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SWR Readings:Differences

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pastormg

SWR Readings:Differences

Good Evening,
This is Mark Griffin, KB3Z and I have some questions regarding the SWR readings I get at my tower versus what I get on my K3. I will give the SWR readings that I got at my tower for a 40 meter rotatable dipole at 55 feet.

Tower:

7000 2.2
7025 1.8
7050 1.5
7075 1.3
7100 1.0
7125 1.1
7150 1.3
7175 1.6
7200 2.0
7225 2.2

K3 Readings:

7000 3.5

7025 3.2

7050 2.9

7075 2.6

7100 2.4

7125 2.3

7150 2.4

7175 2.5

7200 2.6
7225 2.9

What would cause such a big difference. The cable run from my antenna switch on the tower to my K3 is only an additional 75 feet. I am using RG-213 cable. Is there anyway that I can test the SWR reading that my K3 is giving me?

Mark Griffin, KB3Z

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Dick Dievendorff-4

Re: SWR Readings:Differences

Can you use the same SWR bridge in the shack that you used at the base of
the tower so you're comparing apples to apples? I'd take the K3 out of the
equation and figure out why your SWR differs at the base of the tower
compared to in the shack through a 75' coax run and switch.

I'd expect the SWR to be lower in the shack. If it isn't, then I'd put a
dummy load at the base of the tower, thru the switch, and measure the SWR in
the shack of that dummy load.

Dick, K6KR

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of
[hidden email]
Sent: Tuesday, September 02, 2014 5:07 PM
To: [hidden email]
Subject: [Elecraft] SWR Readings:Differences

Good Evening,
This is Mark Griffin, KB3Z and I have some questions regarding the SWR
readings I get at my tower versus what I get on my K3. I will give the SWR
readings that I got at my tower for a 40 meter rotatable dipole at 55 feet.

Tower:

7000 2.2
7025 1.8
7050 1.5
7075 1.3
7100 1.0
7125 1.1
7150 1.3
7175 1.6
7200 2.0
7225 2.2

K3 Readings:

7000 3.5

7025 3.2

7050 2.9

7075 2.6

7100 2.4

7125 2.3

7150 2.4

7175 2.5

7200 2.6
7225 2.9

What would cause such a big difference. The cable run from my antenna switch
on the tower to my K3 is only an additional 75 feet. I am using RG-213
cable. Is there anyway that I can test the SWR reading that my K3 is giving
me?

Mark Griffin, KB3Z

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Fred Townsend-2

Re: SWR Readings:Differences

In reply to this post by pastormg

Hello Mark:
Question? What is the SWR of a mile long piece of coax if it is unterminated.
Answer 1:1. That is because a long length coax will act as a matching transformer. Actually it doesn't have to be too long as you found out. If reading is not better in the shack something is wrong.

Mark what you are seeing is entirely normal. If you want to measure the antenna impedance from the shack you should use something like Time Domain Reflectometer.

73
Fred

-----Original Message-----

>From: [hidden email]
>Sent: Sep 2, 2014 5:06 PM
>To: [hidden email]
>Subject: [Elecraft] SWR Readings:Differences
>
>Good Evening,
>This is Mark Griffin, KB3Z and I have some questions regarding the SWR readings I get at my tower versus what I get on my K3. I will give the SWR readings that I got at my tower for a 40 meter rotatable dipole at 55 feet.
>
>Tower:
>
>7000 2.2
>7025 1.8
>7050 1.5
>7075 1.3
>7100 1.0
>7125 1.1
>7150 1.3
>7175 1.6
>7200 2.0
>7225 2.2
>
>K3 Readings:
>
>7000 3.5
>
>7025 3.2
>
>7050 2.9
>
>7075 2.6
>
>7100 2.4
>
>7125 2.3
>
>7150 2.4
>
>7175 2.5
>
>7200 2.6
>7225 2.9
>
>What would cause such a big difference. The cable run from my antenna switch on the tower to my K3 is only an additional 75 feet. I am using RG-213 cable. Is there anyway that I can test the SWR reading that my K3 is giving me?
>
>Mark Griffin, KB3Z
>
>______________________________________________________________
>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
>Message delivered to [hidden email]

k6dgw

Re: SWR Readings:Differences

In reply to this post by pastormg

I left your message on this, don't normally do that but I think it is
important for context.

1. If the feed point impedance at your antenna is equal to the
characteristic impedance of your coax *at any given frequency,* then the
SWR you measure at the rig will be nominally 1:1. Note that not all SWR
measuring instruments are created equal.

2. Measuring the feed point impedance at an antenna is usually somewhat
hard ... up in the air, maybe not accessible ... you probably get the idea.

3. Measuring the SWR at the accessible bottom of the tower [I'm
assuming that's where you're measuring it], and finding it to be
anything other than 1:1 means that the line is not matched to the
antenna impedance, and begins acting as an RF transformer.

4. The SWR you will see in the shack, and remember that all SWR
indicators are not created equal, will be whatever results in the
impedance transformation along the length of the coax from the tower to
the shack.

