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K3 - Numeric SWR Display

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Cranz Nichols

K3 - Numeric SWR Display

I need to adjust the gamma matches on my 10/15M delta loop.

Is there a way to bypass the internal ATU and have the K3 display the SWR it
sees numerically?

Should dig out my old SWR bridge?

cln
WB5BKL
K3 #231

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Steef PA2A

Re: K3 - Numeric SWR Display

Gary,

The SWR is being displayed when you press TUNE. The tuning power can be set
at TUN PWR, set it higher than 2 Watts.

Steef PA2A
K3 1184

----- Original Message -----
From: "Cranz Nichols" <[hidden email]>
To: "LIST - elecraft" <[hidden email]>
Sent: Wednesday, September 17, 2008 11:53 PM
Subject: [Elecraft] K3 - Numeric SWR Display

>I need to adjust the gamma matches on my 10/15M delta loop.
>
> Is there a way to bypass the internal ATU and have the K3 display the SWR
> it sees numerically?
>
> Should dig out my old SWR bridge?
>
> cln
> WB5BKL
> K3 #231
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
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>

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Bill VanAlstyne W5WVO

Re: K3 - Numeric SWR Display

In reply to this post by Cranz Nichols

Actually, looking at transmission line SWR at the transmitter is a
poor way to adjust an antenna. To get it right, you need to use a
complex impedance analyzer like the now-ubiquitous MFJ-259B (or
equivalant instrument), and put it as close to the antenna
feedpoint as possible. Adjust as close as you can get for Xc=0,
Xl=0, R=50. You can't do that with an SWR bridge! :-)

Bill W5WVO

----- Original Message -----
From: "Cranz Nichols" <[hidden email]>
To: "LIST - elecraft" <[hidden email]>
Sent: Wednesday, September 17, 2008 3:53 PM
Subject: [Elecraft] K3 - Numeric SWR Display

> I need to adjust the gamma matches on my 10/15M delta loop.
>
> Is there a way to bypass the internal ATU and have the K3
display the SWR it

> sees numerically?
>
> Should dig out my old SWR bridge?
>
> cln
> WB5BKL
> K3 #231
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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> Elecraft web page: http://www.elecraft.com
>

Bill VanAlstyne W5WVO

Re: K3 - Numeric SWR Display

In reply to this post by Cranz Nichols

I should add that you CAN adjust an antenna for minimum SWR at the
transmitter, but when you do that, you are in all likehood
including some non-zero feedpoint reactance in the net impedance,
and this is being observed through the length of your transmission
line, which then becomes part of the overall load the transmitter
sees. If you subsequently change the length of the transmission
line, you will no longer have Z=50 ohms at the transmitter. If you
tune the antenna for TRUE resonance (zero reactance, R=50), then
you can put any length of transmission line on it that you want
to, and it will behave just the same.

I know we all got along without the MFJ-259B for years, just going
by guess and by gosh (or sweating over Smith charts), but now that
we can actually tell what is happening in an antenna so easily,
it's crazy not to use one. Beg, borrow, steal, or if necessary buy
one, and learn how to use it. You won't regret it! Greatest thing
since CW killed King Spark. :-)

Bill W5WVO

----- Original Message -----
From: "Bill W5WVO" <[hidden email]>
To: "Cranz Nichols" <[hidden email]>; "LIST - elecraft"
<[hidden email]>
Sent: Wednesday, September 17, 2008 4:39 PM
Subject: Re: [Elecraft] K3 - Numeric SWR Display

> Actually, looking at transmission line SWR at the transmitter is
a
> poor way to adjust an antenna. To get it right, you need to use
a

> complex impedance analyzer like the now-ubiquitous MFJ-259B (or
> equivalant instrument), and put it as close to the antenna
> feedpoint as possible. Adjust as close as you can get for Xc=0,
> Xl=0, R=50. You can't do that with an SWR bridge! :-)
>
> Bill W5WVO
>
> ----- Original Message -----
> From: "Cranz Nichols" <[hidden email]>
> To: "LIST - elecraft" <[hidden email]>
> Sent: Wednesday, September 17, 2008 3:53 PM
> Subject: [Elecraft] K3 - Numeric SWR Display
>
>
> > I need to adjust the gamma matches on my 10/15M delta loop.
> >
> > Is there a way to bypass the internal ATU and have the K3
> display the SWR it
> > sees numerically?
> >
> > Should dig out my old SWR bridge?
> >
> > cln
> > WB5BKL
> > K3 #231
> >
> >
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
> > http://mailman.qth.net/mailman/listinfo/elecraft
> >
> > Help: http://mailman.qth.net/subscribers.htm
> > Elecraft web page: http://www.elecraft.com
> >
>

