[-] [ICOM] ICOM_746PRO_ALC_PROBLEM

[Paul Playford]

As a test ground the keying lead to the amplifier (puts the amplifier in the 
transmit mode independent of the PRO) before you key the PRO.  If the 
problem goes away you have a relay timing problem in the AL811.

If you are talking about the ALC going to 100% when you first key the PRO, 
it is probably because the relay(s) in the amplifier are not fast enough, 
and you are transmitting rf while the antenna relay(s) in the amplifier are 
still switching.  Drives ALC crazy.  The fix is to speed up the relays in 
the amplifier or key it before the PRO.

If you are talking about the amplifier dropping out during a transmission 
and the ALC going to 100%, you probably have rf from the amplifier getting 
back into the keying circuit between the PRO and the amplifier, which turns 
the amplifier back to receive and again the PRO is transmitting while the 
relays are switching.  If this is the case run the key line several times 
through a toroid core.

de Paul, W8AEF

ZF2JL/ZF2TA  FO8DX/FO8PLA  8Q7AA  XZ0A  VU7RG

----- Original Message ----- 
From: "George" <goofyham at highstream.net>
To: "Icom Mailman" <icom at mailman.qth.net>
Sent: Thursday, April 12, 2007 23:25
Subject: [-] [ICOM] ICOM_746PRO_ALC_PROBLEM


A friend asked me to help him try to find out why his 746PRO ALC cuts off 
his SSB transmission for the first second or two while the ALC drops down 
from 100%???
This only happens when we have it running into his Ameritron AL811 amp???
This does not happen when we hook up his backup 746-non pro rig???
The ALC on the pro seems to have a very slow decay time as compared to the 
non pro 746. Why does the pro ALC jump to 100% intermittently when used with 
the amp. It's very annoying to say the least and rendered it useless.
Has anyone else experienced this?
thanks.
George  W2YJ
----