[Elecraft] K3 Antenna static bleed

[Vic K2VCO]

My coax feeds all go through an entry panel on which are mounted ICE lightning protection 
devices. These provide a DC ground on the antenna side and no DC path to the rig. My 
open-wire feedline has a pair of 500K resistors to ground. Finally, I have a relay box 
which selects the antenna per band and is driven by a KRC2. Those relays default to ground 
the rig input when the power is off.


On 2/24/2011 10:23 PM, Ron D'Eau Claire wrote:
> When my antenna is disconnected (as it always is when I'm not operating) it
> is connected to an earth ground.
>
> Ron AC7AC
>
> -----Original Message-----
>    Fred,
>
> While the K3 has static protective devices that have been mentioned by
> others, I prefer to err on the side of caution.  The UHF connector has
> one problem for antenna/feedline static charge - if the antenna has
> built up a static charge, when the feedline is connected to an SO-239
> jack, the center conductor makes contact first, followed by the shield.
> So the best solution is a DC path provided within the antenna/feedline
> system itself rather than relying on any protection in the K3.
>
> Type N and BNC connectors do it differently, the shield is connected
> prior to the center conductor, thus allowing any charge on the feedline
> to be safely discharged through the radio's protective devices.  With
> UHF connectors, the radio's protective devices may not work because only
> the center conductor of the feedline is connected, and there is no
> return path to the coax shield until the shell is properly tightened.
>
> With UHF connectors, any "antenna disconnection" would best be done
> using an antenna switch rather than a physical disconnection.  The
> disconnect will cause no harm, but the re-connection can do damage
> without warning.  The antenna switch itself is a good place to provide
> that DC return path - either an RF Choke (100 uHy) or a high value
> resistor (500k to 1 megohm) between the center conductor and ground of
> the common connection to the transceiver.  When the transceiver is not
> in use, switching to a dummy load is a prudent thing to do, so if you
> have 5 antennas to switch, a 6 position switch is best with a dummy load
> connected to the 6th position.
>
> Note that this is applicable to any transceiver - I know the question
> was asked about the K3 specifically.
>
> 73,
> Don W3FPR
>
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-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/