Blocking Capacitor for Ladder Line

[Steve - K4HX]

And unless it's an autotransformer design, how would the DC get through the link?

[VE3AJM]

Does anyone on here have access or a copy of this ER article from Jan.2013 that was being referred to earlier in this thread.

Maybe that will help to clue us all in to whats going on with any need? for DC blocking caps inline with each side of the OWL, or AA5WG or KJ4OLL could explain.

Al VE3AJM

[DMOD]

AA5WG,

Please take a look at Figures 1 and 2 on Page 45 of this document.

http://www.g4nvh.net/sitebuildercontent/sitebuilderfiles/hfbaltransys.pdf

Is anything here to what you are referring? If not, can you build a schematic using LTSPICE?

All I see here is Hi Impedance to Low impedance tuning capacitors but not what I would denote as DC Blocking capacitors.

Phil - AC0OB


 

[flintstone mop]

AA5WG,

Please take a look at Figures 1 and 2 on Page 45 of this document.

Is anything here to what you are referring? If not, can you build a schematic using LTSPICE?

All I see here is Hi Impedance to Low impedance tuning capacitors but not what I would denote as DC Blocking capacitors.

Phil - AC0OB


 

I get "ERROR READING the document from Adobe.

[DMOD]

I gave a Link to the document. I don't know what happened to the pdf file.

Phil- AC0OB

[KM1H]

If it's a swinger and not a series resonated deal it has a DC short on the 50 ohm side no?

Since the thread is about a balanced OWL feed why muck things up with an unbalanced 50 Ohm ouput?

[W2VW]

Most transceivers whether SS or Tubes and even QRO amplifiers will never put D.C. on the antenna terminals.
Fred

Famous last words!


Same for OWL and link coupling, especially if its a swinger; accidents do happen and a couple of caps is cheap insurance. The cap can be a transmitting mica or a RF rated ceramic.

Carl

If it's a swinger and not a series resonated deal it has a DC short on the 50 ohm side no?

Because the thread is also about link coupled couplers. Mentioning open safety chokes in amplifiers also is a fairly safe assumption of 50 ohm to coupler input somewhere.

[KM1H]

It is rather rare to see a vintage link coupled amp schematic with an antenna choke and many just copy what they see.

 

[Steve - K4HX]

Carl, we're talking about a link coupled TUNER not a link coupling amplifier tank.

[KM1H]

Nope, the OP never said that and hasnt been back to confirm what he is doing.

OTOH drifting well off track from OWL to 50 Ohm unbalanced adds even more confusion.

Carl

[Steve - K4HX]

He did confirm in the third post in this thread. It's clear a link is involved whether it's a tuner or a tank. No DC will get through a link.

Sorry for not being more clear on the blocking capacitor.

The blocking capacitor is a fixed value capacitor that connects the end of the ladder line to the the link coupler.  There will be one blocking capacitor for each side of the ladder line.

Blocking as in DC blocking is what I was looking for.

Chuck

Emphasis added.

Read it for yourself at the link.

http://amfone.net/Amforum/index.php?topic=34128.msg263589#msg263589

[KM1H]

I read that right after it was posted and nothing then or now says it is a tuner. A variable link center COUPLER on the TX/amp can also directly drive OWL and so can a fixed link where the supporting plastic insulators fail.

If I had fired up my HT-9 without taking a close look at the 40M fixed center link tank coil it came with I would very possibly had 1000V on the line to the rear panel feedthrus; it was that close from age deterioration.

My only concern here is safety and not get into another useless nit pickin' discussion with you or the groupie.
I'll leave it up to the OP to clarify what he is doing.

[W2VW]

http://is.byu.edu/site/courses/description.cfm?title=READ-045-101

[Steve - K4HX]

We may never know.  

I can't help it that you choose to run dilapidated equipment. Please don't make it our problem.

If someone has the same point of you, are they your groupie?

I read that right after it was posted and nothing then or now says it is a tuner. A variable link center COUPLER on the TX/amp can also directly drive OWL and so can a fixed link where the supporting plastic insulators fail.

If I had fired up my HT-9 without taking a close look at the 40M fixed center link tank coil it came with I would very possibly had 1000V on the line to the rear panel feedthrus; it was that close from age deterioration.

My only concern here is safety and not get into another useless nit pickin' discussion with you or the groupie.
I'll leave it up to the OP to clarify what he is doing.

[VE3AJM]

AA5WG has been on other forums online in the past discussing and asking questions about link coupled antenna tuners. We won't know for sure? about all of this until he chimes in here again.  

I recall Ashtabula Bill always referring to his antenna matching devices as antenna couplers rather than tuners.

http://lists.contesting.com/archives//cgi-bin/namazu.cgi?query=%2Bfrom%3Aaa5wg%40yahoo.com&idxname=Towertalk&sort=date%3Alate

And on another mail list he also interchanges the terms coupler and tuner himself, and he's not referring to a link output circuit of an old transmitter, but of a tuner or antenna matching device.

http://www.eham.net/ehamforum/smf/index.php?action=printpage;topic=65374.0

Al VE3AJM

[KM1H]

We may never know. 

