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Author Topic: Correct Location For Lightning Arrestor  (Read 11560 times)
10CVALLEYVOL
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« on: July 11, 2006, 11:03:35 AM »

When setting up my new and first shack I elected to mount an I.C.E Model 303/U Coax Inpulse Suppressor/Arrestor on a grounding block which is directly mounted to a ground rod outside my shack. My antenna's feedline is routed through the arrestor which has a short lenght of coax running into the shack to my tuner. I did this to provide any protection I can to the equipment in the shack. The people at I.C.E. recommends connecting the arrestor between my transceiver and/or amplifier and the tuner rather than at the output of the tuner. They indicated that their product wouldn't allow an SWR better than 5:1 if placed on the output of the tuner and that is why they recommend the placement before the tuner. I asked why would I choose to protect everthing else but my tuner and the guy said to try it in both configurations and see if it makes a difference. Can anyone with experience in this area provide some insight on what they have found to be the correct placement of an arrestor for shack protection?
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WB2WIK
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« Reply #1 on: July 11, 2006, 12:02:05 PM »

>Correct Location For Lightning Arrestor       Reply
by 10CVALLEYVOL on July 11, 2006    Mail this to a friend!
When setting up my new and first shack I elected to mount an I.C.E Model 303/U Coax Inpulse Suppressor/Arrestor on a grounding block which is directly mounted to a ground rod outside my shack. My antenna's feedline is routed through the arrestor which has a short lenght of coax running into the shack to my tuner. I did this to provide any protection I can to the equipment in the shack. The people at I.C.E. recommends connecting the arrestor between my transceiver and/or amplifier and the tuner rather than at the output of the tuner. They indicated that their product wouldn't allow an SWR better than 5:1<

::I think you have this wrong.  What they should have said is their product won't allow an SWR *worse* than 5:1.  This is because under some high SWR (mismatch) conditions, the voltage across your feedline can become so high that you'll cause the arrestor to discharge -- it can't tell if high voltage is from lightning or from R.F., it's all the same to the arrestor.


>if placed on the output of the tuner and that is why they recommend the placement before the tuner. I asked why would I choose to protect everthing else but my tuner and the guy said to try it in both configurations and see if it makes a difference. Can anyone with experience in this area provide some insight on what they have found to be the correct placement of an arrestor for shack protection?<

::The best place for the arrestor is always OUTDOORS, and as close to earth as you can get it.  Zero impedance from the arrestor to a very solid earth ground is ideal, and the only way to achieve that is with the arrestor outdoors, and low.  To put an arrestor in between an amplifier and antenna tuner, unless your tuner's located outdoors, is nutty.

WB2WIK/6
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10CVALLEYVOL
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« Reply #2 on: July 11, 2006, 05:57:30 PM »

Steve, thanks for your clarification on the point about the SWR issue. That makes more since now that you mention it. If not, a high SWR would indeed result in an open line from the antenna. I will give them a call tomorrow to see if I misunderstood the person I spoke to, which is probably true, or have him explain the other better to me. On the issue about where they recommend the placement of the arrestor, I am glad someone else besides me thinks it should be installed outside before the line enters the shack. Shouldn't a quality transmatch be able to match the transceiver output to what the arrestor and beyond presents to it? By the way, I sure appreciate all of the advice you have been providing to me in these forums. Checkout my on going problem with RFI in the Elmer's Forum. I still have the noise I have reported in that thread. Pretty sure it is something in the neighborhood causing it. I am trying to find the most economical device/s that I need to locate the external source. It may be a good investment that would come in handy often with alot of sources for RFI when living inside city limits.

Thanks again,

Ed
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KB9CRY
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« Reply #3 on: July 12, 2006, 08:45:11 AM »

On the issue about where they recommend the placement of the arrestor, I am glad someone else besides me thinks it should be installed outside before the line enters the shack. Shouldn't a quality transmatch be able to match the transceiver output to what the arrestor and beyond presents to it?

