Back in the '60s when we were still using mechanical teleprinters, I operated
RTTY on the same bands a notable local DXer operated. He was really upset if
any clicks and pops were present to upset his DX band. Using a polar relay to
key the AFSK oscillator frequency really screwed up the band.
I came up with a 555 circuit running in the astable mode and applied the keying
to the timing resistor in the 555 circuit. I found that generating the signal
at 16 times the output frequency (2125/2975) would allow shifting the frequency
very smoothly and eliminated the clicks and pops the direct keying generated.
I applied the polar relay contacts directly to the frequency shift resistor in
the 555 circuit, and any bounce generated by the relay was absorbed in the
divide by 16 circuit.
A very versital device indeed -
73 - Jim W5ZIT
skipp025 <[EMAIL PROTECTED]> wrote:
The 555 is one of the most useful electronic circuit chips ever
made. It has a fairly large number of possible simply configured
mono & astable (cycle) circuit operations. And it's just as easy
to get lost when trying to use it for specific tasks.
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