[ICOM] IC-751A Key Clicks (Again)

[Clif Holland]

Think about it...

The power control adjusts the max power out. Once the predetermined level 
set by the power control is reached the ALC kicks in to hold that level. 
Ergo when power is set to 10 watts the ALC kicks in to hold it at that 
level. If set at 50 watts, same thing. If power all the way up, until it 
reaches that level the ALC doesn't work.

This is not an older radio where the carrier determined the power out, it 
has a true power control knob.

Clif Holland KA5IPF
www.avvid.com


----- Original Message ----- 
From: "Ed Swynar" <gswynar at durham.net>
To: "ICOM Reflector" <icom at mailman.qth.net>
Sent: Monday, December 19, 2005 4:09 PM
Subject: [ICOM] IC-751A Key Clicks (Again)


Good Evening All,

I wonder if anyone reading this --- and who owns an Icom 751A --- might 
indulge me, please, with a small favour...?

Specifically, with the rig set-up to transmit in semi-break-in CW, turn the 
RF drive fully counterclockwise...now, with the meter selected to the ALC 
position,  hold the key down to send out a carrier. What does your meter 
show for ALC deflection at this point?

Next, gradually turn the RF drive control to maximum (clockwise adjustment) 
while holding the key down, and observe the ALC deflection in the meter...

If your rig is like mine, you will have seen a good half-scale deflection, 
or more, in ALC with low power output, & then even more ALC at maximum 
output.

This confuses me: I always believed that ALC was not activated until such 
time as an overdrive condition was approached...in the low power setting of 
the RF drive control, why would there have even been an ALC indication? On 
my Yaesu FT-980, there is NO ALC meter movement whatsoever until the 
100-watts of specified output is approached, or exceeded --- the 751A starts 
out high in ALC from the get-go!

In fact, the Yaesu manual cautions the operator that generation of key 
clicks may well result at the point of ALC meter deflection...

What got me thinking of this was reference in an 80's issue of QST 
magazine --- a fellow therein stated that improperly "...thresholded" ALC 
can, and does, contribute to the generation of key clicks in modern 
transceivers...

Many thanks for any & all assistance & observations in this regard with your 
own 751A...

~73~ Eddy VE3CUI - VE3XZ
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