W6ODJ

Re: K3 - Numeric SWR Display

An adequate and not too expensive vector analyzer is the VA1 by Autek
Research. It reads resistance and reactance (including its sign)
directly and also has a function that automatically calculates the Z
at your antenna even though you are measuring at the rig end of your
transmission line. It is tiny and and battery operated and hence can
be used on balanced lines without unbalancing things very much.
I have no connection with the company, just a satisfied customer. Use
google to find them.

--Oliver Johns
W6ODJ

On 17 Sep 2008, at 3:52 PM, Bill W5WVO wrote:

> I should add that you CAN adjust an antenna for minimum SWR at the
> transmitter, but when you do that, you are in all likehood
> including some non-zero feedpoint reactance in the net impedance,
> and this is being observed through the length of your transmission
> line, which then becomes part of the overall load the transmitter
> sees. If you subsequently change the length of the transmission
> line, you will no longer have Z=50 ohms at the transmitter. If you
> tune the antenna for TRUE resonance (zero reactance, R=50), then
> you can put any length of transmission line on it that you want
> to, and it will behave just the same.
>
> I know we all got along without the MFJ-259B for years, just going
> by guess and by gosh (or sweating over Smith charts), but now that
> we can actually tell what is happening in an antenna so easily,
> it's crazy not to use one. Beg, borrow, steal, or if necessary buy
> one, and learn how to use it. You won't regret it! Greatest thing
> since CW killed King Spark. :-)
>
> Bill W5WVO
>
> ----- Original Message -----
> From: "Bill W5WVO" <[hidden email]>
> To: "Cranz Nichols" <[hidden email]>; "LIST - elecraft"
> <[hidden email]>
> Sent: Wednesday, September 17, 2008 4:39 PM
> Subject: Re: [Elecraft] K3 - Numeric SWR Display
>
>
>> Actually, looking at transmission line SWR at the transmitter is
> a
>> poor way to adjust an antenna. To get it right, you need to use
> a
>> complex impedance analyzer like the now-ubiquitous MFJ-259B (or
>> equivalant instrument), and put it as close to the antenna
>> feedpoint as possible. Adjust as close as you can get for Xc=0,
>> Xl=0, R=50. You can't do that with an SWR bridge! :-)
>>
>> Bill W5WVO
>>
>> ----- Original Message -----
>> From: "Cranz Nichols" <[hidden email]>
>> To: "LIST - elecraft" <[hidden email]>
>> Sent: Wednesday, September 17, 2008 3:53 PM
>> Subject: [Elecraft] K3 - Numeric SWR Display
>>
>>
>>> I need to adjust the gamma matches on my 10/15M delta loop.
>>>
>>> Is there a way to bypass the internal ATU and have the K3
>> display the SWR it
>>> sees numerically?
>>>
>>> Should dig out my old SWR bridge?
>>>
>>> cln
>>> WB5BKL
>>> K3 #231
>>>
>>>
>>> _______________________________________________
>>> Elecraft mailing list
>>> Post to: [hidden email]
>>> You must be a subscriber to post to the list.
>>> Subscriber Info (Addr. Change, sub, unsub etc.):
>>> http://mailman.qth.net/mailman/listinfo/elecraft
>>>
>>> Help: http://mailman.qth.net/subscribers.htm
>>> Elecraft web page: http://www.elecraft.com
>>>
>>
>
>
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Terry Conboy

Re: K3 - Numeric SWR Display

In reply to this post by Bill VanAlstyne W5WVO

If you have 1:1 SWR at the transmitter, you must have a 50+j0 load at
the other end of a 50 ohm coax, regardless of the line length. Using
a Smith Chart will just show a dot at the center. (Of course, if you
have a very lossy line, it could be a little off 50 ohms at the
load.) This also assumes that you have a reasonable balun at the
antenna, so the outside shield of the coax isn't a coupled part of
the antenna that radiates.

As for the MFJ-259B, it can be a great tool, but it can also give
some pretty crazy readings, especially in the presence of other
nearby transmitters, even when well out of band. I see postings
almost every week on the Topband list about strange feed impedances
of an inverted-L that are probably getting a 100 milliwatt signal
from the local AM station.

