Grounding Ladder Line

[chrissim]

Hello:

I use LMR400 and RG213 on my hex and delta loop antennas, which are grounded correctly and connected to Polyphasers.

My current configuration only allows me to run my delta loop, which I use for 40 and 80 meters, east and west. If I'm not mistaken, this gives me a north and south preference. I'd like to orient an N4GG array north and south, but use ladder line so that I can use my MFJ-962C to tune it to other bands if I so desire. The transmatch has a built in 4:1 balun, which I could use to directly connect the ladder line from antenna.

My concern isn't so much lightning strikes (I disconnect everything in the event of a storm), but rather static buildup. As mentioned, I'm not concerned about the other antennas, but introducing ladder line directly to the station is worrisome.

I spoke to DX Engineering about this, and they suggested one of their baluns from ground to station. Unfortunately, that's for short runs. My station is on the second story of our house, about 25 feet above ground. We both came to the conclusion that the balun approach, which could be grounded properly and transition ladder line to coax, is out of the question due to the long run.

I imagine I should be concerned about running ladder line directly to the transmatch, although many seem to do it. What then should I do to lessen the potential for static issues due to wind, rain, snow, etc? I have considered putting a resistor somewhere inline, but not sure where exactly to implement it.

I should likely add that I do not have my station grounded in the conventional manner due to my station's height, but everything is connected to the same bus bar in an attempt to keep it all at the same potential.

Thanks in advance.

 

[zz0468]

Run the ladder line through a DPDT ceramic knife switch and ground the switch on one side, and run the other side to the tuner. When not on use, throw the switch to send the feedline to ground.

 

[WA0CBW]

Consider that a lightning strike usually travels large distances, do you think disconnecting it a few feet from your equipment will offer any protection? It will find a path to ground. Most damage to equipment is from "flash over" as the energy jumps to find a ground, in your case the building safety ground through your equipment. How do you ground your Polyphasers? There are lightning protectors available for parallel type feed lines. Of course there is always the old fashioned double pole, double throw knife switch with one throw grounded. Being on the second floor I would suggest running a large ground wire from your station ground buss on the second story to a suitable ground rod. Be sure this ground rod is connected to your building ground (See NEC section 800; 810; and 820).
BB

 

[chrissim]

The problem with the knife switch is that it has to be grounded. Again, I am roughly 25 feet above ground on the second story of our house. If I ground from above to below I will effectively create something that could radiate or become an unintended part of the system.

My only concern is static drain. So I won't enter into a dialogue about how best to prevent damage due to direct or nearby lightning strikes.

Thanks for the input.

 

[prcguy]

I've run dipoles fed with balanced line for years right into a balanced tuner with no static issues and I've not heard of any specific static problems with using balanced line. If you lived in the middle east with blowing wind and sand it might be a problem.
prcguy

 

[chrissim]

prcguy:

Do you have your tuner grounded? I have read that if one grounds the tuner (or transmatch if you prefer), you have in turn grounded the balanced line connected to it. However, there is so much misinformation floating around that I tend to be cautious.

Thanks.

 

[prcguy]

Sometimes yes and sometimes no. Some balanced tuners ground the signal internally at some point and others don't.

Most balanced tuners have a ferrite balun and some baluns are a transformer type with no primary to secondary connection while others have a DC path between input and output. I would say RF wise most if not all balanced tuners do not unbalance the signal even though you can measure a DC path from one or both inputs to ground.
prcguy

prcguy:

Do you have your tuner grounded? I have read that if one grounds the tuner (or transmatch if you prefer), you have in turn grounded the balanced line connected to it. However, there is so much misinformation floating around that I tend to be cautious.

Thanks.

 

[chrissim]

Think I found the best solution, one that I can make myself. Two spark plugs. I've read of this method before but was uncertain. I think I'll go for it. See image and description in link below.

Static Voltage Arrestor-Protector for Balanced Line feed lines

Anyone have any objections?

Thanks.

