[ICOM] Pro II vs. Pro III RX-ANT input circuit (was "Smoked ProII")

[W. David Paperman]

This may be a solution to the problem for some:

R.F. Communications (Harris) manufactured a device used primarily in 
their full duplex ARQ RTTY shipboard installations where reducing R.F. 
level to the receivers by antenna separation was not an option. The 
device  essentially consists of two Schottky diodes rated at one kilowatt.

The device resembles in style and size a single section bathtub style 
capacitor. It has two BNC female connectors mounted. It can be mounted 
externally and should be installed in the receiver path post T/R relay 
(or pin diodes).

The R.F. device number was RF-522.

They were a bit pricey but well below the cost of repairs resulting from 
excessive RF energy causing damage to receivers. I do not know if they 
are still being manufactured, but I have come across them from time to 
time and have several spares.

I have been using these for quite some time and never have had a device 
fail or a resulting receiver failure in any of my ICOM transceivers.

Dave, W5WP

Augie (Gus) Hansen wrote:
> On 2/6/06 8:08 PM, "Larry Benko" <w0qe at bnk.com> wrote:
> 
> 
>>While the Pro3 protection circuitry did the job in a single transmitter
>>environment it unfortunately won't help if another radio in your shack
>>is the transmitting and going to damage the Pro3.  Even an external
>>relay won't help in the case of a second transmitter.  In that case you
>>need some external circuit that is not based on the Pro3 transmitting
>>for protection.  Heck in the case of a second transmitter being the
>>problem both the standard antenna and the RX antenna inputs are
>>susceptable.  Of course this is why contesters use single band filters
>>external to radios and 1/2 and 1/4 wave coax stubs.  What I wish Icom
>>would do is to publish a maximum spec that will not cause damage such as
>>+30 or +35dBm.
> 
> 
> Hey Larry,
> 
> Great to hear from you.
> 
> Of course, my comments relate to my small city lot QTH. However, having
> worked in a few multi-multi contest situations, I fully appreciate your
> concerns. I haven't dealt with an SO2R setup yet, but expect to have to slay
> some dragons when I do.
> 
> Anyone dealing with a multi-transmitter configuration would do well to read
> W2VJN's book, "Managing Interstation Interference", which is available from
> George's company, INRAD (www.qth.com/inrad).
> 
> Cheers,
> Gus, KB0YH
> 
> ----
> Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
> 
> .
>