[Antennas] Re: [Icom] Links to icom Service Bulletin 920

Sat, 20 Dec 2003 19:50:45 -0600

I use a quite old coax switch made by Waters to control which of several
radios is connected to which of several antennas (that selection made by a
similar switch by Waters). This switch ground all input terminals except the
one selected. I have one position that is unconnected so that is the
position in which the switch is left when the station is not in use.
Similarly no antenna is selected. Thus, other than when the 746PRO is
actually in use with an antenna connected, it has its antenna input grounded
to the station common and ultimately to the a-c safety ground to provide a
static ground.

My next step is to provide a static drain for all balanced lines entering
the shack via baluns and coax. Belts and suspenders!  <:}

It is a shame that Icom felt compelled to provide back-to-back diode
protection for the VHF receive line but not for the HF line.

73, George W5YR
[email protected]

----- Original Message ----- 
From: "Alan C. Zack" <[email protected]>
To: <[email protected]>
Cc: "Antennas" <[email protected]>
Sent: Saturday, December 20, 2003 12:17 PM
Subject: [Antennas] Re: [Icom] Links to icom Service Bulletin 920

> This is an interesting point.  Something you SHOULD do but may forget
> to do.  Does anyone know of any antenna switching device that
> automatically grounds the antenna when you shut off power to the ant
> switching unit?  I use a Master Power switch in my shack that controls
> power to various HF and VHF power supplies, the station monitor,
> various wall warts for TNC's, etc.  I could connect an antenna
> switching device to this Master Power switch and then when I shut down
> the ham shack the antenna would automatically go to ground.
> 73 & MC
>
> [email protected] wrote:
> >
> > I have many friends who don't ground the antenna when not in use which
is
> > very puzzling to me. In my setup, it is one turn of the antenna switch.
When
> > I know storm activity is about, I disconnect the antenna completely. Is
this
> > overkill?
> >
> > Andy K5VM
> >
> > ----- Original Message -----
> > From: "Jens Schmidt" <[email protected]>
> > To: <[email protected]>
> > Sent: Saturday, December 20, 2003 12:59 AM
> > Subject: Re: [Icom] Links to icom Service Bulletin 920
> >
> > | Hi George,
> > | and Adam, excellent work.
> > |
> > | DC-grounded antennas are also the easiest place to start protecting
> > | your receive input devices.
> > |
> > | Merry Christmas and a Happy New Year / best season wishes
> > |
> > | 73 Jens    ZL2TJT
> > |
> > | "George, W5YR" wrote:
> > |
> > | > Interesting that the VHF receive line is already protected by
> > back-to-back
> > | > diodes as per the Service Bulletin. Guess Icom felt that the HF line
was
> > not
> > | > as vulnerable to static discharge.
> > | >
> > | > I keep all my antenna inputs grounded when the station is not in
use,
> > but
> > | > when one uses the 746PRO there is a risk. Perhaps using external
static
> > | > bleed methods would be a good idea or d-c grounded antenna feeds.
> > | >
> > | > 73, George W5YR
> > | > [email protected]
> > | >
> > | > ----- Original Message -----
> > | > From: "Adam Farson" <[email protected]>
> > | > To: "Icom Reflector" <[email protected]>
> > | > Cc: "Dick Flanagan" <[email protected]>; "IC-746 Reflector"
> > | > <[email protected]>; <[email protected]>
> > | > Sent: Friday, December 19, 2003 9:56 PM
> > | > Subject: [Icom] Links to icom Service Bulletin 920
> > | >
> > | > > Hi Dick,
> > | > >
> > | > > Service Bulletin #920, describing the IC-746Pro/IC-7400
transmitter
> > | > failure
> > | > > fix, is now downloadable in PDF format on the Icom FAQ homepage,
with
> > a
> > | > > mirror on my Icom page.
> > | > >
> > | > > Here are the links:
> > | > >
> > | > > http://www.qsl.net/icom/
> > | > >
> > | > > http://www.qsl.net/ab4oj/icom/icom.html
> > | > >
> > | > > Best 73,
> > | > > Adam, VA7OJ/AB4OJ
> > | > > North Vancouver, BC, Canada
> > | > > http://www.qsl.net/ab4oj/
> > | > > Icom FAQ site:
> > | > > http://www.qsl.net/icom/
> > | > >
>
> -- 
> __________________________________________________________________________
>                                      Alan Zack
>                      Amateur Radio Station K7ACZ
>                          Las Vegas, Nevada, USA
>           Quality Engineer, The Boeing Company, Retired
>   Aviation Chief Warrant Officer, U.S. Coast Guard, Retired
>         U.S. Coast Guard, Always Ready, Always There
> Every hour, Every day, Around the Clock and Around the World
>                                SEMPER PARATUS
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>
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