Ed, I get the sense that you're not understanding what Steve said.  Yes the arrestor NEEDS to be outdoors, just like you've described.  Now you've got your rig and tuner inside the shack, the coax goes outside to the arrestor and then out to the antenna.  The arrestor on it's own will give you a 1:1 match, no problem here.  But if your antenna presents more than 5:1 SWR then as Steve described, there may be high voltage on the coax due to this mismatch and the arrestor may fire and direct that voltage to ground.  Now your tuner will be doing it's job in that it is faking a SWR of 1:1 for the rig.  That's what tuners do, they do not change the SWR out at the antenna, they just fake it so that the rig sees a lower SWR.  Now the problem the ICE is mentioning is that if their arrestor fires to ground when your transmitting, then you'll in effect be shorting your transmitted signal to ground, which is a no no and could ruin your gear.

My suggestion is determin what SWRs you have on your antenna and ensure that none of them are higher than 5:1.  If so, then you'll need to not operate on those bands with that antenna, modify the antenna, or change the antenna.  The arrestor is a good thing and should be in place.  Hope this helps.  Phil  KB9CRY
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10CVALLEYVOL
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« Reply #4 on: July 12, 2006, 10:57:28 AM »

Thanks Phil. I understand both what you and Steve are saying. Perhaps my reply didn't indicate that but i understand the concept. That is a good suggestion to make a point to insure my SWR is 5:1 or better after tuning  before I apply any power through the arrestor. Thanks for everyones responses.

73s

Ed (soon to be liscensed)
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WB2WIK
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« Reply #5 on: July 12, 2006, 11:27:21 AM »

Ed, a tuner doesn't really "fake" anything.  It creates a real match where one didn't exist before.

But the other post is correct, that doesn't change the SWR on the coax, which is whatever it is whether you use a tuner or not.  It changes the SWR at the TRANSMITTER port of the tuner, so the transmitter actually does see a nice, low SWR.  But the SWR at the ANTENNA port of the tuner doesn't change.

So, it's true that if the lightning arrestor would discharge due to high R.F. voltage, it doesn't matter much where you put the arrestor in the feedline if the arrestor is outdoors and the tuner isn't.

Best situation when using coax cable-fed antennas and lightning arrestors is to tune your antennas themselves (by design and adjustment, not using a "tuner" in the shack!) so they never present such a mismatch as 5:1.

The only band where this is difficult to do because the frequency's so low and the band's so "wide" is 160 meters.  An absolutel perfect dipole cut for the center of the 160m band is likely to be >5:1 SWR at the edges of the band, and there's not much you can do about that other than parallel more dipoles with it, with those dipoles cut longer and shorter to make antennas that resonate in different parts of the band.  That does work, but not many people have the patience or space...

On the "higher bands," especially 40m and above, there is zero problem making and using antennas that are well below 5:1 SWR at any point in any band.

WB2WIK/6
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10CVALLEYVOL
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« Reply #6 on: July 12, 2006, 02:23:32 PM »

OK,

Correct me if this is not what ya'll are trying to explain to me. I am trying.........

The Transmatch ie. Tuner's sole purpose is to take the impedence looking into the feedline connector that would mate with the transceiver's RF Output and match it as close as possible to the output impedence of the transceiver (resulting in an acceptable SWR at the transceiver's output. In other words, if the transmatch makes the transceiver sense a SWR of 2:1 at its output, the antenna and feedline impedence on the antenna side of the arrestor could be actually be high enough (> 5:1)  to cause the arrestor to discharge and provide a short to ground. You suggest eliminating any chance of this scenario by making sure that the antenna side of the arrestor has an input of < 5:1 SWR for the frequencies I plan to use the antenna.

Is this correct?

Ed

 
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KB9CRY
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« Reply #7 on: July 13, 2006, 05:54:43 AM »

Yes you've got it.  That's why ICE did mention that you put the arrestor between your rig and the tuner rather than on the antenna side of the tuner.  But to do that the tuner would either have to be outside with the arrestor or you'd run the coax into the house to the tuner then out to the arrestor then back into the hosue.  The big problem with that is if your system took a strike, you then would have lightning inside your house and really bad things would happen.  Best bet would be to check your antenna's actual SWRs across all of the frequencies and see what you get.  Also there may not be a problem if a SWR is higher than 5:1, especially if you're running power into it.

