The AM Forum

Hi to all,

My question is about draining the static off the ladder line to my link antenna coupler.

I believe I can do this by using a shunt inductor on each side of the ladder line to ground. 

How do you calculate the value of these two shunt inductors vs. frequency (one for each side of the ladder line)? 

Do I need different shunt inductors values for all the different HF bands?

Thank you.

Chuck

Hey Chuck,

    I would think all you need is a DC ground. That will drain
the Static. The "Z" of those will be determined by the "Lowest"
Frequency of operation. I Have a Butternut Vert. 80 - 10 M
that uses about 10 turns of #12 about 1.5 inches in dia. to do
that.

GL

/Dan

Chuck....take a look at Array Solutions. They have what they call 'bleeder' coils that are reasonably priced and work well.
I use one on a coax fed antenna and it does the job. No more arcing coaxes.
I think they show how to do it with 2 of these coils....someone on here posted a picture of how he did it using ladder line.

Dave

those Array Sol. drain chokes are $35 each.  I'd try going to a hamfest and buying a couple of pie wound chokes or solenoid plate chokes or maybe even winding something.  But whatever you come up with, put the choke in series between a signal gen. or swr analyzer output and the vertical input on a scope.  load the scope side of the choke with a carbon resistor, 30 ohms or so, with the line to the scope from the resistor choke junction and the other side of the resistor grounded on a scope panel lug.  Adjust the v/div. so you see a big sine wave trace with the choke bypassed then put it in the circuit and start sweeping the bands you operate on.  If you see no RF you are good to try them on the feedline.

Also do a search of the messages.
There was at least one thread that went into this in detail.

You can easily wind your own for $1, anything at 100uH or more is fine down to 160. Do not use a ferrite or iron powder form as it will likely satutate on strong pulses. Use #18 wire as it "should not" absorb any power and still have low DC resistance. Pie chokes or miniature molded made with tiny wire might short from nearby lightning pulses.

Carl

Everyone, thanks for you input.

Which formula should I use if I want to wind my own choke coils to drain the static off ladder line or coax?

Would the 160 meter chokes from Array Solutions work on 10 meters?

Can a static drain choke cover 160 - 10 meters effectively?

Chuck

A couple of plain several hundred Kohm resistors to ground at the coupler end have been reported to work by some.

The impedance where the feedline connects to the antenna coupler varies with band used and antenna/feeder length. It can be very roughly calculated by making note of voltage maximum on end of doublet, then working backward toward the coupler. Don't forget feedline works as transformer too.

If link coupling is used the configuration can also be telltale of output impedance. Not very many couplers used by amateurs can work into a pure high voltage feed. This self limits the impedance a resistor would be in parallel with.

Make a note of bands tried. If the resistors don't turn to dust after using the station on each band at max power all is OK.

Another plus for the AG6K coupler. All wire in the air will be at DC ground if the final has a safety choke.

Yes....I'm doing it.

Several pictures here.....
http://amfone.net/Amforum/index.php?topic=30006.0

ER had an article several months ago on ladder line lightning protection. It used a combination of devices including large RF chokes for DC ground and gas discharge devices. If you are running high power the voltages on ladder line can get quite high.

Ditto on the ER article, great!
It was Number 284, Jan-2013.
"Build your own lightning protection system for ladder line" by AB5WG.

One of the features of the design is draining off accumulated charge.

I have just finished collecting all the parts to build one of these, the only
difficulty was that he specified an EPCOS GDT P/N that no longer exists.
 
When I inquired, he kindly identified Mouser P/N 650-GTCA28-402M-R03 as the replacement.

73
KJ4OLL

Dave thank you for the pictures.

Did the Electric Radio article use resistors or inductors connected to the ladder line to ground?

Chuck

Ke7trp,

Very nice pictures you took of your inductors from arraysolutions.com.

Are your inductors the 80 meter or 160 meter coils? 

What size wire do you think these coils are using?

What type of coil form is used?

Do you know the inductance of these coils?

And, can these inductors be used up to 10 meters?

Thank you,

Chuck

Hi Chuck,
The ER design by used two of these coils:
http://www.mfjenterprises.com/Product.php?productid=10-15197
plus
Two of the Gas Discharge devices as I listed previously ( from Mouser).

Two 4700pf 5kv doorknob caps from this guy:
http://www.ebay.com/itm/4700pF-5KV-Doorknob-Capacitors-Lot-of-2-/151030698573?pt=US_Radio_Comm_Antennas&hash=item232a21924d

Frank

That Ameritron plate choke is a far better choice than the overpriced stuff from A-S plus it is guaranteed to have no ham band resonances 160-10M. The AS stuff is guaranteed to have hot spot resonances somewhere above 20M.

