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KAT500 and KAT500 Utility Question

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Phil Hystad-3

KAT500 and KAT500 Utility Question

First, this is a curiosity question about KAT500 utility only. I don’t intend to use my antenna on 160 meters.

I use the KAT500 with my 80-meter dipole fed by ladder line and a 4:1 Balun to Coax for last 20 feet. This antenna works excellently in concert with the KAT500 for 80, 40, and 30 meter bands. I don’t use it with other bands.

This weekend, I was curious as to how close (or far) the KAT500 could bring the antenna in for the 160 meter band. I knew that it would not work though I was wondering how bad it would be.

So, as I expected, the tuning never closed in on a descent SWR, the best I saw on one test only was SWR about 49:1 as reported by the KAT500 utility. But, the BYPASS SWR reported was about 11:1.

Further tests showed varying bad reports of incomplete tuned SWR while also showing a much lower BYPASS SWR (under 13:1). According to my own tests of the impedance for the antenna on 160 meters, the BYPASS SWR is bogus.

So, I am assuming that unless the KAT500 reaches a tuned SWR value under 1.5:1 (or, whatever threshold I set), the BYPASS SWR is totally meaningless.

73, phil, K7PEH

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KEN-3

Re: KAT500 and KAT500 Utility Question

The results almost totally depend on the length of the ladder line. At
certain lengths, it will act as an impedance transformer and could load
your 80m dipole quite well. An 80m dipole on 160 will have a low
impedance at the feed point. A quarter wave of ladder line will
transform that impedance to a higher impedance. A half wave of ladder
line will give the same impedance (no transformer effect.)

If you have something near a half wave of ladder line, the 4:1 balun is
totally wrong since it will transform a low impedance to one 4x lower!

Try it with a 1: balun and see if the SWR improves or not.

As for actual, honest SWR readings, I assume that most meters are
unreliable in the actual readings when the SWR gets high, especially
10:1 and above. They are really built to operate in the 50 ohm range,
not 500 or 1000.

BTW, IMO the KAT500 is one of the best tuners I've used and I've been
building or using them for over 50 years.

Ken WA8JXM

On 11/4/15 3:59 PM, Phil Hystad wrote:

> First, this is a curiosity question about KAT500 utility only. I don’t intend to use my antenna on 160 meters.
>
> I use the KAT500 with my 80-meter dipole fed by ladder line and a 4:1 Balun to Coax for last 20 feet. This antenna works excellently in concert with the KAT500 for 80, 40, and 30 meter bands. I don’t use it with other bands.
>
> This weekend, I was curious as to how close (or far) the KAT500 could bring the antenna in for the 160 meter band. I knew that it would not work though I was wondering how bad it would be.
>
> So, as I expected, the tuning never closed in on a descent SWR, the best I saw on one test only was SWR about 49:1 as reported by the KAT500 utility. But, the BYPASS SWR reported was about 11:1.
>
> Further tests showed varying bad reports of incomplete tuned SWR while also showing a much lower BYPASS SWR (under 13:1). According to my own tests of the impedance for the antenna on 160 meters, the BYPASS SWR is bogus.
>
> So, I am assuming that unless the KAT500 reaches a tuned SWR value under 1.5:1 (or, whatever threshold I set), the BYPASS SWR is totally meaningless.
>
> 73, phil, K7PEH
>
>

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Wes (N7WS)

Re: KAT500 and KAT500 Utility Question

In reply to this post by Phil Hystad-3

I don't believe that it has anything to do with whether or not a match can be
reached. Some SWRs are simply too difficult to measure accurately, even with an
error-corrected network analyzer. For near ideal reactances or very high or
very low SWR, reflection measurements are inappropriate. In other words, if the
impedance is on or near the periphery of a Smith Chart (rho ~ 1) find another
method.

On 11/4/2015 1:59 PM, Phil Hystad wrote:
> [snip]
>
> So, I am assuming that unless the KAT500 reaches a tuned SWR value under 1.5:1 (or, whatever threshold I set), the BYPASS SWR is totally meaningless.
>
> 73, phil, K7PEH
>
>

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Wes (N7WS)

Re: KAT500 and KAT500 Utility Question

In reply to this post by KEN-3

Some of what you say is true, but has nothing to do with the problem.

