EMRFD Message Archive 9227
Message Date From Subject 9227 2013-10-08 18:53:09 bob_ledoux Using 74HC04 as VFO I'm looking at QST, 2/2005, page 32, "The W6QIF Oscillator." The article discusses use of varicaps, and back-to-back 1N4005 diodes as tuning caps in an oscillator based on a 74HC04 inverter chip.
I'm interested in his selection of the 74HC04 chip. He also describes his circuit as a Vackar oscillator, which suggests it is a low drift circuit.
What experience do we have in building square wave LC VFO's using such a digital chip?
I've seen numerous schematics using the inverter chip as a crystal oscillator for digital applications.
Are there reasons why this application isn't more common?
9228 2013-10-08 19:59:39 Dana Myers Re: Using 74HC04 as VFO 9229 2013-10-09 07:24:16 WA0ITP Re: Using 74HC04 as VFO In his article W6QIF mentions that the TC of the -6 mix toroid he used went negative after boiling it. Interesting, how can that happen?
Real radios weigh less than a pound.
I love this radio stuff !
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9235 2013-10-11 09:54:14 mosaicmerc Re: Using 74HC04 as VFO 9237 2013-10-12 09:18:43 ehydra Re: Using 74HC04 as VFO mosaicmerc schrieb:
> What do u guys think of this item:Yes. Maybe not over full temperature range and lowest VCC, but at 3.3V
> That series include fast D flipflops which can give frequency division. I am thinking of making a custom oven controlled oscillator based around a 100 or 200Mhz crystal with this logic.
> Do you think 200Mhz is reasonable with this logic circuit?
and 0 to 70°C no prob.
9238 2013-10-12 11:39:04 Gene Dorcas Re: Using 74HC04 as VFO