Carl

Exactly which resistors did you use? How long a doublet and feedline? What bands did you use the setup on What type of weather event was happening when they blew out? Did they both blow out in a similar manner?

  I use dual 10 meg-ohm high voltage resistors (about 2" long). I've had no issues before and after adding them. When feeding my 15m vertical loop (16' wide X 8' high) on 40m, the feeders are resonant and I have very high voltage at the tuner output. I can light a CFL lamp 2" away at 20 watts. The resistors are fine with that.

  The whole idea is to bleed off any static charge that can build up from electrostatic forces at cloud level. We don't need much conductivity to ground to do that, and those that want low ohms DC to ground on their feedlines are going that extra step. That said is their system any safer, or is the receive noise level lower?

  If there is a direct or near lightning hit, neither approach offers much protection. It is better to disconnect the feeders away from the house, and ground them.

  I recall fondly years ago while visiting Ozona Bob W5PYT (SK). We were on 75M am on a Saturday evening . This was during a thunderstorm. Bob had the Tec-Rad on (2 X 813, and 2 X 805) when lightning hit the 300' microwave antenna. Bob had a 80m diagonal mounted turnstile hung off the tower. We saw the flash, and heard the boom. The sparks flew in the Tec-Rad, and its meters pegged. Bob paused, looked up, saw that he was still on the air, then proceeded to finish the transmission. Apparently this happened often enough that it wasn't a big deal.

Jim
WD5JKO

  Clark,

   Please help me understand what you just said. First you say the chokes you use have no effect 160-10m, which to me suggests the inductive reactance of the coils is high and resonant free until around 6m frequencies. OK, I am with you so far.

  Then you state that a plate choke rated at 1 amp (actually the MFJ linked to is rated at 1.5 amps) is no good because you use dual ammeters that can read as high as 3 amps. But wait a second, the feeder current is not the coil to ground current because the coil to ground has no effect (your words), so therefore the coil to ground current is close to zero. So why would a plate choke burn up? Please explain that again.

  I am sure your setup is FB. My only issue is I don't quite follow your explanation.


Jim
WD5JKO

  

Thanks for some sense Jim. Sometimes I wonder.....

Jim, Clark doesn't know what he's talking about. People have been using plate chokes and resistors for many decades. But now we are to believe Clark is the only one who has ever put static drain coils on balanced line. He's passing along something he read on another forum and it's clearly erroneous.. Please ignore. It's like noise on the radio.   ::)

Frank, Clark, Carl, W2VW, Jim, Dave and all,

I appreciate very much the ideas and suggestions to help drain static off my open wire feeders.

Are there any other suggestions?

Chuck

C and all,

Array Solutions states that their anti static coils are rated as such:

1.8 MHz = inductive reactance of 850 ohms.  I believe the equates to about 75 uH.

3.5 MHz = inductive reactance of 1,900 ohms.  I think this equates to about 88 uH.

To me this seems backwards.  What do you think?

Chuck

Hi

I believed there is a difference between static dis charger and Lightning protector .

As a static dis charger ,I think we can used the old RF chokes (air wound) 1 Mh or 2 Mh,of course a high current capability  Rf choke is better,
Since it reactant is high .

Just A though

Gito.N

  Chuck,

  Data like what you posted that goes non-linear sure suggests that a resonance is fast approaching. The resonance(s) come from distributed capacitance turn to turn. Remember for parallel resonance, below resonance the coil has inductive reactance, and above resonance the thing behaves more like a capacitor. The reactance could still be high though, and the device still do the intended job. If the reactive current were to get high at certain frequencies, then a small gauge coil could certainly heat up, and possibly fry. One way around this would be to use a heavy gauge coil, and hope the coils contribution to the  complex feedline reactive load could be offset by another setting of the upstream tuner. Having a choke in there designed to be resonant free in any ham band 160-10m sure seems to be an advantage. If a plate choke has these characteristics, then it would not burn up even if the wire used had a small cross section.

Jim
WD5JKO

Those chokes coils are easy enough to make.  They will drain off static build-up from the feeders.  As you go higher in frequency their reactance will increase.  They may become self resonant at some point, something that will have to be checked.

The two coils will not help much with a direct lightning strike because of their high reactance to ground.  The only thing that will help with a direct hit is directly grounding the feeders.

Someone mentioned high value static discharge caps.  Not exactly sure in what manner the caps were to be used.  They would not be connected from the feeders to ground unless you want to short your own signal to ground.

