High SWR on 20 and 40

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High SWR on 20 and 40

Daniel Paul Perez
Dave,

     Thanks for posting this.

      I'm going through the exact same exercise with my KX-1 KXAT1 and
Icom703+.  Glad to know I'm not alone.  The Icom is able to tune just
fine and when I switch the KX1 does not tune all bands – not on 40M.
The KX1 tuner is optimized for shorter lengths of wire.  I too wanted to
use one antenna for both radios.  I wonder if the K2 is optimized for a
shorter wire?  I find the more coax I insert between the 4:1 balun and
radio the better the Icom tunes and performs and the opposite for the
Elecraft -- it then loses 80, 40, 30 and barely tunes 20.  It’s really
odd.  I get perfect SWR with a dummy load and KX1.

     I'll try a few things over the next few days per Elecraft.  But
will be very interested in what you find.  Is the window ladder line 450
ohm?

     Does Elecraft give guidance on how the tuners are optimized?
Eighth to quarter wavelength?

     I want to be sure as you do that the max power goes out.

     Best,

Daniel ad1p

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Re: High SWR on 20 and 40

Daniel Paul Perez

Dave,

     Thanks for posting this.

      I'm going through the exact same exercise with my KX-1 KXAT1 and
Icom703+.  Glad to know I'm not alone.  The Icom is able to tune just
fine and when I switch the KX1 does not tune all bands – not on 40M.
The KX1 tuner is optimized for shorter lengths of wire.  I too wanted to
use one antenna for both radios.  I wonder if the K2 is optimized for a
shorter wire?  I find the more coax I insert between the 4:1 balun and
radio the better the Icom tunes and performs and the opposite for the
Elecraft -- it then loses 80, 40, 30 and barely tunes 20.  It’s really
odd.  I get perfect SWR with a dummy load and KX1.

     I'll try a few things over the next few days per Elecraft.  But
will be very interested in what you find.  Is the window ladder line 450
ohm?

     Does Elecraft give guidance on how the tuners are optimized?
Eighth to quarter wavelength?

     I want to be sure as you do that the max power goes out.

     Best,

Daniel ad1p



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Re: High SWR on 20 and 40

djmd
In reply to this post by Daniel Paul Perez
Hi Daniel!

I too have a KX1/AT1, and in fact, noticed this issue on the KX1 before I was even done building the K2. I just hooked the KX1 back up, and I'm getting nearly the same results.

40m 8.1:1
30m 1.3:1
20m infinity:1

It's been a while since I've used it outside, but I used to hook it up directly to the dipole through the BL2 balun and I could get a great match on 40m and 30m.

I am buying an antenna analyzer today. Not necessarily because I think it will solve this problem (if it does, that's great!) but I'm long overdue for one.

73,

K8DJW

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Re: High SWR on 20 and 40

Don Wilhelm-4
Dave,

It is of great interest that your KX1 tuner could handle the tuning if
you connected it directly to the balun.  Fact is that the KXAT1 range is
quite limited due to only having 3 inductors and 3 capacitors to switch
in and out trying to find a match - the KAT2 has 8 of each and has quite
a wide range.

What is the chance that you have a bad piece of coax or a bad barrel
adapter in the coax line?  Has your coax outside gotten water inside
it?  That is certainly a possibility if you did not seal the connectors
- low loss foam coax can soak up a lot of water.
Do you have a bad balun? (I had one that got water soaked this summer
and quit on me giving high SWR indications).
You might want to try a new length of coax without the balun - connect
the coax directly to the ladder line.  If that works, try adding back
the balun, then add the original coax   At some point, you will identify
what is failing.