73, Terry N6RY

At 03:52 PM 2008-09-17, Bill W5WVO wrote:

AC7AC

RE: K3 - Numeric SWR Display

In reply to this post by Bill VanAlstyne W5WVO

CONTENTS DELETED

The author has deleted this message.

Jessie Oberreuter-2

Re: K3 - Numeric SWR Display

In reply to this post by Bill VanAlstyne W5WVO

On Wed, 17 Sep 2008, Bill W5WVO wrote:

> Actually, looking at transmission line SWR at the transmitter is a
> poor way to adjust an antenna. To get it right, you need to use a
> complex impedance analyzer like the now-ubiquitous MFJ-259B (or
> equivalant instrument), and put it as close to the antenna
> feedpoint as possible. Adjust as close as you can get for Xc=0,
> Xl=0, R=50. You can't do that with an SWR bridge! :-)

Alternately, feeding through one or more half-waves of coax will give
you good accuracy while letting you get far enough away from the antenna
to not affect the measurement.

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Joe Subich, W4TV-3

RE: K3 - Numeric SWR Display

> Alternately, feeding through one or more half-waves of
> coax will give you good accuracy while letting you get far
> enough away from the antenna to not affect the measurement.

Only if the feedline has zero loss. Force 12 are known for
making their antennas "look better" by specifying the SWR
through 100 feet of feedline.

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Jessie
> Oberreuter
> Sent: Thursday, September 18, 2008 2:42 AM
> To: Bill W5WVO
> Cc: LIST - elecraft; Cranz Nichols
> Subject: Re: [Elecraft] K3 - Numeric SWR Display
>
>
>
>
> On Wed, 17 Sep 2008, Bill W5WVO wrote:
>
> > Actually, looking at transmission line SWR at the transmitter is a
> > poor way to adjust an antenna. To get it right, you need to use a
> > complex impedance analyzer like the now-ubiquitous MFJ-259B (or
> > equivalant instrument), and put it as close to the antenna
> feedpoint
> > as possible. Adjust as close as you can get for Xc=0, Xl=0,
> R=50. You
> > can't do that with an SWR bridge! :-)
>
> Alternately, feeding through one or more half-waves of
> coax will give
> you good accuracy while letting you get far enough away from
> the antenna
> to not affect the measurement.
>
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
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Charles Morrison-3

RE: K3 - Numeric SWR Display

In reply to this post by Jessie Oberreuter-2

Since I don't plan on hanging off the side of the tower to operate my
station, isn't it more prudent to tune the entire "system", flaws, feedline
and all if my main concern is what SWR my equipment, in my shack, sees?

Charlie
KI5XP

> -----Original Message-----
> From: [hidden email] [mailto:elecraft-
> [hidden email]] On Behalf Of Jessie Oberreuter
> Sent: Thursday, September 18, 2008 1:42 AM
> To: Bill W5WVO
> Cc: LIST - elecraft; Cranz Nichols
> Subject: Re: [Elecraft] K3 - Numeric SWR Display
>
>
>
> On Wed, 17 Sep 2008, Bill W5WVO wrote:
>
> > Actually, looking at transmission line SWR at the transmitter is a
> > poor way to adjust an antenna. To get it right, you need to use a
> > complex impedance analyzer like the now-ubiquitous MFJ-259B (or
> > equivalant instrument), and put it as close to the antenna
> > feedpoint as possible. Adjust as close as you can get for Xc=0,
> > Xl=0, R=50. You can't do that with an SWR bridge! :-)
>
> Alternately, feeding through one or more half-waves of coax will

give

> you good accuracy while letting you get far enough away from the antenna
> to not affect the measurement.
>
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
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>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

Darwin, Keith

RE: K3 - Numeric SWR Display

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Charles Morrison

Since I don't plan on hanging off the side of the tower to operate my
station, isn't it more prudent to tune the entire "system", flaws,
feedline and all if my main concern is what SWR my equipment, in my
shack, sees?

------------------------

No it isn't. If you're using 50 ohm coax and an antenna that is not 50
ohms resistive, you'll set up standing waves in the coax which will
result in signal loss. Having a tuner at the rig will protect the rig
from the effects of the standing waves, but the line loss will still be
there.