5. A Time Domain Reflectometer will help clarify this for you if you
know how to use one. Sadly, they're very expensive and hard to
interpret if you've never used one. Check around among your friends but
don't hold your breath.

Bottom line, you can prune or un-prune your antenna [if it's wire] a
little, and you can adjust the length of the coax transformer to the
shack to get acceptable SWR at the rig.

Or, if your K3 accepts the SWR, ignore it. Honestly Mark, you'll never
know the difference while operating. There's also the KAT3, your SWR's
are easily within it's range.

There was a time, in my lifetime, when "Standing Wave Ratio" was NOT an
amateur radio term. You "loaded the antenna" and called CQ. Today's
radios are significantly more particular to SWR, but if it works, it works.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 9/2/2014 5:06 PM, [hidden email] wrote:

> Good Evening, This is Mark Griffin, KB3Z and I have some questions
> regarding the SWR readings I get at my tower versus what I get on my
> K3. I will give the SWR readings that I got at my tower for a 40
> meter rotatable dipole at 55 feet.
>
> Tower:
>
> 7000 2.2 7025 1.8 7050 1.5 7075 1.3 7100 1.0 7125 1.1 7150
> 1.3 7175 1.6 7200 2.0 7225 2.2
>
> K3 Readings:
>
> 7000 3.5
>
> 7025 3.2
>
> 7050 2.9
>
> 7075 2.6
>
> 7100 2.4
>
> 7125 2.3
>
> 7150 2.4
>
> 7175 2.5
>
> 7200 2.6 7225 2.9
>
> What would cause such a big difference. The cable run from my antenna
> switch on the tower to my K3 is only an additional 75 feet. I am
> using RG-213 cable. Is there anyway that I can test the SWR reading
> that my K3 is giving me?
>
> Mark Griffin, KB3Z

k6dgw

Re: SWR Readings:Differences

In reply to this post by Fred Townsend-2

Just so we all don't confuse Mark, I think he asked a really good question,

If the coax is loss-less [we'll all let you know when you can buy that
kind:-))], then what the other Fred said is true. Unfortunately, all
transmission lines, of whatever flavor, do have losses. Compared to
open wire lines, loss in coax is high.

In the early 60's at Keesler AFB, I passed my free time at K5TYP ... I
enjoyed the people and the activity there. We had a tribander that
seemed to receive [sort of}, but we couldn't work anyone on it, and the
SWR was 1:1 on 20, 15, and 10. A puzzle. During one of the testing
sessions, someone swept the frequency from 10 down to 20 to go do it
again, and the SWR was 1:1 all the way down. Our coax had lain open on
the ground for several years in Biloxi MS, and was full of water. It
was basically the longest dummy load in Harrison County MS before any RF
got to the antenna. And, it had a 1:1 SWR

Depending on the loss in your coax, your feedline will look more or less
like a transformer. More loss means it begins to dominate the
transformer equation and your SWR at the shack looks better and better.

Again, the bottom line ... Don't stress about SWR unless it causes a
problem for your transceiver. If the transmitter is happy, so you
should be.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 9/2/2014 6:57 PM, Fred Townsend wrote:
>
> Hello Mark: Question? What is the SWR of a mile long piece of coax if
> it is unterminated. Answer 1:1. That is because a long length coax
> will act as a matching transformer. Actually it doesn't have to be
> too long as you found out. If reading is not better in the shack
> something is wrong.

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Vic Rosenthal

Re: SWR Readings:Differences

In reply to this post by pastormg

If your line is lossless (it isn't) you would expect the same SWR
readings anywhere along the line. With practical lines that have some
loss, the SWR should be LOWER farther away from the antenna. You are
getting the opposite result.

One cause of erroneous SWR readings is RF flowing on the outside of the
coax. If your rotary dipole doesn't have a balun, this could be the cause.

It's also possible that you have a bad connector or bad piece of coax
between the tower and the K3.

On 9/3/14 3:06 AM, [hidden email] wrote:

--
Vic, K2VCO/4X6GP
Rehovot, Israel
http://www.qsl.net/k2vco/
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LA8OKA

Vedr: SWR Readings:Differences

In reply to this post by pastormg

The first thing you need to do is to use the same SWR-meter both at the tower and at you're K3.
When measurering close to the K3 and if it is a big difference between you're SWR meter and the K3, the K3 is probably indicating the wrong SWR, or the K3 tuner is coupled in making the SWR to be something quite different than it actually is.

If both SWR-meters show higher SWR in the shack than at you're tower, there is probably something wrong in the last coax run, hook it up to a dummyload and measure SWR. The SWR shall normally be lower in the shack than at you're tower due to the losses in the coax.

Martin Storli
LA8OKA
Oslo, Norway

ARCTICPEAK's Radio pages!
http://www.arcticpeak.com/radio.htm

________________________________
Fra: "[hidden email]" <[hidden email]>
Til: [hidden email]
Sendt: Onsdag, 3. september 2014 2.06
Emne: [Elecraft] SWR Readings:Differences

Good Evening,
This is Mark Griffin, KB3Z and I have some questions regarding the SWR readings I get at my tower versus what I get on my K3. I will give the SWR readings that I got at my tower for a 40 meter rotatable dipole at 55 feet.

