On Sat, 26 Mar 2005 21:56:44 -0500, "Leland C. Scott"
wrote in :


"Frank Gilliland" wrote in message
.. .
On Sat, 26 Mar 2005 11:40:53 -0500, "Leland C. Scott"
wrote in :

snip
Come to think about it, how about just a 567 or 4046? Either chip
would probably do it as long as the radio doesn't drift too much. And
if I'm not mistaken, both have a VFO on the chip. So a CW 'adapter'
could be a single-chip project -- no DSP required.

Those two chips are just simple PLL building blocks. There isn't a way to
do
any tone filtering as such unless you make the VFO frequency range vary
narrow which would have the same effect.


That's the idea.


The 4046 has a range and frequency
offset capability using just two resistors and a capacitor. You would
want
to use the phase-frequency detector, not the simple XOR phase detector
which
could lock on harmonics of the audio tone. That would be the chip to use.
The lock detect circuit could then be used as the visual signal device
for
CW. Something this simple you could breadboard in an evening to see how
it
works.


Actually, it only took about 15 minutes, but it doesn't work. Capture
and release times are too erratic within the bandwidth, and any other
CW signals within about half an octave make the thing go spastic.

Hummmm...., what did you use for the bandwidth? I would have picked
something like 800Hz at the VCO center frequency and a VCO range of 700 to
900 Hz.....


I meant that the circuit didn't work for tuning through the .3-3kHz
bandwidth. Once I narrowed the bandwidth and used the BFO for tuning
it worked fine.


snip
Setting a narrow capture bandwidth, and using the clarifier (or BFO)
for tuning, works pretty well. I also tried a state-variable with a
schmitt trigger. Discrimination was better; but high Q, cumulative
drift and fading made it difficult to get a clear copy.

What was drifting, the filter, the frequency of the tone being transmitted,
or the receiver's frequency causing the tone's frequency to change?


Probably a little bit from everything -- I'm chalking it up to a
cumulative drift effect.


Before
giving up on anything it would be prudent to find out what the problem
happens to be before saying it doesn't work. The problem may be easy to fix,
or it could be the equipment you used for the test isn't representative of
what could be used now days.


I really don't think it's worth the effort since the PLL can track any
minor drifting that would require retuning of a state-variable filter.


I should add that it's been quite interesting trying to read Morse
with an LED..... after a few minutes it's almost hypnotic. I tried
different colors, and while a big green LED was the best it was still
irritating after about 10 minutes.

There are hearing impaired Hams doing something like that for years. I guess
they just get use to it.


I did a web search and found that some of them use a vibrating pad. I
thought about hooking up a relay or buzzer and see how that works. But
since I'm not deaf, my perceptions are probably different than someone
who would use the device regularly. Maybe a 'universal' output will do
the trick. It could then be hooked up to a vibrator, LED, strobe, fog
machine, stun-gun..... or whatever.





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"Frank Gilliland" wrote in message
...
On Sat, 26 Mar 2005 21:56:44 -0500, "Leland C. Scott"
wrote in :


"Frank Gilliland" wrote in message
.. .
On Sat, 26 Mar 2005 11:40:53 -0500, "Leland C. Scott"
wrote in :

snip
Come to think about it, how about just a 567 or 4046? Either chip
would probably do it as long as the radio doesn't drift too much.
And
if I'm not mistaken, both have a VFO on the chip. So a CW 'adapter'
could be a single-chip project -- no DSP required.

Those two chips are just simple PLL building blocks. There isn't a way
to
do
any tone filtering as such unless you make the VFO frequency range
vary
narrow which would have the same effect.


That's the idea.


The 4046 has a range and frequency
offset capability using just two resistors and a capacitor. You would
want
to use the phase-frequency detector, not the simple XOR phase detector
which
could lock on harmonics of the audio tone. That would be the chip to
use.
The lock detect circuit could then be used as the visual signal device
for
CW. Something this simple you could breadboard in an evening to see
how
it
works.


Actually, it only took about 15 minutes, but it doesn't work. Capture
and release times are too erratic within the bandwidth, and any other
CW signals within about half an octave make the thing go spastic.

Hummmm...., what did you use for the bandwidth? I would have picked
something like 800Hz at the VCO center frequency and a VCO range of 700
to
900 Hz.....


I meant that the circuit didn't work for tuning through the .3-3kHz
bandwidth. Once I narrowed the bandwidth and used the BFO for tuning
it worked fine.

Yeah, that's what I would have expected, the bandwidth was too wide.



snip
Setting a narrow capture bandwidth, and using the clarifier (or BFO)
for tuning, works pretty well. I also tried a state-variable with a
schmitt trigger. Discrimination was better; but high Q, cumulative
drift and fading made it difficult to get a clear copy.

What was drifting, the filter, the frequency of the tone being
transmitted,
or the receiver's frequency causing the tone's frequency to change?


Probably a little bit from everything -- I'm chalking it up to a
cumulative drift effect.


Before
giving up on anything it would be prudent to find out what the problem
happens to be before saying it doesn't work. The problem may be easy to
fix,
or it could be the equipment you used for the test isn't representative
of
what could be used now days.


I really don't think it's worth the effort since the PLL can track any
minor drifting that would require retuning of a state-variable filter.

I would think you could use the PLL directly by keeping the VCO frequency
range narrow. The loop filter doesn't have to be anything that complex,
state variable that is.




I should add that it's been quite interesting trying to read Morse
with an LED..... after a few minutes it's almost hypnotic. I tried
different colors, and while a big green LED was the best it was still
irritating after about 10 minutes.

There are hearing impaired Hams doing something like that for years. I
guess
they just get use to it.


I did a web search and found that some of them use a vibrating pad. I
thought about hooking up a relay or buzzer and see how that works. But
since I'm not deaf, my perceptions are probably different than someone
who would use the device regularly. Maybe a 'universal' output will do
the trick. It could then be hooked up to a vibrator, LED, strobe, fog
machine, stun-gun..... or whatever.

Universal plug for an output then let them connect whatever they want.


--
Leland C. Scott
KC8LDO

Linux - The alternative OS to Micro$oft Windows

On Sun, 27 Mar 2005 20:55:46 -0500, "Leland C. Scott"
wrote in :

snip
I really don't think it's worth the effort since the PLL can track any
minor drifting that would require retuning of a state-variable filter.

I would think you could use the PLL directly by keeping the VCO frequency
range narrow. The loop filter doesn't have to be anything that complex,
state variable that is.


I tried the state variable filter as a stand-alone device, not as a
PLL filter. Although it might be interesting to see what happens when
it -is- used as a PLL filter -- probably get all kinds of FM and
intermod distortion......






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"Frank Gilliland" wrote in message
...
On Sun, 27 Mar 2005 20:55:46 -0500, "Leland C. Scott"
wrote in :

snip
I really don't think it's worth the effort since the PLL can track any
minor drifting that would require retuning of a state-variable filter.

I would think you could use the PLL directly by keeping the VCO frequency
range narrow. The loop filter doesn't have to be anything that complex,
state variable that is.


I tried the state variable filter as a stand-alone device, not as a
PLL filter. Although it might be interesting to see what happens when
it -is- used as a PLL filter -- probably get all kinds of FM and
intermod distortion......

The filter should control the speed of phase locking to some extent and will
also help to remove phase noise from the signal you're trying to lock too,
but for your use that doesn't really matter.


--
Leland C. Scott
KC8LDO

Linux - The alternative OS to Micro$oft Windows