High SWR on 20 and 40

[djmd]

Hello,

I have been trying to troubleshoot my antenna system, and have been trying to avoid the dreaded "high swr" post, but I've run out of ideas, so I'm turning here.

First let me explain my system. 67' dipole fed by 16' of window line. That's connected to an Elecraft balun. From the balun, there's a short piece of coax going to a barrel and into the basement (through a piece of cement backerboard. From inside the basement, there is another piece of coax, about 12', connected to the barrel, and going up into the bedroom directly to a K2 with an autotuner.

Before the K2, I was using a Yaesu FT840 with an MFJ tuner. After tweaking the window line length and the actual length of the dipole, I never really had a problem with SWR (well, according to what the MFJ was saying, which may or may not be totally accurate.) Usually 1.5:1 or under on all bands.

With the K2/KAT2 in place, the SWR reported by the tuner is all over the place. The only one that gets less than 1.5:1 is 30m. Most bands are pretty random, anywhere from 3:1 to 7:1. However, on 20 and 40, it generally does not get below 9.9:1.

I've tried 4 different lengths of coax between the barrel (inside) and the rig... 3', 6', 12' 20'. I've tried a couple different lengths between the balun and the barrel on the outside.

When I attach the balun directly to the K2 I get <1.3:1 on all bands (most are 1:1.) With a short piece of coax between the rig and the balun, I get the same results. I've also attached my dummy load to the barrel on the outside of the house, and tested it from the shack, and I saw 1:1 no problem.

I totally understand the concept that if "A" works and "B" works, "A+B" doesn't necessarily work. I understand it's a whole system. But I've tried so many different combinations of coax on each side, and don't understand why my SWR is basically infinity:1 on 20 and 40, when they seemed to match reasonably with the old system. I have not tried different lengths of window line between the dipole due to the fact that I had it perfectly trimmed for my old system. But I have plenty of it and would be open to trying anything.

Just trying to get the most I can out of my modest 10W. :) Any suggestions would be appreciated!

73,

Dave
K8DJW

[Don Wilhelm-4]

Dave,

Is that a 1:1 balun or a 4:1 balun.  Usually a 1:1 works better, but
whichever balun you are using, try the other one and see what happens.
Do you have an antenna analyzer?  or can you borrow one?  If so, what is
the impedance at the end of the coax?  Both the resistive and reactive
components please - just the SWR does not provide much information on
how to advise you to proceed.

You may be better off eliminating the coax entirely and running the
window line all the way into the shack.
73,
Don W3FPR

djmd wrote:

> Hello,
>
> I have been trying to troubleshoot my antenna system, and have been trying
> to avoid the dreaded "high swr" post, but I've run out of ideas, so I'm
> turning here.
>
> First let me explain my system. 67' dipole fed by 16' of window line. That's
> connected to an Elecraft balun. From the balun, there's a short piece of
> coax going to a barrel and into the basement (through a piece of cement
> backerboard. From inside the basement, there is another piece of coax, about
> 12', connected to the barrel, and going up into the bedroom directly to a K2
> with an autotuner.
>
> Before the K2, I was using a Yaesu FT840 with an MFJ tuner. After tweaking
> the window line length and the actual length of the dipole, I never really
> had a problem with SWR (well, according to what the MFJ was saying, which
> may or may not be totally accurate.) Usually 1.5:1 or under on all bands.
>
> With the K2/KAT2 in place, the SWR reported by the tuner is all over the
> place. The only one that gets less than 1.5:1 is 30m. Most bands are pretty
> random, anywhere from 3:1 to 7:1. However, on 20 and 40, it generally does
> not get below 9.9:1.
>
> I've tried 4 different lengths of coax between the barrel (inside) and the
> rig... 3', 6', 12' 20'. I've tried a couple different lengths between the
> balun and the barrel on the outside.
>
> When I attach the balun directly to the K2 I get <1.3:1 on all bands (most
> are 1:1.) With a short piece of coax between the rig and the balun, I get
> the same results. I've also attached my dummy load to the barrel on the
> outside of the house, and tested it from the shack, and I saw 1:1 no
> problem.
>
> I totally understand the concept that if "A" works and "B" works, "A+B"
> doesn't necessarily work. I understand it's a whole system. But I've tried
> so many different combinations of coax on each side, and don't understand
> why my SWR is basically infinity:1 on 20 and 40, when they seemed to match
> reasonably with the old system. I have not tried different lengths of window
> line between the dipole due to the fact that I had it perfectly trimmed for
> my old system. But I have plenty of it and would be open to trying anything.
>
> Just trying to get the most I can out of my modest 10W. :) Any suggestions
> would be appreciated!
>
> 73,
>
> Dave
> K8DJW
>  
>  

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[n7ws]

I think he would be better off throwing away the window line and eliminating the tuner.  