Tower:

7000 2.2
7025 1.8
7050 1.5
7075 1.3
7100 1.0
7125 1.1
7150 1.3
7175 1.6
7200 2.0
7225 2.2

K3 Readings:

7000 3.5

7025 3.2

7050 2.9

7075 2.6

7100 2.4

7125 2.3

7150 2.4

7175 2.5

7200 2.6
7225 2.9

What would cause such a big difference. The cable run from my antenna switch on the tower to my K3 is only an additional 75 feet. I am using RG-213 cable. Is there anyway that I can test the SWR reading that my K3 is giving me?

Mark Griffin, KB3Z

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alsopb

Re: SWR Readings:Differences

In reply to this post by pastormg

My experience with this is that if one is seeing an SWR >2.5 -3 it
usually means either the braid or center conductor isn't connected.

I'd redo the connectors.

You don't say how the measurements were made at the tower. But I'm
guessing it was done with another short piece of coax. Thus both
connectors (ant end and shack end) are suspect.

Testing out the coax (coax problems are really rare these days with new
coax) is a good idea. After connectors are installed, put a dummy load
at one end and measure the SWR. It should be close to 1:1.

73 & GL
Brian/K3KO

On 9/2/2014 8:06 PM, [hidden email] wrote:

> Good Evening,
> This is Mark Griffin, KB3Z and I have some questions regarding the SWR readings I get at my tower versus what I get on my K3. I will give the SWR readings that I got at my tower for a 40 meter rotatable dipole at 55 feet.
>
> Tower:
>
> 7000 2.2
> 7025 1.8
> 7050 1.5
> 7075 1.3
> 7100 1.0
> 7125 1.1
> 7150 1.3
> 7175 1.6
> 7200 2.0
> 7225 2.2
>
> K3 Readings:
>
> 7000 3.5
>
> 7025 3.2
>
> 7050 2.9
>
> 7075 2.6
>
> 7100 2.4
>
> 7125 2.3
>
> 7150 2.4
>
> 7175 2.5
>
> 7200 2.6
> 7225 2.9
>
> What would cause such a big difference. The cable run from my antenna switch on the tower to my K3 is only an additional 75 feet. I am using RG-213 cable. Is there anyway that I can test the SWR reading that my K3 is giving me?
>
> Mark Griffin, KB3Z
>
> ______________________________________________________________
> 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
> Message delivered [hidden email]
>
>
> -----
> No virus found in this message.
> Checked by AVG -www.avg.com
> Version: 2012.0.2247 / Virus Database: 4015/7640 - Release Date: 09/02/14
>
>

PTAa

Re: Vedr: SWR Readings:Differences

In reply to this post by LA8OKA

CONTENTS DELETED

The author has deleted this message.

Don Wilhelm-4

Re: SWR Readings:Differences

In reply to this post by pastormg

Mark,

Any transmission line will have an impedance transformation unless it is
terminated in its characteristic impedance.
The other factor may be that you have some common mode current on the
coax shield - that can skew SWR readings.

73,
Don W3FPR

On 9/2/2014 8:06 PM, [hidden email] wrote:

> Good Evening,
> This is Mark Griffin, KB3Z and I have some questions regarding the SWR readings I get at my tower versus what I get on my K3. I will give the SWR readings that I got at my tower for a 40 meter rotatable dipole at 55 feet.
>
> Tower:
>
> 7000 2.2
> 7025 1.8
> 7050 1.5
> 7075 1.3
> 7100 1.0
> 7125 1.1
> 7150 1.3
> 7175 1.6
> 7200 2.0
> 7225 2.2
>
> K3 Readings:
>
> 7000 3.5
>
> 7025 3.2
>
> 7050 2.9
>
> 7075 2.6
>
> 7100 2.4
>
> 7125 2.3
>
> 7150 2.4
>
> 7175 2.5
>
> 7200 2.6
> 7225 2.9
>
> What would cause such a big difference. The cable run from my antenna switch on the tower to my K3 is only an additional 75 feet. I am using RG-213 cable. Is there anyway that I can test the SWR reading that my K3 is giving me?
>
> Mark Griffin, KB3Z
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

LA7NO

Re: Vedr: SWR Readings:Differences

In reply to this post by LA8OKA

Hi,

Martin makes an important point!
The VSWR indicated on the K3 is measured between tuner and PA. The tuner
does not influence the VSWR on the feeder.