73,
Don W3FPR

djmd wrote:

> Hi Daniel!
>
> I too have a KX1/AT1, and in fact, noticed this issue on the KX1 before I
> was even done building the K2. I just hooked the KX1 back up, and I'm
> getting nearly the same results.
>
> 40m 8.1:1
> 30m 1.3:1
> 20m infinity:1
>
> It's been a while since I've used it outside, but I used to hook it up
> directly to the dipole through the BL2 balun and I could get a great match
> on 40m and 30m.
>
> I am buying an antenna analyzer today. Not necessarily because I think it
> will solve this problem (if it does, that's great!) but I'm long overdue for
> one.
>
> 73,
>
> K8DJW
>
>
>  
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
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>  
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Re: High SWR on 20 and 40

w7aqk
In reply to this post by Daniel Paul Perez
Hi Daniel and all,

I have all four Elecraft rigs, including internal ATU's.  The ATU in the KX1
is the least effective of all of them.  While my K2 and K3 ATU's can tune my
R7, which is optomized for around 7130 khz on  40 meters, to nearly "flat"
on each end of the band (the R7 has fairly sharp tuning on 40 meters), the
KX1 ATU struggles at each end of the band.  I've borrowed a 2nd KX1, and
gotten much the same result, so I don't think it is just my particular ATU.

In such a small package, it's not hard to understand why the KX1 ATU might
not be nearly as versatile.  The ATU in the K3 is the best of any internal
ATU I've ever had.  The K2 ATU is also quite good.  The ATU in my K1 does a
"fair" job, but I've always been somewhat suspect that I might have a small
problem with that ATU.  Occasionally it acts like it doesn't want to
activate.

Since my R7 on 40 meters seems to be a good application for an ATU when
doing wide excursions on the band, maybe it would be interesting to see (and
plot) how each rig's ATU performs across the band.  It's also interesting
(to me at least) that my K3 ATU will tune the R7 on 80 meters.  The K2 might
do that, but I haven't tried it.  Obviously the R7 is very inefficient on
75/80, but at least the radio seems happy.

The bottom line for me is that the KX1 ATU is useful, but not very wide
ranging.  It may work better on some other types of antennas.  I'm glad I
have it, but some situations probably require an outboard unit that is more
versatile.  Since I use balanced feedline type antennas a lot when I am
portable, I usually have an outboard tuner for that reason.  I really like
"Z" match tuners for QRP use.  The NorCal BLT is a good one too.

Dave W7AQK


----- Original Message -----
From: "Daniel Paul Perez" <[hidden email]>
To: <[hidden email]>
Sent: Friday, January 15, 2010 10:02 PM
Subject: Re: [Elecraft] [OT] High SWR on 20 and 40



Dave,

     Thanks for posting this.

      I'm going through the exact same exercise with my KX-1 KXAT1 and
Icom703+.  Glad to know I'm not alone.  The Icom is able to tune just
fine and when I switch the KX1 does not tune all bands – not on 40M.
The KX1 tuner is optimized for shorter lengths of wire.  I too wanted to
use one antenna for both radios.  I wonder if the K2 is optimized for a
shorter wire?  I find the more coax I insert between the 4:1 balun and
radio the better the Icom tunes and performs and the opposite for the
Elecraft -- it then loses 80, 40, 30 and barely tunes 20.  It’s really
odd.  I get perfect SWR with a dummy load and KX1.

     I'll try a few things over the next few days per Elecraft.  But
will be very interested in what you find.  Is the window ladder line 450
ohm?

     Does Elecraft give guidance on how the tuners are optimized?
Eighth to quarter wavelength?

     I want to be sure as you do that the max power goes out.

     Best,

Daniel ad1p



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Re: High SWR on 20 and 40

Don Wilhelm-4
Dave and all,

Are you aware that you can use both tuners "in tandem"?  You can set the
manual tuner quickly for a close match and then let the internal tuner
refine the match.

For instance, you have an antenna that is difficult to match, but you
already have a list of setting for a close match (less than 3:1) on the
manual tuner for that antenna - just turn to those settings and then let
the KX1, K1, K2, K3 tuner clean up for a very ow SWR.

73,
Don W3FPR

> The bottom line for me is that the KX1 ATU is useful, but not very wide
> ranging.  It may work better on some other types of antennas.  I'm glad I
> have it, but some situations probably require an outboard unit that is more
> versatile.  Since I use balanced feedline type antennas a lot when I am
> portable, I usually have an outboard tuner for that reason.  I really like
> "Z" match tuners for QRP use.  The NorCal BLT is a good one too.
>
> Dave W7AQK
>  
>
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Re: High SWR on 20 and 40

alsopb
Of course two tuners doubles the tuner losses.  Tuner losses amount to
10 to 15% per tuner, sometimes higher.  If you're not folding back power
after the first tuner does its match and it's under about 1.8, don't
bother.  There is nothing real to be gained.

