1. Ok, easy question first. Someone has given me a PCB for a QRP
transmitter called "little joe" and the PCB has 9-81 QST. I have
searched on the web but I cannot find the component layout, and,
ideally, a copy of the original article.


2. I have been playing around with a simple transmitter project called
the Michigan Mighty Mite ( http://cs.okanagan.bc.ca/ve7ouc/eng/kc6wdk-
mirror/transmitter.html ) which uses any one of a number of small
signal NPN transistors. As I found a large number of metal cased NPN
power transistors, I was wondering if I can drop one of these as a
direct substitute for say, a 2n2222, or an old BFY51 etc etc. I have,
for example, found a RCA 2n6282 Darlington Pair in my junk box. This
is a VERY meaty little beast. The datasheet for this tranny can be
seen he- http://www.datasheetcatalog.com/datasheets_pdf/2/N/
6/2/2N6282.shtml

Any suggestions?

Stephen Walters
mister 35 mm AT ya-hoo dot co dot uk

mister35mm wrote:

1. Ok, easy question first. Someone has given me a PCB for a QRP
transmitter called "little joe" and the PCB has 9-81 QST. I have
searched on the web but I cannot find the component layout, and,
ideally, a copy of the original article.

My QST collection only goes back to '88 or so. You could buy a CD from
ARRL, if no one here has the article.

2. I have been playing around with a simple transmitter project called
the Michigan Mighty Mite ( http://cs.okanagan.bc.ca/ve7ouc/eng/kc6wdk-
mirror/transmitter.html ) which uses any one of a number of small
signal NPN transistors. As I found a large number of metal cased NPN
power transistors, I was wondering if I can drop one of these as a
direct substitute for say, a 2n2222, or an old BFY51 etc etc. I have,
for example, found a RCA 2n6282 Darlington Pair in my junk box. This
is a VERY meaty little beast. The datasheet for this tranny can be
seen he- http://www.datasheetcatalog.com/datasheets_pdf/2/N/
6/2/2N6282.shtml

Any suggestions?

Don't do it!

Power transistors, particularly vintage ones, are very slow in
comparison to "small signal" types. Darlingtons are a different kind of
thing altogether, they are even slower yet but with significantly higher
current gain.

Find a bag of surplus 2N2222s, or buy a dozen new 2N3904's from Digi-Key
-- you'll be much better served.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

The "Little Joe" is actually Wes Hayward's W7ZOI Universal QRP Transmitter.

Go here for parts and schematic: http://www.qsl.net/k0kp/hbrew/qrp_tx.html

As for part two, in comparing the two datasheets, I don't see all that much
that is similar between the two other than they are both NPN. You could try
it though. If it doesn't work, a handful of PN2222's can be had for less
than a couple of bucks.

73



"mister35mm" wrote in message
oups.com...
1. Ok, easy question first. Someone has given me a PCB for a QRP
transmitter called "little joe" and the PCB has 9-81 QST. I have
searched on the web but I cannot find the component layout, and,
ideally, a copy of the original article.


2. I have been playing around with a simple transmitter project called
the Michigan Mighty Mite ( http://cs.okanagan.bc.ca/ve7ouc/eng/kc6wdk-
mirror/transmitter.html ) which uses any one of a number of small
signal NPN transistors. As I found a large number of metal cased NPN
power transistors, I was wondering if I can drop one of these as a
direct substitute for say, a 2n2222, or an old BFY51 etc etc. I have,
for example, found a RCA 2n6282 Darlington Pair in my junk box. This
is a VERY meaty little beast. The datasheet for this tranny can be
seen he- http://www.datasheetcatalog.com/datasheets_pdf/2/N/
6/2/2N6282.shtml

Any suggestions?

Stephen Walters
mister 35 mm AT ya-hoo dot co dot uk

"Brian" wrote in message
ink.net...

it though. If it doesn't work, a handful of PN2222's can be had for less
than a couple of bucks.

BG Micro has the metal ones, that you tend to use in the final, for a
quarter, the plastic ones you use for anything else for 6 cents. They have
surface mount MMBT2222A's for 4 cents.

