The AM Forum

The past few weeks I have not been able to talk on the radio much due to static building up on my Wire antenna. This antenna is 60 ft up horizontal fed with 600 ohm open wire line.  This line feeds to the Johnson KW matchbox.  It then can feed my 4 stations.

I get a spark from each leg of the open wire line from the insulator on the back of the tuner to the case or to the Ground lug. These arcs are up to 3 inches long!  It is very loud and if you are at the far end of the house you can hear it CRACK CRACK CRACK!

The solution I use is to attach jump leads from ground to the antenna lugs using a long insulated plier. Once its grounded, this stops.  Obviously, I unhook my radios when this happens.

The problem is that this happens nearly all day long and most of the night. So far, I thas not destroyed any of my radios. Although, I am worried about using my 1000D. 

Even if the spark is not jumping in the room, The Reciever gets blanked out for a second through my QSOs. 

It has been suggested to me that I should build some Transmitting chokes.  I am going to look through my handbooks to see if I can find some designs. 

Has anyone built a choke or does anyone have a solution? 

Clark

Try grounding the center of the coil in the matchbox.

Which coil?  I guess you mean the large one? I have seen this on other home brew tuners.

Clark

Yes this will bleed off the static.

Be careful with the matchbox since the CT shifts on the higher bands. I think only 1 additional turn is shorted going from 15 to 10 meters.

So I need to Center tap this large coil?  Thats going to be difficult.. The turns are shorted as the band changes like you suggested.  Where should I ground it?

I think the CT only shifts on 15 or 10 meters the lower bands will have the CT in the same spot since the shorted turns are equal on 40 and 20 each side of ct. which is the same as 80m.  Also you could put small spark gaps on the feed line just wide enough to not spart while in TX. Might only need .1 to .25 inch gap.

Any drawbacks to doing this?  I have a spare KW matchbox. I can take it apart and test this in realtime with a Clip lead to see if it helps. I had to get off 40 meters a few minutes ago as it was starting to spark.

Clark

An rf choke from each feeder to ground will do the trick also.

This is what the guys suggested on 40..  Where do I get some and what kind? How do they hook up?

C

The RF chokes should just be some heavy xmtg type units..value not critical, just a few millihenries...use identical chokes for each side. 

Are you near a high tension power line?  I hope you aren't seeing some induced energy on your antenna from a power line.  Seems like that static build-up is rather severe.  Chokes should fix it though.

73,  Jack, W9GT

I think about 40 to 50 uH will do it. Connect 1 to each feed line just before the feeders enter the house and then connect them to a GOOD GROUND.......a 10 foot ground rod should do it.

All the lines are underground here.  I think its the weather.  This happens every year and sometimes through the year.

My vertical has been up on the tower for years. It will throw 1 foot!  Arcs out the top to the atmosphere like a bull whip about 3 or 4 times a year. This takes out the cable modem (I have been through 8 of them now!), the digital cable box reboots and phones stop working..

You really cant use anything electronic during this time. I have had people next door come over and knock on my door as they hear this LOUD Cracking sound and they can see the big arcs.  It also arcs from the attachment point of each section of the antenna.  It killed a few radios over the years.  MOST of the time this is never an issue..  But certain times of the year right BEFORE the storms hit, I get the big arcs.  Most of the time its static crashes and or minor sparking at the back of the tuner.

I have mentioned this over the years and have had little help. A few radio friends of mine have been over then this happens and there eyes look like silver dollars when they see those arcs!  LOL.  I am used to it..  My main quest is just to stop this Noise and crashes on my Reciever so I can use the radios!

I need to find a source or make some chokes.. Any more information would be great!

I am sure there are alot of people that have had this issue and I am sure there are alot of solutions!

Will any of these from RF parts work?

http://www.rfparts.com/choke.html

With my kw matchbox......the arcing happens from the unused pl259. It arcs from the center conductor of the jack to the threaded outside of the connector.

Bill

Hi Clark,
This link will take you to Array Solutions and his static/surge coils. I use them and they will end your static problem. Tie one to each feeder and ground the other end.

http://www.arraysolutions.com/Products/staticsurgecoils.htm (http://www.arraysolutions.com/Products/staticsurgecoils.htm)

Collins did it with high voltage resistors (couple megs or so) in the 180L auto tuners.

Thats the answer.. $70 and an hour of time and I can have those coils installed on the outside of the house. I bet that solves my issues. Then, I can get a Coax style one for the big vertical.