Soapbox comment: Personally, I would (and do) rather use Heliax before I would
ever use ladder line.

On 11/4/2015 2:21 PM, Ken wrote:

> The results almost totally depend on the length of the ladder line. At certain
> lengths, it will act as an impedance transformer and could load your 80m
> dipole quite well. An 80m dipole on 160 will have a low impedance at the feed
> point. A quarter wave of ladder line will transform that impedance to a
> higher impedance. A half wave of ladder line will give the same impedance (no
> transformer effect.)
>
> If you have something near a half wave of ladder line, the 4:1 balun is
> totally wrong since it will transform a low impedance to one 4x lower!
>
> Try it with a 1: balun and see if the SWR improves or not.
>
> As for actual, honest SWR readings, I assume that most meters are unreliable
> in the actual readings when the SWR gets high, especially 10:1 and above.
> They are really built to operate in the 50 ohm range, not 500 or 1000.
>
> BTW, IMO the KAT500 is one of the best tuners I've used and I've been building
> or using them for over 50 years.
>
> Ken WA8JXM
>
>
>
> On 11/4/15 3:59 PM, Phil Hystad wrote:
>> First, this is a curiosity question about KAT500 utility only. I don’t
>> intend to use my antenna on 160 meters.
>>
>> I use the KAT500 with my 80-meter dipole fed by ladder line and a 4:1 Balun
>> to Coax for last 20 feet. This antenna works excellently in concert with the
>> KAT500 for 80, 40, and 30 meter bands. I don’t use it with other bands.
>>
>> This weekend, I was curious as to how close (or far) the KAT500 could bring
>> the antenna in for the 160 meter band. I knew that it would not work though
>> I was wondering how bad it would be.
>>
>> So, as I expected, the tuning never closed in on a descent SWR, the best I
>> saw on one test only was SWR about 49:1 as reported by the KAT500 utility.
>> But, the BYPASS SWR reported was about 11:1.
>>
>> Further tests showed varying bad reports of incomplete tuned SWR while also
>> showing a much lower BYPASS SWR (under 13:1). According to my own tests of
>> the impedance for the antenna on 160 meters, the BYPASS SWR is bogus.
>>
>> So, I am assuming that unless the KAT500 reaches a tuned SWR value under
>> 1.5:1 (or, whatever threshold I set), the BYPASS SWR is totally meaningless.
>>
>> 73, phil, K7PEH
>>
>>
>
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k6dgw

Re: KAT500 and KAT500 Utility Question

In reply to this post by Phil Hystad-3

On 11/4/2015 12:59 PM, Phil Hystad wrote:

> I use the KAT500 with my 80-meter dipole fed by ladder line and a 4:1
> Balun to Coax for last 20 feet. This antenna works excellently in
> concert with the KAT500 for 80, 40, and 30 meter bands. I don’t use
> it with other bands.

Feed point Z's:
1.9: 5.6-j1149
3.9: 78+j2
7.2: 2703+j2201

Your ladder line will transform these impedances to something else ...
unless it happens to be a multiple of a half-wave at one of those
frequencies. Tell me how long it is and we can calculate what it looks
like on the high side of your 4:1 transformer. I don't recommend
holding your breath that it will be good on all three bands though.
>
> This weekend, I was curious as to how close (or far) the KAT500 could
> bring the antenna in for the 160 meter band. I knew that it would
> not work though I was wondering how bad it would be.

The radiation resistance on 160 will be very low and the 4:1 transformer
will divide it by 4, meaning just a tad above 1 ohm. It is also very
reactive.

If you really want to use it on 160, try shorting the ladder line at the
feed end, remove the transformer, and connect the shorted end to the
coax through a variable cap. Run 1 or 2 wires on the ground from the
coax shield and see if you can feed it as a Marconi-T.

If your ladder line is 60 ft long, feed Z at the shorted end of the
ladder line will be about 110+j1400 and an Xc of 1400 ohms will probably
work fine for the KAT500.
>
> So, as I expected, the tuning never closed in on a descent SWR, the
> best I saw on one test only was SWR about 49:1 as reported by the
> KAT500 utility. But, the BYPASS SWR reported was about 11:1.

SWR meters, which usually measure VSWR are fairly unreliable at high
values of mismatch.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org

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Wes (N7WS)

Re: KAT500 and KAT500 Utility Question

Guys, read what he wrote, not what you think he wrote.