Cut the length of the dipole for resonance on 40M and then add a 20M dipole in parallel at the feed point.  There will be some interaction, which can be lessened by orienting the dipoles at right angles to each other or at least getting some angular separation.

Conventional wisdom (not always correct) says to use a 1:1 current balun at the antenna.

With only 10W you don't want to be throwing it away in lossy tuners and mismatched transmission lines.

Wes  N7WS

ps. The only tuner I use in my shack is the pi-net in my L4-B.


--- On Fri, 1/15/10, Don Wilhelm <[hidden email]> wrote:

> From: Don Wilhelm <[hidden email]>
> Subject: Re: [Elecraft] [OT]  High SWR on 20 and 40
> To: "djmd" <[hidden email]>
> Cc: [hidden email]
> Date: Friday, January 15, 2010, 1:45 PM
> Dave,
>
> Is that a 1:1 balun or a 4:1 balun.  Usually a 1:1
> works better, but
> whichever balun you are using, try the other one and see
> what happens.
> Do you have an antenna analyzer?  or can you borrow
> one?  If so, what is
> the impedance at the end of the coax?  Both the
> resistive and reactive
> components please - just the SWR does not provide much
> information on
> how to advise you to proceed.
>
> You may be better off eliminating the coax entirely and
> running the
> window line all the way into the shack.
> 73,
> Don W3FPR
>
> djmd wrote:
> > Hello,
> >
> > I have been trying to troubleshoot my antenna system,
> and have been trying
> > to avoid the dreaded "high swr" post, but I've run out
> of ideas, so I'm
> > turning here.
> >
> > First let me explain my system. 67' dipole fed by 16'
> of window line. That's
> > connected to an Elecraft balun. From the balun,
> there's a short piece of
> > coax going to a barrel and into the basement (through
> a piece of cement
> > backerboard. From inside the basement, there is
> another piece of coax, about
> > 12', connected to the barrel, and going up into the
> bedroom directly to a K2
> > with an autotuner.
> >
> > Before the K2, I was using a Yaesu FT840 with an MFJ
> tuner. After tweaking
> > the window line length and the actual length of the
> dipole, I never really
> > had a problem with SWR (well, according to what the
> MFJ was saying, which
> > may or may not be totally accurate.) Usually 1.5:1 or
> under on all bands.
> >
> > With the K2/KAT2 in place, the SWR reported by the
> tuner is all over the
> > place. The only one that gets less than 1.5:1 is 30m.
> Most bands are pretty
> > random, anywhere from 3:1 to 7:1. However, on 20 and
> 40, it generally does
> > not get below 9.9:1.
> >
> > I've tried 4 different lengths of coax between the
> barrel (inside) and the
> > rig... 3', 6', 12' 20'. I've tried a couple different
> lengths between the
> > balun and the barrel on the outside.
> >
> > When I attach the balun directly to the K2 I get
> <1.3:1 on all bands (most
> > are 1:1.) With a short piece of coax between the rig
> and the balun, I get
> > the same results. I've also attached my dummy load to
> the barrel on the
> > outside of the house, and tested it from the shack,
> and I saw 1:1 no
> > problem.
> >
> > I totally understand the concept that if "A" works and
> "B" works, "A+B"
> > doesn't necessarily work. I understand it's a whole
> system. But I've tried
> > so many different combinations of coax on each side,
> and don't understand
> > why my SWR is basically infinity:1 on 20 and 40, when
> they seemed to match
> > reasonably with the old system. I have not tried
> different lengths of window
> > line between the dipole due to the fact that I had it
> perfectly trimmed for
> > my old system. But I have plenty of it and would be
> open to trying anything.
> >
> > Just trying to get the most I can out of my modest
> 10W. :) Any suggestions
> > would be appreciated!
> >
> > 73,
> >
> > Dave
> > K8DJW

     
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[djmd]

It's the BL-2 switched balun that I have been using, and have tried both modes. Forgot that detail. I have also tried one of those baluns built from PVC - can't remember the manufacturer. It's a 1:1 as well. Same results.

