K2: Erratic action of the Hand Key "Autodetect" function

[Jim Sheldon]

I posted this problem several months ago and never received an answer from
anyone on it.  

My K2 (and I've talked with several other K2 owners with the same problem),
Serial #4338, will not always detect a hand key properly -- Autodetect is
turned on in the menu - and I am using 2 1N914 diodes between the hand key
contacts and the dot and dash inputs to the K2.  The keypaddles function
properly at all times, but when using the hand key, at random times, a key
down on the hand key produces the same results as a paddle press - namely
automatic dots or dashes.  This has proved to be a nasty problem, especially
in a contest when needing to rapidly slow down to re-send information.  You
get part way through the exchange and the characters get all messed up due
to the aforementioned erratic action.  

Is there any known fix for this problem????

Would appreciate any information available on the subject.

Jim Sheldon, W0EB
Wichita, KS
K2 #4338

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[Jim Sheldon]

HI Tom,
Yes, I am aware of the ability to switch to "Hand" operation.  This, however
is a pain in the butt, especially when operating mobile in motion.  This is
one of my main types of operation, and I switch often between the hand key
and the paddles.  I would really like the autodetect to work properly for
just this reason.

I had posted on this subject several months ago, and received no answer at
all.  This was brought to my attention at OzarkCon by several other K2
owners experiencing the same problem, and they were wondering if I had ever
received any info on it.  Mine is one of the newer ones, and I didn't write
down the calls of the others with the same problem, and I also forgot to get
serial #'s of their K2's so I could see if it was a function of the newer
firmware, or spanned several generations.  

Hopefully someone at Elecraft will read this and recall my earlier post.  

Jim - W0EB

> -----Original Message-----
> From: Tom Hammond [mailto:[hidden email]]
> Sent: Monday, May 09, 2005 8:37 AM
> To: Jim Sheldon
> Subject: Re: [Elecraft] K2: Erratic action of the Hand Key
> "Autodetect" function
>
>
> Hi Jim:
>
> Of course, the HARD-WIRED way to fix the problem should be to
> just go to
> MENU and select INP HAND.
>
> I've used my K2 in Autodetect mode for several years now and never
> experiences the problem you mention, but most of my
> 'external' keying is
> from an external keyer, rather than from a hand key or a bug.
> Though, when
> I HAVE used a hand key or bug, I've still never had the problem.
>
> Possibly a kludgey way to get around it might be to key a
> single transistor
> (better yet, a 2N7000 FET) and let the transistor output key
> the K2. Maybe
> add a little capacitance across the base of the transistor,
> to slow it up
> just a bit so any 'noise' on the hand key output might be
> filtered out.
>
> Good luck,
>
> Tom   N0SS
>
>
> At 06:35 AM 5/9/05, you wrote:
> >I posted this problem several months ago and never received
> an answer
> >from anyone on it.
> >
> >My K2 (and I've talked with several other K2 owners with the same
> >problem), Serial #4338, will not always detect a hand key
> properly --
> >Autodetect is turned on in the menu - and I am using 2 1N914 diodes
> >between the hand key contacts and the dot and dash inputs to
> the K2.  
> >The keypaddles function properly at all times, but when
> using the hand
> >key, at random times, a key down on the hand key produces the same
> >results as a paddle press - namely automatic dots or dashes.
>  This has
> >proved to be a nasty problem, especially in a contest when
> needing to
> >rapidly slow down to re-send information.  You get part way
> through the
> >exchange and the characters get all messed up due to the
> aforementioned
> >erratic action.
> >
> >Is there any known fix for this problem????
> >
> >Would appreciate any information available on the subject.
> >
> >Jim Sheldon, W0EB
> >Wichita, KS
> >K2 #4338
> >
> >_______________________________________________
> >Elecraft mailing list
> >Post to: [hidden email]
> >You must be a subscriber to post to the list.
> >Subscriber Info (Addr. Change, sub, unsub etc.):
> >  http://mailman.qth.net/mailman/listinfo/elecraft
> >
> >Help: http://mailman.qth.net/subscribers.htm
> >Elecraft web page: http://www.elecraft.com
>
>

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[Don Wilhelm-3]

Jim,

I have also had that occasional problem, and it seems to happen more
frequently if the key contacts are dirty.  Slip a piece of clean paper
between the contacts and close the key just enough to grip the paper gently
as you pull it through - the paper will burnish the contacts and the problem
will likely go away.  I found this out early on (just after the K2 Field
Test).  It does not seem to happen when the K2 is driven from a computer,
but will hppen occasionally when hard key contacts are used, so it must be
due to contact bounce coupled with slight propagation delay differences
through the diodes.

