[Icom] PRO II relay (hot-switching)

[Ed Parish K1EP]

At 04:52 PM 5/7/03 -0700, Adam Farson wrote:

>Hi Greg,
>
>Many thanks for the kind comments about the Icom FAQ site. By raising the
>hot-switching issue, you have brought up a very valid point. The best way to
>minimise the risk of hot-switching on keying is to use a high-speed relay,
>such as a reed, or a solid-state buffer circuit, with current/voltage
>ratings sufficiently high to handle the amplifier's keying line.

At 19:30 5/6/03 -0700, Greg Ordy wrote:

>    Any delay present in an external interface directly reduces the time
>interval between the radio relay closure and the start of the RF (at the amp
>input).
>At the extreme, the device added to protect the radio does so, at the
>expense of
>damaging the amplifier.

I haven't read the entire thread, so I don't know for sure if this point was made already.  There are two places to drive your external relay.  One is the RCA connector and the other is the ACC jack (actually both jacks have it I think, but they are the same signal).  The RCA output is the output of the internal relay, while the ACC jack signal is the voltage that drives that relay.  You will get the  delay of the internal relay if you just use the RCA output.  It is safer to use it, as it is just relay contacts.  But if you want a signal faster, then you can use the ACC send information and build a transistor interface.  You then can get clever and make use of the fact that that signal is bidirectional and therefore you can make a sequencing box...