Far better is to have the tuner at the actual antenna feed point (or to
adjust the antenna to be 50 ohm resistive). Then you'll have a happy
rig AND minimal loss in the coax.

- Keith N1AS -
- K3 711 -
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Bill VanAlstyne W5WVO

Re: K3 - Numeric SWR Display

That was the point I was trying to make originally. However, to be
fair, the feedline loss generated by SWR is significant only where
the loss is substantial enough to make a meaningful difference. At
HF, particularly the lower bands, the SWR loss is, from a
practical standpoint, insignificant.

However, I'm a VHF weak-signal operator, and I tend to think in
those terms. Having a non-reactive load at the feedpoint is
important at VHF/UHF, as feedline losses due to SWR can be
significant on both transmit and receive.

Bill W5WVO

----- Original Message -----
From: "Darwin, Keith" <[hidden email]>
To: "LIST - elecraft" <[hidden email]>
Sent: Thursday, September 18, 2008 8:40 AM
Subject: RE: [Elecraft] K3 - Numeric SWR Display

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Charles
Morrison
>
> Since I don't plan on hanging off the side of the tower to
operate my
> station, isn't it more prudent to tune the entire "system",
flaws,
> feedline and all if my main concern is what SWR my equipment, in
my
> shack, sees?
>
> ------------------------
>
> No it isn't. If you're using 50 ohm coax and an antenna that is
not 50
> ohms resistive, you'll set up standing waves in the coax which
will
> result in signal loss. Having a tuner at the rig will protect
the rig
> from the effects of the standing waves, but the line loss will
still be
> there.
>
> Far better is to have the tuner at the actual antenna feed point
(or to
> adjust the antenna to be 50 ohm resistive). Then you'll have a
happy

> rig AND minimal loss in the coax.
>
> - Keith N1AS -
> - K3 711 -
> _______________________________________________
> Elecraft mailing list
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>

AC7AC

RE: K3 - Numeric SWR Display

In reply to this post by Charles Morrison-3

CONTENTS DELETED

The author has deleted this message.

Jim Brown-10

Re: K3 - Numeric SWR Display

In reply to this post by Bill VanAlstyne W5WVO

On Thu, 18 Sep 2008 09:35:45 -0600, Bill W5WVO wrote:

>as feedline losses due to SWR can be
>significant on both transmit and receive

It depends on your definition of "significant" and the degree
of mismatch. This is another one of those "old wives' tales
that is a wild exageration of reality. A graph of the loss due
to mismatch has appeared in every version of the ARRL Handbook
and the ARRL Antenna Book for many years. It shows that the
WORST CASE additional loss for a 1.5:1 VSWR is 0.18 dB, no
matter how much the matched loss of the line! That worst case
number is 0.5 dB for a 2:1 VSWR and 1.2 dB for 3:1 VSWR.

If the loss in the line for a perfect match were 1 dB, the
additional loss due to SWR is about 0.05dB for 1.5 VSWR, 0.2 dB
for 2:1, and 0.46dB for 3:1. You've got to have a VSWR of 5:1
for there to be 1 dB of additional loss due to mismatch!

Yes, the loss in any transmission line causes the VSWR to come
closer to 1:1 as we move along the line from the antenna to the
transmitter. The lossier the line, the greater this effect. BUT
-- coax of reasonable size and quality is NOT very lossy on the
HF bands. Decent RG8X (Belden 9258 or LMR240) has only about 1
dB/100 ft on 20M, and less than 0.5dB/100ft on 80M. Loss rises
t about 1.6dB on 10M, and 2 dB/100 ft on 6M. The best RG8s have
roughly one-third that loss. This graph is in Chapter 19 of my
2002 ARRL Handbook, and Chapter 24 of the ARRL Antenna Book.
Both publications also show the equation from which the graphs
are derived, and the ARRL Antenna Book comes with a calculator
(by N6BV) that will compute the loss in the line for any length
of line, frequency, and value of termination impedance that you
plug in, based on its database of loss for many popular coax
cables (Belden, LMR, and a few others). You can also plug in
the VSWR or complex impedance you've measured at the
transmitter and the length of the line, and it will compute the
line loss and the VSWR at the antenna.

The bottom line is that unless your antenna is badly mismatched
(far off resonance or broken), the additional loss due to VSWR
on the HF bands is truly insignificant.

