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Viking II to tune or not to tune




 
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Author Topic: Viking II to tune or not to tune  (Read 11941 times)
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Jerry-n5ugw
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« on: July 27, 2009, 02:02:32 PM »

Ok here's the preverbial question. the Antenna is a 123ft diapole fed with #14ga ladderline with a 4:1 Balun fed by 50ohm coax. The  Viking II it's pi network will tune to a 600ohm resistance load and about 200mohs of reactance.
Question #1 would you use a tuner if the Viker will load into the current antenna
Question #2 would you remove the balun and coax, then add the tuner

Just wondering what others say before I make up my mind when putting the Viker inline.
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K3ZS
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« Reply #1 on: July 27, 2009, 02:35:26 PM »

If you can load it up on the bands you want without a tuner then why bother with one.    You probably will have problems on 160 and 80 though without an external tuner.   In that case build a balanced tuner for those bands and don't use the balun.    On the higher bands you may get away with what you have.   This is all a big quess on my part though.  To really crunch the numbers you need to know the length of the feedline also.


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ke7trp
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« Reply #2 on: July 27, 2009, 02:59:35 PM »

Remove the coax and the balun.  Run the ladder line into a Johnson 250 or KW matchbox.  Or other balanced tuner. Your losses with the coax are huge on different bands.  Me and others have been down this road before.

Clark
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K3ZS
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« Reply #3 on: July 28, 2009, 10:43:12 AM »

If the ladder line is the main feedline, and a short coax run to a good balun is used, the losses would not be huge, probably undetectable on the receive end, if the TX loads up.   By all means use a Johnson Matchbox if you have one though.
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W1GFH
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« Reply #4 on: July 28, 2009, 11:16:15 AM »

Quote
Question #1 would you use a tuner if the Viker will load into the current antenna

Practically speaking, if your other rigs (assuming you have other rigs) will load into the current "antenna system" (coax + balun + ladder line) on the frequencies of interest, the Viking should load also.

As others have said, losses will be less using a balanced tuner into ladder line, but if you're not fussy, use what you have.

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ke7trp
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« Reply #5 on: July 28, 2009, 11:34:14 AM »

I have used both.  Never again will I use a great balanced antenna to a balun and coax. The losses are huge when you start changing bands. The Balun is just not needed and just gets warm.  I have first hand experience with this and since two others have listened to me and ran the Ladder to the balanced tuner they have seen the light also. Running the setup you have not only a waste, You will probably get very frusterated in trying to get the RFI out of the shack. 

You can run what you want but I am the type of guy that was the most performance I can get. 

Some guys wont walk across the room for one DB of gain.

I will walk across the room 10 times.


Clark
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Steve - WB3HUZ
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« Reply #6 on: July 28, 2009, 01:49:12 PM »

Do a smoke test. If the balun doesn't get warm after a long transmission, the difference between the two setups will be zero. If the balun gets warm, remove it and go with the tuner. It's a safe bet that the tuner option will be more versitile and generally less loss.
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K3ZS
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« Reply #7 on: July 28, 2009, 03:12:00 PM »

I have used both.  Never again will I use a great balanced antenna to a balun and coax. The losses are huge when you start changing bands. The Balun is just not needed and just gets warm.  I have first hand experience with this and since two others have listened to me and ran the Ladder to the balanced tuner they have seen the light also. Running the setup you have not only a waste, You will probably get very frusterated in trying to get the RFI out of the shack. 

You can run what you want but I am the type of guy that was the most performance I can get. 

Some guys wont walk across the room for one DB of gain.

I will walk across the room 10 times.


Clark
I have used both also for many years.    A good balun such as made by DX Engineering with 6 feet of coax to the balun and then ladder line, when used will yield no difference if you can load the transmitter to full power.     If your loading changes and/or the balun heats up, its not a good balun.   Nothing beats a good real balanced tuner but to build or buy one good enough for high power or AM duty cycles is not cheap if you don't have some parts on hand.

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ke7trp
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« Reply #8 on: July 28, 2009, 03:24:30 PM »

Thats the balun I used.  6 ft of coax is nothing.  Most use runs from the shack to the balun mounted outside on the tower or wall ect..  So 20 to 30 ft of coax is common.  Why anyone, would run 6ft is beyond me.. I guess I understand why the Open wire line would not just to the balanced tuner at that point.

