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K2 dual keying problem

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David Pratt

K2 dual keying problem

Mindful that I am neglecting my hand keying, my sending being spoilt by
the ease of using an iambic paddle, I have connected a straight key
across the paddle keying line using a pair of 1N4148 diodes as shown in
the K2 Manual. This works reasonably well, but occasionally when
pressing the straight key I get a string of alternate dots and dashes.

I presume that the problem is caused by the reverse resistance of the
diodes being too low. I tried putting two 1N4148 diodes in series in
both lines. This is better but has not cured the problem completely. Has
anyone else had this problem? Or does anyone have a suggestion as to how
both a paddle and straight key may both be connected to the K2 with
reliable results.

73 de David G4DMP

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Don Wilhelm-3

RE: K2 dual keying problem

David,

I would rather speculate that it is a uP timing situation coupled with
contact bounce at the key and the forward voltage drop of the diodes. If
one of the diodes is a bit slower than the other, the voltage seen at the uP
pins may actually look like one pin has gone to a low state before the other
(that is the condition to generate the iambic alternating dots and dashes).
This problem can be caused by contact bounce at the hand key - cleaning the
hand key contacts will help, but one can never cure contact bounce at a
mechanical closure point.

The net of the story is that the uP must believe that both the dot and dash
contact closures occurred together, and the only way that can be known is
for it to sense a low voltage on both its input pins. If the polling of
those pins happens to occur during a contact bounce period and one of the
diodes is a bit slower than the other it will appear to the microprocessor
that only one of the contacts was closed.

I am surprised that two diodes in series appears to work better - in fact it
will make the low state at the uP pins at an even higher voltage than one
diode. I would suggest that you try using Shottky diodes (like 1N5711)
instead to lower the voltage at the uP pins when the hand key is closed.

So clean your key contacts and go back to one diode for each side and if
still a problem switch to Schottky diodes.

73,
Don W3FPR

> -----Original Message-----

>
> Mindful that I am neglecting my hand keying, my sending being spoilt by
> the ease of using an iambic paddle, I have connected a straight key
> across the paddle keying line using a pair of 1N4148 diodes as shown in
> the K2 Manual. This works reasonably well, but occasionally when
> pressing the straight key I get a string of alternate dots and dashes.
>
> I presume that the problem is caused by the reverse resistance of the
> diodes being too low. I tried putting two 1N4148 diodes in series in
> both lines. This is better but has not cured the problem completely. Has
> anyone else had this problem? Or does anyone have a suggestion as to how
> both a paddle and straight key may both be connected to the K2 with
> reliable results.
>
> 73 de David G4DMP
>
>

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David Pratt

Re: K2 dual keying problem

Thank you, Don, for your technical description as to what might be
happening.

I have polished my straight key silver contacts and replaced the diodes
with 1N5821 Schottky diodes, but am still getting the problem
occasionally.

It does look as though I shall have to fit a separate jack to the
straight key and change the InP menu setting to HAnd when I want to use
the straight key. I had hoped to have avoiding doing that. Perhaps I
shall try and to get hold of some 1N5711 diodes and see if they are any
better.

73 de David G4DMP

In message <[hidden email]>, Don
Wilhelm <[hidden email]> writes
>I would rather speculate that it is a uP timing situation coupled with
>contact bounce at the key and the forward voltage drop of the diodes. If
>one of the diodes is a bit slower than the other, the voltage seen at the uP
>pins may actually look like one pin has gone to a low state before the other
>(that is the condition to generate the iambic alternating dots and dashes).
>This problem can be caused by contact bounce at the hand key - cleaning the
>hand key contacts will help, but one can never cure contact bounce at a
>mechanical closure point.
..........

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Don Wilhelm-3

RE: K2 dual keying problem

David,

You could leave the physical connections as they are now and simply change
the menu to INP Hand. If your current diodes are Shottky type, there will
be no further benefit to changing them - I only mentioned the 1N5711 as one
example type.

It has been noted that the diodes work well when using a connection from a
computer or other device to key the K2, but it occasionally fails when
using a hand key - I attribute that to the contact bounce part of the
problem.

