| |
CE2LM > KAM 01.06.00 04:08l 106 Lines 3607 Bytes #-9074 (0) @ WW
BID : 23693_CE2LM
Read: DJ9KV OK1XHC DL9MEC DB1VQ GUEST
Subj: KAM mods
Path: DB0AAB<DB0SL<DB0RGB<OE5XBL<OE6XAR<OE6XYG<9A0BBS<9A0YKZ<9A0YRB<PP5BLU<
HA3PG<SV1AAW<CE2LM
Sent: 000531/2246Z @:CE2LM.VAL.CHL.SA #:23693 [Vi¤a] FBB7.00g25 $:23693_CE2LM
From: CE2LM@CE2LM.VAL.CHL.SA
To : KAM@WW
Subject: Kantronics KAM HF frontend modifications
From: Warren Stone <ar772@chebucto.ns.ca>
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
***
(Copied from QRZ! Vol.14, dir /MODS4 on CE2LM BBS)
Read previous mail | Read next mail
| |
