Ladder Line Static Drain/Shunt Inductors

[aa5wg]

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

[N8ETQ]

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

[Dave K6XYZ]

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

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

[K5UJ]

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.

[KF1Z]

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

[KM1H]

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

[aa5wg]

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

[W2VW]

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.

[Dave K6XYZ]

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

Yes....I'm doing it.

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

[wa3dsp]

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.

[KJ4OLL]

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

[aa5wg]

Dave thank you for the pictures.

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

Chuck

[aa5wg]

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

[KJ4OLL]

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

[KM1H]

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

[W2VW]

Skip the resistors if you live in an area with alot of static electricity. I tried them and had them blow out.

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?

[WD5JKO]

Skip the resistors if you live in an area with alot of static electricity. I tried them and had them blow out.

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

[WD5JKO]

Chuck,  The coils work from 160 to 10 meters with NO effect on the tuning of the antenna. I swept the coils. They wont get into play until up near 6 meters. On any of the bands from 160 to 10, I can unhook the coils with no effect on the analyzer. I used the wire antenna on 10 meters many many times at legal limit power.

I would not use the ameritron plate chokes if you plan to run more than 100 watts.  You have to understand that a plate choke is designed to be in a plate circuit and that choke is rated for 1 amp. The wire is very thin.  In an amplifier, this is ok since the plate current would be under 1 amp.  

If you put that plate choke in the antenna side, You can and will have several amps of current.  I have a dual ammeter inline with Open wire line antenna right before those chokes and I see 1, 2 and 3 full amps of current on the line depending on frequency, match/mismatch and power level.  

This is why taking advice from someone who has never used the such a system is a bad idea...  Plate chokes are great for low power or a known load like in a unbalanced coax fed antenna, You can measure/calculate the current and pick a plate choke that will work.  On open wire line you are best to wind some coils with heavy gauge wire or just get the AS coils and be done.

Good luck.

C

  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

  

[W2VW]

Exactly which resistors ..... 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.

Jim
WD5JKO

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

[Steve - K4HX]

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.  

[aa5wg]

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

[aa5wg]

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

[Gito]

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

[WD5JKO]

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

  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

[KA2DZT]

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