Cya

Clark
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KD6VXI
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« Reply #9 on: July 28, 2009, 03:27:21 PM »

I have used both.  Never again will I use a great balanced antenna to a balun and coax. The losses are huge when you start changing bands. The Balun is just not needed and just gets warm.  I have first hand experience with this and since two others have listened to me and ran the Ladder to the balanced tuner they have seen the light also. Running the setup you have not only a waste, You will probably get very frusterated in trying to get the RFI out of the shack. 

You can run what you want but I am the type of guy that was the most performance I can get. 

Some guys wont walk across the room for one DB of gain.

I will walk across the room 10 times.


Clark
I have used both also for many years.    A good balun such as made by DX Engineering with 6 feet of coax to the balun and then ladder line, when used will yield no difference if you can load the transmitter to full power.     If your loading changes and/or the balun heats up, its not a good balun.   Nothing beats a good real balanced tuner but to build or buy one good enough for high power or AM duty cycles is not cheap if you don't have some parts on hand.



I COULD be wrong, but the baluns Clark has used are the built-in  baluns, and the ones on the OUTPUT of the tuna.

The ones where you float the tuna, and use a balun or choke on the INPUT of the tuna are a completely different ball game.

Using the tuna on the OUTPUT means your balun will NEVER see the same impedance.   Using it on the INPUT of the tuna means you ALWAYS have a conjugate match, and the balun can be built, designed and used as a 50 ohm to 50 ohm BalUn, not a BalUn that has 50 ohms on one side, and anywhere from a fraction of an ohm to megohms on the output, with additional losses factored in from the reactance (if) present.

Two completely different scenarios.  Also, using a balun on a REMOTE tuna, with a coaxial  coupling to it, and the tuna AT THE FEEDPOINT, the ferrite baluns tend to work a bit better, but not as good as a nice, short piece of coaxial cable to a tabletop tuna.

Just my .02.

--Shane
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« Reply #10 on: July 28, 2009, 03:29:44 PM »

Thats the balun I used.  6 ft of coax is nothing.  Most use runs from the shack to the balun mounted outside on the tower or wall ect..  So 20 to 30 ft of coax is common.  Why anyone, would run 6ft is beyond me.. I guess I understand why the Open wire line would not just to the balanced tuner at that point.

Cya

Clark

Using a piece of coax to the balun that is long means you have to factor in the loss of the balun and the coaxial cable.  If the tuner is NOT at the balun, your 'conjugate match' is going to be going THROUGH the balun.

If the balun is mounted with a short piece of coax, a balun on the INPUT of the tuner, rather than the output, the balun always sees 50 ohms on each side, and won't burn up.  Putting it at the OUTPUT of the tuner means the balun ALWAYS sees the complex impedance... And baluns DON'T work into a complex impedance (air core coaxial work best in this regard), run cool, and NOT generate harmonics.

THAT's the difference.

--Shane
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ke7trp
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« Reply #11 on: July 28, 2009, 03:38:26 PM »

I/we are talking about people using Open wire line dipole antennas with a balun and coax.  The balun is used to convert the open wire line to coax.  Then the Coax is run to the tuner(or transmitter with Pi net) inside the shack or like the other poster said, a short run. The balun will have loss and of course the coax will impose loss.  The difference can be astounding if you go to different bands.  On Joe's setup, It was the difference from him at 8 to 9 in the noise to 20DB over solid.  I guess its one of those things that someone will have to try back to back before they will believe it. Most hams will stick a balun in every place they can and they will fight long and hard to prove they need them. 

Cya

Clark
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Steve - WB3HUZ
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« Reply #12 on: July 28, 2009, 03:51:36 PM »

Some good info on the various losses here.

http://www.vk1od.net/balun/W2DU/index.htm


Even in the second scenario, the coax and the tuner accounted for far more loss than the balun.
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K3ZS
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« Reply #13 on: July 28, 2009, 03:57:43 PM »

Many people use a short piece of low loss coax to connect from a transmitter or tuner to a balun which is then connected to the main balanced feedline.   This is more for a practical physical setup than any other reason.   You don't want the ladder line running around among all the other wires and connections in the station.  If you look up the loss of 6 ft of low loss coax and the additional loss at a high  SWR in the handbooks you will see what I mean.     The baluns that are built into most of the tuners are crap, they are either lossy or have poor balance.   That is why I use an external balun now.    I plan on building a true balanced tuner for the lower bands.   But what I have now works fine from the performance I experience and signal reports received on all bands.