Clark

Just a quick comment......
These chokes are NOT meant to be lightning arrestors (the spell check on this board sucks!) The values of the chokes I sent u was considering the antenna was going to be used on 160. If the antenna is NOT going to used on 160, then the value of the chokes can be reduced to about 20uH.....

Bill

I'vbe witnessed what Clark is talking about, at his QTH about 2 years ago.  On a 10 meter 'stick' style antenna, it turns into QUITE the tesla.

If you look at the schematic of MOST upper end CB radios, you will find a choke that goes from the SO239 center pin to the ground lug.  This is to bleed off EXACTLY what you are seeing.  Older radios used a resistor, but as anyone who has an SB220 can tell you, lots of overvoltage over the years can cause them resistors to change values, and sometimes a LOT.

If you want to test it, and can find them, grab a couple 5 dollar Cobra 20 series radios from the local swap meet.  Remove the choke from the SO239 connector on the back, and do one to ground from each side of your feedline, or as others have said, center tap the Johnson.  Any old carcasses of 10 meter amps usually have them as well...  More a solid state radio thing, and for some reason, a tubed amplifier thing.....  The solid state amps I've seen lately don't have them.  Guess they count on the radio having it installed.

Also, on a related subject...  A local truck driver friend went through 3 Galaxy radios in his truck...  The newer MOSFET style output ones.  As SOON as he got rid of the Wilson Silver Load (fiberglass) and went to a stainless style antenna, no more blown MOSFETS.  I had to send the company a pic of the MFJ screen...  They couldn't believe it was happening and the installation was good.

Now, they ask people who return their radios what type of antennas they have...  Fiberglass or covered, and they tell them to go to a 'metal' antenna.

Your antennas are all covered, huh?  And them DAMN desert winds blowing across all that insulation causes problems, huh?  Like, static buildup.

Same thing I told you years ago, when I saw it on your fiberglass antenna at the time.

Kill the insulation, and I bet your problem goes away.  If the antenna and feeders, etc. are ALL bare copper, I'm at a loss.

--Shane

50 uH would be about 2 inches of #18 wire on a 1.5" pvc pipe.  Or 48 turns and 6 yards of wire.

I don't begrudge some entrepreneur making a buck but this really seams like a nice and simple homebrew project.

No one has mentioned those gas discharge gizzmos MFJ sells.  They are intended for coax but you could use two for a balanced line.  I believe one the hookers is that they have a limited life time and get used up.

This whole issue of 3" sparks boggles my brain and I am sure glad I don't have this problem.

However, I do have similar thoughts on the spell checker on this list and was actually going to post a thread on the issue because my complaints go unremarked.

As far as I can tell, all it does it red line an incorrectly spelled word and offer no help correcting it.

My wife and I spent about 10 minutes working out the spelling of categorically for a previous posting .  Couldn't even find it in the dictionary until we tried changing an a to an e.  This spell checker just produces a guessing game.

js

I don't think that is the point of that choke and it certainly offers no help in the receive mode which is where the antenna spends most of its time.

That choke is used in pi output tank circuits to limit the voltage on the loading cap and as a safety measure to blow a fuse if the blocking cap should short out and try to put high voltage on the antenna system.  All pi net output transmitters should have this choke for both reasons.

js

I guess I could make my own.  I will look into it. 

My Wire is bare. No insulation. The Feeder does have insulation on it though.  I have this problem on my Vertical, and on the Zep antenna. I dont have this problem on the 160M L antenna that is coax fed, grounded to the tower and uses bare wire.

I dont think those small chokes will take the 1500 watts I put through this antenna.

Clark

A 1mH choke on 160M looks like a 12K resistor...  Why not just stick a 50K resistor from each side of the feedline to ground - no more static buildup.

as long as the resistor can handle the flash over voltage of the tuner 7000 v.

Option 1.  Install 50K resistors from feedline to ground (what wattage?)

Option 2. Ground the coil in the KW matchbox. (may lose 10/15)

Option 3.  Buy Transmitting coils and install them outside.

Option 4.  Wind my own Coils.


?????

CLark

1. A 2 watt resistor is good for about 300 volts so series a bunch of them
4. find a nice pair of coil forma you will quickly find out if they resonate. Aviod PVC it gets lossy on higher bands. Fibergalss and teflon insulated wire should work fine #22. It does not need to be a round form. You could form a triangle or X with strips of PC board material without copper.
3 will work as long as they don't series resonate Not sure about the insulator material and outside wx.
2. I'm pretty sure the CT will be offset on 10 because onlt 1 additoinal turn of the big coil is shorted. It needs to be an even number for CT to be in the same place.

