[Elecraft] [K3] how connect a Pactor modem to the K3?

[Dave G4AON]

Hello Werner

My favourite subject! There is currently an issue between the SCS Pactor 
modems and the K3, basically the K3 has a TX DSP delay of around 12 mS 
and the SCS modems appear to have no "post TX" PTT delay. I have been 
conducting some experiments with Brendan, EI6IZ, on Amtor and have a 
"work around" where you need to use the VOX as well as PTT in order to 
avoid truncating the trailing edge of Amtor transmissions. The following 
settings work for me using a K3 and SCS PTC-IIex modem, both on Amtor 
and Pactor:

Line in/line out (line in is MONO - just use the tip of a stereo plug)
PTT rear panel phono socket

SCS Modem setting, TXD = 5, tone levels need to be higher than the 
default as the line in is quite low sensitivity, suggest 500 mV from the 
modem.

K3 settings, assign SYNC DT to one of the PF keys, this speeds up the 
DSP processing by bypassing some of the code, shows an "-s" on the 
display when enabled. USB, VOX delay 0.05, VOX enabled, AGC-F.

I am using Alpha Software version 2.2

Lyle (KK7P) sent me a later version of DSP firmware (1.78) which reduces 
the DSP delay by 5 mS (was I guess around 17 mS)... The additional delay 
had crept in by accident in recent firmware releases. I understand there 
may be a variable "PTT off" delay in a later firmware release from 
Elecraft, I have also been in touch with the SCS over the matter as it's 
likely to be a problem with other DSP IF transceivers.

I can e-mail you off list with oscilloscope images of the various 
delays, etc. Oddly enough I also have a Kantronics KAM Plus which has a 
POStkey command which allows for up to 12 mS of post PTT delay! For what 
it's worth the PK232 doesn't appear to have a similar command, so they 
may have issues with the K3 too. If you want an Amtor or Pactor (II/III) 
sked to test your set-up let me know.

73 Dave, G4AON
K3/100 #80
----------------
hi all,
has anybody connected a Ptc-2 to the K3 and how this was done?
I think I could use Line in / Line out and PTT in.
Line is stereo, should I use the tip? or connect tip and ring?

any comments on how this should be done and how does it work?


73! de Werner OE9FWV