Fred

This is why I dont suggest using a thin wire plate choke. If you get anywhere near a hot spot of the plate choke, its going to open at the high antenna current.  From $25 to $35 for the large gauge wire AS chokes, I dont think its worth it to chance it with open wire line antennas.  Then, I think they would probably open up due to near by strikes and static electricity in this area.  Those chokes are putting very high voltage and current to ground before a monsoon storm or a dust storm rolls through.  But, maybe I dont know anything like steve says.  That might be true since Steve is never wrong. Ever.

C

It's not about me Clark. It's about you and your incorrect info.

People have been using resistors as static drains for decades. This is nothing that can be argued. It's been done. Now you come  along, a guy that doesn't even understand simple concepts like, self resonance and inductive reactance, and you want us to believe that you know better. That is laughable.

It's obvious to anyone with a basic understanding of what's going on here that the antenna current DOES not flow through the static chokes. Why waste our time with such nonsense? You only serve to make yourself look silly.

Others have asked you questions in this thread. You did not answer them. Why not? Do you not have the answers? You should given your claim of preeminent knowledge. Or are you just being rude and ignoring the questions? Either way, you are adding zero to the discussion.

So, you aren't arguing with me. You are arguing with decades standard practice and well known basic electronics and RF knowledge developed by people far smarter than me. The fact that you want to try to make this personal shows you've got nothing of substance on the actual technical subject.

Take your smart ass confrontational crap somewhere else.

I'm not so sure that Clark's comments are wrong.

Given,  a high value resistor will drain off a steady build-up of static charges.  With a resistor you may want to consider the limited voltage ratings of ordinary resistors.  So, you could use a string of them to increase the overall voltage handling ability.  Also, carbon or Globars might be needed to avoid resonant points that might occur with wire-wound types.  You could use non-resonant wire-wound types, not sure if they are still made, but I have many of them 2K 50watt.

Clark speaks to using heavier gauge wire chokes to avoid burn-out from the large antenna currents.  Well, we all know that the antenna current is not flowing through these shunt chokes.

In Clark's last post he mentions getting near a "hot spot of the plate choke".  What does he mean by "hot spot"??

I'm going to assume he means a self-resonant frequency in the choke.  The resonance is caused by the distributive capacitance between the windings.  This capacitance is in series with the inductance of the coil.  Series resonant circuits have a very low impedance, allowing for very high currents to flow.

So, maybe Clark is not so wrong when he is concerned about high antenna currents flowing through thin-wire plate chokes.  Of course, we hope that a good plate choke doesn't have any self-resonant points, but who knows for sure.

Just my .02 cents, now $3.85 with inflation.

Fred

  Fred,

   Lets ponder on what you just said. I agree that the coil resonance will be from turn to turn capacitance, but that resonance is parallel resonance, and not series resonant. So at || resonance we have a higher impedance (a good thing), but what happens as we go up in frequency from there? Classical parallel resonance above the resonant frequency shows a increasing capacitive load. But wait, this isn't coil current..instead it is reactive capacitor current from the turn to turn capacitance.

   The area where I am struggling to understand is the loss characteristic of the distributed turn to turn capacitance, and whether a single layer linear wound coil would only have one resonant point, or multiple?

   So when someone uses a plate choke in its intended application (plate circuit), and it fails, is the failure due to a parallel resonance in one of the sections where at resonance the turn to turn voltage soars beyond the wire insulation rating?

   Consider series resonance where at resonance we have a low impedance. Below the resonant point there is a capacitive circuit, and above that we have an inductive circuit. So this seems N/A to the topic. Take a grid dip meter, and a 0.01uf disc capacitor Wrap the leads around the GDO coil form, and twist the ends together. Then sweep the frequency. You should see a sharp series resonance (the inductance is the short wire leads) at about 7 Mhz. So consider that when you use a .01 uf bypass capacitor at the upper reaches of HF....It looks like an inductor!

Sorry for my rambling...

Jim
WD5JKO

Because of the above, critical RF circuits would have a .01 cap in parallel with a 100 pF.

Jim,

Thanks for your input on my comments.  I pondered on which resonance it is, series or parallel.  I finally decided to go with series.  I knew I would get some different opinions.  At this point I'm not really sure one way or the other.  I'm going to try to research this further.  I would think even with parallel resonance you still get some high circulating currents.

After Steve beat the hell out of Clark I had to do something to try to save his behind. ;D

I'll re-read and study further your comments.  You may very well be right as I never had any of my plate chokes burn up to see what actually occurs.