Now, I DO use big coax (RG8 and RG11) on my high wire dipoles
that are up about 110 ft (and the lines are about 140 ft). I do
that because I am contesting (high duty cycle) with legal power
and over rather wide bandwidths (a single dipole for all of
80/75 and for 160M), AND because I use the 80/40 fan dipoles on
30M, 17M, and 12M. The fact that I'm using the big coax saves
me a dB or so in these far off resonance conditions, and allows
them to work pretty well!

73,

Jim Brown K9YC

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Tom Hammond-2

RE: K3 - Numeric SWR Display

In reply to this post by Charles Morrison-3

Hi Charlie:

>Since I don't plan on hanging off the side of the tower to operate my
>station, isn't it more prudent to tune the entire "system", flaws, feedline
>and all if my main concern is what SWR my equipment, in my shack, sees?

'Tuning' things so the rig sees what it wants is not always the best...
since things could be REALLY BAD at the antenna end, but you'd never
know it at the radio end.

You wan the BEST MATCH available AT THE ANTENNA END so you'll get maximum
(most efficient) RF power transfer from the feedline to the antenna. Once
you get this, you can worry about performing and additional matching at the
TX end.

Using a transmatch, you can make darn near any level of mismatch 'appear'
to be a 1:1 SWR at the transmitter, but if the match AT THE ANTENNA is not
acceptable, you won't be getting the most efficient transfer of RF to the
antenna... e.g. you'll be heating your feedline with the RF that was to go
into the antenna... a place where it'll do little good.

FIRST - Ensure that the feedline-to-antenna match is appropriate for good
power transfer.

THEN - Ensure that the match between your feedline and the transmitter is
appropriate for good power transfer from the transmitter to the feedline
and ultimately to the antenna.

73,

Tom Hammond N0SS

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AC7AC

RE: K3 - Numeric SWR Display

In reply to this post by Joe Subich, W4TV-3

CONTENTS DELETED

The author has deleted this message.

N5GE

Re: K3 - Numeric SWR Display

In reply to this post by AC7AC

On Thu, 18 Sep 2008 09:44:42 -0700, "Ron D'Eau Claire" <[hidden email]> wrote:

>That's true. Indeed, if you have an "antenna tuner" (built-in automatic or
>external manual) you don't even need to do that. That's what made them so
>popular in recent years; they "fix" impedance problems at the rig end
>without fiddling around with the antenna at all.
>
>The issue then becomes feed line loss. It can get quite high, especially at
>the higher frequencies and with longer lengths of coax. It's not unusual to
>throw away 50%, 75% or more of your RF as heat along a coaxial line that
>way.
>
>But, if your antenna is designed to provide a decent match, or if you've
>done some adjustments 'on the ground' that suggest you're at least
>approximately correct, you're not likely to experience such drastic losses
>even though things will change when the antenna is raised to its final
>position.
>
>Doing measurements up on a tower is one of the major reasons for the
>popularity of the modern "antenna analyzers". They're self contained and
>small enough you can carry one up to the feed point. Most Hams only need to
>do that at rare intervals, which is why many Ham clubs have a "club
>analyzer" everyone's contributed to buying so members can borrow it on
>occasion.
>
>A much cheaper approach is, as Bill says, to cut some coax to a multiple of
>1/2 wave, electrically. Then the impedance you see at the end on the ground
>will be the impedance at the antenna. The issue there is "how many times do
>you want to climb the tower"? Perhaps a buddy at the rig on the ground and
>you in the air with some HT's is the answer to that.
>
>Ron AC7AC
>
>-----Original Message-----

[snip]

I bought an AIM 4170 analyzer at the Ft Worth Hamfest this year and love it.
When measuring antennas with it I calibrate the coax before making the antenna
measurement with a piece of 100 ft RG213 on a ten foot mast. After I have done
that I can measure the antenna as though the analyzer is attached to the
terminals at the antenna. Then I put the antenna on the tower and measure it
again with the same calibrated coax to find out what changed at the additional
height. If it checks ok I connect the LMR600 to the antenna and call it good.

Tom, N5GE - SWOT 3537 - Grid EM12jq

"Those who would give up
Essential Liberty to
purchase a little Temporary
Safety deserve neither
Liberty nor Safety"

An excerpt from a letter
written in 1755 from the
Assembly to the Governor
of Pennsylvania.

Support the entire Constitution, not
just the parts you like.

http://www.n5ge.com
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Amateur Radio Operator N5GE