Hello,
I am getting back to ham radio and homebrewing (qrp) after many
years. I wanted to start by building the simple low power Picokeyer
given in http://www.arrl.org/qst/2003/12/0312038.pdf
I am currently in India and the MOSFET 2N7000 is not available
here. The article says that I can use a 2N2222 with a current limiting
resistor in the base or emitter. Can anyone help me with what resistor
value to use? Also is there an older MOSFET that I can use instead of
the 2N7000 since a MOSFET inherently uses very low current? Electronic
parts are fairly inexpensive in India but only the older and more
generic/popular ones are available.
Also has anyone enhanced the original software for the picokeyer in
open source/freely available form?

I am also looking around to purchase a good paddle for qrp work
(both qth and mobile) in the USA. I know from my previous stint in the
hobby (qro) that Bencher paddles were just about the best, but they
are also a little pricy - they have gone up 50% since the last time I
checked. Is there a below $100 iambic paddle that is good for home and
mobile use?

Please post your replies.

Thanks & Regards,
Jay
KC5TQS

I am getting back to ham radio and homebrewing (qrp) after many
years. I wanted to start by building the simple low power Picokeyer
given in http://www.arrl.org/qst/2003/12/0312038.pdf
I am currently in India and the MOSFET 2N7000 is not available
here. The article says that I can use a 2N2222 with a current limiting
resistor in the base or emitter. Can anyone help me with what resistor
value to use?

I think you'd need to experiment a bit, to determine how much current
into the base is required to turn a 2N2222 on hard enough to key your
rig reliably, while still using the least amount of current. 3k0 in
the base leg would be low enough to turn the 2N2222 on quite hard
(it'd put 1 mA into the base), but this is probably overkill (the
rig's probably not going to require more than a few mA to key up
properly, I'd guess). I'd suggest starting at 10k0 and working
upwards, until you find that the rig no longer keys up reliably, and
then go down a bit.

You might want to try a pair of 2N2222s in a Darlington arrangment,
with a high-value pulldown/turnoff resistor between the second
transistor's base and ground. This would let you use a high-value
resistor between the PIC and the first transistor's base (47k or
higher). A Darlington pair would be slower than a single transistor,
but unless you're in the thirteen-gabillion-word-per-minute class I
don't think it'll matter in this application :-)

Also is there an older MOSFET that I can use instead of
the 2N7000 since a MOSFET inherently uses very low current? Electronic
parts are fairly inexpensive in India but only the older and more
generic/popular ones are available.

They probably are available, but you're going to have to look to see
what the MOSFET's threshold voltage is. The Picokeyer uses a very low
battery voltage, and you'll need to pick an enhancement NMOSFET which
will turn on reasonably well with only 3 volts on the gate. A lot of
the older MOSFETs require between 5 and 10 volts to turn on solidly.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!