Fred

Fred, if you need any help burning components up just let me know. I would be glad to help.
Dave

I suspect he is concerned that most modern plate chokes have a resonance on 11M ;D

At $20 the Ameritron has the best price and highest reactance on all ham bands while maintaining a very low DC resistance.  Do regular resistance checks especially during T storm season.

Carl

Dave,

Thanks,  I can always count on you for much needed help.

Jim,

I just located some info on this subject.  In the ARRL Handbook there is a section on distributive circuit elements, page 53 in the 1973 book.

It seems that every capacitor is a series tuned circuit with any inductance the cap may have.  You are right, it further states that every inductor is a parallel tuned circuit with its distributive capacitance.

So, I guess at this point, Clark is on his own. ;D

I should have done some research before I decided on series resonance in my previous post.

Fred

It's OK Fred. You still have more transformers in your transmitter than everyone else.

Thanks Dave, now I feel much better.

You're right about the transformers, but, not everyone is actually connected to anything. ;D

Fred

Ok, I'll show my ignorance, would the idea of using a small fuse at the ground end of the inductor, perhaps one amp, serve  an indicator that the antenna took a hit? This is of course for static drain and not lighting protecting. Who would regularly check the RFC anyway, so this fuse displayed in an open area could be what is needed for these pesky HV spikes ??? ??? ???   

Hi

Ladder line means Twin balanced Line?

When We used link coupling does not it mean A coil  connected between this

two wire ladder line as the link coupling  to the coil  system  from the transmitter

That means a floating coil?

How if we Ground the CT of this coil to Ground.

Gito.N

Gito

A center tapped coil that is grounded at the CT would certainly seem to be the ideal thing to do.  Not sure what exact tuner circuits are generally used with ladder line.

Fred

Hi Fred

Maybe this tuner will Help,found this circuit in an Old Hand book


Gito

Hello Gito,

   A center tap to ground would work. The problem is any error in center tap will cause the coupler to introduce common mode feedline current.

Many of these couplers are homebrew without regard to perfect symmetry. Symmetry is not necessary unless grounding the center tap of the coil.

A further problem exists with series tuning as the center tap would not be connected to anything. See series and parallel link tuning diagrams.

2VeryWeak

Hy Every Weak

You are right .But I found this "solution" after reading the old Amateur hand book
ARRL,
The design is for Home brew,so I think they has already know about this grounding center Tap , to find a"perfect" balance

And the circuit can be used as Parallel Tuning Or Series tuning with a  change in the Circuit

Gito

Hi

After rereading this parallel ling coupling and Series link coupling .I found out that we used Series link coupling when we had a low impedance ( load) at the output of the Tuner.

But with this Parallel link coupling ,we can used as an alternative,set the feeder taping coil point close to  the CT of the Coil. to get A low impedance Output

Depending the Taping feeder point,We can get a high impedance output or A low impedance output

So A series link Coupling is not needed.


Gito

Series coupling is used where component limitations begin to waste power. Experimenting with QRO can be very instructive concerning antenna coupler component limitations.

Again, the center tap becomes a liability if the radio equipment is located in a modern neighborhood. Feedline isolation can make the difference between hearing many as well as staying out of RF susceptible consumer junk.

Simple resistors do the trick here. If building from scratch some type of center tap arrangement could be used. Always many ways to skin the cat Gito.

I gave up on link coupled designs back when running a BC-610 on 160 into an 80 meter length doublet. This was after trying a lot of configurations. Some made fine photographs (R.U. there VJB?). The AG6K type coupler (yes Frank we all know he didn't invent it) allows the entire antenna to be run at DC ground with only the addition of a parallel R.F. choke at the predictable 50 ohm port.

I get plenty of very intense precipitation static directly off the Atlantic. 

Hi

I know that You have a lot of experience trying to Used link coupling,

But as I wrote before after rereading this books I found this picture in ARRL hand book (CT at the Coil   X point)

An article of Parallel and link Coupling

It reads on 7 Mhz for Example the Impedance is Low and the series circuit of the figure 13.35a would be used ..............Alternatively the Parallel tuned coupling circuit fig 13, 55 b  could  be used  and the feeder taping points  set close to the center of the coil (RSGB) hand book

The conclusion I have after reading it We don not need a series  link coupling

So it is not my only opinion,but ARRL and RSGB book has the same opinion


Gito

Yes, you can tap down on the coil in parallel link arrangement and you will be able to tune the system. At some point the Q becomes too high and it is usually better to go with series tuning or change the length of the feedline.

Hi

You are right Steve , here I attached another picture from  an article  Tuna X-treme    

Just showing people does used CT ground   , I found it in   Super Massive Tuna  

- WZ5Q


Gito

Thank you to all for the static drain information.

Chuck