73,
Don W3FPR

> -----Original Message-----

>
> Thank you, Don, for your technical description as to what might be
> happening.
>
> I have polished my straight key silver contacts and replaced the diodes
> with 1N5821 Schottky diodes, but am still getting the problem
> occasionally.
>
> It does look as though I shall have to fit a separate jack to the
> straight key and change the InP menu setting to HAnd when I want to use
> the straight key. I had hoped to have avoiding doing that. Perhaps I
> shall try and to get hold of some 1N5711 diodes and see if they are any
> better.
>
> 73 de David G4DMP
>

Sverre Holm-2

RE: K2 dual keying problem

In reply to this post by David Pratt

> -----Original Message-----
> Thank you, Don, for your technical description as to what
> might be happening.
>
> I have polished my straight key silver contacts and replaced
> the diodes with 1N5821 Schottky diodes, but am still getting
> the problem occasionally.
>

David

If you have many diodes available, then as a last resort you could try to
match the diodes for forward voltage drop. It could be that differences here
could result in slightly different turn-on times and upset the automatic
hand-key detection.

73

Sverre
LA3ZA
http://www.qslnet.de/la3za/

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David Pratt

Re: K2 dual keying problem

Thank you for your suggestion, Sverre, I am planning doing that. I have
12 1N5821 diodes here and with try and match a pair on them tomorrow.

73

David G4DMP

In a recent message, Sverre Holm <[hidden email]> writes
>
>If you have many diodes available, then as a last resort you could try to
>match the diodes for forward voltage drop. It could be that differences here
>could result in slightly different turn-on times and upset the automatic
>hand-key detection.
>Sverre
>LA3ZA

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Alexandra Carter

Re: K2 dual keying problem

In reply to this post by Don Wilhelm-3

Is is possible to add a de-bounce circuit to the hand key? 73 de Alex
NS6Y

On Feb 5, 2006, at 5:41 AM, Don Wilhelm wrote:

> David,
>
> I would rather speculate that it is a uP timing situation coupled with
> contact bounce at the key and the forward voltage drop of the diodes.
> If
> one of the diodes is a bit slower than the other, the voltage seen at
> the uP
> pins may actually look like one pin has gone to a low state before the
> other
> (that is the condition to generate the iambic alternating dots and
> dashes).
> This problem can be caused by contact bounce at the hand key -
> cleaning the
> hand key contacts will help, but one can never cure contact bounce at a
> mechanical closure point.
>
> The net of the story is that the uP must believe that both the dot and
> dash
> contact closures occurred together, and the only way that can be known
> is
> for it to sense a low voltage on both its input pins. If the polling
> of
> those pins happens to occur during a contact bounce period and one of
> the
> diodes is a bit slower than the other it will appear to the
> microprocessor
> that only one of the contacts was closed.
>
> I am surprised that two diodes in series appears to work better - in
> fact it
> will make the low state at the uP pins at an even higher voltage than
> one
> diode. I would suggest that you try using Shottky diodes (like 1N5711)
> instead to lower the voltage at the uP pins when the hand key is
> closed.
>
> So clean your key contacts and go back to one diode for each side and
> if
> still a problem switch to Schottky diodes.
>
> 73,
> Don W3FPR
>
>> -----Original Message-----
>
>>
>> Mindful that I am neglecting my hand keying, my sending being spoilt
>> by
>> the ease of using an iambic paddle, I have connected a straight key
>> across the paddle keying line using a pair of 1N4148 diodes as shown
>> in
>> the K2 Manual. This works reasonably well, but occasionally when
>> pressing the straight key I get a string of alternate dots and dashes.
>>
>> I presume that the problem is caused by the reverse resistance of the
>> diodes being too low. I tried putting two 1N4148 diodes in series in
>> both lines. This is better but has not cured the problem completely.
>> Has
>> anyone else had this problem? Or does anyone have a suggestion as to
>> how
>> both a paddle and straight key may both be connected to the K2 with
>> reliable results.
>>
>> 73 de David G4DMP
>>
>>
>
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> Elecraft web page: http://www.elecraft.com
>

Don Wilhelm-3

RE: K2 dual keying problem

Alex,

It certainly is, but most circuits using a single pole single throw switch
(normal key contacts) suffer from the same difficulties as the K2 key input
circuits - one must make some assumption about the duration of the bounce
and decide if it is a valid key closure or not. To do it in a foolproof
manner requires a SPDT switch, and the closure of the NO contact sets a
latch, the closure of the NC closed contact resets it - simple set/reset
latch, no clocking required.

