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Author Topic: Ladder Line to Coax  (Read 12515 times)
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W2VW
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« Reply #25 on: December 18, 2009, 02:18:50 PM »


I asked you a specific question with specific parameters. The question is answered easily when understanding of impedance transformation is understood. You answered it incorrectly. Use this as a learning experience. Everyone makes mistakes. No dancing necessary.


Dude, I'm going to be the better person here because itís totally obvious you are trying to goat me into getting mad. My answer was in response to what he was using and to your question combined. It was NOT a direct answer to your question about using it on 75 meters only.

I've had way too many years on experience working on antennas with coax, baulns, etc., etc., etc., and I know what works and what doesn't. I could care less about what the total Z is of the antenna at the transmitterís output with the ladder line on 75 meters only, it will be different on the other bands and thatís what matters.

I made no mistakes..


STOP trying to make this a personal issue. Stay focused.

It's obvious you have experience. That's not the issue. Answering questions based entirely on what you have seen is going to lead to wrong answers.

Experience is great but it makes some people overconfident.

4:1 baluns are usually worse for power transfer when used following a T match into balanced line and a doublet. They are only better than a 1:1 when the impedance presented in the shack is relatively high.

Model or guestimate Fredd's antenna's impedance on different bands based on experience. Use a feedline transformation calculator with a typical feedline length or Fredd's spec. Look at the impedance presented to the load in the shack. Do you still want to divide it by four???
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K3ZS
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« Reply #26 on: December 18, 2009, 03:41:32 PM »

One lesson I have learned on this board to avoid controversy, never talk about religion, sex, politics and baluns.
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W1GFH
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« Reply #27 on: December 18, 2009, 03:53:28 PM »

I'll bite. What exactly is the average loss of power in watts in a balun-coupled feedline vs a link coupled feedline?
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"A perfect 1:1 SWR is for sissies" - Joe W1GFH
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« Reply #28 on: December 18, 2009, 04:42:15 PM »

I'll bite. What exactly is the average loss of power in watts in a balun-coupled feedline vs a link coupled feedline?

That question cannot be answered.

It's like asking to quantify the blueness of the sky.

You need specific information to even start.

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KX5JT
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John-O-Phonic


« Reply #29 on: December 18, 2009, 11:10:23 PM »

....
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w5hro
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« Reply #30 on: December 20, 2009, 11:47:51 AM »

Opps is right  Grin

What was overlooked was the fact that all of those ready made baluns, both 1:1 and 4:1, will leave common mode on the ladder line unless you build one yourself using two separate windings. That in itself changes everything and using normal calculations to obtain the source Z of the antenna system with a tuned feeder will be thrown out the window.

It's the reason why all of the modern "T" network antenna tuners that have output terminals for balanced line have a 4:1 toroid balun inside and not a 1:1.

Anyway, you just canít argue with some people, itís not worth it.
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« Reply #31 on: December 20, 2009, 01:11:48 PM »

Opps is right  Grin

What was overlooked was the fact that all of those ready made baluns, both 1:1 and 4:1, will leave common mode of the ladder line unless you build one yourself using two separate windings. That in itself changes everything and using normal calculations to obtain the source Z of the antenna system with a tuned feeder will be thrown out the window.

It's the reason why all of the modern "T" network antenna tuners that have output terminals for balanced line have a 4:1 toroid balun inside and not a 1:1.

Anyway, you just canít argue with some people, itís not worth it.

Where do you come up with this stuff?

The real reason 4:1 is used in ham T matches is the ability to tune low SWR impedance range for a given set of tuner parts is larger. I need an editor.

Unfortunately the losses are  higher than a 1:1 in a lot of cases. Happy appliance ops will never know the difference though.

Common mode is not a problem in real life typical setups.

I have homebrew and commercial 1:1 baluns in service at several installations. They all work fine when you use them within their limitations. The commercial toroid units do much better over a wide freq range.
 
Realize the antenna coupler needs to match the impedance presented by the antenna system including the transformation taking place in the feedline and not the impedance of the balanced line itself.

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WA1GFZ
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« Reply #32 on: December 20, 2009, 01:40:20 PM »

a modern t section tuner  is sold to people who don't know any better. The balun is added to make them feel better about getting ripped off. The added feature that they are usually high pass networks makes it even more funny.

50 feet of 1/4 inch tubing, a couple feet of PVC pipe and a couple flea market caps. Maybe $100 to build a tuner.....Oh yea the added price of a hunk of plywood
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w5hro
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« Reply #33 on: December 20, 2009, 07:57:58 PM »

Where do you come up with this stuff?

The real reason 4:1 is used in ham T matches is the ability to tune low SWR impedance range for a given set of tuner parts is larger. I need an editor.

Unfortunately the losses are  higher than a 1:1 in a lot of cases. Happy appliance ops will never know the difference though.