 

[joeuser]

Think I found the best solution, one that I can make myself. Two spark plugs. I've read of this method before but was uncertain. I think I'll go for it. See image and description in link below.

Static Voltage Arrestor-Protector for Balanced Line feed lines

Anyone have any objections?

Thanks.

Interesting concept!

 

[prcguy]

Do you currently have a static problem? If you do it would present the same problem to the radio with coax or balanced line. It would take a couple of kV to arc a spark plug and before it arcs the equipment downstream will be susceptible to the building static HV.

I think its better to use a high value bleeder resistor at the radio end if it doesn't already have one. Its common to see a 1meg ohm or a little less bleeder in a 50ohm system since its fairly transparent. Some values of chokes like 1mh can effectively place a DC short in a 50ohm system at HF.
prcguy

Think I found the best solution, one that I can make myself. Two spark plugs. I've read of this method before but was uncertain. I think I'll go for it. See image and description in link below.

Static Voltage Arrestor-Protector for Balanced Line feed lines

Anyone have any objections?

Thanks.

 

[chrissim]

Thanks for the replies. I don't have a static problem only because I have followed classic textbook schemes for preventing it. I have always read that wind, rain, snow and the like can cause voltage buildup on elements. The only exception I can think of is when I owned a Pixel loop. The rep told me that such a design was electronically closed and that there was no need for static precautions.

I don't have a static issue, but I don't want to experience one. Using ladder line is a new concept for me and I'm rather reluctant. But I do like the idea of having such a wide breadth of band options which ladder line affords (with a tuner, of course).

The antennas I use are grounded near the feed point and use quality surge suppressors. As mentioned in my initial post, it was discovered that using conventional means such as a balun to transition ladder line to coax (and thus grounding the antenna to a ground bar) is out of the question due to height restrictions. This explains my concern using ladder line. I can't ground it in the traditional sense. However, Array Solutions does make a product that will serve the purpose and will allow me to connect ladder line to their product and in turn continue the ladder line to the second story station. It's likely the safest solution.

AS-309H

Maybe the spark plug contraption isn't such a great idea.

Thanks again!

 

[JnglMassiv]

I think that reasonable precautions are prudent.
Here's a couple videos of snow static sparks.
You don't want that nailing your rig.
https://www.youtube.com/watch?v=_7HSTPl6e-I
https://www.youtube.com/watch?v=1bDPWGUfwlY

 

[SCPD]

If you haven't found a good solution to prevent static buildup, perhaps I can help. I run 550-ohm ladder line here to a full-wave loop. So much wire is required that static can build up and cause a "hash" type of noise in the receiver. It is a very simple matter to resolve this. You have had some suggestions that I consider bad advice. Let me know if you are still in need.

Quickly, one great solution (the one I use here) is to add an RF bypass to ground. This is simply an RF choke that passes DC (Static charges are DC) yet, the choke is invisible (or nearly so practically speaking) to your RF signals on the feed line. With loop antennas, you only need add it to one side of the line. The balance is preserved, also practically speaking. However, if it makes you feel better, add a RF choke on both sides to ground. You can easily wind your own chokes. Take a piece of 2" PVC, 18-inches long and fill it from end-to-end with #14 insulated copper wire. You can cover it with electrical tape when your done. Or, what I do (I have mine just outside the window) is spray them with liquid rubber (home depot). This weatherproofs them and holds the windings together. These are your RF bypass chokes. Make two of them and connect each one from each side of your feedline to ground. Some hams have a mental block and wonder about "grounding" each side of their feed line. If you have concerns, tune your antenna with and without the chokes. In my case, the SWR does not change. This is proof that the impedance seen by the tuner is the same with the chokes in or out of the circuit. Yet, to static, there is a direct short to ground.

BTW, tuners with 4:1 baluns in the output are not the best available matching solution for balanced antennas. The old Johnson Viking Matchbox is your best bet but must be modified to cover the 30-m band. The mod is simple however and can be found on QRZ.com, AA4BQ callsign search.

