On 02-28-95 email@example.com wrote to firstname.lastname@example.org:
> I am building W1FB's QSK QRP T/R switch and have a question about what
> transistor to use in the circuit. The circuit is on page 141 of the
> _QRP Notebook_. "Q1 may be any PNP transistor that can safely pass
> 300mA or greater DC current." The circuit shows a 2N2801 but I can't
> find this transistor in the Mouser catalog. I have access to some
> device data-books and would like to find a transistor that can "pass
> 300mA or greater DC current" but I don't know what column to look at
> in the books!
Look right below the 2N2801 and you'll see another number, TIP-30, which is
MUCH more common and easy to find!
Advice: You do not need two pairs of diodes as found in this circuit. I have
used only the lower pair, even without the protection diodes back to back, and
got less than 1 volt p-p into the RX at 5 watts output.
Use 1000 uH chokes if you want to work as low as 160 meters.
You can eliminate the RF chokes and blocking caps at either end, IF your
circuit provides a DC return to ground via a transformer. This is often true
in the transmitter, and in the RX if you have a link coupled input circuit.
I can provide schematics in PostScript and more details of one that has a
switching transistor added so you can just ground a key line to put the switch
in transmit mode. Also an approach that Ten Tec used in the Argosy, using
1N4007 diodes, power diodes which incidentally have a PIN structure. You have
to back bias these with a little rectifier/filter circuit from the transmitted
RF. This is good to 50 watts.
: John Seboldt email@example.com / "Should I go
: Amateur radio K0JD... / left or right?"
: Church of the Annunciation, / "No... go deeper."
: Minneapolis /
-> Alice4Mac 2.3 E QWK Eval:05Mar94
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