P-T / LA7NO

On 3 September 2014 12:18, Martin Storli - LA8OKA <[hidden email]>
wrote:

> The first thing you need to do is to use the same SWR-meter both at the
> tower and at you're K3.
> When measurering close to the K3 and if it is a big difference between
> you're SWR meter and the K3, the K3 is probably indicating the wrong SWR,
> or the K3 tuner is coupled in making the SWR to be something quite
> different than it actually is.
>
> If both SWR-meters show higher SWR in the shack than at you're tower,
> there is probably something wrong in the last coax run, hook it up to a
> dummyload and measure SWR. The SWR shall normally be lower in the shack
> than at you're tower due to the losses in the coax.
>
> Martin Storli
> LA8OKA
> Oslo, Norway
>
> ARCTICPEAK's Radio pages!
> http://www.arcticpeak.com/radio.htm
>
>
> ________________________________
> Fra: "[hidden email]" <[hidden email]>
> Til: [hidden email]
> Sendt: Onsdag, 3. september 2014 2.06
> Emne: [Elecraft] SWR Readings:Differences
>
>
> Good Evening,
> This is Mark Griffin, KB3Z and I have some questions regarding the SWR
> readings I get at my tower versus what I get on my K3. I will give the SWR
> readings that I got at my tower for a 40 meter rotatable dipole at 55 feet.
>
> Tower:
>
> 7000 2.2
> 7025 1.8
> 7050 1.5
> 7075 1.3
> 7100 1.0
> 7125 1.1
> 7150 1.3
> 7175 1.6
> 7200 2.0
> 7225 2.2
>
> K3 Readings:
>
> 7000 3.5
>
> 7025 3.2
>
> 7050 2.9
>
> 7075 2.6
>
> 7100 2.4
>
> 7125 2.3
>
> 7150 2.4
>
> 7175 2.5
>
> 7200 2.6
> 7225 2.9
>
> What would cause such a big difference. The cable run from my antenna
> switch on the tower to my K3 is only an additional 75 feet. I am using
> RG-213 cable. Is there anyway that I can test the SWR reading that my K3 is
> giving me?
>
> Mark Griffin, KB3Z
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

73,

Per-Tore / LA7NO

Guy Olinger K2AV

Re: SWR Readings:Differences

In reply to this post by Vic Rosenthal

Here is a small, non-inclusive list of things that can be bad with a coax
run to the house. I have personally seen all of them at some time or place.
Some big names, too.

1) At either or both ends, the shield was not soldered to the PL259 shell,
and the connection has dwindled to a small percentage of the shield due to
gradual destruction of the fine wire touching points.

1a) Ditto for the center conductor to the hollow center conductor pin of
the PL259. Amazing how many PL259's are not soldered in a hurry to 'hear
how it works". I've done it myself and forgotten I didn't. For years.

2) "Balun" is cheep junk, or burned up/melted/shorted
turns/cracked/destroyed core, now junk.

3) Coax on tower is not high quality, and does not have it's weight
supported. The stretch has changed the separation of shield and center
conductor, and the characteristic impedance has shifted, introducing an
unwanted transformation into the equation.

3a) Coax is very old, but still "looks OK" even though it isn't. Much coax
material undergoes very slow (even decades) chemical changes which can
change characteristics. Wide frequency and TDR scans of coax into opens,
shorts, checked 50 ohm and 200 ohm terminations are only way to check for
still-OK-ness.

4) Water has invaded the coax, from a nick, tear or critter bite in the
jacket, or non/poorly sealed coax connector, and capillary action has
wicked along it's entire length. This can be hundreds of feet in the worst
of cases. The loss-added coax does not necessarily stay at 50 ohms Z zero.
I have seen coax shields green (copper oxide) their entire length.
Interestingly the practical outcomes of this extra loss was initially most
often blamed on the transceiver.

5) Coax has been wrapped around a pipe by rotator torque. See 3)

6) Coax has had something heavy dropped on it. See 3)

7) Coax shield was only ground path for induced current for a close
lightning strike. (Usually a direct strike smokes coax beyond any
confusion.)

8) PL259 shell was not pliers-tightened and has worked loose, gradually
producing burned points of connection.

9) Long coax run was laid tight in summer heat, and stretched in the
winter. See 3)

10) Constant flexing of coax finally breaks the center conductor. After
that, "connection" is strange.

11) Unsupported aerial coax over-weighted by ice and stretched, pulled out
of connectors, see 8).

12) Coax is innocent and it's really the antenna.

13) Operator in fact does not know how to operate the instrument or how to
interpret readings.

14) Short lengths of coax and "other boxes" are ignored, and those in fact
contain the problem.

15) Measuring instrument has been damaged or was defective from the
factory.

15a) Measuring instrument is cheep junk.

16) Operator was "told" what the trouble was by a "trusted source" and is
having a lot of trouble thinking outside of the "trusted box" when the
trusted source was in fact in error for this instance.

17) Dummy load used to calibrate/provide 50 J zero comparison or reference
termination is not 50 J zero for any number of reasons, including the likes
of several seconds of QRO on a 2 watts worth of 50 ohms. Didn't turn black
on the outside, but the resistor innards were already toast. Didn't *look*
burned, so must be fine, right?

18) Dummy load while accurate at DC has significant reactive components at
RF.

19) Coax was not 50 ohms from the get-go (try 56). But it looks good so it
must be good. And the seller had a nice looking web page and the best price.

20) I need to wrap this up, but I know I'm not remembering something really
juicy, which will come to mind after I hit the send button.

