Can U4 be a 78HCT240, instead of a 78HC240? I'd think not, based on
information in the Data Book by NA5N. But RS had the "T" version,
not the regular version ...
What would be the result of using a "T" version, which has a higher
response time, but is a bit tighter on voltages? Seems we're
overdriving the chip anyway, since the expectation is for 7.8v on
several pins of U4. (The Data Book shows the Vcc of the normal
78HC240 as 2.0-6.0v, the "T" version is 4.5-5.5v). The Vhi is a bit
lower (1.1 V). By the way, just what is Vcc? I'm assuming it's
some sort of operating voltage range, but I'm an idiot, and not sure
of such things ...
BTW, Paul, NA5N, has done an absolutely wonderful job on this book,
which arrived today. Now I can at least *sound* the fool that I am!
I think it should be renamed the QRP Handbook. Could be developed
and give the ARRL version a real run for its money! (Standard
disclaimers apply).
72 es 73 de
Marty, KM7W
__________________________________________________________________
Jackson, Tennessee e-mail: mdwatt@usit.net
http://www.public.usit.net/mdwatt
"The Curmudgeon's Corner"
NorCal #???? - ARCI #7514 - QRP-L #953 - AK/QRP #098 - Grid EM55oq
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