# Transistor compatibility

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#### Twiggy

##### New Member
Hey, i'm an electronics hobbyist still in the breadboard stage, and felt a little confused over transistor compatibility. I'm trying to locate a 2N4401 transistor, but they seem a little hard to come by, so was wondering which more frequent transistor would function similarly. Its use would be in this circuit.

#### Hero999

##### Banned
Try the PN2222A or BC546, it's not too critical so long as it has a GBWP of over 150MHz or so.

#### mneary

##### New Member
The author says
many kinds of transistors will work fine in this application...............I used an 2N4401 because I have a lot of them. I like 2N3904 and MPSH34 for this too.
In fact, almost any small signal NPN BJT will work. If you reverse the battery, you can use a PNP such as 2N2219 or 2N3906. As Hero says, it just needs a GWB of 150M or so, and most of them do.

You'll read in another ongoing thread that it's easy to build a better FM transmitter.

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#### Iceman-

##### New Member
I would definitely stick to using a more standard npn transistor, such as the 2N3904. They have been in use for a long time and have become commoditized. Digikey carriers the 2N3904BU from Fairchild Semiconductor for less than 20 cents.

#### mneary

##### New Member
I would definitely stick to using a more standard npn transistor, such as the 2N3904. They have been in use for a long time and have become commoditized. Digikey carriers the 2N3904BU from Fairchild Semiconductor for less than 20 cents.
OP has withheld (his) location, and has mentioned that 2N4401 is difficult to obtain. 2N4401 and 2N3904 should be equally available in North America, generally for $0.05 down to$0.015 depending on quantity.

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#### audioguru

##### Well-Known Member
I bet he is in Australia.
He will soon find out all the problems with that too-simple FM transmitter.

#### Twiggy

##### New Member
yes, well in the buliding stage now, and while i am not in australia, i am infact in London, I was wondering what problems you were refering too. As it happens I am wondering how I work out what to tune my radio to with a Spectrum Analyser, which i think is the tool i would use.

#### audioguru

##### Well-Known Member
These are the problems with that extremely simple FM transmitter:
1) Its antenna is connected to its tuned circuit so the frequency will change when something moves toward or moves away from the antenna.
2) It does not have a voltage regulator so its frequency will change as its battery runs down.
3) It does not have pre-emphasis (treble boost) like all FM radio stations have so it will sound muffled like your stereo with its treble tone control turned all the way down since all FM radios have de-emphasis (treble cut).
4) It is mono, not stereo.
It is garbage.

#### Twiggy

##### New Member
right good to know. thanks anyway.

#### audioguru

##### Well-Known Member
You forgot to say where you are in this huge world.

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#### Twiggy

##### New Member
lol actuallly i did, look up i say london in the earlier post. i have found a 2n3904 at Maplin. ive made a complete shift from farnell.

#### audioguru

##### Well-Known Member
Most people mention their country but you did not and I didn't hear your Cockney accent in your typing.

#### Twiggy

##### New Member
okay, but im sure most people can place London on a map. i hope.

#### audioguru

##### Well-Known Member
London, Ontario, Canada has a nice university. There are many pretty young ladies running around there.

#### Twiggy

##### New Member
i've heard that pretty university girls are particularly partial to middle-age electronics hobbyists.

#### Mike_2545

##### Super Moderator
Lots of places named London

London, England, a city in the United Kingdom
London, Ontario, a city in Canada
London, Belize, a village
London, Equatorial Guinea, a village
London, Finland, a section of Jakobstad
London, Kiribati, a small city on Kiritimati
London, Nigeria, a village
London, Limpopo, a village in South Africa
London, Mpumalanga (Noordprovincie) in South Africa
London, Mpumalanga (Graskop) in South Africa

In the United States:
London, Conecuh County, Alabama, an unincorporated community
London, Montgomery County, Alabama, an unincorporated community
London, Arizona, an unincorporated community
London, Arkansas, a city
London, California, a census-designated place
London, Indiana, an unincorporated community
London, Kentucky, a city
London, Michigan, an unincorporated community
London, Minnesota, an unincorporated community
London, Missouri, an unincorporated community
London, Ohio, a city
London, Richland County, Ohio, an unincorporated community
London, Oregon, an unincorporated community
London, Pennsylvania, an unincorporated community
London, Tennessee, an unincorporated community
London, Texas, an unincorporated community
London, West Virginia, an unincorporated community
London, Wisconsin, an unincorporated community

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#### Twiggy

##### New Member
good point. I am based in London, England.

#### Hero999

##### Banned
I think most people would assume London England as it's the largest and most famous London.

#### audioguru

##### Well-Known Member
i've heard that pretty university girls are particularly partial to middle-age electronics hobbyists.
I am way past middle-age but I still notice pretty girls.
I was an electronic hobbiest about 48 years ago, but then I became a professional electronic engineer for my career. But now I am retired and am having a great time since every day is a Saturday.

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