A group of Olde Pharte hams sitting around a table in a Lunche Jointe, came
up with a napkin version of this that had over 40 items on it. The napkins
were used for the inevitable outcome of ribs, and so was lost to posterity.
One of these included a male F connector that had not had its threads
grooved into the shell. This ignominious occurrence is not mentioned above,
because it could not ever be part of a "working" setup. But it was amazing
how many other things were blamed for "not fitting", including calls to an
equipment maker about female chassis connectors, before the lack of threads
was noticed.

Good luck to all and 73,

Guy K2AV

On Wed, Sep 3, 2014 at 12:18 AM, Vic, K2VCO <[hidden email]> wrote:

> If your line is lossless (it isn't) you would expect the same SWR
> readings anywhere along the line. With practical lines that have some
> loss, the SWR should be LOWER farther away from the antenna. You are
> getting the opposite result.
>
> One cause of erroneous SWR readings is RF flowing on the outside of the
> coax. If your rotary dipole doesn't have a balun, this could be the cause.
>
> It's also possible that you have a bad connector or bad piece of coax
> between the tower and the K3.
>
>
> On 9/3/14 3:06 AM, [hidden email] wrote:
>
>> Good Evening, This is Mark Griffin, KB3Z and I have some questions
>> regarding the SWR readings I get at my tower versus what I get on my
>> K3. I will give the SWR readings that I got at my tower for a 40
>> meter rotatable dipole at 55 feet.
>>
>> Tower:
>>
>> 7000 2.2 7025 1.8 7050 1.5 7075 1.3 7100 1.0 7125 1.1 7150
>> 1.3 7175 1.6 7200 2.0 7225 2.2
>>
>> K3 Readings:
>>
>> 7000 3.5
>>
>> 7025 3.2
>>
>> 7050 2.9
>>
>> 7075 2.6
>>
>> 7100 2.4
>>
>> 7125 2.3
>>
>> 7150 2.4
>>
>> 7175 2.5
>>
>> 7200 2.6 7225 2.9
>>
>> What would cause such a big difference. The cable run from my antenna
>> switch on the tower to my K3 is only an additional 75 feet. I am
>> using RG-213 cable. Is there anyway that I can test the SWR reading
>> that my K3 is giving me?
>>
>> Mark Griffin, KB3Z
>>
>
> --
> Vic, K2VCO/4X6GP
> Rehovot, Israel
> http://www.qsl.net/k2vco/
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Re: SWR Readings:Differences

Good list, and here at least is one more.

# PL-259 male or female connector made of some non-solderable material. Looks like it soldered but isn't. Cheap import.

Mel, K6KBE

On Wednesday, September 3, 2014 6:57 AM, Guy Olinger K2AV <[hidden email]> wrote:

Here is a small, non-inclusive list of things that can be bad with a coax
run to the house. I have personally seen all of them at some time or place.
Some big names, too.

1) At either or both ends, the shield was not soldered to the PL259 shell,
and the connection has dwindled to a small percentage of the shield due to
gradual destruction of the fine wire touching points.

1a) Ditto for the center conductor to the hollow center conductor pin of
the PL259. Amazing how many PL259's are not soldered in a hurry to 'hear
how it works". I've done it myself and forgotten I didn't. For years.

2) "Balun" is cheep junk, or burned up/melted/shorted
turns/cracked/destroyed core, now junk.

3) Coax on tower is not high quality, and does not have it's weight
supported. The stretch has changed the separation of shield and center
conductor, and the characteristic impedance has shifted, introducing an
unwanted transformation into the equation.

3a) Coax is very old, but still "looks OK" even though it isn't. Much coax
material undergoes very slow (even decades) chemical changes which can
change characteristics. Wide frequency and TDR scans of coax into opens,
shorts, checked 50 ohm and 200 ohm terminations are only way to check for
still-OK-ness.

4) Water has invaded the coax, from a nick, tear or critter bite in the
jacket, or non/poorly sealed coax connector, and capillary action has
wicked along it's entire length. This can be hundreds of feet in the worst
of cases. The loss-added coax does not necessarily stay at 50 ohms Z zero.
I have seen coax shields green (copper oxide) their entire length.
Interestingly the practical outcomes of this extra loss was initially most
often blamed on the transceiver.

5) Coax has been wrapped around a pipe by rotator torque. See 3)

6) Coax has had something heavy dropped on it. See 3)

7) Coax shield was only ground path for induced current for a close
lightning strike. (Usually a direct strike smokes coax beyond any
confusion.)

8) PL259 shell was not pliers-tightened and has worked loose, gradually
producing burned points of connection.

9) Long coax run was laid tight in summer heat, and stretched in the
winter. See 3)

10) Constant flexing of coax finally breaks the center conductor. After
that, "connection" is strange.

11) Unsupported aerial coax over-weighted by ice and stretched, pulled out
of connectors, see 8).

12) Coax is innocent and it's really the antenna.

13) Operator in fact does not know how to operate the instrument or how to
interpret readings.

14) Short lengths of coax and "other boxes" are ignored, and those in fact
contain the problem.

15) Measuring instrument has been damaged or was defective from the
factory.

