I had a discussion about the N7KSB xmtr going to 50mHz with Ori who you
remember designed the 38 Special. He discribes one way I could get the
74HC240 up to 6m.
I expressed a small fear that the 74hc240 may not be practical at that
freq. But Im just guessing. The chip does 500mw at 14-21mHz, and 470mw
at 28mHz.. so not sure how much pwr its gunna do at 50mHz.
We need some experiments here - Ori expressed that the Pixie circuit is
better suited for 6M in his opinion... I asked and recieved his
permission to reprint the text.
Below is the text of our discussion in case anyone wants to go further
--->
Ori,
I think i have a 46 or something mhz xtal from a cordless fone - and
will have to see if I can get that going - if so I can play hell with
cordless fone folks :) (just kidding) - OR use that as a test to see if
50.090mhz has a chance.
With Jan's xtals going for $12-14. bux I figure its a good idea to try
the 46mhz 1st!
Jim,
Let's fix that problem... take a standard 10.0 MHz crystal and build a
fifth-overtone oscilator!!! You can easily cover 30-40 KHz range right
around the 50.090 MHz with a VXO.
Don't forget the traps for 10.0 and 30.0 MHz!!!
I'd build them both from a tapped toroidal inductor with tiny trimcaps.
Use the same core for an output transformer for the 50.0 MHz and
you get one clean and cheap oscillator for less than two bucks, with
excellent impedance matching from a single transistor circuit.
In the 49er configuration, follow the circuit in the Signetics data book
for an overtone oscillator. Same circuit as the Pixie, using the
internal transistor in the NE602.
I'll go with a Pixie circuit, much more solid at 6 meters.
73 Ori AC6AN
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