No, that choke is there exactly for the function I mentioned.

It is mentioned in the ARRL Manual, and Orr's books, in the RX parts.

It's the same thing as the blocking choke, and on my old trusty cobra 148 in the truck, it is there.  Factory.

But, we are only arguing apples to persimmons, as we both know exactly what we are talking about :)

--Shane

Clark,

The coils I was talking about out of the junk chassis was to use as a test, before you slam dollars down on something from Array Solutions or ??? and find out it DOESN'T work.....  Although I bet it will.

You only need something that provides enough reactance that it doesn't become part of the circuit (the antenna or feeders), and is a DC short.

If you only want to know if it is going to work, grab a choke coil out of a radio that has enough turns to give you the inductance so it is 'invisible'.  Ground your feeders to ground / together.  Install said chokes.  Check receive.  You don't have to TX to test the corona problem (or does it only start AFTER you put fire to the wire...  THAT would be really wierd!).

The antennas you are having problems with are 'floating' in respect to ground, no?  The ones you DON'T are DC grounded.

DC grounded antennas are great.  Static buildup, rain noise, even to an extent lightning crashes, can all be eliminated or at least partially brought down.

--Shane

My fugly tuner is at DC ground but an approaching storm will flash over the caps with 1/4 inch spacing. The inductance of the coil will blochk a high frequency transient say waveform 3 lightning. This is the reason many tuners use high value noninductive resistors.

Clark,

I have had those Array Solutions inductors in line for 6 years now and they work great. The coil forms show no UV or weather damage. They are virtually invisible from 160 through 10 meters to my system and solve the static problem period. As mentioned you will want a good lightening suppressor as well on each leg.

Give John at Array Solutions a call if you have any doubt. I'm just a very satisfied customer.

Mike

I understand they make special johnny ball strain insulators for breaking up the guy wires in broadcast towers for this very purpose.  Some kind of impurity is mixed into the ceramic material so that instead of being perfect insulators, they have several megohms of resistance.

I would recommend a static drain rather than a spark gap.  The gap will still discharge and make a lot of noise in the receiver even if the equipment is protected.

I have had this to happen in winter during blustery weather with wind and snow, and also just as a t-storm front is moving in.  Also at times when it is raining, especially if it is windy at the time.  This static discharge sometimes completely blocks the receiver with white noise.  My 127' vertical has insulators every 18' to make it rf transparent through 40m.  You can imagine all the racket close to 100 isolated sections of cable can create.  Fortunately, this occurs only occasionally.  Sometimes I can get good  reception with the indoor loop or beverage even though the receiver is completely wiped out on the tx antenna.

If you use chokes anywhere but at the rf null point on the coil, make sure it is wound on low loss material, since its inductance will become part of the resonant circuit.  Also, you may notice a  slight shift in tuner settings.  If the rf choke attaches to a cold point on the coil, about any old choke will do and it won't be critical.  The high resistance drain resistors would work, too.  I would experiment and use the highest resistance that is still effective, since it will drain away a small amount of rf as well, unless connected to a cold spot on the coil.

I use a large drain choke from the feed point of the vertical to ground.  It is commercially built, wound on a bakelite form.  One of the balanced tuners has a choke from the cold spot on the  coil to ground.  This one is hand wound on a ceramic form.  See attached photos.

Guys.  High voltage resistors.  You see 'em at just about every hamfest, and about $5 on eBay.  Brown, with a black internal spiral.  Exactly what's in the Collins 180L3 auto tuner, which was the mate for the 618T 500 watt airborne xmitter and end fed a random wire on the aircraft.

(http://www.cableform.com/images_products/i-hvr.jpg)

   For apx 30 years I have used Several 2 Watt Resistors in series around 300K to 500 K Total at the balanced tuner from each balanced terminal to a station ground rod outside. Yes the tuner box is also grounded and I run 1500 PeP sometimes.

   When we have a high antenna this is necessary to continue listening with out whistles from snow, rain or fog masking even strong stations I.E. "Precipitation Static". Regards  John

Wirewound? I would have thought those would be a bit too inductive, but I guess they must have worked if Collins used them in aircraft tuners.

What about Carborundum resistors? They can take quite a jolt, as long as it's not the physical kind. They also don't have the inherent inductance of a wirewound.

They have a spiral of carbon in them, and for this purpose it doesn't matter if they're inductive or not.  Several megohms, just to drain of static, will have negiligible inductance compared to the resistance.  In fact, a bit of extra inductance would actually be a benefit here.