So if one were willing to swap their favorite hand-key for one with a SPDT
set of contacts, it would work flawlessly - perhaps someone else will come
up with a better method, but that is the circuit that I have used for
de-bouncing when complete assurance of a contact closure is required. Noise
on the set contacts may get through, but will not set the latch because the
reset contacts are still closed. A couple of 2 input NAND logic gates and a
couple of inverters will do the job nicely.

In the meantime, I will use an external keyer and leave the K2 set to INP
Hand to accomplish the same task - the K1EL K12 keyer is small, can run a
long time from a coin battery and does the job for me. I am not knocking
the K2 keyer, but I am getting used to my K1EL keyer and I can use it with
any rig with no time to become accustomed to a particular internal keyer.

73,
Don W3FPR

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]]On Behalf Of Alexandra Carter
> Sent: Sunday, February 05, 2006 8:04 PM
> To: [hidden email]
> Cc: [hidden email]
> Subject: Re: [Elecraft] K2 dual keying problem
>
>
> Is is possible to add a de-bounce circuit to the hand key? 73 de Alex
> NS6Y
>
> On Feb 5, 2006, at 5:41 AM, Don Wilhelm wrote:
>
> > David,
> >
> > I would rather speculate that it is a uP timing situation coupled with
> > contact bounce at the key and the forward voltage drop of the diodes.
> > If
> > one of the diodes is a bit slower than the other, the voltage seen at
> > the uP
> > pins may actually look like one pin has gone to a low state before the
> > other
> > (that is the condition to generate the iambic alternating dots and
> > dashes).
> > This problem can be caused by contact bounce at the hand key -
> > cleaning the
> > hand key contacts will help, but one can never cure contact bounce at a
> > mechanical closure point.
> >
> > The net of the story is that the uP must believe that both the dot and
> > dash
> > contact closures occurred together, and the only way that can be known
> > is
> > for it to sense a low voltage on both its input pins. If the polling
> > of
> > those pins happens to occur during a contact bounce period and one of
> > the
> > diodes is a bit slower than the other it will appear to the
> > microprocessor
> > that only one of the contacts was closed.
> >
> > I am surprised that two diodes in series appears to work better - in
> > fact it
> > will make the low state at the uP pins at an even higher voltage than
> > one
> > diode. I would suggest that you try using Shottky diodes (like 1N5711)
> > instead to lower the voltage at the uP pins when the hand key is
> > closed.
> >
> > So clean your key contacts and go back to one diode for each side and
> > if
> > still a problem switch to Schottky diodes.
> >
> > 73,
> > Don W3FPR
> >
> >> -----Original Message-----
> >
> >>
> >> Mindful that I am neglecting my hand keying, my sending being spoilt
> >> by
> >> the ease of using an iambic paddle, I have connected a straight key
> >> across the paddle keying line using a pair of 1N4148 diodes as shown
> >> in
> >> the K2 Manual. This works reasonably well, but occasionally when
> >> pressing the straight key I get a string of alternate dots and dashes.
> >>
> >> I presume that the problem is caused by the reverse resistance of the
> >> diodes being too low. I tried putting two 1N4148 diodes in series in
> >> both lines. This is better but has not cured the problem completely.
> >> Has
> >> anyone else had this problem? Or does anyone have a suggestion as to
> >> how
> >> both a paddle and straight key may both be connected to the K2 with
> >> reliable results.
> >>
> >> 73 de David G4DMP
> >>
> >>
> >
> > _______________________________________________
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> >
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> > Elecraft web page: http://www.elecraft.com
> >
>
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Vic K2VCO

Re: K2 dual keying problem

In reply to this post by Alexandra Carter

Alexandra Carter wrote:
> Is is possible to add a de-bounce circuit to the hand key? 73 de Alex NS6Y

The easiest way to do it is with old technology. I debounced my bug by
having it key a Radio Shack 12v reed relay. There is a 10 uf capacitor
accross the relay coil, or otherwise it is fast enough to follow the bounce!

The bug relay (as well as an opto-isolator hooked to the parallel port
of my computer for contest loggers) are connected accross the paddles
with a pair of Schottky (sp?) diodes. The K2 works great with the
paddles, the bug, or the computer with no changes needed.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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