If you need both tuners, the real need is for a better matched antenna
or a single tuner with a wider matching range.

73 de Brian/K3KO


Don Wilhelm wrote:

> Dave and all,
>
> Are you aware that you can use both tuners "in tandem"?  You can set the
> manual tuner quickly for a close match and then let the internal tuner
> refine the match.
>
> For instance, you have an antenna that is difficult to match, but you
> already have a list of setting for a close match (less than 3:1) on the
> manual tuner for that antenna - just turn to those settings and then let
> the KX1, K1, K2, K3 tuner clean up for a very ow SWR.
>
> 73,
> Don W3FPR
>
>> The bottom line for me is that the KX1 ATU is useful, but not very wide
>> ranging.  It may work better on some other types of antennas.  I'm glad I
>> have it, but some situations probably require an outboard unit that is more
>> versatile.  Since I use balanced feedline type antennas a lot when I am
>> portable, I usually have an outboard tuner for that reason.  I really like
>> "Z" match tuners for QRP use.  The NorCal BLT is a good one too.
>>
>> Dave W7AQK
>>  
>>
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Re: High SWR on 20 and 40

Jim AB3CV
There is one benefit to a low match at the tranceiver. Most builtin power
meters are only accurate at 1:1. If you're trying to ensure you are "qrp"
and your transmitter measures output power to maintain that level you need
to ensure the match is correct.

jim ab3cv
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Re: High SWR on 20 and 40

Don Wilhelm-4
In reply to this post by alsopb
Brian,

While all that is true, the operating convenience that is afforded by
using that method can be more significant than the added loss - it all
depends...

An L network usually is a low loss tuner.  All the Elecraft tuners are
of the L network type, as are many other 'auto-tuners'
The old link coupled tuners such as the Johnson Matchbox are also very
low loss.  The popular "T" networks can be very bad with multiple
matching points, but they do have a very large range and bandswitch easily.

Using a manual tuner to bring the SWR on a difficult to feed antenna
down to a reasonable level and then refining the match with an internal
auto-tuner provides the same convenience as operating with only the
autotuner - and the manual tuner can be in a remote location.  After
all, matching networks at an antenna can be thought of as "manual tuner"
whose tuning is not changed - it brings the impedance down to a level
where it can be easily fed with coax, and a tuner in the shack provides
the final match required for large excursions across the band.

Yes, at HF, an SWR of 2:1 or less does not increase the coax loss enough
to be significant.  At VHF and UHF it does make a difference because the
additional loss caused by SWR grows as the matched line loss increases,
and matched line losses increase with increasing frequency.

73,
Don W3FPR

Brian Alsop wrote:

> Of course two tuners doubles the tuner losses.  Tuner losses amount to
> 10 to 15% per tuner, sometimes higher.  If you're not folding back power
> after the first tuner does its match and it's under about 1.8, don't
> bother.  There is nothing real to be gained.
>
> If you need both tuners, the real need is for a better matched antenna
> or a single tuner with a wider matching range.
>
> 73 de Brian/K3KO
>
>
> Don Wilhelm wrote:
>  
>> Dave and all,
>>
>> Are you aware that you can use both tuners "in tandem"?  You can set the
>> manual tuner quickly for a close match and then let the internal tuner
>> refine the match.
>>
>> For instance, you have an antenna that is difficult to match, but you
>> already have a list of setting for a close match (less than 3:1) on the
>> manual tuner for that antenna - just turn to those settings and then let
>> the KX1, K1, K2, K3 tuner clean up for a very ow SWR.
>>
>> 73,
>> Don W3FPR
>>
>>    
>>> The bottom line for me is that the KX1 ATU is useful, but not very wide
>>> ranging.  It may work better on some other types of antennas.  I'm glad I
>>> have it, but some situations probably require an outboard unit that is more
>>> versatile.  Since I use balanced feedline type antennas a lot when I am
>>> portable, I usually have an outboard tuner for that reason.  I really like
>>> "Z" match tuners for QRP use.  The NorCal BLT is a good one too.
>>>
>>> Dave W7AQK
>>>  
>>>
>>>      
>> ______________________________________________________________
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>>
>>    
>
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Re: High SWR on 20 and 40