Interesting subject. Was wondering how high resistance value wire wounds could develop meaningful inductance...so pulled a few from the junkbox and put them on the HP Q meter.

100 k ohm / 25 watt Ohmite - no indication of inductance

50 kohm / 25 watt Clarostat VP25K - no indication of inductance

25 kohm / 50 watt Ohmite 270 series - no indication of inductance

250 ohm / 25 watt Ohmite - 35 uH / Q~1

25 ohm / 25 watt Ohmite 270 - 5.6 uH / Q7.5

25 ohm / 25 watt Clarostat VP25KA (adjustable) - 17 uH / Q8.5

2 ohm / 25 watt Ohmite 270 - 3.2 uH / Q23

This is just a Q meter measurement...further study on a bridge and/or a search for resonance might prove interesting. Think it's safe to say the high resistance values that would be used in this application are probably okay. 



 

     

  Thanks Jay for helping us all.  And allowing our solid state receiver to have a chance working stably longer.

 How many of us have ben a Ben Franklin ?  And during a precip whistling time placed our finger near one of the balanced line feeders to conclude " I ain't ever doing that again.'

    Its amazing how the Tuner manufacturers and ARRL are out to lunch about suggesting simple safety measures. Must we leave our HV security issues to Fatherland Insecurity ?   Perhaps Not.

  Let us not be afraid of Insurance under (glub) writers and add the resistors quickly during a safe moment!
Of course we could wire the resistors to our metal frame bed for better health !
No frank-ly, there ain't no magnets near my mattress or the chewing gum on my bedposts, but only in my loudspeakers and headphones.
Regards  John

Well, that's infinitely more measurement than I put into it!

My bad in assuming the resistors Johnny was referring to were wirewound (I judged that book by its cover). A carbon helix would be a whole different ball game.

That, and the fact that I was forgetting the fact that this is a more constant static charge than lightning EMP, and inductance really isn't that much of an issue in that case.

So now I'll go back to being an interested reader. I was a bit more constructive that way.

I tried two small Chokes like you suggested.  Just in the listening mode.  This took the noise down.. Then, they both exploded into smoke. I guess this was the voltage hitting.. LOL.  They did work for a little while. I never transmitted through them.  I will need the large coils to drain that huge voltage and current.

Clark

That's some bad static...

The object is to continually drain it off so it doesn't have the chance to build up. If you've got 25k ohm or higher, 10 or 25 watt wire wound resistors laying around give 'em a try.

   

Maybe you could rig up something to use this as an alternative energy source.  Put up a  couple of tall towers on insulators, and connect a mesh made of chicken wire between them.  Perhaps you could even get federal funding.  ;D

A dude named Mahlon Loomis (http://www.smecc.org/mhlon_loomis.htm) back in the 1800's successfully tested a wireless telegraph system between two mountain tops in Virginia, about 20 miles apart, pre-dateding Hertz's experiments.  Each "station" consisted of a kite, later on a wooden tower.  Evidently the static build-up and discharge generated enough radiation that its effect on a galvanometer was measurable at the other site.  But he was thought to be a nutcase or a fraud, so his creation went nowhere.  One more in the long list of failed or ripped off inventors like Tesla, Stubblefield, Fessinden, Armstrong, Farnsworth, etc.

Just my 2 cents. Use the resistors. High value is OK. 47K-470K. Leave them there all the time. When your not using the antenna, ground it. During storms, ground it. Make sure your ground is in good shape because that's where all those loose electrons will be going. If you have a zorch it's just some cheap resistors, just replace them. I have been watching Tina do this for years. Get's rid of the noise and keeps the voltage down enough that zorches are at a minimum.
Keith

Clark,

Glad to see you're finally working on that problem.  I'm really surprised that you didn't blow any of the solid state stuff up over the years with it, but then again, most cheap stuff has the resistor across the antenna jack, or a coil.....  It seems the upper end radios 'eliminated' this, makes ya wonder why.....  I can't see a drawback, the R is high enough that it won't detune anything.

Have fun.  I'd use carbon comp resistors, if you can find them, if that's the way you're going to go, as wirewound will add extra L, which might not be a good thing.  HV rated resistors can be found fairly inexpensively at EBay, or your local Antique Electronics might have some. 

If you go the coils route, I'd suggest 10 times the feeder R amount for each leg, at the lowest freq you operate on.  The biggest problems with coils is, your GOING to have a resonance somewhere.....  And when you do, it's a direct short to ground and the coils get interesting REAL quick.

Pros and cons.