15a) Measuring instrument is cheep junk.

16) Operator was "told" what the trouble was by a "trusted source" and is
having a lot of trouble thinking outside of the "trusted box" when the
trusted source was in fact in error for this instance.

17) Dummy load used to calibrate/provide 50 J zero comparison or reference
termination is not 50 J zero for any number of reasons, including the likes
of several seconds of QRO on a 2 watts worth of 50 ohms. Didn't turn black
on the outside, but the resistor innards were already toast. Didn't *look*
burned, so must be fine, right?

18) Dummy load while accurate at DC has significant reactive components at
RF.

19) Coax was not 50 ohms from the get-go (try 56). But it looks good so it
must be good. And the seller had a nice looking web page and the best price.

20) I need to wrap this up, but I know I'm not remembering something really
juicy, which will come to mind after I hit the send button.

A group of Olde Pharte hams sitting around a table in a Lunche Jointe, came
up with a napkin version of this that had over 40 items on it. The napkins
were used for the inevitable outcome of ribs, and so was lost to posterity.
One of these included a male F connector that had not had its threads
grooved into the shell. This ignominious occurrence is not mentioned above,
because it could not ever be part of a "working" setup. But it was amazing
how many other things were blamed for "not fitting", including calls to an
equipment maker about female chassis connectors, before the lack of threads
was noticed.

Good luck to all and 73,

Guy K2AV

On Wed, Sep 3, 2014 at 12:18 AM, Vic, K2VCO <[hidden email]> wrote:

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alsopb

Re: SWR Readings:Differences

Add to the list.
The PL-259 has an undersized center pin. I've seen these.

73 de Brian/K3KO

On 9/3/2014 14:20, Mel Farrer via Elecraft wrote:

> Good list, and here at least is one more.
>
>
> # PL-259 male or female connector made of some non-solderable material. Looks like it soldered but isn't. Cheap import.
>
> Mel, K6KBE
>
>
>
>
>
> On Wednesday, September 3, 2014 6:57 AM, Guy Olinger K2AV <[hidden email]> wrote:
>
>
>
> Here is a small, non-inclusive list of things that can be bad with a coax
> run to the house. I have personally seen all of them at some time or place.
> Some big names, too.
>
> 1) At either or both ends, the shield was not soldered to the PL259 shell,
> and the connection has dwindled to a small percentage of the shield due to
> gradual destruction of the fine wire touching points.
>
> 1a) Ditto for the center conductor to the hollow center conductor pin of
> the PL259. Amazing how many PL259's are not soldered in a hurry to 'hear
> how it works". I've done it myself and forgotten I didn't. For years.
>
> 2) "Balun" is cheep junk, or burned up/melted/shorted
> turns/cracked/destroyed core, now junk.
>
> 3) Coax on tower is not high quality, and does not have it's weight
> supported. The stretch has changed the separation of shield and center
> conductor, and the characteristic impedance has shifted, introducing an
> unwanted transformation into the equation.
>
> 3a) Coax is very old, but still "looks OK" even though it isn't. Much coax
> material undergoes very slow (even decades) chemical changes which can
> change characteristics. Wide frequency and TDR scans of coax into opens,
> shorts, checked 50 ohm and 200 ohm terminations are only way to check for
> still-OK-ness.
>
> 4) Water has invaded the coax, from a nick, tear or critter bite in the
> jacket, or non/poorly sealed coax connector, and capillary action has
> wicked along it's entire length. This can be hundreds of feet in the worst
> of cases. The loss-added coax does not necessarily stay at 50 ohms Z zero.
> I have seen coax shields green (copper oxide) their entire length.
> Interestingly the practical outcomes of this extra loss was initially most
> often blamed on the transceiver.
>
> 5) Coax has been wrapped around a pipe by rotator torque. See 3)
>
> 6) Coax has had something heavy dropped on it. See 3)
>
> 7) Coax shield was only ground path for induced current for a close
> lightning strike. (Usually a direct strike smokes coax beyond any
> confusion.)
>
> 8) PL259 shell was not pliers-tightened and has worked loose, gradually
> producing burned points of connection.
>
> 9) Long coax run was laid tight in summer heat, and stretched in the
> winter. See 3)
>
> 10) Constant flexing of coax finally breaks the center conductor. After
> that, "connection" is strange.
>
> 11) Unsupported aerial coax over-weighted by ice and stretched, pulled out
> of connectors, see 8).
>
> 12) Coax is innocent and it's really the antenna.
>
> 13) Operator in fact does not know how to operate the instrument or how to
> interpret readings.
>
> 14) Short lengths of coax and "other boxes" are ignored, and those in fact
> contain the problem.
>
> 15) Measuring instrument has been damaged or was defective from the
> factory.
>
> 15a) Measuring instrument is cheep junk.
>
> 16) Operator was "told" what the trouble was by a "trusted source" and is
> having a lot of trouble thinking outside of the "trusted box" when the
> trusted source was in fact in error for this instance.
>
> 17) Dummy load used to calibrate/provide 50 J zero comparison or reference
> termination is not 50 J zero for any number of reasons, including the likes
> of several seconds of QRO on a 2 watts worth of 50 ohms. Didn't turn black
> on the outside, but the resistor innards were already toast. Didn't *look*
> burned, so must be fine, right?
>
> 18) Dummy load while accurate at DC has significant reactive components at
> RF.
>
> 19) Coax was not 50 ohms from the get-go (try 56). But it looks good so it
> must be good. And the seller had a nice looking web page and the best price.
>
> 20) I need to wrap this up, but I know I'm not remembering something really
> juicy, which will come to mind after I hit the send button.
>
> A group of Olde Pharte hams sitting around a table in a Lunche Jointe, came
> up with a napkin version of this that had over 40 items on it. The napkins
> were used for the inevitable outcome of ribs, and so was lost to posterity.
> One of these included a male F connector that had not had its threads
> grooved into the shell. This ignominious occurrence is not mentioned above,
> because it could not ever be part of a "working" setup. But it was amazing
> how many other things were blamed for "not fitting", including calls to an
> equipment maker about female chassis connectors, before the lack of threads
> was noticed.
>
> Good luck to all and 73,
>
> Guy K2AV
>
>
>
>
> On Wed, Sep 3, 2014 at 12:18 AM, Vic, K2VCO <[hidden email]> wrote:
>
>> If your line is lossless (it isn't) you would expect the same SWR
>> readings anywhere along the line. With practical lines that have some
>> loss, the SWR should be LOWER farther away from the antenna. You are
>> getting the opposite result.
>>
>> One cause of erroneous SWR readings is RF flowing on the outside of the
>> coax. If your rotary dipole doesn't have a balun, this could be the cause.
>>
>> It's also possible that you have a bad connector or bad piece of coax
>> between the tower and the K3.
>>
>>
>> On 9/3/14 3:06 AM, [hidden email] wrote:
>>
>>> Good Evening, This is Mark Griffin, KB3Z and I have some questions
>>> regarding the SWR readings I get at my tower versus what I get on my
>>> K3. I will give the SWR readings that I got at my tower for a 40
>>> meter rotatable dipole at 55 feet.
>>>
>>> Tower:
>>>
>>> 7000 2.2 7025 1.8 7050 1.5 7075 1.3 7100 1.0 7125 1.1 7150
>>> 1.3 7175 1.6 7200 2.0 7225 2.2
>>>
>>> K3 Readings:
>>>
>>> 7000 3.5
>>>
>>> 7025 3.2
>>>
>>> 7050 2.9
>>>
>>> 7075 2.6
>>>
>>> 7100 2.4
>>>
>>> 7125 2.3
>>>
>>> 7150 2.4
>>>
>>> 7175 2.5
>>>
>>> 7200 2.6 7225 2.9
>>>
>>> What would cause such a big difference. The cable run from my antenna
>>> switch on the tower to my K3 is only an additional 75 feet. I am
>>> using RG-213 cable. Is there anyway that I can test the SWR reading
>>> that my K3 is giving me?
>>>
>>> Mark Griffin, KB3Z
>>>
>>
>> --
>> Vic, K2VCO/4X6GP
>> Rehovot, Israel
>> http://www.qsl.net/k2vco/
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
> 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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>
>

