From: Cecil_A_Moore
Newsgroups: rec.radio.amateur.misc
Subject: Ramsey FX transceiver kits
Date: 8 Jun 93 22:20:07 GMT
Organization: ucsd usenet gateway
Lines:29
Message-ID: <930608142007_2
Nntp-Posting-Host: ucsd.edu
Originator:daemon
For all you Ramsey FX transceiver kit owners, here are some needed
modifications.
1. How to cure the transmit audio problem.
Ramsey engineers forgot to put load resistors on the outputs of the
LM324 so above a certain level the transmit audio has cross-over
distortion. Install a 10k ohm resistor from U4 pin 1 to ground and
another 10k ohm resistor from U4 pin 7 to ground.
They forgot to put in a transmit audio gain control for loud mouths,
like me. Replace the audio gain resistor, R58, with a 2k ohm pot which
allows gain control so loud voices do not saturate the op-amps.
2. How to cure the squelch problem.
The squelch circuit does not have enough hysteresis.
Turn R24 around so the bottom is where the top used to be. Solder the
anode of a 1N34A to the new top of R24 and solder the cathode of the
1N34A to where the bottom of R24 used to be. Solder a 10k ohm resistor
from the anode of the 1N34A to +5v (top of R11).
This allows pin 10 of U1 to swing 0 to +5v like it was designed to do,
instead of swinging 0 to 2.7v with not enough hysteresis.
73...KG7BK
Cecil_A_Moore
SOURCE: The QRZ Windows Ham Radio CDROM |