--Shane

Tried to use the radio last night.  It was useless. 20DB of static and lightning crashes. I am going to work on this today starting with grounding the coil on the second KW matchbox.  Then, I am going to order the resistors.

Am I to understand I cannot use the HV bleeders I have?  I have 25, 50 and 100w....

Clark

Most bleeders are wirewound resistors.  The problem with wirewounds are they introduce inductance (and usually not enough to do what you want here) into the system.

HV carbon resistors are spirally wound (in most cases), but made of carbon (usually), instead of wire.  The carbon has VERY little inductance to add.

You could actually try both...  Use a high value resistor to keep surge current down on the choke....  Although the R would serve to detune the L, possibly causing more problems.

As others have said, too bad you can't harness this..  You have lotsa volts there, and the current isn't anything to sneeze at, either.  I'm bettin it would knock ya on your butt, from what I remember.

--Shane

I must be missing something.. The WW resistors still have a pure resistive, and an inductive reactive value. Wouldn't the two be in series, effectively increasing the impedance above the R value?? I don't see why the inductance wouldn't beneficial?

Pete

We've all heard the mantra that wire wounds are inductive...so we tend to think that all wire wound resistors are alike and are predominantly inductive. The Q meter measurements show that low resistance value wire wounds do look like inductors with moderate Q but also shows that high resistance value wire wounds do not exhibit much in the way of inductive properties.

If you need to prove this take the highest Q inductor you can measure and put a 50k or 100k resistor in series and then recheck it's performance...

Not sure why a carbon spiral wound resistor would be any different from a nichrome wound resistor...if the resistance is the same and has the same number of 'turns'. It's just a different type of lossy material.

Good point Pete...any inductive reactance just lengthens the impedance vector. In the application we're talking about here the 50k or 100k resistance will dominate.





       

What about interturn capacitance?  The LC network WILL, at some frequency, become resonant.

As to the R across the L, that's been a way of lowering Q of rf inductors for quite some time....  I've never done it with a WW, but...  Another thing to consider there is this:  HV Resistors are wound like an 'edge wound' inductor (being done with VERY little cross sectional area, using strap).  Wirewounds are wound, like a standard inductor.

The edge wound (like a piece of strap) will have WAY less C between turns than the standard one will...  Hence the properties of the inductor acting different (when looking at a HV rated carbon resistor vs. toaster wire).....


I just measured a 5w, 5ohm, and it had .3uH of inductance across it.

Just looked at it with the VNA, and the same resistor listed above gets squirrelly above 6 mhz.  Would make a great resistor for the use above, but gets all kinds of nice odd resonances that I wouldn't want in my feedline straight to ground above 6 mhz.

--Shane

I twist the end of the feeders around a pig tail on my service entrance ground when I don't play radio at the new QTH. Yesterday morning there was a storm approaching so thought I would get up and watch the show. I was sitting next to the cat and all of a sudden she lets out a meow. A couple seconds later I hear about a three second arc outside, then ka-bang. I guess the antenna took a bit of a hit and the cat must have felt the voltage change. No the cat's fur wasn't standing on end.

Does the VNA ever show the impedance going much below the marked resistance?
Resonant or not, L reactance is still in series with R component.

Pete

Spent the afternoon working on the system.

Opened up the KW matchbox and found that some IDIOT bypassed the relay by jamming electrical tape into the relay. This was done many man years ago and the contact was now showing signs of wear..  I unbolted the RF feed strap from the Coil to the Relay and moved it over to the incomming stud.. This is the way to bypass the relay.. Now My RF has a solid in and out path NOT through the contacts.

We also found one of the LINE Studs was loose on the inside.. Also found about 4 or 5 loose screws holding the variable caps down.

My LARGE coil is grounded. I tested it with a meter. I can see the ground path. 

I also put in connectors on my open wire line and bolted them to the back of the tuner so I had a good connection.

All of this totaly through off the tuning chart. I had to sit down and make a new one. I cant tune 20 meters anymore. at best its 1.5 to 1. I guess usable.

I also noticed that the lower ground lug is the one you want to use as it is the one that runs to the coil.  The one up at the top is just grounded to the case. I am now using the lower one and it has a shorter path.

Right now I have 9 SU of static with Crashes up to 40DB. 

We tried 200K and 20K resistors from the open wire line to ground.  The 200,s and 20s where both 50 watts each. This had NO effect on Recieve or Transmit. The tuning was unchanged. So the BIG 50 watt HV resistors work fine on 80 meters. I did not try other bands. 

The resistors had no effect on the RX pops at this time. I looked on intelicast and the cont US is COVERED in Lightning strikes.  Cant fix that with resistors.