Guy, K2AV
In reply to this post by Jim AB3CV
There are many kinds and configurations of tuners, each one having
differing weak spots.  There is not a single one outside of military
prices which does not have impedance ranges that are inappropriate for
the particular tuner design.  Some tuners use CONTINUOUSLY variable
inductors AND capacitors to get around most of those "blind spots" but
there will still be matching points where it can't be brought down.
Often where circulating currents in that particular design MUST become
so high as to destroy components or waste half the power or more .

You can fit a hundred KX1's inside of the case of many tuners, so in
the KX1, the overriding issue is to use a design that CAN be
MINIATURIZED. That you have an auto tuner AT ALL in a KX1 is already
on the wonderful side of remarkable.  To criticize it for not having
the range of a larger tuner with continuously variable components
seems unfairly critical to an extreme.

Tuners designed with switched components necessarily have a "lumpy"
performance but are the only method that can be made small enough for
internal use in a K2 or KX1, etc. None of these that I have seen will
deal with 1000+ ohm loads.

But the real root of the calling these no-match ranges a "problem"
seems a lacking in basic antenna understanding.  ANY wire with ANY
feedpoint will have harmonically related frequency ranges where the
feed impedance can go into the thousands of ohms. If you have put up a
wire antenna for all band use and haven't MEASURED what these are for
your antenna on intended frequencies of use, you are quite short of
putting forward a reasonable case for a tuner not working or having
poor design.

Loading any antenna to all ham bands in any location with any
miscellaneous conductors around REMAINS a very sticky problem.  For
sure, NOT among god-given rights, is that any auto-tuner in any rig
(including a KX1) must able to tune ANY antenna to ALL bands in any
circumstance and provide a 1:1 SWR.

There is an antenna, manufactured for decades by B&W, that is a folded
dipole with with a feedline on one wire at the center, and a high
power RF termination resistor on the other wire at center.  The
termination resistor prevents the nodes of very high feed Z, reducing
the range of Z extremes to values easily matched across the spectrum.

There are tens of thousands of these antennas in use over the world at
military sites, embassies and other installations where frequency
agility is important, particularly in spread-spectrum modes. The
"wasted" watts on certain frequency ranges are made up for by removing
the high-Z nodes at the feedpoint. That this is an entirely successful
approach and design fulfilling a continuing need is proven by
continued sales to this day.

Designing a single antenna that does not have Hi-Z nodes on
wide-spread wanted frequencies is a pastime that goes back to the dawn
of radio, and continues to this day.  G5RV's, 86 and 43 foot end-fed
wires, off-center fed dipoles, are but a few of the answers, and each
has characteristics here or there that make it unusable or less
desireable in a given circumstance.

If you can't match it, START WITH THE ANTENNA, THEN THE FEEDLINE.
Random collections of elevated wire and feedline usually DON'T work
everywhere. But if it doesn't work and you don't get it, you have a
challenging and possibly highly entertaining education in front of
you.  Something like learning to play chess.  Join the century-old
society of antenna designers and tinkerers going back to Marconi and
beyond.

Dumping it on tuner manufactures is just so ......

Never mind.

73, Guy.
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Re: High SWR on 20 and 40

James Duffey
In reply to this post by Daniel Paul Perez
Dave - If an antenna suddenly changes its behavior, the cause is usually a broken connection somewhere, or a problem with the feedline, either shorted or open. So check these all first. It is easy for there to be a break in the ladder line, particularly if it uses a solid conductor that is hard to detect. Use an ohm metro from one end to the other. You should also look at the antenna with and without the balun (1:1) position) in place, the tuning shouldn't change a whole lot. If it does, look at the balun construction for a poor connection or bad solder joint. An antenna analyzer is a big help here, if you don't have one, I am sure that you can borrow one if you ask at a club meeting or speak up on the local repeater.

Having said that, if everything is in good shape, the first thing I suggest that you do is to model the antennas and transmission line and see what impedances you can expect to see where. This will help you understand what to do to match the antenna or where there are problems. Otherwise you are pretty much flying blind.