2N2222's are handy little transistors that show up everywhere, and any time
you need any old NPN, a 2N2222 will generally do, so it never hurts to have
a few hundred in the parts drawer. And at $6/100, it doesn't hurt the
wallet all that bad, either.

Of course, BG shipping to merrie auld England probably isn't all that
pretty, but Farnell or some other local supplier must have something
comparable. I'm sure there must be a BC equivalent ... I bet if you found
the cheapest NPN it would be the same thing. You might shoot off a note to
George or Ian, or perhaps take a peek at the G-QRP's Circuit Handbook. They
seem to love the daylights out of the BC108, so I bet it is comparable
(although I don't have any data on that to compare).

...

My company doesn't charge for shipping. We're surplus new old stock....the
selection isn't huge but it's cheap.

http://www.hamradparts.com



"xpyttl" wrote in message
...
"Brian" wrote in message
ink.net...

it though. If it doesn't work, a handful of PN2222's can be had for less
than a couple of bucks.

BG Micro has the metal ones, that you tend to use in the final, for a
quarter, the plastic ones you use for anything else for 6 cents. They
have surface mount MMBT2222A's for 4 cents.

2N2222's are handy little transistors that show up everywhere, and any
time you need any old NPN, a 2N2222 will generally do, so it never hurts
to have a few hundred in the parts drawer. And at $6/100, it doesn't hurt
the wallet all that bad, either.

Of course, BG shipping to merrie auld England probably isn't all that
pretty, but Farnell or some other local supplier must have something
comparable. I'm sure there must be a BC equivalent ... I bet if you found
the cheapest NPN it would be the same thing. You might shoot off a note
to George or Ian, or perhaps take a peek at the G-QRP's Circuit Handbook.
They seem to love the daylights out of the BC108, so I bet it is
comparable (although I don't have any data on that to compare).

..

Hi Brian .... I think I've seen that call on QRP-L or maybe the Microchip
forum.

If you're willing to ship to mister35mm and you got 'em for $6/100, $1/5 in
the TO18, that's pretty darn hard to beat

...


"Brian" wrote in message
hlink.net...
My company doesn't charge for shipping. We're surplus new old
stock....the selection isn't huge but it's cheap.

http://www.hamradparts.com



"xpyttl" wrote in message
...
"Brian" wrote in message
ink.net...

it though. If it doesn't work, a handful of PN2222's can be had for less
than a couple of bucks.

BG Micro has the metal ones, that you tend to use in the final, for a
quarter, the plastic ones you use for anything else for 6 cents. They
have surface mount MMBT2222A's for 4 cents.

2N2222's are handy little transistors that show up everywhere, and any
time you need any old NPN, a 2N2222 will generally do, so it never hurts
to have a few hundred in the parts drawer. And at $6/100, it doesn't
hurt the wallet all that bad, either.

Of course, BG shipping to merrie auld England probably isn't all that
pretty, but Farnell or some other local supplier must have something
comparable. I'm sure there must be a BC equivalent ... I bet if you
found the cheapest NPN it would be the same thing. You might shoot off a
note to George or Ian, or perhaps take a peek at the G-QRP's Circuit
Handbook. They seem to love the daylights out of the BC108, so I bet it
is comparable (although I don't have any data on that to compare).

..

Ooops...free shipping to the US only...DX needs to pay the freight...but
there is no upcharge.

Sorry about that.

Yeah, I'm on the QRP-L.ORG list....not the QRP-L on qth.net

73 de KB9BVN



"xpyttl" wrote in message
...
Hi Brian .... I think I've seen that call on QRP-L or maybe the Microchip
forum.

If you're willing to ship to mister35mm and you got 'em for $6/100, $1/5
in the TO18, that's pretty darn hard to beat

..


"Brian" wrote in message
hlink.net...
My company doesn't charge for shipping. We're surplus new old
stock....the selection isn't huge but it's cheap.

http://www.hamradparts.com



"xpyttl" wrote in message
...
"Brian" wrote in message
ink.net...

it though. If it doesn't work, a handful of PN2222's can be had for
less than a couple of bucks.

