[Elecraft] K3 Power Reading/SWR/ALC Problem

[Don Wilhelm]

Knut and all,

Yes, BUT...
Lightning is a static charge which *will* produce transients in the 
antenna system.  As will wind static, rain static and snow static. 
Large voltages can build up on the antenna and feedline, and will remain 
until dissipated.  Sort of like a charged capacitor that holds that 
charge until dissipated.  Some of those events can produce very large 
voltages.

So yes, I believe it is a matter of semantics.  Charges of any kind on 
the antenna feedline can cause damage.  The K3 has more protection than 
the K2/KPA100, but that does not make it immune to all events.

Have you ever touched across the terminals of a feedline after a nearby 
lightning event and felt a 'tickle' or even worse?  I have, and it is 
not nice.  A bleeder resistor of 2500 ohms to 50k across the feedline 
will bleed off a static charge in short order.

Even with a lightning suppression device in the feedline, there is still 
a threshold voltage that it responds to.  At voltages less than that 
threshold, the protection device will not be of any assistance in 
bleeding off the charge.

73,
Don W3FPR

On 1/21/2018 4:42 PM, ab2tc wrote:
> Hi Don and all,
> 
> I really don't understand why static build up on the antenna should be a
> problem with the K3. Due to the (good) design of the SWR bridge (a two
> transformer design with a voltage transformer right across the output) the
> antenna port presents a dead short circuit at DC both in receive and
> transmit. I just verified this with an ohm-meter (in receive only - no need
> to check in transmit since the SWR bridge is surely present then - don't
> want to kill my DMM).
> 
> Maybe we are talking semantics here but it appears to me that the cause of
> diode damage in the SWR bridge circuit is more likely caused by transients
> induced into the antenna system by nearby lightning strikes than static
> buildup.
>