Get a good antenna modeling program, something like EZNEC, even the trial demo version will work for your case:

< http://www.eznec.com/ >

MMANA will work too and is free:

< http://www.smeter.net/antennas/mmana.php >

Model your antenna. You should see a reasonably low impedance on 80M, a high impedance on 40M, a moderate impedance on 30M, a high impedance on 20M, and well you should really do the modeling to get precise values. You will probably see a lot of loss on 80M as the antenna appears to be less than 0.1 wavelengths high. Anyway, record these values on the different bands.

The 16 ft of ladder line acts as a transformer to transform the impedance. You can calculate what the transformation will be with transmission line program; TLW is included with the Antenna Book and is good; W9CF has a nice java based app on the web:

< http://fermi.la.asu.edu/w9cf/tran/ >

which you can also download and run locally. It is nice as it runs on any machine that runs Java. You can also see how to do the transformations by hand in the Antenna Book.

Now, enter the antenna impedance values into the transmission line program and see where they get transformed. You will need to do this twice, once for the antenna - ladder line - coax run and once for the balun - coax - tuner run. Use the balun at 1:1 for the time being. You should try to borrow an antenna analyzer to verify your calculations, although with the high impedances the analyzer may not give too useful results.

None of these will be exact, but they should be in the ball park and give you an idea of what you should be doing to get a match.

This procedure will tell you what impedance you are expecting the tuners to tune. My guess is that it is within the range of your tuners and that you have a problem elsewhere, but do the math. If the impedance is outside the range you are expecting to tune, then you can change antenna or transmission line lengths until you get a match that is acceptable. That is far better than cutting and adding line and antenna lengths without an idea of what to expect.

The 16 ft of ladder line will have different effects on different bands. On 80M the electrical length of the transmission line will be small and you won't see much transformation. It is pretty much equivalent to lengthening the antenna. You should still see a low to moderate impedance here that the tuner is capable of matching. On 40M you will see more effect, but I suspect that the impedance will still be very high, perhaps too high for the tuner to match. On 20M the line length is a quarter wave, which should transform the high antenna impedance to a low to moderate impedance which the tuner can match easily.

The K-2 is pretty portable so you could try hooking it up to the antenna at the various junctions and see what happens. You should be able to get a match on 20M at the end of the ladder line. Try it with and without the balun in the 1:1 position. If that doesn't work, I suspect that you have problem in the K2 tuner or SWR circuit. You should be able to get an acceptable match with or without the balun, it won't be the same, but it should be close. You may or may not get a match here on 40M with the 1:1 balun, but you should get one with the 4:1 balun.

While the first thing I Would do is look for shorts or opens or bad connections in the system, you should probably read the Antenna Book chapter on transmission lines to get a feel for what is happening to the impedance at the various transmission line junctions.

Having encouraged you to measure and model, my gut feel is that you should be able to match this system with the K2 tuner and the 4:1 balun on all bands above 80M. I suspect that you have a problem in the antenna feedline and connections somewhere.

Let us know how this all works out and if you have further questions, feel free to ask. - Duffey
--
KK6MC
James Duffey
Cedar Crest NM





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Re: High SWR on 20 and 40

djmd
Hi James,

Thanks so much for the extremely informative reply! I will dig deep into a lot of your suggestions later tonight. I think I may have overcomplicated the issue, so let me see if I can give it a shakedown.

First off, lets forget everything besides 40m. That's really the band I am concerned with first and foremost.

Before Elecraft came into my life, I was using a Yaesu FT840 with an MFJ941E tuner. Coax (10' or so) out of the tuner, through the floor, into a barrel that goes through cementboard to the outside. From there, short coax up to a W2DU 4:1 current balun. Then 16' or so of windowline, and the dipole up about 20', about 67' long. I have a very restricted yard for antennas and just wanted to get on the air.

Anyway, after some poking and prodding I was able to consistently tune up on 40m fairly well, 1.5 or less. I made several CW contacts across the country as well as Canada and South America.

