[ICOM] AMP INTERFACE TO 756 PRO II (CONTINUED)

[Adam Farson]

Hi Dan,

According to the OMR-109 relay data sheet, the operate and release times are
1.0 and 0.5 mS respectively. Using a reed relay as an auxiliary relay, one
would double the time between transmitter keying and closure of the
amplifier's PTT line to approx. 2 mS. By using a solid-state keying buffer,
one could largely eliminate the additional keying delay.

The exciter probably applies RF a few mS after extending a ground on the
SEND line. One could shorten this interval by using the ACC(2) Pin 3 SEND
line to turn on a solid-state buffer, which would in turn ground the amp's
PTT line.

http://www.qsl.net/icom/auxrelay.html

In any event, the output reflectometer in the exciter will sense the brief
open RF interval and turn down the drive to protect its PA. One should not
count on this exclusively, though - hence it is best to shorten  as much as
possible the interval between transmitter keying and amplifier PTT closure.

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of Dan Coleman W8KMX
Sent: 17 June 2005 11:19
To: icom at mailman.qth.net
Subject: [ICOM] AMP INTERFACE TO 756 PRO II (CONTINUED)

I big thanks to all that answered my broadcast message.  I posted my inquiry
and then left town for a few days so sorry that I did not answer promptly.

As to interfacing the Ameritron ALS-600 to the ICOM 756 Pro II the consensus
is:
    1) Although it will "likely" be OK, it would be best to use an outboard
relay that can be driven easily by the Pro II ("cheap insurance").
    2) Although some have had good results without ever hooking up the ALC,
again it is best to use it.

One thing that was not mentioned by anyone is the time delay required to
pull in the slave or ALS-600 relay for that matter, thereby causing the Pro
II to transmit into an open load for a short time period.  I have seen some
comments in the past as to the need for a delay to make sure the Pro II is
fully connected to the AMP before your first word (using VOX) produces RF
output.  One person (in a previous conversation) said he did not use VOX for
that reason and, he made sure the PTT was depressed an instant before he
spoke etc.

Any comments on this?

73,
Dan

p.s. Yes I would like to talk with K5CWO and since you have unlimited
calling, you can call me at (864) 638-3001 (I don't have unlimited calling).

DGC 


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