No analyzer yet, but I really should think about getting one. Planning on a lot of antenna experimentation this year.

I have actually thought of eliminating the coax. I'm not sure if I can use the same route as the coax, with the metal window frames, gas pipe, water pipes, all nearby in the basement. But what about going right through the brick? I would not be opposed to doing something like this.

And re: your follow up - all the testing was done with the KAT2. I have never disconnected it.

I also should have mentioned that I do plan on using this antenna system with my old radio as well. Only 10w on the K2, but 50 or so with the Yaesu as well. (mostly digital and CW.)

Don Wilhelm-4 wrote

Dave,

Is that a 1:1 balun or a 4:1 balun.  Usually a 1:1 works better, but
whichever balun you are using, try the other one and see what happens.
Do you have an antenna analyzer?  or can you borrow one?  If so, what is
the impedance at the end of the coax?  Both the resistive and reactive
components please - just the SWR does not provide much information on
how to advise you to proceed.

You may be better off eliminating the coax entirely and running the
window line all the way into the shack.
73,
Don W3FPR

djmd wrote:
> Hello,
>
> I have been trying to troubleshoot my antenna system, and have been trying
> to avoid the dreaded "high swr" post, but I've run out of ideas, so I'm
> turning here.
>
> First let me explain my system. 67' dipole fed by 16' of window line. That's
> connected to an Elecraft balun. From the balun, there's a short piece of
> coax going to a barrel and into the basement (through a piece of cement
> backerboard. From inside the basement, there is another piece of coax, about
> 12', connected to the barrel, and going up into the bedroom directly to a K2
> with an autotuner.
>
> Before the K2, I was using a Yaesu FT840 with an MFJ tuner. After tweaking
> the window line length and the actual length of the dipole, I never really
> had a problem with SWR (well, according to what the MFJ was saying, which
> may or may not be totally accurate.) Usually 1.5:1 or under on all bands.
>
> With the K2/KAT2 in place, the SWR reported by the tuner is all over the
> place. The only one that gets less than 1.5:1 is 30m. Most bands are pretty
> random, anywhere from 3:1 to 7:1. However, on 20 and 40, it generally does
> not get below 9.9:1.
>
> I've tried 4 different lengths of coax between the barrel (inside) and the
> rig... 3', 6', 12' 20'. I've tried a couple different lengths between the
> balun and the barrel on the outside.
>
> When I attach the balun directly to the K2 I get <1.3:1 on all bands (most
> are 1:1.) With a short piece of coax between the rig and the balun, I get
> the same results. I've also attached my dummy load to the barrel on the
> outside of the house, and tested it from the shack, and I saw 1:1 no
> problem.
>
> I totally understand the concept that if "A" works and "B" works, "A+B"
> doesn't necessarily work. I understand it's a whole system. But I've tried
> so many different combinations of coax on each side, and don't understand
> why my SWR is basically infinity:1 on 20 and 40, when they seemed to match
> reasonably with the old system. I have not tried different lengths of window
> line between the dipole due to the fact that I had it perfectly trimmed for
> my old system. But I have plenty of it and would be open to trying anything.
>
> Just trying to get the most I can out of my modest 10W. :) Any suggestions
> would be appreciated!
>
> 73,
>
> Dave
> K8DJW
>  
>  
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[djmd]

oh, and yes, I was definitely getting a 1:1 on the KAT2 between the radio and the dummy load. I put the dummy load in at all points and saw 1:1.

[Don Wilhelm-4]

Dave,

If you did not disconnect the KAT2, then please tell us the setup (all
the connections) when you have SWR readings below 1.5.
That may be capable of providing some sort of clue.

