[ICOM] 756 Pro blown Ant 1 input

[Joe Oski]

Folks,
I have two suggestions:
 
Multiple Field Day transmitters with antennas within 100 Ft of each other will couple significant RF Power into each other. I mean Watts not microvolts !
 Limiting ONLY ONE Tx to a band is not enough protection.
A manual ATU will attenuate out of band signals but the max possible physical separation of the antennas is a must.
 
In a metal minibox with two SO239 connectors:
 Install a Radio Freq Choke (RFC) from ground to center-pin (across the coax).
 This will prevent any static discharge from building up. The DC path resistance is typically 24 Ohms, RF impedance very high. The RFC will handle a Kilowatt at 50 Ohms.
I use Ameritron HP amplifier output chokes. Cost less than $10.
 
73
Joe Ostrowski, KI5FJ

--- On Mon, 6/28/10, Adam Farson <farson at shaw.ca> wrote:


From: Adam Farson <farson at shaw.ca>
Subject: Re: [ICOM] 756 Pro blown Ant 1 input
To: "'ICOM Reflector'" <icom at mailman.qth.net>
Date: Monday, June 28, 2010, 5:52 PM


Hi Larry,

In the IC-756Pro, fuse bulb DS111 (RF Unit) protects the RX-ANT input only.
It sounds as if the NC contacts of the ANT 1/2 selection relay (RL3, CTRL
Unit) is blown. The 756Pro must have taken a huge belt of RF to cause such
damage, as RL3 is 2 X Form C with both contact sets in parallel.

This is why I am delighted to let our club use their rigs at FD! We do FD as
Class 2F at our EOC.

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 Larry Young
Sent: 28-Jun-10 08:43
To: ICOM Reflector
Subject: Re: [ICOM] 756 Pro blown Ant 1 input

If I remembr correctly, there is a protection device in the ant input
circuit. I believe it is either a fuse or a small series bulb.
Larry K4LXV

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