What kind of antenna and for what bands is it to be used on?

Phil
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10CVALLEYVOL
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« Reply #8 on: July 13, 2006, 06:52:43 AM »

Thanks for the reply Phil.

For my first antenna I wanted to go with a multiband wire antenna to experience as much as I could from the get go. I purchased my antenna from Radioworks. It is a Carolina Windom 80 Short, designed for 10-80 meters and designed for any one of three configurations depending on what bands I would primarily be using. It is rated at 1.5 Kw for CW and SSB use. I have read many positive reviews on this antenna so I decided to purchase from them rather than constructing one myself for my first antenna. I plan to build some antennas once I get my feet wet and aquire more experience in this area. I am fortunate to live on a piece of property with tall trees located in my back yard that will allow me to run some wire antennas in almost any configuration up to about 60 feet with no obstructions. This one is about 45 feet high running North to South. Based on the recommendations and advice I am getting from you and Steve, I am going to contact Jim at radioworks and ask him what a typical SWR is at each band from 10 thru 80, if they have that data. They should. The antenna is advertised as not having an SWR as low as 2:1 and an antenna tuner is required. When I purchased the antenna I hadn't looked into adding an arrestor, therefore I didn't know about the 5:1 SWR limitation. In any case I plan to purchase an antenna analyzer of some sort that will allow me to read SWR among other things to ensure any antenna I put up meets the specs for how I plan to use it. I will be sure to check it out before I apply any appreciable poer to it.

Thanks again,

Ed
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KB9CRY
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« Reply #9 on: July 13, 2006, 10:38:09 AM »

I'd bet that you'll be fine Ed.  The folks at both ICE and Radioworks, in my experience, are very helpful and both will give you any guidance you need.

Thinking of the high SWR concern, I've always used ICE arrestors in my systems and I can't tell you how many times I've transmitted 80M into my R5 or 10M into my HF2V, and sometimes with the amp on!  I now that I had really high SWRs on the line during those times and nothing got broke!

But do record the data and then start making contacts.   Phil  KB9CRY
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WB2WIK
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« Reply #10 on: July 13, 2006, 10:46:30 AM »

Actually, even if the lightning arrestor discharges, that shouldn't "break" anything.  What you'd normally see is a spike in the SWR, which is probably already high anyway.  Whether any of your station equipment cares or not is a variable.  

Most of us with any experience in ham radio, antennas, patch cables, antenna switches, amplifiers and so forth have transmitted into absolutely nothing a time or two (meaning, "no load," and theoretical SWR of infinity) without necessarily causing anything to break.

WB2WIK/6
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K9KJM
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« Reply #11 on: July 18, 2006, 02:32:46 PM »

Lightning arrestors at commercial repeater sites, Cellphone systems, etc etc. are all mounted INDOORS, Right where the coax enters the building, On the SINGLE POINT ground buss. (This buss is attached to the outdoor ground system by two 6 inch wide copper straps)  Lacking such a wide copper strap system, Outdoors right where the coax enters would be a good place, However then you have the problem of sealing the coax connectors.........
I have all of my arrestors mounted indoors on flat copper sheet, Which is grounded to the outdoor ground system with the copper strap. And I take direct lightning strikes most every large storm, With NO damage to any equipment.
In addition to the arrestors, Be SURE to BOND ALL grounds together! (Power, Phone, CATV, Etc)

(BTW I.C.E. arrestors ARE a top quality product!)

For good information on lightning protection see:
http://members.cox.net/pc-usa/station/ground0.htm
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10CVALLEYVOL
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« Reply #12 on: July 27, 2006, 07:20:54 AM »

Thanks to all for their inputs and Ken, thanks to the link to that great article on grounding. I have bookmarked it for future reference. There are a lot of informative things discussed in it. Perhaps a required reading for those needing to understand this subject.

73s to all!

Ed
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