Incidentally, instead of the PVC choke above, you can use a ferrite core instead and create the same result but with a much smaller size. Depending on the power you are running, you can get quite small with this -- down to the size of a silver dollar, for example, is easily done but be sure to use high-voltage insulation for the toroid windings. Good luck. I have great success with mine.

 

[KG6ABF]

Think I found the best solution, one that I can make myself. Two spark plugs. I've read of this method before but was uncertain. I think I'll go for it. See image and description in link below.

Static Voltage Arrestor-Protector for Balanced Line feed lines

Anyone have any objections?

Thanks.

You might want to read what he says about the use of it. It appears he says it Will Not work for direct or even indirect lightning hits.

Since you already posted a link and it still up to read take a look at it. I have spoken with some amateurs who live in the Mid West and they do all sorts of things to help against lightning damage. One fellow Ham said he has some ladder line insulators and coax chassis mount connectors affixed to a solid metal plate with the center as well as the outside of the connectors connected directly with solid copper wire and braid to a grounding rod system.

He screws the connectors of the coax to these when lightning activity is announced in his area. This outside grounding is about 12 feet from his feed through into his shack and claimed he has had any damage for an indirect lightning issue since installed by him years ago .

I was just talking to friend in Texas who was doing something similar because he says they get lightning and thunder storms in the spring and summer not just fall and winter.

He said he changed over to this after he suffered a non or indirect lightning strike damage. It sounded like he was happy with the change.

It seems to me I have read about lightning doing damage across fairly large distances and some Ham I have talked to over the almost 30 years of being licensed seem to know from personal experience or at least through another person about trying to avoid lightning damage, It sounds like separating the coax or feed line as far as you can will help minimize the potential damage, but to me it would always be something that no matter what it could still happen. I venture to guess doing something is far better than doing nothing and get insurance if possible to cover equipment if it does happen.

There used to be a publication or a book from ARRL and another source CQ? that had articles covering this area maybe search the internet and see if you can find it.If memory serves it was a chapter or two in a book on grounding and I also saw an Electrician's Handbook with info on Lightning prone areas and what to do to minimize the issues.

 

[SCPD]

Spark plug static solutions

Thank you for the reminder of this technique for lightning
and static discharge.

One thing to keep in mind with this technique. First, yes,
it will definitely provide a path to ground for relatively low
(and high) static voltages. That said, I keep in mind that
this is a "parallel" solution. That is, unless the rig is disconnected,
whatever voltage potential is seen at the spark plug terminals
also appears across the receiver antenna input terminals. More
directly, unless the rig is disconnected from the antenna, it will
not be protected from any voltages at all. The spark plugs are
simply a way to provide a path to ground IF high enough static
voltages are reached which would break down the air gap of
the spark plug. This voltage can be estimated but is in the
1000's if not 10's of thousands of volts (depending on ionization
and gap distances). Now, compare that to the shunt coil
technique where even 1/2 volt or less of static charge would be
safely shorted to ground. The two methods could be connected
in parallel for a dual-purpose setup. The shunt coil will work
to discharge any static charges far below the air-gap breakdown
voltages -- effectively reducing/eliminating the static hash in the
receiver. That said, if the receiver/xcvr is connected at the time
of an actual strike, it's curtains for the rig - no question about that.

I will stay with a shunt coil arrangement and simply disconnect
the transceiver when there is a risk of lightning. Once disconnected,
I connect all antennas directly to a very large (04 gauge) wire directly
to station/external ground rods and power ground outside.

Still, there is no control of direct strikes. I have seen a friend's
shack where lightning struck his beam and entered his shack,
blowing a hole directly through both sides of a filing cabinet and
disintegrating a Heathkit paddle keyer sitting on his desk along
with wiping out his Henry 2K. It's ugly stuff. That's why I constantly
watch the weather and disconnect everything. Of course, living in
lightning alley (Florida), you must.

