[ICOM] Pro3 and Beverage Antennas

[Joe Oski]

As ESD raises it's ugly head again, I must repeat an earlier suggestion.
 
Here in the Desert Southwest, dust storms in addition to traditional sources
of static are common. 
 
To minimize the ESD into the transceiver use a DC grounded antenna.
 
If using a NON-DC grounded antenna, such as a dipole or some verticals, 
install a Radio Freq Choke (RFC) or NON-Inductive resistor, 10K to 100 Kohm across the antenna line.
 
A typical insertion point is in the External ATU on the transceiver SO-239 connector. 
I have used a  $8 RFC from Ameritron, normally used across the output 
of their KW tube ampifilers.
 
Some Balun and Unun designs provide the DC ground.
If you are not sure about your antenna system, using a DC ohmmeter, in the shack, disconnect the antenna cable and measure across the center pin to shield. 
 
The concept of dissipating the charge before it builds up to dangerous levels is the key.
 
73
Joe Ostrowski, KI5FJ
NNNN

--- On Tue, 11/3/09, Phil Krichbaum <vailphil at sopris.net> wrote:


From: Phil Krichbaum <vailphil at sopris.net>
Subject: Re: [ICOM] Pro3 and Beverage Antennas
To: "ICOM Reflector" <icom at mailman.qth.net>
Date: Tuesday, November 3, 2009, 11:09 PM


    I have used the KD9SV DXpedition II with my Pro II and Pro III as I 
understood the RX antenna is not disconnected from the RX during TX. 
(FT1000MP and others have the same issue) The PROIII seems over 
sensitive to ESD and it does not take out the RX but you loose TX as 
some FET(s) blows in the tuner along with some diodes rated at 300V. 
I've had this happen 5 times at about $250 per incident! I've not had it 
happen while using the KD9SV box with the beverages, it was always while 
RX on the TX antenna so be careful of ESDs coming in when using the TX 
antenna for RX.
Probably not good to use a polyphaser that needs to jump a gap to 
discharge ESD buildup.
    Phil N0KE
Adam Farson wrote:
> Hi Bob,
>
> The RX-ANT circuit in the Pro3 will isolate the RX-ANT jack if the incident
> signal power exceeds +10 dBm.
>
> http://www.ab4oj.com/icom/ic756pro3/rxant.html 
>
> Even so, I recommend a grounding switchbox such as the KD9SV Front-End
> Saver, which grounds the receive antenna feedline whilst transmitting.
>
> The T/R relay (RL3, CTRL-A Unit) doe not ground the receive RF signal path
> during transmit.
>
> 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 Bob Beatty
> Sent: 3-Nov-09 06:27
> To: icom at mailman.qth.net
> Subject: [ICOM] Pro3 and Beverage Antennas
>
> It is finally cooling off here in Florida and the noise level is dropping.
> Time to unroll the beverage and string it up for the lowband season.
>
> Having recently acquired a new Pro3, and not fully understanding the
> schematic that came with it, does the relay contact shown in line with the
> RX Antenna connection in the RF-B Unit ground the beverage when transmitting
> or should I use my external beverage grounder?  The RX Ant function does not
> seem to be addressed in the manual.  The nomenclature and reference
> designators in the Icom schematic leave something (actually, a
> lot) to be desired.
>
> Thanks and 73,
>
> Bob W4VQ
>
> ----
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