Clark

Pete,

I'm not the one to interpret the readings here, but I swept the resistor from the lower end of the VNA to 50 mhz....  It got REALLY squirrely above 30 mhz.

MHZ     R     X
 1.7     5     0
 2.1     6     0
 2.9     7     0
 3.7     8     0
 4.39   8     1
 7.8     9     1
11.3    10    17
17.5    11    29
24.6    12    43
27.4    13    49
44.8    8     90
45.28  0     100
46.5   19    101


In all measurements above, ALL the x was inductive, so you are correct in that it would be additive...   Although I'm not sure I still like introducing any unnecessary reactance into my feeders, since we all use tuners on balanced lines, I'm thinking it's a moot point.

The problem is, a WW resistor is nothing more than a plate choke, on a smaller scale.  Look above, and see what happens from 44 to 46 mhz.  OUCH, a direct 'short' would work a tuner out.

Bottom line, if you where to do the wirewound resistor method, I'd sweep each resistor to ensure it's Fresonance wasn't in a band you want to work.  Otherwise, as Pete said, it would be an additive quality, the inductive reactance it would add, as long as you can tune it out.

Also, in the 'graph' above, The VNA I have 1.7 mhz IS the lowest measurable freq.  I'm not sure if it has any resonances below, but 'probably' not.  BUT, this resistor, would be safe everywhere in HF...  in VHF low (I didn't test mid or hi), it's a losing proposition.

--Shane

At VHF, that might make sense, since stray capacitive reactances might be present directly across the two poles of the resistor. My guess is that the R and L reactive components are pretty much intermingled, making a series-resonant  L - C low-impedance path around the resistance unlikely.  I hope my babbling  is halfway coherent  :P

Pete

Don't recall anyone suggesting that a 5 ohm wirewound resistor was appropriate in this application...

I am going to install the RF chokes next week outside in a box. I think this is going to be the best bet for my situation. I already have a solid Ground rod right at the window.

I wanted to point out that I believe grounding the coil inside the KW matchbox wont do anything. The reason is that the lines run through the variable caps.  I studied the inside of mine and the schematic and it would seem that you would still have to arc over the plates of the cap if the coil was grounded. Here is a schematic of the KW so you can see what I mean.

For now, I am using TWO, 200K, 25 watt bleeder resistors from each leg of the open wire line to ground. These have no effect on 40 and 80 meters. Tuning is unchanged on the transmitter or tuner with them hooked up. Maybe this will save the Solid state rigs I run sometimes and limit the noise on the tube recievers.

Clark

Your correct........it wont do a thing.

Your best bet is the chokes.....just get the correct size.

Bill

Makes total sense.

Might also be a double whammy, as it would make a dandy low pass filter, as well.

I'm going to try to find some more ww resistors around here to see if any of them get squirrely at HF...   If not, learned something new....  If so, we all learn.

--Shane

This is not rocket science here folks.............u need a "device" that will pass dc and block ac...in this case rf frequency's.......and that "device" is a choke.

What is the problem?

Example........in every toob amplifier there is a choke at the output of the amp to ground. Guess what its for.......if the plate coupling cap shorts, this choke will short the HV to ground keeping the high voltage DC from the power supply from reaching the antenna and hopefully blowing the power supply fuse.


Bill

I think the first assumption the problem was related to a slow build up of a static charge until the voltage reached a flashover point some where in the antenna system.

But, if this is blowing RF chokes apart I'm beginning to wonder if the OP isn't experiencing atmospheric discharges direct to the antenna instead. It doesn't seem to be wind induced static buildup. Something more onerous? ???

Pedro

Pedro,
The chokes should not allow ANY dc voltage to buildup on the ant. Any DC voltages  will be passed to ground. Anyway that is the theory.....
Bill

This is quite amazing when it happens.

Literally, lightening bolts shoot from his vertical (I haven't seen the wire antennas, been a couple years since at his QTH).  I always thought it was from the wind picking up sand and that inducing static across the fiberglass vertical, but Clark said his wire antennas are NOT covered, so I can't see that being the problem here, unless they are enameled or ???...  And then I'd question it.

I was only worried about a LC combo finding it's way across the thing and him blowing something up because of a resonance.  I only had a 5 ohm 5 watt to test with, and since I am incapable of getting up and out of bed at the moment, any additional testing will have to wait.  The resistor I had here to look at, I could only find a resonance in the VHF range....  Learned something new.