73,
Don W3FPR

djmd wrote:

>
> And re: your follow up - all the testing was done with the KAT2. I have
> never disconnected it.
>
>
>
>
>
> Don Wilhelm-4 wrote:
>  
>> Dave,
>>
>> Is that a 1:1 balun or a 4:1 balun.  Usually a 1:1 works better, but
>> whichever balun you are using, try the other one and see what happens.
>> Do you have an antenna analyzer?  or can you borrow one?  If so, what is
>> the impedance at the end of the coax?  Both the resistive and reactive
>> components please - just the SWR does not provide much information on
>> how to advise you to proceed.
>>
>> You may be better off eliminating the coax entirely and running the
>> window line all the way into the shack.
>> 73,
>> Don W3FPR
>>
>> djmd wrote:
>>    
>>> Hello,
>>>
>>> I have been trying to troubleshoot my antenna system, and have been
>>> trying
>>> to avoid the dreaded "high swr" post, but I've run out of ideas, so I'm
>>> turning here.
>>>
>>> First let me explain my system. 67' dipole fed by 16' of window line.
>>> That's
>>> connected to an Elecraft balun. From the balun, there's a short piece of
>>> coax going to a barrel and into the basement (through a piece of cement
>>> backerboard. From inside the basement, there is another piece of coax,
>>> about
>>> 12', connected to the barrel, and going up into the bedroom directly to a
>>> K2
>>> with an autotuner.
>>>
>>> Before the K2, I was using a Yaesu FT840 with an MFJ tuner. After
>>> tweaking
>>> the window line length and the actual length of the dipole, I never
>>> really
>>> had a problem with SWR (well, according to what the MFJ was saying, which
>>> may or may not be totally accurate.) Usually 1.5:1 or under on all bands.
>>>
>>> With the K2/KAT2 in place, the SWR reported by the tuner is all over the
>>> place. The only one that gets less than 1.5:1 is 30m. Most bands are
>>> pretty
>>> random, anywhere from 3:1 to 7:1. However, on 20 and 40, it generally
>>> does
>>> not get below 9.9:1.
>>>
>>> I've tried 4 different lengths of coax between the barrel (inside) and
>>> the
>>> rig... 3', 6', 12' 20'. I've tried a couple different lengths between the
>>> balun and the barrel on the outside.
>>>
>>> When I attach the balun directly to the K2 I get <1.3:1 on all bands
>>> (most
>>> are 1:1.) With a short piece of coax between the rig and the balun, I get
>>> the same results. I've also attached my dummy load to the barrel on the
>>> outside of the house, and tested it from the shack, and I saw 1:1 no
>>> problem.
>>>
>>> I totally understand the concept that if "A" works and "B" works, "A+B"
>>> doesn't necessarily work. I understand it's a whole system. But I've
>>> tried
>>> so many different combinations of coax on each side, and don't understand
>>> why my SWR is basically infinity:1 on 20 and 40, when they seemed to
>>> match
>>> reasonably with the old system. I have not tried different lengths of
>>> window
>>> line between the dipole due to the fact that I had it perfectly trimmed
>>> for
>>> my old system. But I have plenty of it and would be open to trying
>>> anything.
>>>
>>> Just trying to get the most I can out of my modest 10W. :) Any
>>> suggestions
>>> would be appreciated!
>>>
>>> 73,
>>>
>>> Dave
>>> K8DJW
>>>  
>>>  
>>>      
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>>
>>    
>
>  
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[djmd]

Thanks Don. There are multiple scenarios.

1) K2  -  BL2  -  windowline  -  dipole

2) K2  -  2' Mini-RG8  -  BL2  -  windowline  -  dipole

3) K2  -  10' RG8  -  BL2  -  windowline  -  dipole

All coax is terminated PL-259, so there are BNC-SO239 adapters at the K2 and Balun.

Where the system starts to fail is when I go from the K2, through any length of coax, into a 4" barrel  (entry point) , then to another short piece of coax between the barrel and the balun. The only sort of testing I've done through this barrel (it's going through cement backerboard) is attaching an MFJ dummy load in place of the balun.

K2 - 10' RG8 - 4" barrel - 2' RG8 - Dummy Load

That's where I saw the 1:1 across the bands from the K2/KAT2. I suppose that may not be a good enough test to give this part of the system a "thumbs up," but it's all I got at this point.  