Then I built the KX1 with the autotuner, and was not able to get under 5:1 from the same point with all the same components in place. No big deal, I didn't intend on using the KX1 in the 'shack' anyway. But then I built the K2/KAT2, and was getting pretty much the same result. As it stands right now, I cannot break below 9.9:1 on the KAT2 on 40m from the shack. I've tried different coax types and lengths on each side of the barrel and have seen no improvement. Also, it doesn't matter which balun I use, or whether I select 1:1 or 4:1 on the BL2. Results are the same.

Now, when I attach the K2 directly to the balun (now an Elecraft BL2) I can get a great match on 40m. As I can add a very short piece between the K2 and the balun with no ill effect, but once the coax is longer than about 5', the SWR shoots up.

I picked up an analyzer today (259B). It's my first one, and I hardly know what I'm doing, but I can tell you right off the bat that whether I attach it to the coax in the shack, or directly to the balun, it's appearing to be resonant at the same 3 places. Around 10mhz, 20mhz, and 26mhz. If there is any other information you would like to know from the analyzer at any specific frequency and connnection point, please let me know.

I hope this helps... I sincerely appreciate everyone's assistance. I'm still learning and it's nice to have a place to get good info and not made to feel like I'm an idiot.




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Re: High SWR on 20 and 40

Mike WA8BXN

 
 
It sounds like you have a broken/shorted wire somewhere. For testing, could
You run coax all the way to the antenna and see how that does? If you
Antenna is insulated wire, don't overlook the possibility of a break in the
Antenna itself. With 67 feet of wire, you should get a fairly decent match
 
 
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Re: High SWR on 20 and 40

Don Wilhelm-4
In reply to this post by djmd
Dave,

No, you are not an idiot, nor drunk, but you may be confused by the
impedance transformation effects of a feedline.
I suggest you take a look at the ARRL Handbook or Antenna Book chapter
on Transmission Lines, especially the sections dealing with transmission
line matching sections if you want an understanding of what is going on.

The most common feedline matching section used by radio amateurs is the
quarter wavelength section - that one is relatively easy to understand
and the math is not complex.  The underlying mechanism is that a low
impedance at one end will transform to a high impedance at the other
end.  For example, if a 50 ohm electrical quarter wave of coax is used
and one end is connected to a 100 ohm load, the other end will have the
equivalent of a 25 ohm load - and if the far end of that same coax is
shorted, it will have a very high impedance (theoretically infinity, but
practically >4000 ohms) at the near end

Any length of feedline (and any impedance feedline) that is not matched
in its characteristic impedance at the load will act as an impedance
transformer.

It is nice to know the resonance points for your antenna system, but
what is really needed is the impedance (both resistive and reactive) at
the desired frequencies of operation.  If we knew all your feedline
parameters (type, velocity factor, precise length, etc) we could likely
compute the impedance at any other frequency, but it is easier to just
measure it since your MFJ259 provides you with a tool to do exactly that.

There is no impedance transformation on a transmission line (of any
length) at the points where the antenna is matched to that line - that
is the situation at your "resonance" points if you only looked at the
SWR to determine resonance.  The actual resonance point of the antenna
*system* is where the reactance goes to zero (or very low as indicated
on the MFJ259) - then at the resonance points you would look at the
resistive component - it is not likely to be 50 ohms.

One other piece of information that may help your 40 meter situation is
based on the fact that you can use the tuner successfully at the balun
location - and that is that an electrical half wavelength of
transmission line will repeat the impedance at each end - so if you
connect a total of a  half wavelength  transmission line between the
tuner and the balun, the tuner will tune it.  A 40 meter electrical half
wave of solid dielectric coax will be in the vicinity of 42 feet
(VF+0.66, and the length of the foam dielectric coax will be close to
55.5 feet (VF+0.84).  The lengths you have been trying are closer to a
quarter wavelength.

