[Icom] FW: Keying Amplifiers with an Icom Exciter

[Adam Farson]

Here is some general information on this much-batted-about topic:

To determine whether or not an interface (buffer) is required in the keying
line between an Icom HF transceiver and an amplifier, one should measure the
keying voltage and current of the amplifier's keying line with a digital
multimeter, as follows:

1. Measure the open-circuit voltage between the amplifier keying line and
chassis.

2. Measure the closed-circuit current between the amplifier keying line and
chassis.

If the open-circuit voltage exceeds 16V DC, and/or if the current exceeds
0.2A (the current Icom spec is 0.5A, but a safety factor is  recommended),
an interface is required. A solid-state interface will minimise the latency
associated with the switching time of an open-frame relay. In some cases, a
reed-relay interface will be sufficiently fast to keep the latency to a
minimum.

The Icom FAQ site carries an excellent article on this topic:
http://www.qsl.net/icom/auxrelay.html  Included on this page are links to
several keying interfaces. Also refer to
http://www.qsl.net/icom/keyspecs.html for amplifier keying-line specs.

Many current tube amplifiers, and all solid-state amplifiers, have a
low-level (typically TTL-level) keying line which requires no interface.
Some of the Alpha amplifiers have a 28V/7mA keying voltage/current rating;
this is well within the 50 VA rating of the OMR-109F relay.
Refer to: http://www.qsl.net/icom/download/omr.pdf

Caution: Heathkit amplifiers, and the Kenwood TL-922 series, have
open-circuit keying-line voltages in
excess of 100V.

Best 73,
Adam, VA7OJ/AB4OJ
North Vancouver, BC, Canada
http://www.qsl.net/ab4oj/
Icom FAQ site:
http://www.qsl.net/icom/