With the system in place right now (K2 - coax - barrel - coax - balun - antenna) here's what I'm seeing on the KAT2 with the power set to 2.0w.

80m  8.3:1
40m  9.9:1
30m  1.3:1
20m  9.9:1
17m  6.3:1
15m  2.2:1
12m  1.0:1
10m  1.0:1

[djmd]

Just one more quick note tonight. I put the W1 inline, and in most cases it's reporting much higher SWRs than the KAT2 is. Particularly those 1:1s in the high bands... the W1 is reporting >5.

I also attached the W1 between the K2 and the KAT2, and it none of the SWR LEDs light up; I'm assuming this is to mean 1:1.

So, I'm a tad more confused now... but starting to think that it is indeed a KAT2 issue.

[Guy, K2AV]

The 16 feet of window line makes me wonder if you're not trying to do
a half-size G5RV, but got the top dimensions wrong.  It would be 51'
(instead of 67 which is REALLY bad on 20 meters), or a little longer,
say 54' if you wanted to load on 17m and 12m.

My K2/10 and the auto tuner will match most anything, but your lengths
are not anything I would do on purpose for multiband  : >)

On Fri, Jan 15, 2010 at 7:49 PM, Don Wilhelm <[hidden email]> wrote:

> Dave,
>
> If you did not disconnect the KAT2, then please tell us the setup (all
> the connections) when you have SWR readings below 1.5.
> That may be capable of providing some sort of clue.
>
> 73,
> Don W3FPR
>
> djmd wrote:
>>
>> And re: your follow up - all the testing was done with the KAT2. I have
>> never disconnected it.
>>
>>
>>
>>
>>
>> Don Wilhelm-4 wrote:
>>
>>> Dave,
>>>
>>> Is that a 1:1 balun or a 4:1 balun.  Usually a 1:1 works better, but
>>> whichever balun you are using, try the other one and see what happens.
>>> Do you have an antenna analyzer?  or can you borrow one?  If so, what is
>>> the impedance at the end of the coax?  Both the resistive and reactive
>>> components please - just the SWR does not provide much information on
>>> how to advise you to proceed.
>>>
>>> You may be better off eliminating the coax entirely and running the
>>> window line all the way into the shack.
>>> 73,
>>> Don W3FPR
>>>
>>> djmd wrote:
>>>
>>>> Hello,
>>>>
>>>> I have been trying to troubleshoot my antenna system, and have been
>>>> trying
>>>> to avoid the dreaded "high swr" post, but I've run out of ideas, so I'm
>>>> turning here.
>>>>
>>>> First let me explain my system. 67' dipole fed by 16' of window line.
>>>> That's
>>>> connected to an Elecraft balun. From the balun, there's a short piece of
>>>> coax going to a barrel and into the basement (through a piece of cement
>>>> backerboard. From inside the basement, there is another piece of coax,
>>>> about
>>>> 12', connected to the barrel, and going up into the bedroom directly to a
>>>> K2
>>>> with an autotuner.
>>>>
>>>> Before the K2, I was using a Yaesu FT840 with an MFJ tuner. After
>>>> tweaking
>>>> the window line length and the actual length of the dipole, I never
>>>> really
>>>> had a problem with SWR (well, according to what the MFJ was saying, which
>>>> may or may not be totally accurate.) Usually 1.5:1 or under on all bands.
>>>>
>>>> With the K2/KAT2 in place, the SWR reported by the tuner is all over the
>>>> place. The only one that gets less than 1.5:1 is 30m. Most bands are
>>>> pretty
>>>> random, anywhere from 3:1 to 7:1. However, on 20 and 40, it generally
>>>> does
>>>> not get below 9.9:1.
>>>>
>>>> I've tried 4 different lengths of coax between the barrel (inside) and
>>>> the
>>>> rig... 3', 6', 12' 20'. I've tried a couple different lengths between the
>>>> balun and the barrel on the outside.
>>>>
>>>> When I attach the balun directly to the K2 I get <1.3:1 on all bands
>>>> (most
>>>> are 1:1.) With a short piece of coax between the rig and the balun, I get
>>>> the same results. I've also attached my dummy load to the barrel on the
>>>> outside of the house, and tested it from the shack, and I saw 1:1 no
>>>> problem.
>>>>
>>>> I totally understand the concept that if "A" works and "B" works, "A+B"
>>>> doesn't necessarily work. I understand it's a whole system. But I've
>>>> tried
>>>> so many different combinations of coax on each side, and don't understand
>>>> why my SWR is basically infinity:1 on 20 and 40, when they seemed to
>>>> match
>>>> reasonably with the old system. I have not tried different lengths of
>>>> window
>>>> line between the dipole due to the fact that I had it perfectly trimmed
>>>> for
>>>> my old system. But I have plenty of it and would be open to trying
>>>> anything.
>>>>
>>>> Just trying to get the most I can out of my modest 10W. :) Any
>>>> suggestions
>>>> would be appreciated!
>>>>
>>>> 73,
>>>>
>>>> Dave
>>>> K8DJW
>>>>
>>>>
>>>>
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>>
>>>
>>
>>
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>>
>>
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>> Checked by AVG - www.avg.com
>> Version: 9.0.725 / Virus Database: 270.14.142/2623 - Release Date: 01/15/10 02:35:00
>>
>>
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[djmd]