73,
Don W3FPR

djmd wrote:

> I picked up an analyzer today (259B). It's my first one, and I hardly know
> what I'm doing, but I can tell you right off the bat that whether I attach
> it to the coax in the shack, or directly to the balun, it's appearing to be
> resonant at the same 3 places. Around 10mhz, 20mhz, and 26mhz. If there is
> any other information you would like to know from the analyzer at any
> specific frequency and connnection point, please let me know.
>
> I hope this helps... I sincerely appreciate everyone's assistance. I'm still
> learning and it's nice to have a place to get good info and not made to feel
> like I'm an idiot.
> :drunk::confused:
>  
>
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Re: High SWR on 20 and 40

n7ws
In reply to this post by djmd
If you are really interested in 40M only, why on earth don't you simplify your life and get rid of the tuners, the ladderline and the BL2.  Run coax from the antenna spigot on the radio to the antenna.  Coil up a few turns of it at the feed point if you insist on a balun (I don't necessarily), trim the length of the wire for minimum SWR at your frequency of interest and get on and operate.

Wes  N7WS

--- On Sat, 1/16/10, djmd <[hidden email]> wrote:

> From: djmd <[hidden email]>
> Subject: Re: [Elecraft] [OT]   High SWR on 20 and 40
> To: [hidden email]
> Date: Saturday, January 16, 2010, 3:05 PM
>
> Hi James,
>
> Thanks so much for the extremely informative reply! I will
> dig deep into a
> lot of your suggestions later tonight. I think I may have
> overcomplicated
> the issue, so let me see if I can give it a shakedown.
>
> First off, lets forget everything besides 40m. That's
> really the band I am
> concerned with first and foremost.
>
> Before Elecraft came into my life, I was using a Yaesu
> FT840 with an MFJ941E
> tuner. Coax (10' or so) out of the tuner, through the
> floor, into a barrel
> that goes through cementboard to the outside. From there,
> short coax up to a
> W2DU 4:1 current balun. Then 16' or so of windowline, and
> the dipole up
> about 20', about 67' long. I have a very restricted yard
> for antennas and
> just wanted to get on the air.
>
> Anyway, after some poking and prodding I was able to
> consistently tune up on
> 40m fairly well, 1.5 or less. I made several CW contacts
> across the country
> as well as Canada and South America.
>
> Then I built the KX1 with the autotuner, and was not able
> to get under 5:1
> from the same point with all the same components in place.
> No big deal, I
> didn't intend on using the KX1 in the 'shack' anyway. But
> then I built the
> K2/KAT2, and was getting pretty much the same result. As it
> stands right
> now, I cannot break below 9.9:1 on the KAT2 on 40m from the
> shack. I've
> tried different coax types and lengths on each side of the
> barrel and have
> seen no improvement. Also, it doesn't matter which balun I
> use, or whether I
> select 1:1 or 4:1 on the BL2. Results are the same.
>
> Now, when I attach the K2 directly to the balun (now an
> Elecraft BL2) I can
> get a great match on 40m. As I can add a very short piece
> between the K2 and
> the balun with no ill effect, but once the coax is longer
> than about 5', the
> SWR shoots up.
>
> I picked up an analyzer today (259B). It's my first one,
> and I hardly know
> what I'm doing, but I can tell you right off the bat that
> whether I attach
> it to the coax in the shack, or directly to the balun, it's
> appearing to be
> resonant at the same 3 places. Around 10mhz, 20mhz, and
> 26mhz. If there is
> any other information you would like to know from the
> analyzer at any
> specific frequency and connnection point, please let me
> know.
>
> I hope this helps... I sincerely appreciate everyone's
> assistance. I'm still
> learning and it's nice to have a place to get good info and
> not made to feel
> like I'm an idiot.
> :drunk::confused:
>
>
>
>
> --
> View this message in context: http://n2.nabble.com/High-SWR-on-20-and-40-tp4403006p4406096.html
> Sent from the [OT] mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> 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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Re: High SWR on 20 and 40

djmd
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In reply to this post by Don Wilhelm-4
Funny you should bring that up, Don. Last night at about 10pm I found myself sitting on the couch with the '09 Handbook on my lap, opened up to page 21-1. I didn't get to 21.2, as the TV kinda took over my brain...

Definitely time to hit the books.

73 all!


Don Wilhelm-4 wrote
Dave,

No, you are not an idiot, nor drunk, but you may be confused by the
impedance transformation effects of a feedline.
I suggest you take a look at the ARRL Handbook or Antenna Book chapter
on Transmission Lines, especially the sections dealing with transmission
line matching sections if you want an understanding of what is going on.