But, there is a serious amount of power here.  It's blowing apart chokes rated for 1A or more current.  If he's using the ones I'm thinking, I've used them to pass > a couple amps, when using them as bypass on DC lines for bias in solid state stuff.  The things should NOT be blowing apart on RX, period.

The antennas at his QTH, with NO radios attached, can at times resemble a Van de Graff or a Tesla coil.  And they are blowing apart chokes grounding the feeders rated at LEAST at a half amp.  Regardless of how it's done, that's a bit of power to dissipate.

--Shane

Not what I meant... Would the choke stop a lightning discharge?
I know it would drain static buildup. But it sounds like he is experiencing
something quite different.

Chokes are NOT lightning protection............they bleed off any dc voltages that slowly build up on the antenna. The only way to protect ANY antenna from lightning is to take it down OR disconnect it from your shack and hard ground it before it enters the house. Even if u do this and the ant takes a direct lightning strike.......all bets are off.


Bill

Let me explain further. 


Today while on 40 meters AM, my friends T368 was showing 40DB over solid.  Then, I hear Zeeeorch POP. The arc is inside the tuner on that one.  The SX100 S meter goes to 0 and slowy comes back up and I gain Recieve again. 

This happens on the 1000D, FT450, SX100, 101, 110,390 ect ect ect..

Its a Discharge inside or mainly outside the tuner to ground of high voltage. When a storm approaches this happens in 1 second intervals.. POP.........pop.......pop........pop.....pop.  This can go on for an hour.

I have noticed that if I am on certain bands with the tuner it will arc internal and other bands it arcs external. There is a simple explination for that. The plates are close on the caps on some bands where others they are open.

I have the chokes comming. They will be here next week. I will report back as to if this solves the issue.  As for the vertical.. I have tried many different things.  I just unplug it and stick the hardline in a glass Jar.  If you use a Coax style Lightning arrestor, It blows the Gas tube and you have to put in another, only to blow that one.

What I am worried about is that even with the chokes, I will still have the ARCs on the antenna and it will still blank out the RXer.

Clark

Don't forget, their is literally, 12 to 24 inch long bolts of HV that shoot off the vertical antenna when this is happening...  Not just in the tuner.

The vertical is(was) hooked directly to hardline...  You could get a 'zap' across a PL connector, as well as watch lightening bolts shoot off the van de graf....  err...  Vertical antenna.


--Shane

Yes.. The old vertical which was a Sheakspeare unit, Died.. Something inside of it fried.  THe Imax 2000 that is up now gets arcs from the scew together sections and off the tip.. Normaly.. For some odd reason, the bolts go Northwest.  I use Half inch Andrews hardline that is Grounded to the tower as it goes up.  The insulation was stripped back and it is grouned to the round tower sections and sealed with coax seal. This is how Andrews suggests this line be installed.   

So far after 3 years+ the I max is not dead.  It covers all of 10 meters, 12, 15 and 17 just fine!

The wire antenna just arcs in the house at the tuner.


Clark

What bugs me the most, is what the heck is causing this in the first place?

I mean, yes, "snow-static", blowing dust, obviously a nearby lightning storm....

But happening on a daily basis?  ???

Do you live really close to any of those BIG high voltage lines?

I'm just amazed you could be experiencing this on such a regular basis.....


Wow, I'm glad I don't have to contend with any of that. !

Huh, you said the "bolts" go North-West.....

Directly towards Phoenix then ?

Curious...........       :o



Somewhat makes more sense to me, now I know where you are...
Guess the dry air would make a huge difference, from up here in th emoist north-east...

Guys. This does not happen every day...  It is a seasonal/weather thing.  I might go for months in the winter and not have the issue.  This last month was really bad.  Its arcing over today.  But let me make this clear that it is not daily. It just happens during dust storms or overcast weather.. If its real clear out.. Then I dont have the issue.

For some strange reason, we noticed that off the tip of the Vertical.. The bolts go North to northwest. Someone was commenting on that one night as we sat out in the night and watched the discharges.

Clark

(http://www.fathom.com/course/10701020/112_tower.jpg)

Yeah..  I took everyones advice...

I have the two 200K 50 watt resistors across the open wire line and I ordered the Array solutions chokes.

As for the vertical.. Its up at 85 ft and need a bucket truck to get up there.  Its not worth the effort. I just leave it unplugged and in a glass jar unless its clear and I want to use that antenna.  10 meters is dead for me now so its realy not a big deal.

If I grab the open wire leads in storm will this happen?

