2N2222 vs. MPS2222A
Randon Loeb
1. I have substituted MPS2222A tranistor for 2N2222. Is this ok for
this type of application? I was just guessing that the 2222 means they
are similar ;-)
2. How can you measure a coil's inductance? If you make the coil
yourself, can you be sure its "correct" somehow?
3. For testing, I have a 555 timer creating an a sound, that when
hooked up to a speaker sounds like a high pitched tone. at close range,
the tone is heard on FM radio, even without being hooked up to the
transmitter circuitry. Why is this? If the tone is audible, how are
radio waves in the FM band being produced? Is it ok to substitute such
a circuit for an electret mike, which will eventually be a feed from the
guitar or effects board?
4. How can I tell if I'm even getting RF waves out of my circuit? Can
an oscilliscope hooked up to the antenna tell me if i'm atleast getting
oscillation?
This is my first basic circuit that doesn't have led's or sound or
something to allow me troubleshoot and "see" what's happening. Any tips
on how to troubleshoot RF circuits like these?
Thanks
SkrewBall
i subbed a MPS2222A for a 2N2222
in a small RF transmitter and it worked fine.. (More power too,I'm sure its
over the legal limit now though..)
Dave M
pretty much the same gain, leakage, characteristic curves, etc. as the
2N2222 but doesn't have the collector current rating of the 2N2222 model.
Don't remember the specifics, but that's the big difference.
--
Dave M
"SkrewBall" <pta...@qwest.net> wrote in message
news:3AA572E3...@qwest.net...
SkrewBall
Bill Knight
They DO vary! Check the data sheets to be certain you have
the circuit wired correctly.
Regards
-Bill Knight
R O SoftWare
Randon Loeb
E-B-C from bottom to top?
--
Randon Loeb CIO
CTI Consulting and Training
rl...@cticonsulting.net
954-971-6888
DO NOT ADD THIS ADDRESS TO ANY JOKE LISTS OR OTHER LISTS
Ken
Randon Loeb wrote:
>
> I thought all transistors with a "D" shape (looking down) would have
> E-B-C from bottom to top?
A dangerous assumption that is entirely false.
--
Ken Tyler
Randon Loeb
tonite. Hopefully the transistors haven't been destroyed by the error,
if there was one.
I must say though, that being new to electronics, it seems that the only
standards sometimes are resistor color bands. This is both fun and
frustrating.
--
~^Johnny^~
<rloeb...@cticonsulting.net> did apparently write:
>2. How can you measure a coil's inductance? If you make the coil
>yourself, can you be sure its "correct" somehow?
Make an impedance bridge. It's similar to a wheatstone bridge, but
it has at least one capacitor in one oof the legs, and is excited
with an AC signal, usually 1000 Hz.
Alternatively, you can use a grid-dip meter, if you don't need great
accuracy.
>3. For testing, I have a 555 timer creating an a sound, that when
>hooked up to a speaker sounds like a high pitched tone. at close range,
>the tone is heard on FM radio, even without being hooked up to the
>transmitter circuitry. Why is this? If the tone is audible, how are
>radio waves in the FM band being produced?
The 555 puts out a pulse waveform, and the radio is picking up the
harmonics. Since the rf energy is quite weak up in teh VHF range,
the receiver is not going into full limiting, sometimes known as
"full quieting", so you are likely hearing an AM component, due to
intermodulation of the fundamental frequency with it's harmonics.
--
-john
~~~~~~~~
"Always listen to experts. They'll tell you what can't be done and why.
Then do it."
- Robert Heinlein
~~~~~~~~
Mark Kinsler
>1. I have substituted MPS2222A tranistor for 2N2222. Is this ok for
>this type of application? I was just guessing that the 2222 means they
>are similar ;-)
Yup. Just be careful of differences in the pin locations.
>2. How can you measure a coil's inductance? If you make the coil
>yourself, can you be sure its "correct" somehow?
Only by experimentation, really. There are inductance testers
available, and you can also place the coil in series with an RF
generator, a known capacitor, and a resistor. Find the frequency at
which the voltage across the resistor peaks, and apply the formula for
resonant frequency. This isn't so easy to do at VHF, however.
>3. For testing, I have a 555 timer creating an a sound, that when
>hooked up to a speaker sounds like a high pitched tone. at close range,
>the tone is heard on FM radio, even without being hooked up to the
>transmitter circuitry. Why is this? If the tone is audible, how are
>radio waves in the FM band being produced? Is it ok to substitute such
>a circuit for an electret mike, which will eventually be a feed from the
>guitar or effects board?
Your timer is creating some truly heroic harmonics, and your radio is
receiving them. You can do something similar by running a vacuum
cleaner or hair dryer near the radio, too. The corners of the
square/spiky waves produced by all these devices contain very high
frequency energy. However, such circuits don't make very good radio
transmitters because their frequency is too difficult to control.
>4. How can I tell if I'm even getting RF waves out of my circuit? Can
>an oscilliscope hooked up to the antenna tell me if i'm atleast getting
>oscillation?
A radio will be lots more sensitive than an oscilloscope, and most
oscilloscopes won't pick up VHF. So use your radio.
>This is my first basic circuit that doesn't have led's or sound or
>something to allow me troubleshoot and "see" what's happening. Any tips
>on how to troubleshoot RF circuits like these?
Welcome to RF. What I'd suggest you investigate is the amateur radio
literature. Poke through the library to see what's available and read
as much as you can understand. Amateurs are very good at making
home-made instrumentation, and they like to share their ideas.
Your wireless microphone project is not the world's easiest, however.
VHF circuits can be rather ticklish to build properly. Persist,
however, and you'll learn a lot.
Mark Kinsler
512 E Mulberry St Lancaster Ohio USA 740.687.6368
http://www.frognet.net/~kinsler
abpc...@gmail.com
Jasen Betts
> On Tuesday, March 6, 2001 11:41:45 AM UTC-7, Randon Loeb wrote:
>> Trying to build a wireless mike for a guitar, not having much luck:
>> 1. I have substituted MPS2222A tranistor for 2N2222. Is this ok for
>> this type of application? I was just guessing that the 2222 means they
>> are similar ;-)
--
⚂⚃ 100% natural
--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---
Michael Black
> On 2013-04-02, abpc...@gmail.com <abpc...@gmail.com> wrote:
>> On Tuesday, March 6, 2001 11:41:45 AM UTC-7, Randon Loeb wrote:
>>> Trying to build a wireless mike for a guitar, not having much luck:
>>> 1. I have substituted MPS2222A tranistor for 2N2222. Is this ok for
>>> this type of application? I was just guessing that the 2222 means they
>>> are similar ;-)
>
>> Using hearsay as a source of specific manufacture specifications information is full of misinformation. Spec. sheets are just a click away.
>
> I reckon he's figured it out by now.
>
looked further, they'd have seen a string of replies that actually helped
him. I can't be bothered checking google, but that's the norm every time
I've checked one of these time warp posts.
But yes, even if he hadn't got an answer back then,he likely would have
had the chance to figure it out after 12 years.
Michael