K3 & SSTV

[Simon (HB9DRV)]

You've heard the K3 (SSB), you've read the K3 (CW, PSK and RTTY), now see
the K3 receiving SSTV:

http://www.hb9drv.ch/sstv/sstv.htm

DM780 / HRD with SSTV support should be available in a few weeks.

Simon Brown, HB9DRV

_______________________________________________
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

[Don Ehrlich]

As many already know the K3 AGC kicks in when the MH2 mic PTT switch is
pressed and that causes the first few words to be attenuated after keying
the mic.

Elecraft told me that was caused by the mechanical noise the PTT switch in
the mic makes and they plan to address it by and by.

Not so!  The stimulation of AGC is caused by a current transient in the PTT
switch circuit that is coupled into the mic audio line in the mic cable
going to the K3.
My guess is that a filter capacitor in the K3 is being discharged by the PTT
switch and that generates a sufficiently high current spike to cause the
problem.

I just performed surgery on my mic connector to add a 150 ohm resistor in
series with pin 2 (PTT line) and that is all it took to eliminate that AGC
transient.  No more lost words.  It was messy surgery and not for the faint
of heart but it works.

Don K7FJ




_______________________________________________
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

[David Pratt-2]

In a recent message, Don Ehrlich <[hidden email]> wrote
...
>As many already know the K3 AGC kicks in when the MH2 mic PTT switch is
>pressed and that causes the first few words to be attenuated after
>keying the mic.
>
>Elecraft told me that was caused by the mechanical noise the PTT switch
>in the mic makes and they plan to address it by and by.

I am pleased to hear this, Don.  This delay is particularly noticeable
when using a powered mike such as the D104.  I am sure the delay is not
caused by mechanical noise but by transients in switching power onto the
mike.

73
--
David G4DMP
Leeds, England, UK
------


_______________________________________________
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

[David Pratt-2]

In a recent message, Don Ehrlich <[hidden email]> wrote
...
>Elecraft told me that was caused by the mechanical noise the PTT switch
>in the mic makes and they plan to address it by and by.
>
>Not so!
[Snip]
>I just performed surgery on my mic connector to add a 150 ohm resistor
>in series with pin 2 (PTT line) and that is all it took to eliminate
>that AGC transient.  No more lost words.  It was messy surgery and not
>for the faint of heart but it works.

That looks a good solution, Don, but surely this would invalidate the
warranty.  Perhaps wiring a 150 ohm into the plug would be a better
answer until Elecraft issue the Issue B RF board.

73
--
David G4DMP
Leeds, England, UK
------


_______________________________________________
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