[Premium-Rx] Lightning hitting your Premium RX

Fri Apr 8 11:46:40 EDT 2005

Considerinig the fact that Lightning is a huge energy pulse which is basically a combination of short duration signals from dc to daylight, most methods of supression are simply attempts to do best we can to suppress it. As Peter mentioned to suppress this energy clever design techniques are needed.

i personally think that to protect receivers, we should start from
a well designed antenna system, then consider the feedline to the
receivers, then protection at the front end. i think as we get closer to the front end, we are at higher risk of getting damage
to the receivers. therefore protection should start at the antenna.

It turns out balanced antennas are relatively easier to use protection devices on as the design is more predictable than unbalanced ones. Unbalanced antennas will create differential mode 
currents which basically end up in the shack.
However with balanced antennas with matching done at the 
antenna and isolated with current baluns, and with lightning protection devices such as Gas Tube Arresters,... etc, the incoming induced energy is gradually carried towards the feedline with much less differential currents.  

Antennas where impedance matching is not done well, and where impedance is high, higher voltages will be induced and currents will be carried to the shack.

A well designed balanced antenna system, with protection circuits and a feedline with current baluns is a good start. then comes the protection circuits in the shack including grounded switches and the circuits in the receivers.

i think we need to be careful with the grounded switches as they may not be effective enough to get rid of the energy of surge and leak it to the RX antenna connections.  absorptive rather than reflective solutions may be better.

regards, ahmet

> 
> 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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> >
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> >
> >
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