could not open /dev/kbd to get keyboard type US keyboard assumed could not get keyboard type US keyboard assumed Subject: Kantronics KAM HF frontend modifications From: Warren Stone Mods for the original Kantronics KAM. It is for improvements to both the HF and VHF ports of the TNC. -- Kantronics KAM HF frontend modification update -- I recently received a Kantronics KAM-Plus modem. After comparing the schematics of the KAM and the KAM-Plus, I came up with this modification for the KAM to upgrade it to the improved frontend AGC and limiter used in the KAM-Plus hf modem. The specs from the manuals for the KAM and the KAM-Plus are as follows; Audio Input: HF FM sensitivity 20mVpp (KAM) 2mVpp (KAM+) AM sensitivity 100mVpp (KAM) 40mVpp (KAM+) Dynamic range >60dB (KAM) >80dB (KAM+) With the help of the schematic and the component layout diagram for the KAM the location of components is simple and the use of a solder sucker to clear the holes for the double sided PCB will facilitate a clean job. Components to replace; OLD NEW R17 470 100 (All 1/4 watt carbon resistors) R18 47K 68K R19 2.2K 10K R27 15K 2.7K Remove CR11 and reinstall with polarity reversed Remove CR5 and discard Lift the end of R13 that is common with R1. Insert one end of a .1uF 50V capacitor into the PCB hole vacated by the end of R13 common to R1; solder in place. Connect the other end of this cap to the free end of R13. Install a 100K 1/4W resistor between the free end of R13, the .1UF CAP and ground. Use the PCB hole vacated by removing CR5 (ground side). You end up with a tripod of components. CAUTION: Some PCB holes having double sided traces may need to be soldered on both sides of the board to ensure a through board solder job. This completes the update modification for the KAM. You will notice a better dynamic range for input signals to the KAM and an improved limiter using the FM/AM front panel switch. I noticed an improvement in throughput when operating AMTOR/PACTOR. I also noted improved CW reception using the 'AM' position of the FM/AM switch providing perfect copy on 160M CW signals. I would appreciate any feedback on this modification or other improvements: K5HK @ K7BUC.AZ.USA.NA (APLINK) OR mail to my home address. 73, CARL YOUNG, K5HK /MM2 ABOARD SS KAINALU HOME QTH: 983 LESTER AVE. RENO, NV 89502 --------------------------------------------------- KAM VHF front end improvement 7 April 1995 Original KAM VHF port audio sensitivity 20mVpp, >60dB dynamic range KPC9612, KPC3 VHF port audio sensitivity 5mV, 70dB dynamic range The KAM uses the same modem IC as used in both the KPC3 and KPC9612. By changing some components the KAM VHF performance can be improved to the same specs as the KPC3 or KPC9612. To improve the KAM VHF performance; Remove R4, R8, Q4 Remove and place jumpers in place of C14 and R6 Replace R9 6.8k with 100k Replace R26 6.8k with 100k Replace R28 15k with 470k Replace C6 0.001uF with 0.01uF K1 position 2 or off, equalization off K1 position 1, equalization on This will change the configuration of the original KAM VHF front end to be similar to the KPC3 and KPC9612. I use a Mocom70 with direct audio feed from the discriminator. There is no way to simply increase the volume level to get more audio. There is a great improvement in the VHF port performance of my KAM since making these changes. 73 de Warren VO1KS Packet VO1KS @ VE1BBS.NS.CAN Email ar772@chebucto.ns.ca