Thanks for the input Guy,

Actually, the lengths are just a result of me trying to get this antenna optimized for 40m with my Yaesu 840 and the MFJ unbalanced tuner. This is my first HF antenna, and I never intended for it to be a true multibander. And yes - it never performed well on 20m at all. I live on a small lot and can't get anything too high, so it was just a means to get on the air. It did well on 40m and 30m with the old setup, so more than anything, I am curious why the K2/KAT2 can't seem to tune it up on 40.

40/30/20 is all I'm interested in right now, so perhaps the half G5RV might be something I should explore?! I certainly would not be opposed to lopping 8 feet off each end of this antenna.

Thanks again!

Dave

Guy, K2AV wrote

The 16 feet of window line makes me wonder if you're not trying to do
a half-size G5RV, but got the top dimensions wrong.  

[Julius Fazekas n2wn]

Dave,

Have you tried putting a dummy load in line and seeing if the tuner will tune 1:1 with it?

This might tell you if the problem is in the tuner. You could also place the load further along the coax and see if the problem disappears.

My KAT2 can tune almost anything it seems, but it is possible that your bridge diodes got zapped and that would cause problems.

73,
Julius
n2wn

djmd wrote

Hello,

I have been trying to troubleshoot my antenna system, and have been trying to avoid the dreaded "high swr" post, but I've run out of ideas, so I'm turning here.

First let me explain my system. 67' dipole fed by 16' of window line. That's connected to an Elecraft balun. From the balun, there's a short piece of coax going to a barrel and into the basement (through a piece of cement backerboard. From inside the basement, there is another piece of coax, about 12', connected to the barrel, and going up into the bedroom directly to a K2 with an autotuner.

Before the K2, I was using a Yaesu FT840 with an MFJ tuner. After tweaking the window line length and the actual length of the dipole, I never really had a problem with SWR (well, according to what the MFJ was saying, which may or may not be totally accurate.) Usually 1.5:1 or under on all bands.

With the K2/KAT2 in place, the SWR reported by the tuner is all over the place. The only one that gets less than 1.5:1 is 30m. Most bands are pretty random, anywhere from 3:1 to 7:1. However, on 20 and 40, it generally does not get below 9.9:1.

I've tried 4 different lengths of coax between the barrel (inside) and the rig... 3', 6', 12' 20'. I've tried a couple different lengths between the balun and the barrel on the outside.

When I attach the balun directly to the K2 I get <1.3:1 on all bands (most are 1:1.) With a short piece of coax between the rig and the balun, I get the same results. I've also attached my dummy load to the barrel on the outside of the house, and tested it from the shack, and I saw 1:1 no problem.

I totally understand the concept that if "A" works and "B" works, "A+B" doesn't necessarily work. I understand it's a whole system. But I've tried so many different combinations of coax on each side, and don't understand why my SWR is basically infinity:1 on 20 and 40, when they seemed to match reasonably with the old system. I have not tried different lengths of window line between the dipole due to the fact that I had it perfectly trimmed for my old system. But I have plenty of it and would be open to trying anything.

Just trying to get the most I can out of my modest 10W. :) Any suggestions would be appreciated!

73,

Dave
K8DJW