[TowerTalk] zapped with my dipole. OUCH!

[K8RI on TT]

On 5/14/2011 4:40 PM, K0DAN wrote:

IMO Grounding the transmission like during storms is more important than 
disconnecting it, not that the line shouldn't be disconnected. I just 
rate the grounding at a higher priority, particularly if the feedline 
into the shack can not be separated by a substantial distance from the 
point where it's disconnected.  IOW, if you disconnect it, throw it out 
the window.

An antenna and feed line left floating (ungrounded) can develop a very 
high, and dangerous potential even without lightening.  The typical 
strike a mile away can induce as much as a 1000 volts per meter into 
that antenna and feed line. If it's floating, there is no way for it to 
bleed off safely.  Grounded the precipitation static can not build up 
and the induced charge is rapidly bled off.

All antennas here are at DC ground.  The tower has taken at least 17 
strikes since it was put up, yet I've had no damage to antennas or 
equipment since installing a good/elaborate ground system.

73

Roger (K8RI)


> Put a pair of lawnmower sparkplugs from each leg of ladderline to ground. If
> you can't visualize this, I'll send you some photos (they'll help bleed
> static to ground). Also, put around 3-6 megohm resistor from each leg to
> ground....it'll shunt the DC to ground but will be invisible to RF at low
> freqs. Of course, neither of these tricks will have any value if you get a
> direct lightning hit, at which point all components will likely vaporize!
>
> Disconnecting&  grounding the ladderline outside the shack, during a storm,
> is your best line of defense. If this is not easy/possible, at least ground
> the ladderline during a storm using a knifeswitch, but be aware this could
> bring very HV into the shack.
>
> 73
>
> Dan
> K0DAN
>
> ----- Original Message -----
> From: "K2VI"<k2vi at cox.net>
> To:<towertalk at contesting.com>
> Sent: Saturday, May 14, 2011 3:29 PM
> Subject: [TowerTalk] zapped with my dipole. OUCH!
>
>
>> It seems every time there's distant lightning and i go to disconnect the
>> dipole i get this nasty discharge when i touch the pl-259. Im concerned it
>> will eventually damage my tuner and or radio. The antenna is not dc
>> grounded like my beam or vertical are. It is a ladder line fed antenna
>> terminating into a 4:1 balun outside the shack and a 3' run of rg8 coax to
>> the tuner. How can i bleed this static off? I heard from a ham friend the
>> jump a 2.5 MH RF choke between the two terminals of the 4:1 balun where
>> the ladder line connects.Any advice would be greatly apreciated.73
>> tony k2vi
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