Common mode is not a problem in real life typical setups.

I have homebrew and commercial 1:1 baluns in service at several installations. They all work fine when you use them within their limitations. The commercial toroid units do much better over a wide freq range.
 
Realize the antenna coupler needs to match the impedance presented by the antenna system including the transformation taking place in the feedline and not the impedance of the balanced line itself.

Using a "T" network tuner period will create losses, mainly on 75 and 160 meters even with a 50-ohm antenna system and no balun. "T" network tuners do in fact stink, but nevertheless, connecting the typical 300 to 450 ohm ladder line to a "T" tuner will require a 4:1 balun so the tuner will adequately tune on all bands. You donít want to use a 1:1 bauln with the "T" tuner on all bands using ladder line. The tuner's components are going to get hot as a result.

Common mode may not be a problem in real life typical setups, 90% of all modern HAMs and CBer's have it because unbalanced coax use is the norm. However, it will affect the use of balanced feedline. Your antenna systems Z without common mode will be different with it.
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WA1GFZ
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« Reply #34 on: December 20, 2009, 08:17:12 PM »

I wish I had some common mode, maybe I would look better and be smarter.
Santa please bring me some common mode.
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w5hro
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« Reply #35 on: December 20, 2009, 08:30:59 PM »

I wish I had some common mode, maybe I would look better and be smarter.

It wouldn't help  Grin Grin Grin Grin Grin Grin Grin Grin Grin Grin Grin Grin Grin Grin

I need to get on the air and just forget this Internet junk.
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W2VW
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« Reply #36 on: December 20, 2009, 08:33:20 PM »

Where do you come up with this stuff?

The real reason 4:1 is used in ham T matches is the ability to tune low SWR impedance range for a given set of tuner parts is larger. I need an editor.

Unfortunately the losses are  higher than a 1:1 in a lot of cases. Happy appliance ops will never know the difference though.

Common mode is not a problem in real life typical setups.

I have homebrew and commercial 1:1 baluns in service at several installations. They all work fine when you use them within their limitations. The commercial toroid units do much better over a wide freq range.
 
Realize the antenna coupler needs to match the impedance presented by the antenna system including the transformation taking place in the feedline and not the impedance of the balanced line itself.

Using a "T" network tuner period will create losses, mainly on 75 and 160 meters even with a 50-ohm antenna system and no balun. "T" network tuners do in fact stink, but nevertheless, connecting the typical 300 to 450 ohm ladder line to a "T" tuner will require a 4:1 balun so the tuner will adequately tune on all bands. You donít want to use a 1:1 bauln with the "T" tuner on all bands using ladder line. The tuner's components are going to get hot as a result.

Common mode may not be a problem in real life typical setups, 90% of all modern HAMs and CBer's have it because unbalanced coax use is the norm. However, it will affect the use of balanced feedline. Your antenna systems Z without common mode will be different with it.

Please tell me of an impedance/frequency where a 1:1 balun on the output of a T match tuner will make the components in said tuner run hotter than a 4:1.

My antenna system has negligible common mode energy on the feedline. Just like many others. It isn't that hard to accomplish.  
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WA1GFZ
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« Reply #37 on: December 20, 2009, 08:48:15 PM »

Dave, I think your problem is you have too much common sense and not enough common mode.
Want me add your name to my letter to Santa?
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« Reply #38 on: December 20, 2009, 09:27:44 PM »

Dave, I think your problem is you have too much common sense and not enough common mode.
Want me add your name to my letter to Santa?

Will Santa send me a 1099 form along with any gift?
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w5hro
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« Reply #39 on: December 20, 2009, 09:47:03 PM »

Please tell me of an impedance/frequency where a 1:1 balun on the output of a T match tuner will make the components in said tuner run hotter than a 4:1.

My antenna system has negligible common mode energy on the feedline. Just like many others. It isn't that hard to accomplish.  

It solely depends on the length of your feedline and the length of your ground system because the feedline is going to act like a single wire Marconi and both transmission lines are at the end open circuited.

In most cases the Z at the input to the feedline with common mode will be very low, but you still only have a single wire Marconi with an insufficient ground in most cases. Imagine tuning a single ľ wavelength wire without the other ľ wave mirror half/ground connected.

Anyway, Iím done with this topic for now so you guys can take it from here. You can believe what you want, thatís your choice.
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K3ZS
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« Reply #40 on: December 21, 2009, 12:06:51 PM »

The DX Engineering web site recommends using a 1:1 current balun as an add-on to an unbalanced tuner.  The reason is that by chance the impedance could just as much be much lower that 50 ohms at the end of the feedline than higher.   In that case the 4:1 makes it even lower.   If you know that your impedances are always going to be higher then the 4:1 is the better choice.    Seems to me if you have to make a choice it would be better to calculate or measure your actual impedance at all the bands you want to use.   The same would go for link coupled tuners, whether to use series or parallel tuning.
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Steve - WB3HUZ
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« Reply #41 on: December 21, 2009, 12:42:23 PM »

You would have to imagine this because that's not what exists with balanced line.