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kc6mcw
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« Reply #14 on: July 28, 2009, 04:06:21 PM »

If you are going to use a dipole on multiple bands, balanced line with a balanced tuner IS THE BEST SETUP! Do not even think of coax and a balun. I have put in 100's of hours testing the differences. I am not one for trusting what I hear or read. Coax is ONLY good in a 50 ohm environment. If you are happy with 9 s unit signals, then run coax. If you are interested in 20 over 9 signals, then do it right the first time. That statement only applies to using an antenna on multiple bands!


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K3ZS
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« Reply #15 on: July 28, 2009, 04:39:23 PM »

6 feet of RG-8 will not give you a 20 dB loss.    Even at 20:1 SWR at 30 MHz it will be around 1 dB, a lot less under most circumstances.     There seems to be confusion here between using a short coax to a balun and using coax as the feedline.    In what I have been saying, the feedline to the antenna is ladder line or window line, the only coax is between the tuner and external balun and it is short.
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KD6VXI
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« Reply #16 on: July 28, 2009, 05:48:31 PM »

I/we are talking about people using Open wire line dipole antennas with a balun and coax.  The balun is used to convert the open wire line to coax.  Then the Coax is run to the tuner(or transmitter with Pi net) inside the shack or like the other poster said, a short run. The balun will have loss and of course the coax will impose loss.  The difference can be astounding if you go to different bands.  On Joe's setup, It was the difference from him at 8 to 9 in the noise to 20DB over solid.  I guess its one of those things that someone will have to try back to back before they will believe it. Most hams will stick a balun in every place they can and they will fight long and hard to prove they need them. 

Cya

Clark

Try running from the transciever / transmitter to the balun, then the tuner, then ladder line to the antenna.

I betcha a 12 pack (or your home's AC for a week hehe) you won't see 20 dB difference between that and a Johnson matchbox..

Run the balun on the OUTPUT of the tuner, and it's a piece of crap, no matter the feedline length, even if you run ladder line to the antenna....  The balun will always see a variable impedance, and NOT work.

Hope that helped to clarify what I was trying to say.

--Shane
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W1AEX
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« Reply #17 on: July 28, 2009, 06:38:23 PM »

6 feet of RG-8 will not give you a 20 dB loss.

I would agree with K3ZS on this. With my 256 foot center-fed, I have run open wire feed lines right into the station and of course it does work fine on multiple bands. I have also run the open wire to an external balun and then run a 15 foot length of LMR-400 through a barrel connector installed under a window threshold to a T-match and it also works fine. No RF in the station, even at a kilowatt, no problems routing the coax past a computer and a TV. The balun does not get warm. The major telling factor is that a pair of RF ammeters mounted in-line with the open wire showed very little difference in current traveling to the antenna when compared to the open wire directly connected to the tuner. Readings from 160 - 40 meters showed very little difference between the two setups. A field strength meter on a step ladder across the yard told the same tale. To be honest, I think this is one of those purist arguments where neither side will be convinced by the other. I only know that at least from 160-40 the external transition balun works fine.

For the purists, you could use a multi-element setup with open wire. This would serve two purposes, it would theoretically keep losses lower through the coax run, and should keep the pattern cleaner on each band. Obviously, the absolute purist will have a dedicated coax fed antenna for each band, but then again, for me anyway, it's only a hobby!



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WA1GFZ
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« Reply #18 on: July 28, 2009, 07:19:27 PM »

consider the voltage ratings of the fixed loading caps before you think the pi network will tune a high Z
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ke7trp
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« Reply #19 on: July 28, 2009, 07:49:28 PM »

I think the missing link that is not being discussed is that with the open wire line, you are running a balanced tuner. With the coax and Balun, You are not.  The loss in the tuner is great. 

Its the same as running open wire line to a tuner with a BUILT in balun.  You still have huge losses now. 

To the original poster... My advice is to NOT rely on the Johnsons Pi net to match the antenna.  Its there but the components are small.  You are better off using the Johnson matchbox balanced tuner with your ladder line hooked to the back. Then the Tuner matches to your transmitter at 50 ohms.

I try to never use the Pi net to try to match loads out of any of my transmitters. I use them to match to a 1 to 1 50 ohm load.. For example.. Tune the Johnson into a 50 ohm load.  Tune the tuner so the readings are the same on the transmitter.

