Fwd: [Premium-Rx] Lightning hitting your Premium RX

[Peter Gottlieb]

Where to start.

A spark gap will protect the equipment even when it is on but the TR relay 
scheme only protects when it is off (unless you count the contact gap).

An induced strike, if close enough, does as advertised and does indeed induce 
significant voltages.  Last year I had a nearby strike and while none of my 
radio gear was affected I did lose about half the ports on my home 100 Base T 
network switch and also a few computer network cards.  And those things are 
pretty well isolated.

As mentioned, lightning has a very fast risetime and thus high energy in high 
frequencies.  What this means is that any protection circuits must be designed 
with good RF design practices.  They must also be installed properly.  One 
anecdote from my power protection days:  we found that customers who had a pile 
of power cords all jumbled up behind the computer were not always protected by 
our surge suppresors which we absolutely knew were effective.  It turned out 
that the lightning pulses were being induced between the line side of the surge 
strip and the load side through the power cords!

I have TR relays on my rigs but they are set up for protection from excess RF. 
For example, when my RF-350K transmits a Dowkey relay pulls in and disconnects 
the RF-590A from its separate HF antenna and shorts its input.  Crude, but 
effective, but does nothing for lightning protection.

Peter


Eugene Hertz wrote:
> Howdie. thought I'd run something by you. I had an idea for lightning 
> protection, not direct hit, but induced voltage. I have been seeing 
> these gizmos that have a gap which the spark will jump if the kv goes 
> too high and then short to ground. My idea was to use a TR relay mounted 
> outside in a weather proof enclosure. In the energized state, the 
> antenna connects to the shack, in the unenergized state the antenna 
> connects directly to ground.  I thought I might run the relay from some 
> power source either in my Tx or Rx. Whch would require that, say, the Rx 
> would need to be on otherwise the antenna is grounded. 
> 
> Would this accomplish the same thing as the gaps? Or is there something 
> superior to the gaps? Also, I know the gap devices need replacing every 
> so often, would the TR relay get zapped with induced voltage on it?
> 
> -----Original Message-----
> From: Gary Mitchelson - N3JPU [mailto:n3jpu at speakeasy.net]
> Sent: Tuesday, April 5, 2005 03:58 PM
> To: ''Cecil Acuff'', ''Premium-Rx (E-mail)''
> Subject: RE: [Premium-Rx] Lightning hitting your Premium RX
> 
> The hybrid AC protectors provide the lighting protection on the AC line
> side.
> 
> The crude drawing shows the ground lines going out straight, the do really
> curve around but do not go all the way around, a long way to do that.
> Hopefully the runs I have will launch enough of the strike into the ground.
> Won't know until it happens though. Didn't have access to a Megger so do 
> not
> know what the final impedence. I have good soil for conductivity so I'm
> hoping it's down below 5 ohms.
> 
> Their HF protector goes down to 100KHz.
> 
> Documents: http://www.arraysolutions.com/Products/ice/10.html
> 
> Products: http://www.arraysolutions.com/Products/ice/3.html
> 
> Polyphaser's article on Ham Shack protection
> http://www.polyphaser.com/ppc_TD1016.aspx
> 
> Gary Mitchelson
> N3JPU Montgomery Co. MD FM19
> http://www.mitchelson.org/
> 
> 
> 
> -----Original Message-----
> From: Cecil Acuff [mailto:chacuff at cableone.net]
> Sent: Tuesday, April 05, 2005 16:39
> To: Gary Mitchelson - N3JPU; 'Premium-Rx (E-mail)'
> Subject: Re: [Premium-Rx] Lightning hitting your Premium RX
> 
> 
> Gary,
> 
> I looked over your pictures. Looks great. Typical with what I see
> at most of the commercial tower sites I frequent. The question remains as
> to whether you have your house electrical ground tied to your tower
> grounding system. It appears you do by virtue of the AC power protectors
> plugging into AC outlets in your shack. Curious why the ground runs with
> the rods went out at angles away from the shack. Common wisdom in the
> commercial tower business is to create a ring around the building being
> protected. May have been inconvenient to circle the house...
> 
> What is the lower end frequency of the Coax protectors? I typically use
> Polyphasor systems at work but that is for VHF/UHF stuff. I'm not sure
> their stuff goes down to LF or not. Seems protecting to 500Khz or even to
> 1.8 Mhz is a little more difficult.
> 
> You've done what most folks are unwilling to do...that is to spend as much
> on your protection systems as a new high end transceiver costs. Should be
> well protected!
> 
> What did your final ground point impedance end up being?
> 
> 
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