Happy days. 73, Bill

 

[K7MEM]

I have a experience with static charges and how big they can be.

About 2 years ago I changed the location of my 5BTV. I mounted it on the top of a 18 foot length of 2" iron pipe. The bottom 4-5 feet was secured to a corner section of iron pipe fencing (horse fence), which was cemented in the ground. All of that is about 75 feet from the barn, which is where my shack is located. I used the antenna for a while with my IC-735 and didn't have any problems.

But I switched to a different antenna and left the coax laying on the floor. After a while I started hearing a ticking noise. Just one tick every few minutes. I tracked it down to the coax that was laying on the floor. When I picked it up I could see the discharge from the center pin on the PL-259, to the shield. I don't know how much voltage is needed to jump that kind of gap. But I plugged it into a dummy load and proceeded to forget about it.

About a week later I connected the 5BTV back up to the IC-735 and didn't have any issues so I left everything connected. That evening a storm moved in. About 9:00 PM I heard an explosion. It sounded like a stick of dynamite. I didn't hear any sirens and that kind of thing isn't uncommon in my area, so I forgot about it. The next morning, when I went to the barn, I found out that the explosion was the 80 meter resonator at the top of the 5BTV. It blew it to smithereens. The only thing left was scraps of Bakelite and wire.

When I entered my shack I found that the charge had bore a hole in my tuner and welded all of the capacitor plates together. Oddly enough, the IC-735 was not harmed. I think possible that the tuner saved the transceiver.

The rest of the antenna also survived. It still worked fine on 10, 15, 20, and 40 meters. But even without the 80 meter resonator, it still gets charged up enough to cause an arc at the end of the coax. Recently, the ground radials were taken out by a back hoe, so it is not in service. When I get back to it, I'll add a choke at the antenna base.

This isn't "lightening alley", like AA4BQ. This is high desert, south of the Grand Canyon.
Usually the only time we get lightening storms is around mid July and August, during the monsoon season.

Martin - K7MEM

 

[AG6CX]

Comment on Matchbox Mods for 30m

If you haven't found a good solution to prevent static buildup, perhaps I can help. I run 550-ohm ladder line here to a full-wave loop. So much wire is required that static can build up and cause a "hash" type of noise in the receiver. It is a very simple matter to resolve this. You have had some suggestions that I consider bad advice. Let me know if you are still in need.

Quickly, one great solution (the one I use here) is to add an RF bypass to ground. This is simply an RF choke that passes DC (Static charges are DC) yet, the choke is invisible (or nearly so practically speaking) to your RF signals on the feed line. With loop antennas, you only need add it to one side of the line. The balance is preserved, also practically speaking. However, if it makes you feel better, add a RF choke on both sides to ground. You can easily wind your own chokes. Take a piece of 2" PVC, 18-inches long and fill it from end-to-end with #14 insulated copper wire. You can cover it with electrical tape when your done. Or, what I do (I have mine just outside the window) is spray them with liquid rubber (home depot). This weatherproofs them and holds the windings together. These are your RF bypass chokes. Make two of them and connect each one from each side of your feedline to ground. Some hams have a mental block and wonder about "grounding" each side of their feed line. If you have concerns, tune your antenna with and without the chokes. In my case, the SWR does not change. This is proof that the impedance seen by the tuner is the same with the chokes in or out of the circuit. Yet, to static, there is a direct short to ground.

BTW, tuners with 4:1 baluns in the output are not the best available matching solution for balanced antennas. The old Johnson Viking Matchbox is your best bet but must be modified to cover the 30-m band. The mod is simple however and can be found on QRZ.com, AA4BQ callsign search.

Incidentally, instead of the PVC choke above, you can use a ferrite core instead and create the same result but with a much smaller size. Depending on the power you are running, you can get quite small with this -- down to the size of a silver dollar, for example, is easily done but be sure to use high-voltage insulation for the toroid windings. Good luck. I have great success with mine.