The other thing you can do is to match the diodes for timing (requires a
dual trace 'scope and a square wave generator)  - sometimes one diode is
slower than the other which will create a timing condition, 1N4148 diodes
are usually more consistent than 1N914s in my experience.

I am solving the problem altogether here with a K1EL K12 keyer packaged
externally.

73,
Don W3FPR

> -----Original Message-----
>
> I posted this problem several months ago and never received an answer from
> anyone on it.
>
> My K2 (and I've talked with several other K2 owners with the same
> problem),
> Serial #4338, will not always detect a hand key properly -- Autodetect is
> turned on in the menu - and I am using 2 1N914 diodes between the hand key
> contacts and the dot and dash inputs to the K2.  The keypaddles function
> properly at all times, but when using the hand key, at random times, a key
> down on the hand key produces the same results as a paddle press - namely
> automatic dots or dashes.  This has proved to be a nasty problem,
> especially
> in a contest when needing to rapidly slow down to re-send
> information.  You
> get part way through the exchange and the characters get all messed up due
> to the aforementioned erratic action.
>
>

--
No virus found in this outgoing message.
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[Vic K2VCO]

Jim Sheldon wrote:

>   The keypaddles function
> properly at all times, but when using the hand key, at random times, a key
> down on the hand key produces the same results as a paddle press - namely
> automatic dots or dashes.  

I have been using autodetect successfully for some time.  My thought is that
perhaps the forward voltage drop of the diodes is slightly different and this is
confusing the K2.  You can check this by measuring forward resistance with your
DVM (some actually measure voltage drop, but if not you want to match the
measured resistances).  I used a pair of low-drop schottky diodes -- I don't
know whether this is necesary, but I haven't had this problem.

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco

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[Sverre Holm]

-----Original Message-----
My K2 (and I've talked with several other K2 owners with the same problem),
Serial #4338, will not always detect a hand key properly -- Autodetect is
turned on in the menu - and I am using 2 1N914 diodes between the hand key
contacts and the dot and dash inputs to the K2.  The keypaddles function
properly at all times, but when using the hand key, at random times, a key
down on the hand key produces the same results as a paddle press - namely
automatic dots or dashes.  
----

I have resolved a similar problem some time ago that hopefully may shed some
light on your problem also. The symptom appeared similar, seemingly random
keying.

The series diodes in the autodetect circuit will make the K2 input no longer
0, but say 0.7 Volts (for Si diodes) when keyed. When I tried to key the K2
using autodetect and the diodes from my PC via an optocoupler I got into
trouble. The saturation voltage of the optocoupler was not small enough and
when added to the 0.7 Volts, the total was not low enough for the K2 to
reliably sense a key-down.

The optocoupler (4N31) had a voltage of 0.65 to 1.8 V in saturation. I
lowered it by increasing the drive current in the LED, but still had almost
1.4 V (opto 0.65 + Si diode 0.7). The remedy was to replace the autodetect
diodes with Shottky diodes. I have several hundreds of PRLL5818 in my shack
so I used one of them, but the type is not critical at all. The data says Vf
< 0.33 V at I = 100 mA, so the forward voltage with the low current here is
even smaller than that.

73

Sverre
LA3ZA
http://www.qsl.net/la3za/
 

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[Tom Hammond-3]

If Sverre's solution to the problem (Schottky diodes) is the answer, then
the 1N5711 should work nicely... and they are pretty easy to find... even
if you order them from Elecraft.

73,

Tom   N0SS

At 02:14 PM 5/9/05, Sverre Holm wrote:

>-----Original Message-----
>My K2 (and I've talked with several other K2 owners with the same problem),
>Serial #4338, will not always detect a hand key properly -- Autodetect is
>turned on in the menu - and I am using 2 1N914 diodes between the hand key
>contacts and the dot and dash inputs to the K2.  The keypaddles function
>properly at all times, but when using the hand key, at random times, a key
>down on the hand key produces the same results as a paddle press - namely
>automatic dots or dashes.
>----
>
>I have resolved a similar problem some time ago that hopefully may shed some
>light on your problem also. The symptom appeared similar, seemingly random
>keying.
>
>The series diodes in the autodetect circuit will make the K2 input no longer
>0, but say 0.7 Volts (for Si diodes) when keyed. When I tried to key the K2
>using autodetect and the diodes from my PC via an optocoupler I got into
>trouble. The saturation voltage of the optocoupler was not small enough and
>when added to the 0.7 Volts, the total was not low enough for the K2 to
>reliably sense a key-down.
>
>The optocoupler (4N31) had a voltage of 0.65 to 1.8 V in saturation. I
>lowered it by increasing the drive current in the LED, but still had almost
>1.4 V (opto 0.65 + Si diode 0.7). The remedy was to replace the autodetect
>diodes with Shottky diodes. I have several hundreds of PRLL5818 in my shack
>so I used one of them, but the type is not critical at all. The data says Vf
>< 0.33 V at I = 100 mA, so the forward voltage with the low current here is
>even smaller than that.
>
>73
>
>Sverre
>LA3ZA
>http://www.qsl.net/la3za/
>
>
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
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>  http://mailman.qth.net/mailman/listinfo/elecraft
>
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[Jim Sheldon]

