On Thu, 2006-12-28 at 18:44 -0500, Mike Bryce wrote:
> Hola...
>
> It's gray, muddy and out and out nasty outside.. great time to play
> with some older ten tec radios.
>
> I've been playing with a simple 1 MHz oscillator that is divided by
> ten to produce 100 kHz signal.
>
> works great! lots of square waves coming out of the divider. the
> output is right on the money 100kHz..
>
> now, the question...
>
> hooked this oscillator up to the argosy I. gots all kinds of signal
> on 3.500, a good 20 over s-9.. switch over to 7.000 and the marker is
> very weak.
>
> now..
>
> move to 7.1000 and it's 20 over, weak on 7.2 and 20 over on 7.300
>
> on 80 meters..
>
> 3.500 is 20 over while 3.600 is very weak... 3.700 strong, 3.800 weak..
>
> just the opposite of the 40 meter band..
>
> on 20 and up, things seem to be right
>
> so, why does this happen? I am at a loss to explain it...
>
> mike
>
>
> Mike Bryce, WB8VGE
> the heathkit shop
> SunLight energy systems
> J e e p
> o|||||||o
>
>
A perfect square wave is made up of only odd harmonics. 7.000 is an even
harmonic. If its marker you want, take that square wave and feed it to
one gate of an XOR. Take that same signal delayed through one gate of
any kind to the other gate of the XOR. The output of the XOR will be a
short pulse with length equal to the delay of the second gate. It will
have virtually equal signal strength on all harmonics, but will roll off
at higher frequencies depending on the speed of the chips used. If you
use 74AC it should be good to a couple hundred MHz at least. You can
even use a foot of wire for the delay to the second input of the XOR to
make a 1 nanosecond pulse at the output with 74AC logic.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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