Nick Kennedy

Re: SWR Readings:Differences

In reply to this post by Don Wilhelm-4

SWR meters don't generally tell you the SWR on the line they're connected
to, except in special cases. That's independent of the line losses
discussion.

If the SWR on the line is other than 1:1 and you move the meter along the
line, the indicated SWR will change but the actual SWR on the line does not
change. Again, independent of line losses.

73-

Nick, WA5BDU

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Jeffrey Otterson

Re: SWR Readings:Differences

In reply to this post by pastormg

Unless your antenna is exactly the same impedance as your feedline at the
desired frequency (pretty unlikely) then the feedline is going to
transform the antenna impedance based on distance from the antenna. The
exception to this is feedline lengths that are perfect multiples of a half
wave, electrically (that is to say, accounting for the velocity factor)

Any other length will result in a transformed impedance, and corresponding
different VSWR.

You can demonstrate this by changing the feedline length and watching the
VSWR change. Try adding some small fraction of a electrical wavelength of
coax at 40M and see what your meter shows. You might be surprised.

TLDR; try adjusting the length of your coax and see if the readings change.

Jeff n1kdo

> Good Evening,
> This is Mark Griffin, KB3Z and I have some questions regarding the SWR
> readings I get at my tower versus what I get on my K3. I will give the SWR
> readings that I got at my tower for a 40 meter rotatable dipole at 55 feet.

>
______________________________________________________________
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Wes (N7WS)

Re: SWR Readings:Differences

In reply to this post by Nick Kennedy

You're kidding, right?

On 9/3/2014 10:46 AM, Nick Kennedy wrote:

> SWR meters don't generally tell you the SWR on the line they're connected to,
> except in special cases. That's independent of the line losses discussion.
>
> If the SWR on the line is other than 1:1 and you move the meter along the
> line, the indicated SWR will change but the actual SWR on the line does not
> change. Again, independent of line losses.
>
> 73-
>
> Nick, WA5BDU

Wes (N7WS)

Re: SWR Readings:Differences

In reply to this post by Jeffrey Otterson

Oh dear me!

