From: hugh@ivy.unisys.com (Hugh Pepper)
Subject: KAM / TS850S noise problems
Organization: Paramax Systems, Ivyland, PA
Date: Thu, 23 Jul 1992 18:03:46 GMT


From: hugh@ivy.unisys.com (KE3BI)
To: All TS-850S and KAM owners
Subject: Reducing Noise from KAM into TS-850S 

I recently purchased a Kenwood TS-850S and really love the rig. I also
use a Kantronics KAM TNC for all of the digital modes (HF and VHF) that 
I use.  The following describes some of the problems and frustrations 
which I encountered while attempting to connect these two pieces of 
equipment together. I hope that some of my experiences explained below 
can save someone else the many headaches I have endured.

The TS-850S has an accessory plug ACC2 on the back panel (one of many)
which has 13 pins. In the owner's manual these pins are described 
fairly well as to which pin is used for which function.  Many of 
the control and output signals from the KAM can be brought into the 
TS-850S from this jack.  This is a little less cluttered that using a 
modified 8-pin microphone jack and going in from the front panel.  

Anyway, I used the interface cable supplied with the KAM from the HF 
output port (8-pin DIN) and wired the ACC2 plug supplied with the TS-850S 
as follows:
 

  KAM     WIRE                         TS-850S ACC2   or  TS-850S
PIN OUT   COLOR                         PIN NUMBER         JACK
   1      White  - AFSK OUT     -----       11                -
   2      Black/Shield          -----      4,8,12    CW/RTTY jack grounds
   3      Brown  - PTT SWITCH   -----       9                 -
   4      Orange - CW KEY       -----       -         CW KEY JACK (tip)
   5      Red    - FSK OUT      -----       -        RTTY-FSK JACK (tip)


All digital modes worked fine (AMTOR, RTTY, PACKET..etc) by using AFSK 
tones generated in the KAM, setting the TS-850S to LSB or USB, and 
modulating the RF signal with these tones.

The problem occured when I would use voice LSB or USB while the ACC2 
plug was plugged into the the back of the TS-850S. Even though the KAM 
was in a receive mode only, and not keying the transmitter, I would get 
distortion on my voice signal. This distortion was heard over the air 
by others, and also could be heard using the monitor button on the front 
of the TS-850S while wearing headphones to listen to my own signal as I 
was transmitting. This distortion and noise was present when I was using 
my vertical, dipole, and dummyload.

I thought this distortion/noise was maybe RF energy in the shack being 
rectified in the KAM and being sent back into the TS-850S through one 
of the lines on the ACC2 cable and plug.  I called Kantronics to inform 
them of my findings and they said, "Oh, you must have a ground loop 
or something --- make sure all grounds are properly connected, 
especially since many Kenwood radios have a separate audio ground 
which is not at the same ground potential as the case or chassis ground."
(loads of technical support, huh??!! ) 

So I went back and made sure all grounds from the KAM and Kenwood 
were secure, and that the shield on the cable between the KAM and 
the TS-850S was well connected to the ground for the TNC and the rig.
The distortion was still there!!!

I also tried RF ferrite beads/cores on the outside of the cable with
no difference in distortion or noise. 

I found that the noise and distortion would go away completely by 
either unplugging the cable between the KAM and TS-850S, or by simply 
shutting off the KAM with the interface cable still connected to the
ACC2 jack on back of the TS-850S.  

THE PROBLEM is that there is noise (RF or microprocessor clock noise) 
coming from pin 1 of the KAM HF port (8-pin DIN plug) and traveling 
down the white audio lead of the interface cable and entering the rig 
through pin 11 of the ACC2 plug on the rear panel of the TS-850S.  

I guess that Kenwood can`t shunt this line to ground during SSB, 
(or any voice mode for that matter), because AFSK uses this input to 
inject the audio signals from a TNC onto the output signal.  But maybe 
Kantronics might be able to do more than just a blocking cap to ground 
to keep internal noise off of the audio lead coming out from the KAM.

MY SOLUTION was to install a small SPST switch in line with this white 
audio lead from the KAM to the TS-850S. I placed it very close to the 
ACC2 plug in back of the rig so as not to leave a large antenna for RF 
to enter the TS-850S when this audio lead switch is open.  

I leave this switch open most of the time because usually I use the FSK
mode on the TS-850S for most digital modes.  In this mode, the mark and 
space tones are GENERATED in the TS-850S itself but SWITCHED by the FSK 
OUT line from the KAM (RED wire, pin 5) and into the TS-850S via the 
RTTY plug on back of the rig.

The standard shift out of the TS-850S is 170 HZ which is fine for RTTY 
and AMTOR, but for PACKET, the standard shift is 200 HZ. This shift can 
be changed in the TS-850S, however it has to be done from the power-up 
menu function and this is tedious and inconvenient with powering down and 
powering back up the rig to change this parameter.

So normally I use the FSK mode on the RIG and have the KAM send data 
using the RTTY output (the switch installed on white audio lead is open), 
but if I want to use HF Packet (200 HZ shift instead of 170 HZ), I use LSB 
on the TS-850S (the switch installed on white audio lead from KAM is 
closed), and the tones are generated in the KAM (AFSK).

Note: the data from the KAM is sent out both ways all of the time.  The 
AFSK audio goes to the TS-850S via the white wire from pin 1 on the KAM 
HF port to pin 11 of the ACC2 plug in the TS-850S, and RTTY (open/close) 
shift data goes to the TS-850S via the RED line from pin 5 on the KAM HF 
port to the RTTY/FSK jack on the back of the TS-850S. 

I hope my ramblings above help some of you out there fighting similar 
problems.  I am always looking for more info on the TS-850S, ie. 
undocumented features, mods, etc.
 
I have already done the MARS/CAP all band XMIT, and the Broadcast AM 
band attenuator defeat mods. Really love the rig ...
Any Questions or other Info always welcome.

73 de HUGH     K
               E
               3
               B-ad
               I-nfluence
	

E-MAIL  to hugh@ivy.Unisys.Com
------------------------------------------
Hugh M. Pepper, KE3BI ('B`ad 'I`nfluence)

email: Hugh@ivy.unisys.com