25/rf-100w-bly94-power-amplifier/

[@danyboy130]

can you please draw a schematic for the transmitter?

[@electronicsNmore]

There's a link in the video description area. Thanks for watching!

[@TheManeliss]

And the diagram? Where is it?

[@gerardofire69]

nice work and knowledge...thanks for sharing it

[@electronicsNmore]

Thanks for watching! Be sure to share and rate thumbs up.

[@MiiMaker]

What do the coils do?

[@electronicsNmore]

They're inductors. Refer to the link below. Thanks for watching! www.analogictips.com/what-are-rf-inductors-faq/

[@ashotgghg]

Can i have the transmitter circuit (not the amplifier) Thanks

[@electronicsNmore]

That transmitter I made over 20 years ago. It was a kit I bought online. If you look through my video playlist below, you'll see other FM transmitters that work very good. The crystal controlled transmitter and loop transmitter are the best. Thanks for watching! kzbin.info/aero/PLQ6IOhUBblU3L0gIY6axV7OqRvBTqDNoP

[@EeenaMeenaDeeka]

Good..... what is the range in KM ?

[@electronicsNmore]

Hi there, Due to many factors it is very hard to say what the range is. If your terrain is flat, or you are broadcasting across open water, then range will be excellent(5+ kilometers). If the antenna is placed high up, then you will have even greater range. If your in a city or rough terrain, then expect shorter range(maybe a couple km). If your broadcasting on the side of a big hill or mountain, then the range will only be high on the side of the mountain you are on facing outward. You will have reflected radiation off the mountain. Thanks For Watching!

[@EeenaMeenaDeeka]

Thanks for your reply 👍

[@mohammadalfauomey3443]

thanks, what about the circuit diagram?

[@electronicsNmore]

Mohammad Alfauomey Video description area

[@fredymredy]

can you tell me schematic for theese your fm transmitter.

[@electronicsNmore]

The schematic for the 1W RF amplifier is located in the video description area. Unfortunately I assembled the FM transmitter 18 years ago. I have no schematic. I do have other FM transmitters shown on this channel. Watch my "FM Transmitter" playlist. Thank You!

[@TheSudiptheory]

does it work properly???

[@electronicsNmore]

Grow Up Of course it does.

[@Frank55]

The 10 ohms resistor at the output makes no sense at all. It only reduces the output power.

[@electronicsNmore]

I think the designer who owns a RF products company in TX, that also sells to the US military, knows what he's doing. :-) www.wenzel.com/

[@aliafghan9081]

Can you share the diagram of this Amplifire

[@electronicsNmore]

+Ali Asir Video description area.

[@electronicsNmore]

***** FM

[@radarsonic6227]

how long the range it transmit ?

[@electronicsNmore]

All depends on the terrain. Across a desert or open water, probably 1.5 - 2 miles, on a mountain possibly 3+ miles, and in a city, under 3/4 mile.

[@elektronik-toy-boy4719]

bueno!

[@thomasrjansen8626]

how to change the frequency?

[@electronicsNmore]

Please refer to the link in the video "About" section for more details/schematic. Thank You

[@uniquetechchip]

👌👌👌👌👌👌👌👌

[@electronicsNmore]

Unique TechChip Glad you enjoyed the video! Be sure to check out my extensive video playlists and share. Thanks!

[@mohammadalfauomey3443]

What about the circuit diagram?

[@electronicsNmore]

Mohammad Alfauomey Video description area.

[@ruudvansteenis]

The 100 ohms (10 ohms according to the schematic) resistor only wastes output power. It would not be necessary if the output circuit would match both the output impedance of the transistor, and the termination (antenna) impedance. Also the input of the circuit is not impedance matched to the driving source. All and all the design of the circuit is at least a bit dubious...

[@electronicsNmore]

Ruud van Steenis The individual that designed this circuit is a very smart engineer friend of mine that owns a successful business selling RF devices and much more to the US Govt, as well as Space modules(Lunar, etc). I would say he knows his stuff. :-) Thanks For Watching

[@ruudvansteenis]

electronicsNmore OK, maybe in that case he can explain the function of the 10 (100) ohms resistor... (Just curious, because I don't see the reason for this, although I have a degree in electronics.)

[@Dazzwidd]

I agree, that resistor on the output is only limiting the circuits potential. I would put a 5 element chebychev low pass filter on it straight after the second of the two output coils and move the 1nf cap to being in series with the first of the two output coils (the one that connects to the 2N3866 collector).

[@electronicsNmore]

Dazzwidd I myself would never question the circuit designer. He is very successful, and his company designs and sells many components/devices to the govt/aerospace industry. I am sure he had a reason for doing what he did. Thanks for watching.

[@Dazzwidd]

I myself worship no man to be greater than the governing laws of physics

[@danielacostajr9025]

over a mile transmitter ?! how do you get 2

[@electronicsNmore]

+Daniel Acosta You have to make your own. :-) Thanks For Watching

[@electronicsNmore]

**ADDITIONAL INFO: A Low Pass Filter was added to the amplifier board(lower left open area) AFTER this video was made. You can get that circuit in the video description area. You can use an online "air coil calculator" to figure out how to make the coils w/o an inductor meter. Use a drill bit set to wrap the coils. Just choose the correct size bit! **CORRECTION: The input side resistor was a 10 ohm resistor, not 100 ohm.

[@letitrotfuckit]

what about the limiter and compressor? Low pass filter will not help really, it sometimes makes things worse. Question: if i give it 20 volts and 10 amps, what will be the output?

[@tarstarkusz]

Electricity doesn't work that way. If you raise the voltage that high it will probably blow the electronics. Amps are drawn, not fed. You can hook up a 50 amp power supply, and it will still only draw like, I think he said, 125ma. The $5 store sells a pretty good unit and if you add an antenna and clip the resistor limiting the power, it will greatly increase the range. With line of sight you would get well over a mile.

[@Shmannel]

alls ya gotta do is ...

[@tvdia4220]

Cuantos alcance ?

[@electronicsNmore]

No, la señal puede ir muy lejos.

[@tvdia4220]

@@electronicsNmore Gracias !!!

[@ON3MR]

schematic ????

[@electronicsNmore]

Video Description Area

[@electronicsNmore]

In the video description area! Techlib.com

[@electronicsNmore]

@XXVorteXX Hello. coaxial cable for tv is usually 75 ohms, but you can get by using it. Please refer to my video which shows how to make a folded dipole antenna. Thanks For Watching! Link Here: kzbin.info/www/bejne/f2KZdqRjoqifec0

[@davidkerl1431]

Too bad there is no schematic diagram for it here.

[@electronicsNmore]

Link is no longer active?

[@Shmannel]

lol fcc no want you to build these

[@electronicsNmore]

Shmannel True, but I ignore FCC rules because I live outside the USA. :-)