KAM / TS850S noise problems ------------------------------------------------------------ Hugh Pepper 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