I can't help it that you choose to run dilapidated equipment. Please don't make it our problem.

If someone has the same point of you, are they your groupie?

Thats a typical response from you and your boy wonder sidekick Steve...snotty comments with nothing intelligent to support the thread.

Not everyone is as perfect as you who has never been wrong and constantly likes to remind others.

Just looking at some of the photos on here over the years of potential deathtraps is enough to be concerned, it only takes one slip and BANG

[Steve - K4HX]

And this is a typical response from you and your name calling...snotty comments with nothing intelligent to support the thread.

Not everyone is as perfect as you who has never been wrong and constantly likes to remind others, as in you capacitor replacement tirades. After all, only dummies would do radio repair differently than the all knowing, almighty radio god KM1H. Then there's your current Heathkit tirades. No kits exist today because Carl says no kits exist. He has spoken. All hail.

Please, continue to bless us with your presence and righteous knowledge. We couldn't live without you.

[KM1H]

Steve, you are a serious piece of work and just love to put your own very distorted spin on everything I say. You remind me of the media, simply trash anyone that says something they dont like.

Im thru wasting my time with your replies, just ignoring you is the way to deal with it and many others on here will soon get the same idea and you can have your own little clique to amuse.

Carl

[WB2CAU]

Steve, you are a serious piece of work and just love to put your own very distorted spin on everything I say. You remind me of the media, simply trash anyone that says something they dont like.

Im thru wasting my time with your replies, just ignoring you is the way to deal with it and many others on here will soon get the same idea and you can have your own little clique to amuse.

Carl

I should remind you in case you've forgotten; this is Steve's website.  You are essentially an invited guest in his home by being here.  It might be wise to behave yourself like a polite guest. 

[KM1H]

Im well aware of that fact without your "help", thank you, and have even contributed to the sites financial upkeep fund for the past 2 years. I dont see you on any of the contributor lists tho. Nor do you even bother to list your name in a thread.

There are 3-4 others (not sure of those numbers as the list may have not been updated) in the co admin/moderator capacity on here that are not into the continuous bully mode harassment and like the top people they are they only make their presence known when needed.

As other members have commented to me Steve has been very changed recently in general and having met him a few times and sat with him at an AM Dinner at Nearfest I dont understand the reason in my own case. I dont drink or do drugs either

Carl

[wa3dsp]

Getting back to the original question which was what value and rating of series cap to put in both sides of a balanced line to block DC. This of course depends on the lowest frequency and the highest power to be used. While the original question was (apparently) posed to eliminate the danger of plate potential DC on the antenna the article cited in this thread by KJ4OOL in the January 2013 ER on lightning protection for ladder line is a good reference. The author used two 4700pf 5000 volt series capacitors. He stated that he has used legal limit power, long AM transmissions, and all HF bands without a problem.

If you are worried about plate DC on your ladder line you should also be, maybe even more, worried about lightning or static buildup. The unit shown in January ER deals with all of this using a combination of RF chokes, gas discharge tubes, and series capacitance. See KJ4OOL's message in the first page of this thread.

I might also add that all of this applies to single wire antennas also. You would just use one half of the circuit.

 

[w1vtp]

WOW!

[W7TFO]

This all started out with a misnomer concerning OWL and DC.  I think it came about due to inexperience of the poster.  No big deal, we'll figure it out.

As to the rest of the thread, the moderators here are eloquent and guiding folks, however;

Steve is the money guy, so what he says pretty much goes.

There is always the California forum, with a REALLY opinionated owner.

73DG

[aa5wg]

Gentleman,

I have been out of town and will get back to you all soon.

73,

Chuck

[flintstone mop]

Getting back to the original question which was what value and rating of series cap to put in both sides of a balanced line to block DC. This of course depends on the lowest frequency and the highest power to be used. While the original question was (apparently) posed to eliminate the danger of plate potential DC on the antenna the article cited in this thread by KJ4OOL in the January 2013 ER on lightning protection for ladder line is a good reference. The author used two 4700pf 5000 volt series capacitors. He stated that he has used legal limit power, long AM transmissions, and all HF bands without a problem.

If you are worried about plate DC on your ladder line you should also be, maybe even more, worried about lightning or static buildup. The unit shown in January ER deals with all of this using a combination of RF chokes, gas discharge tubes, and series capacitance. See KJ4OOL's message in the first page of this thread.

I might also add that all of this applies to single wire antennas also. You would just use one half of the circuit.

 

Sorry to "RE-Quote " your reply. But the explanation of the circuitry pictured, and shame on me for not looking in my ER's, takes all of the mystery out of the thread. The picture posted looked quit involved with components that might really affect performance of the ladder line / antenna.
And AMFONE still stands out as a great gathering place of knowledgeable RF people who have years and years of experience with the tech world. Innovators and inventors and folks making things we call goodies or toys for our Man Caves.
Fred