It solely depends on the length of your feedline and the length of your ground system because the feedline is going to act like a single wire Marconi and both transmission lines are at the end open circuited.

In most cases the Z at the input to the feedline with common mode will be very low, but you still only have a single wire Marconi with an insufficient ground in most cases. Imagine tuning a single ľ wavelength wire without the other ľ wave mirror half/ground connected.

Anyway, I’m done with this topic for now so you guys can take it from here. You can believe what you want, that’s your choice.
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w5hro
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« Reply #42 on: December 21, 2009, 01:02:45 PM »

The DX Engineering web site recommends using a 1:1 current balun as an add-on to an unbalanced tuner.  The reason is that by chance the impedance could just as much be much lower that 50 ohms at the end of the feedline than higher.   In that case the 4:1 makes it even lower.   If you know that your impedances are always going to be higher then the 4:1 is the better choice. Seems to me if you have to make a choice it would be better to calculate or measure your actual impedance at all the bands you want to use.   The same would go for link coupled tuners, whether to use series or parallel tuning.

Yep, I agree with most of that. Using 50-ohm coax for feedline you can never have too many 1:1 baluns inline. The more the better; one at the antenna, one just after the tuner, and one right before the tuner to keep everything happy. However, on certain bands your antenna might work better using a 1:1 balun if you feedline is ladder line, but it depends. That generally wonít be the case for operation on all the bands.


The issue with "T" tuners is the components on the two lowest bands are usually barely adequate to work. They often get too hot and they also create loss. The loss is usually not all that not great and I doubt if its even noticeable to anyone on the air. You might see a slight difference in signal strengths on the receiver, but thatís about it I think. Nobody is going to notice the loss of a couple of watts on 75 and 160 meters even if a 4:1 balun is used.

If you look at those 4:1 toroid baluns used inside of all modern tuners and ready-made remote baluns the center of the windings are grounded. Depending on the length of the feedline and the length of the ground system the common mode Z can be really low. It just depends on where that feedline length is resonate. The 4:1 baulns will usually get pretty warn on 75 and 160, but itís better than overheating and burning up the components inside of the tuner. I posted earlier that the main issue was the balunís power rating.

Anyway, this spin off topic has been worn out more than once. Every time it comes up everyone wants to bring it back to the original argument instead of focusing on the question at hand.
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« Reply #43 on: December 21, 2009, 01:10:50 PM »


If you look at those 4:1 toroid baluns used inside of all modern tuners and ready-made remote baluns the center of the windings are grounded. Depending on the length of the feedline and the length of the ground system the common mode Z can be really low. It just depends on where that feedline length is resonate. The 4:1 baulns will usually get pretty warn on 75 and 160, but itís better than overheating and burning up the components inside of the tuner. I posted earlier that the main issue was the balunís power rating.



Soooo you think the common mode current on a balanced feedline depends on resonance somewhere??
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WA1GFZ
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« Reply #44 on: December 21, 2009, 02:40:37 PM »

WOW
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K3ZS
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« Reply #45 on: December 21, 2009, 04:40:08 PM »

My last post I assumed this was with balanced ladder or window line.    I found out the hard way that the balun built into my MFJ just was not providing a very good balance on 40 and 80 meters.   On 160 it might as well not been there at all.    I salvaged the situation by getting an external high power balun.    I plan on building something like the K1JJ tuner for 160-40.   Will be curious to compare that with what I have now.
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« Reply #46 on: December 21, 2009, 04:51:34 PM »

You will have a real tuner if you build one then you can sell the toy on epay
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Ed/KB1HYS
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« Reply #47 on: December 21, 2009, 06:09:04 PM »

The MFJ baluns are tiny, barely adequate for 100w SSB. Well atleast mine was.  It got baked when i was running my Valiant.

A good link-coupled tuner is easy to build, costs a lot less per watt of power handling (compared to commercial products) and will be able to tune just about anything from the gutter & Down spout to a Multiband OW fed Dipole - no balun required.
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73 de Ed/KB1HYS
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« Reply #48 on: December 21, 2009, 08:45:02 PM »

The MFJ baluns are tiny, barely adequate for 100w SSB. Well atleast mine was.  It got baked when i was running my Valiant.

A good link-coupled tuner is easy to build, costs a lot less per watt of power handling (compared to commercial products) and will be able to tune just about anything from the gutter & Down spout to a Multiband OW fed Dipole - no balun required.


A link coupled tuner used this way IS a balun.
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« Reply #49 on: December 21, 2009, 09:05:46 PM »

yes very true Dave. And a T tuner is an UN-UN
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