My 1 transistor FM Super-Regen Receiver!

[transistor495]

one transistor fm radio

Friends,
I've successfully made Patrick Cambre's single transistor regenerative FM Radio using BF245C in place of MPF102 suggested. I didn't have any trouble except my BF256 didn't work on first turn ON! Just replaced and it works very fine. I've used a 2K regen pot in place of 1K suggested, but its funny that my later experiments with 1K and 5K didn't work at all!!

It may be due to the transistor variations.

I recommend you to build this little wizard. It was really an amazing experience that it picked up stations without any antenna initially. The audio was 90% clear and contains bass treble frequencies made me shocked.

It is a very sensitive and selective regen receiver. Try it!

 

[Audioguru]

regen receiver

Hi again.
I am surprised that the extremely simple radio works.
The sound posted on the other website has about 20% distortion, probably because it doesn't have an FM detector and needs to be tuned to one side of an FM station using the resulting "slope detection".

The quench frequency must be very high so that beat whistles are not produceded by the stereo and SCA sidebands from FM stations.

 

[zlatkoMM]

1 transistor fm radio

EXCELLENT - transistor495

I have two question for you.

First wich variable capacitor you use -18pF or 25pf ?
Second , wich diametar of air coil you use and wich is diametar of wire is ?
(please in mm if is no problem)
thanks advance...

 

[transistor495]

single transistor fm receiver

Hi zlatkoMM, nice to see ur feedback.

Answering ur questions,
I've used a 50pf trimmer cap first, but reduced the 15p before the tuning cap to 10p. Later I've changed it to 4.7p when used with an fm gang cap glued on to the board.

For the drain coil I've used a 22SWG(0.711mm dm) enameled wire wound on a 7mm dm threaded bolt. 7 loosely wound turns. 20SWG(.914mm) might work.

Source coil was made using 32SWG(0.274mm) wire 26 turns close wound on an 8mm plastic former. 30SWG might work.

Keep the RF parts close possible and I've followed my own convenient way for audio section wiring.

Good Luck!

 

[deepak007]

single transistor fm radio

hello transistor495,

congratulations! what you did using a single fet was amazing. now, i want to build it too. can i use BF245C fet for the project? i want to use it with my home brew fm transmitter. what is the sensitivity? is bf245c an exact equivalent to mpf102? can i build it for 2mband? . please give me the link to the schematic.please help.

 

[Audioguru]

one transistor fm receiver

The single transistor super-regen radio is called The Radio Shack Special because Radio Shack stores used to carry most of its parts.
The complete project with all the latest details is here:
http://braincambre500.freeservers.com/rss(1)(1)(1).htm

 

[transistor495]

one transistor receiver

Hi Deepak,

BF245C is a close equivalent for MPF102. But I was a little doubtful about it while constructing. But it worked awesome! If you are going for this project using BF245C, I suggest you to follow the directions I put here in this thread along with the component layout and placement from the pictures.

I've tried it for VHF FM radio band only(upto 105MHz). Also I'm sure that the aircraft band also can be covered by this little genius which is very sensitive! All you need is to reduce the drain coil turns and a little experiment with tuning caps. I'm not sure about catching above 130MHz.

 

[zlatkoMM]

homebrew one transistor radio

Hi transistor...
I have one request for you .
I wannt that you put here shematic with parts wich you use.
That would be nice.
thanks advance...

 

[transistor495]

one transistor fm

OK. Here's the schematic for BF245C.

Follow the component placement from the pictures. Good Luck!

More information:
http://braincambre500.freeservers.com/rss(1)(1)(1).htm

 

[zlatkoMM]

superregen

Thanks i will try...

 

[deepak007]

small regen receiver

hello transistor495,

can you please tell me what value variable capacitor you used? i didn't find MPF102 ,so i want to use BF245C,like you said. i don't think i can find a quality trimmer in INDIA.can i use a variable capacitor found in the Am/Fm radios? if so,should i increase the drain capacitor to 15pf?

i am planning to design and etch a pcb. in radioshack construction notes,they left a large area for ground plane. but they didnot connect it to the ground terminal.just left it floating.so,what about the ground plane and layout. if i change the layout,will it work?


thanks in advance.

 

[Audioguru]

small regen radio design

hello transistor495,

can you please tell me what value variable capacitor you used? ........... i don't think i can find a quality trimmer in INDIA.can i use a variable capacitor found in the Am/Fm radios?

The insrtuctions for the project say to buy a cheap FM radio and use its tuning capacitor.

i am planning to design and etch a pcb. in radioshack construction notes,they left a large area for ground plane. but they didnot connect it to the ground terminal.just left it floating.so,what about the ground plane and layout. if i change the layout,will it work?

The instructions and pcb layout do not have a large ground area.

 

[deepak007]

homebrew super regenerative receivers

please take a look at this link: **broken link removed**

 

[Audioguru]

india radio circuit gang capacitor

The pcb is in the upper left of the pic.
The part labelled, "ALL COPPER" is thrown away.

EDIT:
You are looking at the original obsolete old pcb.
Here is the new pcb:

 

[transistor495]

radio schematic transistor

Hi Deepak,
Actually it has taken a longtime for me to track out that link from the original website. It's just a description about making pcbs using an older version of the circuit. Do not use it. The website clearly mentions to return back and proceed with the latest design.

It is very important to read everything carefully and get a clear picture of what you are going to do.

Some directions for 100% success..

1. Use the schematic I've posted for BF245C and use the pcb layout from the original website.
2. Make source and drain coils exactly as shown in the pictures.
3. You can use an AM/FM gang capacitor salvaged from an old radio. Make sure that you are using the correct leads.. In this case use minimum 4.7pF before the gang initially.
4. Trace out dry joints and incorrect polarities/leads before switching ON.
5. After switched ON, adjust 2K regen pot accordingly, experiment with tuning cap and the cap before it(try between 4.7pF-15pF).

 

[sumeeshc]

2n3904 super regen

transistor495,
Very nice project.I can not find the transistor bf245. Can you please suggest a equivalent one.Also what value of inductor used as I can find a readily avilable choke coil from the nearest shop in Chennai.
thanks.

 

[vfone]

receiver one transistor

Here is an improved version of the Regenerative Receiver, using a preamplifier.

 

[transistor495]

homebrew fm receiver

I think the above circuit might work well with BF256. Thanks for sharing friend.

Hey Sumeesh,
I won't recommend any other transistors here. MPF102 might work without hassles and may be adjustable with some small mistakes or placement problems. In other words, it should oscillate and ready easily than other transistors.

BF245 should be tried exactly I told here and you will hit on success. I'm sure. Have a good mind for little experiments if it doesn't work on first turn ON. Source coil inductance may be something near to 5 micro henrys.

I've collected a list of replacement trannys that can be tried. No guarantee...
BF246,247,256
2N3819,J310 etc.

 

[austin hellier]

Hi folks,
I'm a first time poster from downunder, and I've built up one of these myself. I used a blank pc board with copper side up initially, and used small oblongs of another board, glued to the top of the ground plane, to act as soldering points.

Last week I turned this arrangement on its head and glued to solder points to the fibreglass side of the board, and drilled small holes in the board where I needed to ground a component lead or two.

This week, I'm experimenting with using 10 megohm resistors, soldered to the coper side, to act as high z stays - these will become my solder points about 1 inch off the ground plane. Will let you all know how I got on, and will upload a pic or two for you to see.

Austin Hellier
Downunder

 

[vfone]

In RF, better option than using 10Meg resistors as solder points, is to use a so named: "ugly construction".

**broken link removed**
http://www.njqrp.org/regen/index.html