If I take a lossless 50-ohm line and terminate it in 100 ohm and measure the
VSWR using an ideal bridge/coupler/VNA/etc that is calibrated for a 50-ohm
system, I will measure 2:1 SWR no matter how long the line is, from zero to
infinity. The transformed Z will change with length, but the SWR will not.
That's why one can draw a circle of constant SWR on a Smith Chart. Any point on
the circle will have a different Z from another, but they all have the same SWR.

If you change line length and the SWR reading changes, then: 1) the line has
loss, 2) the line Z and the SWR meter Z are different, 3) the source match is
poor, 4) the bridge/coupler directivity is poor, or 5) all of the foregoing.
With most ham stuff, it's 5.

Wes N7WS

On 9/3/2014 1:19 PM, Jeffrey Otterson wrote:

> Unless your antenna is exactly the same impedance as your feedline at the
> desired frequency (pretty unlikely) then the feedline is going to
> transform the antenna impedance based on distance from the antenna. The
> exception to this is feedline lengths that are perfect multiples of a half
> wave, electrically (that is to say, accounting for the velocity factor)
>
> Any other length will result in a transformed impedance, and corresponding
> different VSWR.
>
> You can demonstrate this by changing the feedline length and watching the
> VSWR change. Try adding some small fraction of a electrical wavelength of
> coax at 40M and see what your meter shows. You might be surprised.
>
> TLDR; try adjusting the length of your coax and see if the readings change.
>
> Jeff n1kdo
>
>
>
>

Stephen G4SJP

Re: SWR Readings:Differences

Wes,

As someone involved in the design and manufacture of couplers for VSWR
measurement for the aviation industry (admittedly some 30 odd years ago!),
I would say that you are 100% correct, although I suspect that in amateur
gear number 4 in your list is probably the biggest culprit of all. We had
people on the production tweaking bridges to maximise directivity and it
was a job that required some skill, e.g. bending leads of matched zero bias
Schottky diodes until the spec was achieved - admittedly this was in the
days before the large scale adoption of lead-less components, which must
have made things a bit easier.

73 Stephen G4SJP

On 3 September 2014 22:12, Wes (N7WS) <[hidden email]> wrote:

> Oh dear me!
>
> If I take a lossless 50-ohm line and terminate it in 100 ohm and measure
> the VSWR using an ideal bridge/coupler/VNA/etc that is calibrated for a
> 50-ohm system, I will measure 2:1 SWR no matter how long the line is, from
> zero to infinity. The transformed Z will change with length, but the SWR
> will not. That's why one can draw a circle of constant SWR on a Smith
> Chart. Any point on the circle will have a different Z from another, but
> they all have the same SWR.
>
> If you change line length and the SWR reading changes, then: 1) the line
> has loss, 2) the line Z and the SWR meter Z are different, 3) the source
> match is poor, 4) the bridge/coupler directivity is poor, or 5) all of the
> foregoing. With most ham stuff, it's 5.
>
> Wes N7WS
>
> On 9/3/2014 1:19 PM, Jeffrey Otterson wrote:
>
>> Unless your antenna is exactly the same impedance as your feedline at the
>> desired frequency (pretty unlikely) then the feedline is going to
>> transform the antenna impedance based on distance from the antenna. The
>> exception to this is feedline lengths that are perfect multiples of a half
>> wave, electrically (that is to say, accounting for the velocity factor)
>>
>> Any other length will result in a transformed impedance, and corresponding
>> different VSWR.
>>
>> You can demonstrate this by changing the feedline length and watching the
>> VSWR change. Try adding some small fraction of a electrical wavelength of
>> coax at 40M and see what your meter shows. You might be surprised.
>>
>> TLDR; try adjusting the length of your coax and see if the readings
>> change.
>>
>> Jeff n1kdo
>>
>>
>>
>>
>>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

Alan Bloom

Re: SWR Readings:Differences

In reply to this post by Wes (N7WS)

On 09/03/2014 02:12 PM, Wes (N7WS) wrote:

> Oh dear me!
>
> If I take a lossless 50-ohm line and terminate it in 100 ohm and
> measure the VSWR using an ideal bridge/coupler/VNA/etc that is
> calibrated for a 50-ohm system, I will measure 2:1 SWR no matter how
> long the line is, from zero to infinity. The transformed Z will
> change with length, but the SWR will not. That's why one can draw a
> circle of constant SWR on a Smith Chart. Any point on the circle will
> have a different Z from another, but they all have the same SWR.
>
> If you change line length and the SWR reading changes, then: 1) the
> line has loss, 2) the line Z and the SWR meter Z are different, 3) the
> source match is poor, 4) the bridge/coupler directivity is poor, or 5)
> all of the foregoing. With most ham stuff, it's 5.

Or 6) there is common-mode current on the feedline. In other words, the
feedline is part of the antenna so when you change its length you change
the SWR.

Alan N1AL

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