BG Micro has the metal ones, that you tend to use in the final, for a
quarter, the plastic ones you use for anything else for 6 cents. They
have surface mount MMBT2222A's for 4 cents.

2N2222's are handy little transistors that show up everywhere, and any
time you need any old NPN, a 2N2222 will generally do, so it never hurts
to have a few hundred in the parts drawer. And at $6/100, it doesn't
hurt the wallet all that bad, either.

Of course, BG shipping to merrie auld England probably isn't all that
pretty, but Farnell or some other local supplier must have something
comparable. I'm sure there must be a BC equivalent ... I bet if you
found the cheapest NPN it would be the same thing. You might shoot off
a note to George or Ian, or perhaps take a peek at the G-QRP's Circuit
Handbook. They seem to love the daylights out of the BC108, so I bet it
is comparable (although I don't have any data on that to compare).

..

OK OK boys... yes I know 2n2222's are wonderful and plentiful, but I
have a heap of geriatric bipolar power transistor I thought it might
be worth experimenting with:-

2n3055 (three)

2n3054 (four)

2n3739 (two)

2n4800 (one)

Sony D292 U38 (two)

Sony 2sc895 (one)

I thought if you can get anything up to 500mW with a general purpose
NPN, then what can you get out of an old power transistor?

I also have a load of BD139 medium-power transistors...?

Any thoughts?

In addition, I am still looking for the COMPONENT LAYOUT for the PCB
for a QRP
transmitter called "little joe" described in 9-81 in QST. I am not
looking for just the circuit diagram but where the parts GO on the
PCB!

Stephen G7VFY

07956-544202

The problem with power transistors is that they are big, and all other
things being equal, more size spells more capacitance, and mosr capacitance
spells more trouble at higher frequencies.

Chances are, you might do some good with some of them on 80, but you're not
likely to make them play nice on 20. If you notice, the 3055 has an Ft of
2.5 MHz, 3054 3 MHz. The 2N2222 has an Ft of 250 MHz, so you can see
there's a little difference there.

Your 3739 has a 10 MHz Ft, so you might get a little gain out of it on 80.
The 2SC895 I *think* is 20 (could only find a bad copy of the datasheet).
It will take a fair bit of tinkering to make parts like that work at all,
and they won't work well.

...

"mister35mm" wrote in message
oups.com...
OK OK boys... yes I know 2n2222's are wonderful and plentiful, but I
have a heap of geriatric bipolar power transistor I thought it might
be worth experimenting with:-

2n3055 (three)

2n3054 (four)

2n3739 (two)

2n4800 (one)

Sony D292 U38 (two)

Sony 2sc895 (one)

I thought if you can get anything up to 500mW with a general purpose
NPN, then what can you get out of an old power transistor?

I also have a load of BD139 medium-power transistors...?

Any thoughts?

In addition, I am still looking for the COMPONENT LAYOUT for the PCB
for a QRP
transmitter called "little joe" described in 9-81 in QST. I am not
looking for just the circuit diagram but where the parts GO on the
PCB!

Stephen G7VFY

07956-544202

On Sat, 3 Feb 2007 19:48:34 -0500, "xpyttl"
wrote:


Chances are, you might do some good with some of them on 80, but you're not
likely to make them play nice on 20. If you notice, the 3055 has an Ft of
2.5 MHz, 3054 3 MHz. The 2N2222 has an Ft of 250 MHz, so you can see
there's a little difference there.

Your 3739 has a 10 MHz Ft, so you might get a little gain out of it on 80.
The 2SC895 I *think* is 20 (could only find a bad copy of the datasheet).
It will take a fair bit of tinkering to make parts like that work at all,
and they won't work well.

The current gain drops to unity at fT, but you might still get some
voltage and power gain around such frequencies in a common base
configuration. This is the case in many microwave bipolar amplifiers,
since you can not get transistors (or would be too expensive) with fT
sufficiently high for common emitter configurations on a particular
band.

However, I have not seen common base amplifiers for HF, since RF power
transistors with sufficiently high fT are easily available for HF.

Paul OH3LWR