Clark
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Jerry-n5ugw
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« Reply #20 on: July 29, 2009, 07:18:56 AM »

Thanks for the discussion guys. I think I'll set up the Viker with both the MFJ-962c and Murch 2000B in series and run direct on one and use the other as a tuner. One has a roller inductor the other is fixed tapped and see which does a better job. I'm running a 15 foot peice of coax into the balun and that has the 450 ohm ladder line after the 4:1 balun. I am running out of my RV, which I work out of during the week. So antenna placement is not the best in the world. I'll check the heat at the Balun to see if I can detect any issues there. I did try running the 450 ohm ladder line into the murch once and I had RF in evrything inside the tin can RV. With the Coax not a problem. So we do what we can and live with it's results.
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K3ZS
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« Reply #21 on: July 29, 2009, 10:21:17 AM »

The balun I use on the output of my tuner is one that is designed for that purpose.   The blanket statement that baluns don't work in a "variable load", probably meaning a reactive load is just a well worn generalization.   The one made by DX Engineering (no I have no pecuniary interest here) for this purpose is made to hold up to 15 KV in its windings.     It uses large ferrites that have a 3:1 mismatch rating of 5KW of continous power.     If the ferrite is saturated it can produce harmonics.    If the reactance is high it can produce voltage breakdown.  These are the limitations of baluns, if you don't exceed limitations they will work as designed as W1AEX has shown.     With the length of my balanced line, balun and the short length of coax, I have a 3:1 SWR on 20, 17 and 10 meters without the tuner in line.    This would easily tunes up with my Ranger, without using the tuner.   On 80 and 40 the tuner is necessary.    On 160, using a 135 ft dipole and using a W2AU kilowatt balun, the balun heats up quickly and the loading changes rapidly.    I don't notice that with the DXE balun but in that case I am sure a balanced tuner would be much better anyway.    That is my $.02 and my experience.
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ke7trp
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« Reply #22 on: July 29, 2009, 11:04:18 AM »

Thanks for the discussion guys. I think I'll set up the Viker with both the MFJ-962c and Murch 2000B in series and run direct on one and use the other as a tuner. One has a roller inductor the other is fixed tapped and see which does a better job. I'm running a 15 foot peice of coax into the balun and that has the 450 ohm ladder line after the 4:1 balun. I am running out of my RV, which I work out of during the week. So antenna placement is not the best in the world. I'll check the heat at the Balun to see if I can detect any issues there. I did try running the 450 ohm ladder line into the murch once and I had RF in evrything inside the tin can RV. With the Coax not a problem. So we do what we can and live with it's results.

Good Deal Jerry.   Keep in mind that if you have RFI issues off the 450 ohm line your feedline is not the correct length.  450 ohm line is not going to radiate if its balanced and the length is correct.

A very common mistake made by hams.   The though process is that the ladder line is an antenna in the room..  THe coax, and balun is purchased to "move" the antenna outside. 

Clark

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« Reply #23 on: July 29, 2009, 11:16:23 AM »

The balun I use on the output of my tuner is one that is designed for that purpose.   The blanket statement that baluns don't work in a "variable load", probably meaning a reactive load is just a well worn generalization.   The one made by DX Engineering (no I have no pecuniary interest here) for this purpose is made to hold up to 15 KV in its windings.   

Check yahoo ham_amplifiers and find out just how good that balun can be when you use it at RATED output.

And as far as a blanket generalization, I put this to you.

My balun will NOT get hot at 50 ohms -j0.  It CRACKED and was nearly showing color (outside at night) when I tried to load it up with an unmatched (about 150 ohms antenna, with a LOT of reactance, capacitive if IIRC).

I never had this problem after putting the balun on the input of the tuner.  I tried it coaxial fed from about 100 feet of 9913 with a coaxial choke at the bottom of the balun.

I have no interest in any of the baluns.  They CAN be made to work, but they are NOT a cure-all... ESPECIALLY if you put the WRONG kind into the picture.

The BEST method of employing a balun is at the input of the tuner, and then run a tuner designed for ladder / balanced line.

The BEST method of matching would be a pi that could actually match balanced line out of the box...  or maybe a link coupled output, but I don't see that on much store bought equipment.

Hope that serves to clarify my point.  It wasn't heresey, it wasn't "a generalization" or anything else.

Incidentally, the balun cores (unmarked) where also used as a W2DU style balun at 10Kilowatts of carrier with no problem, so I DON'T think it was the wrong cores.  I have sent Walt a pic of the balun.

Just my experience, and that of thousands of amateurs around the world... Again, YMMV, IIRC, LOL, LMMFAO, etc., etc., etc.

--Shane
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ke7trp
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« Reply #24 on: July 29, 2009, 11:37:05 AM »

Agreeeeed. 

Its like the ham down the street..  He has 6 Baluns on his station and antennas.. I asked why?  He said, Cause I have run them for 20 years. Why?  He said. I was told you have too!

Clark
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