AA4BQ de AG6CX

1.Couldn't find reference to your Matchbox mods for 30 m. Could you lead me to them, or send info to edwmccann at AOL.com?

2. Rough calculation on your pic choke looks like 168 uH. Is this sufficient to block RF?

3. Could you be specific in recommendations of Inductance and current rating of chokes you have used from each side of open wire to ground?

4. Have you had similar results with resistors? What value and power rating do you suggest?

5. Concern here in Sausalito is continuous bleeding
release of static buildup, not lightening.

Read about your Step-Out antenna. Sounds great!

73

Ed McCann

 

[prcguy]

Every balanced line system is different and a particular value of choke that works on one system may not be right for another due to wide ranges in impedance along the line that will change on each band. Its known that bypassing with a 1mh choke (+/- .25mh) in a 50 ohm system works as does a high value of resistance across the line. So why not do your static grounding on the 50 ohm side of your tuner or right at the radio?
prcguy

If you haven't found a good solution to prevent static buildup, perhaps I can help. I run 550-ohm ladder line here to a full-wave loop. So much wire is required that static can build up and cause a "hash" type of noise in the receiver. It is a very simple matter to resolve this. You have had some suggestions that I consider bad advice. Let me know if you are still in need.

Quickly, one great solution (the one I use here) is to add an RF bypass to ground. This is simply an RF choke that passes DC (Static charges are DC) yet, the choke is invisible (or nearly so practically speaking) to your RF signals on the feed line. With loop antennas, you only need add it to one side of the line. The balance is preserved, also practically speaking. However, if it makes you feel better, add a RF choke on both sides to ground. You can easily wind your own chokes. Take a piece of 2" PVC, 18-inches long and fill it from end-to-end with #14 insulated copper wire. You can cover it with electrical tape when your done. Or, what I do (I have mine just outside the window) is spray them with liquid rubber (home depot). This weatherproofs them and holds the windings together. These are your RF bypass chokes. Make two of them and connect each one from each side of your feedline to ground. Some hams have a mental block and wonder about "grounding" each side of their feed line. If you have concerns, tune your antenna with and without the chokes. In my case, the SWR does not change. This is proof that the impedance seen by the tuner is the same with the chokes in or out of the circuit. Yet, to static, there is a direct short to ground.

BTW, tuners with 4:1 baluns in the output are not the best available matching solution for balanced antennas. The old Johnson Viking Matchbox is your best bet but must be modified to cover the 30-m band. The mod is simple however and can be found on QRZ.com, AA4BQ callsign search.

Incidentally, instead of the PVC choke above, you can use a ferrite core instead and create the same result but with a much smaller size. Depending on the power you are running, you can get quite small with this -- down to the size of a silver dollar, for example, is easily done but be sure to use high-voltage insulation for the toroid windings. Good luck. I have great success with mine.

 

[k9wkj]

remember there is no contol of a direct strike !
the best you can do is get it jump a right angle corner to heavy ground (give it a more tempting direct path)
at the bottom of the feedline.
every thing else we do is trying to dissipate charge before a strike.
remember strikes start from the ground up.
things like wide grounding systems and spiny balls work well
one needs to ask themselves "why dont old fashioned windmill towers take hits very often?"
because the dissipate charge from a wide ground system.
I always called that "the cone of influence"

 

[AG6CX]

Comment on 1mh choke use

Its known that bypassing with a 1mh choke (+/- .25mh) in a 50 ohm system works as does a high value of resistance across the line.

Can you direct me to some source of the math on this selection of choke size. It may be that "its known". but I haven;t yet run across that one. Be grateful for a direction.

So why not do your static grounding on the 50 ohm side of your tuner or right at the radio?

Using expensive and sensitive antenna analyzers (AA-54 and Sark 110) on the side upstream and downstream of tuner for various measurements, and don't want to run risk of front-end blow out from static electricity.

Elecraft forum carries suggestions for high resistance fro each side of feedline to ground, and even across the ladder line (one side to the other).

Thanks for your comments. Looking for your reply.