Picked up a couple of 5711's from our local "surplus" electronics dealer.
They appear to do the trick - hasn't glitched once since I switched out the
4148 (914) diodes.

Jim

> -----Original Message-----
> From: Tom Hammond [mailto:[hidden email]]
> Sent: Monday, May 09, 2005 4:15 PM
> To: [hidden email]; 'Jim Sheldon'; [hidden email]
> Subject: RE: [Elecraft] K2: Erratic action of the Hand Key
> "Autodetect" function
>
>
> If Sverre's solution to the problem (Schottky diodes) is the
> answer, then
> the 1N5711 should work nicely... and they are pretty easy to
> find... even
> if you order them from Elecraft.
>
> 73,
>
> Tom   N0SS
>
> At 02:14 PM 5/9/05, Sverre Holm wrote:
> >-----Original Message-----
> >My K2 (and I've talked with several other K2 owners with the same
> >problem), Serial #4338, will not always detect a hand key
> properly --
> >Autodetect is turned on in the menu - and I am using 2 1N914 diodes
> >between the hand key contacts and the dot and dash inputs to
> the K2.  
> >The keypaddles function properly at all times, but when
> using the hand
> >key, at random times, a key down on the hand key produces the same
> >results as a paddle press - namely automatic dots or dashes.
> >----
> >
> >I have resolved a similar problem some time ago that
> hopefully may shed
> >some light on your problem also. The symptom appeared similar,
> >seemingly random keying.
> >
> >The series diodes in the autodetect circuit will make the K2
> input no
> >longer 0, but say 0.7 Volts (for Si diodes) when keyed. When
> I tried to
> >key the K2 using autodetect and the diodes from my PC via an
> >optocoupler I got into trouble. The saturation voltage of the
> >optocoupler was not small enough and when added to the 0.7
> Volts, the
> >total was not low enough for the K2 to reliably sense a key-down.
> >
> >The optocoupler (4N31) had a voltage of 0.65 to 1.8 V in
> saturation. I
> >lowered it by increasing the drive current in the LED, but still had
> >almost 1.4 V (opto 0.65 + Si diode 0.7). The remedy was to
> replace the
> >autodetect diodes with Shottky diodes. I have several hundreds of
> >PRLL5818 in my shack so I used one of them, but the type is not
> >critical at all. The data says Vf < 0.33 V at I = 100 mA, so the
> >forward voltage with the low current here is even smaller than that.
> >
> >73
> >
> >Sverre
> >LA3ZA
> >http://www.qsl.net/la3za/
> >
> >
> >_______________________________________________
> >Elecraft mailing list
> >Post to: [hidden email]
> >You must be a subscriber to post to the list.
> >Subscriber Info (Addr. Change, sub, unsub etc.):
> >  http://mailman.qth.net/mailman/listinfo/elecraft
> >
> >Help: http://mailman.qth.net/subscribers.htm
> >Elecraft web page: http://www.elecraft.com
>

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[Sverre Holm]

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jim Sheldon
Sent: 9. mai 2005 23:41


Picked up a couple of 5711's from our local "surplus" electronics dealer.
They appear to do the trick - hasn't glitched once since I switched out the
4148 (914) diodes.
---------

Good to hear that Shottky does the trick!

The PIC16F77 datasheet is a bit overwhelming, see
http://ww1.microchip.com/downloads/en/DeviceDoc/30325b.pdf, but on page 125
it has the Input Low Voltage condition. Among them one can read "Input Low
Voltage is minimum VSS and maximum 0.8V". Then it should not be a surprise
that an input voltage in the 0.7-0.8 Volt range sometimes may cause erratic
behavior.

73

Sverre
LA3ZA
http://www.qsl.net/la3za/
 

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