 ;D

I NEVER said they were lightning protection. But, from a previous post:

"I tried two small Chokes like you suggested.  Just in the listening mode.  This took the noise down.. Then, they both exploded into smoke. I guess this was the voltage hitting.. LOL.  They did work for a little while. I never transmitted through them.  I will need the large coils to drain that huge voltage and current.

Clark"

It seems there is something more potent than simple static build up going on, or the chokes wouldn't have smoked. 

Pete

Ok OK....
I use 2 chokes on my feedline and I run A LOT of power and have never had a problem.....this uhf, vhf stuff is a lot of bunk in my opinion..........sorry.

Keep in mind that the chokes I ran where the small type you see inside a CB or 10 meter radio. THe ones that have three sections of wire (looks like string) wound on a bobbin.  They are made for low power. One hit off that wire and they smoked.  THe big coils I ordered are just heavy wire on a form. I dont think they will be bothered.. Time will tell.


Clark

again..........I use as an example that most toob transmitters and toob amps use a CHOKE to protect the output.
I rest my case................ ::)

And the texts written since we mastered the silicon junction call them static bleed chokes.

You're case was understood days ago, just a bit on the 'DATED' side.

--Shane

Umm, they shouldn't be across the line, they should be from each leg of the feeders to ground..

I'm guessin that's what you meant, but just to be safe...

--Shane

Yeah... From the open wire line to Ground on each side. 

They dont effect 20 meters..   I just talked to ea1abt in Spain with the 1000D using this antenna and about 100 watts :)  14.288.85

Clark

HOW FUNNY!!!!

Not 10-15 minutes ago, I was listening to him!  My son must have gotten off the bus around the time you made the contact.

He had a good signal into cent cal, with my ATAS120 dummy load.

Just found my marine tuner and fired it up.  On 10 meters, it was able to load up a test lead from my Fluke.  I can't find a manual ANYWHERE on it, but it hooks up exactly like the icom auto tuners from the 90s. 

If I can find a CB type whip somewhere, I'd like to A/B compare it against the ATAS.

--Shane

shane, You need to get that wire up man. 

Thats funny you heard him.  I dont spend much time on 20 meters. But 75 is so noisey here that its useless. 40DB over with the antenna hooked up.. 0 with it unhooked.  The people I can hear are just washed out.


Oh and yes, Those are the coils I got.  I just got shipping notification on them today.  I should have them by monday. 

I am going to mount them just like the picture that was posted.  I have a Ground rod right outside. Its an 8Ft rod. The leader from coils to rod will be 3ft or less. That rod is also tied to two others and the tower. It will have a solid ground. I hope I dont have any issues with harmonics. I will have to keep an eye on that.

THe big resistors are inline but they sure dont stop any noise. I still get pops that wipe out the RX for a second.

What kind of Choke are you talking about for the Recievers?  Can you post a picture or show me which ones to get from RF parts? I posted the RF parts link to the chokes in this thread.   The only two I have got fried as I had them on the open wire line.

CLark

How does a mH choke at the receiver terminals eliminate noise?

I will try that out on my Reciever.  From Center to ground correct? 

The chokes I used where just slightly smaller then that on the open wire line. Thats the ones that smoked. They had the brown wire that looks like string.

I did try some 20K 50 watt resistors.. It seemed the 200Ks helped more with the noise. Maybe it was me. 

Thanks for helping me!

Clark

With the resistors and the coils in parallel, you shouldn't ever have the CHANCE to burn out the coils.  The R in parallel with the L will also lower the Q of the inductors, making them even more broad, although it looks like that isn't going to be an issue.

The 160 full dipole is up.  I have a marine tuner I found in my junkbox, pretty much a clone of the ICOM AT103, but I'm not capable of doing much now....  On the 14th, I fell down my stairs carrying my puppy (he just finished a worm treatment and was pretty sick).  My broken leg ended up bending a HARD rt turn at my knee.  Possible another break at the knee, or at the bare minimum, a torn ligament....  They can't MRI because I have the pin in my rt leg from the motorcycle wreck a year ago.

Oh yeah, the fall down the stairs happened on the 1 year anniversary of the wreck.  Someone isn't / wasn't happy with me for somethin I did on a May 14th SOMEWHERE!

Anywho, I figure if I can get a stainless steel whip somewhere (nobody local has one, and I'll be DAMNED if I'm going to spend 30 dollars + shipping) I'm going to try it and the marine tuna next.  If I can't get anything going with that, finally, I have the legal limit ++ mobile solid state amplifier I'll have to shove into the pickup truck :).  Last time it was up and running, it was good for 6 to 800 watts of carrier fully modulated :) 

One way or another, I'll be heard. 

--Shane