He had a question about the operation of the metering in the KAT500, he wasn't
looking for advice on antenna design or on the use of ladder line.

If he wants that he can read my paper here: http://k6mhe.com/n7ws/Ladder_Line.pdf

11/4/2015 3:37 PM, Fred Jensen wrote:

> On 11/4/2015 12:59 PM, Phil Hystad wrote:
>
>> I use the KAT500 with my 80-meter dipole fed by ladder line and a 4:1
>> Balun to Coax for last 20 feet. This antenna works excellently in
>> concert with the KAT500 for 80, 40, and 30 meter bands. I don’t use
>> it with other bands.
>
> Feed point Z's:
> 1.9: 5.6-j1149
> 3.9: 78+j2
> 7.2: 2703+j2201
>
> Your ladder line will transform these impedances to something else ... unless
> it happens to be a multiple of a half-wave at one of those frequencies. Tell
> me how long it is and we can calculate what it looks like on the high side of
> your 4:1 transformer. I don't recommend holding your breath that it will be
> good on all three bands though.
>>
>> This weekend, I was curious as to how close (or far) the KAT500 could
>> bring the antenna in for the 160 meter band. I knew that it would
>> not work though I was wondering how bad it would be.
>
> The radiation resistance on 160 will be very low and the 4:1 transformer will
> divide it by 4, meaning just a tad above 1 ohm. It is also very reactive.
>
> If you really want to use it on 160, try shorting the ladder line at the feed
> end, remove the transformer, and connect the shorted end to the coax through a
> variable cap. Run 1 or 2 wires on the ground from the coax shield and see if
> you can feed it as a Marconi-T.
>
> If your ladder line is 60 ft long, feed Z at the shorted end of the ladder
> line will be about 110+j1400 and an Xc of 1400 ohms will probably work fine
> for the KAT500.
>>
>> So, as I expected, the tuning never closed in on a descent SWR, the
>> best I saw on one test only was SWR about 49:1 as reported by the
>> KAT500 utility. But, the BYPASS SWR reported was about 11:1.
>
> SWR meters, which usually measure VSWR are fairly unreliable at high values of
> mismatch.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the Cal QSO Party 1-2 Oct 2016
> - www.cqp.org
>
> Message delivered to [hidden email]

Phil Hystad-3

Re: KAT500 and KAT500 Utility Question

Wes…

Thanks, you are exactly right. My curiosity is about what the KAT500 was doing and the value of the BYPASS SWR versus the values I saw of the Tuned (or, not tuned) SWR.

Dick’s answer was right on and satisfied all my curiosity needs.

Though thanks to all that took the time to write something down and Wes, I will read your paper at your link. In fact, just downloaded it.

73, phil, K7PEH

> On Nov 4, 2015, at 3:04 PM, Wes (N7WS) <[hidden email]> wrote:
>
> Guys, read what he wrote, not what you think he wrote.
>
> He had a question about the operation of the metering in the KAT500, he wasn't looking for advice on antenna design or on the use of ladder line.
>
> If he wants that he can read my paper here: http://k6mhe.com/n7ws/Ladder_Line.pdf
>
>
> 11/4/2015 3:37 PM, Fred Jensen wrote:
>> On 11/4/2015 12:59 PM, Phil Hystad wrote:
>>
>>> I use the KAT500 with my 80-meter dipole fed by ladder line and a 4:1
>>> Balun to Coax for last 20 feet. This antenna works excellently in
>>> concert with the KAT500 for 80, 40, and 30 meter bands. I don’t use
>>> it with other bands.
>>
>> Feed point Z's:
>> 1.9: 5.6-j1149
>> 3.9: 78+j2
>> 7.2: 2703+j2201
>>
>> Your ladder line will transform these impedances to something else ... unless it happens to be a multiple of a half-wave at one of those frequencies. Tell me how long it is and we can calculate what it looks like on the high side of your 4:1 transformer. I don't recommend holding your breath that it will be good on all three bands though.
>>>
>>> This weekend, I was curious as to how close (or far) the KAT500 could
>>> bring the antenna in for the 160 meter band. I knew that it would
>>> not work though I was wondering how bad it would be.
>>
>> The radiation resistance on 160 will be very low and the 4:1 transformer will divide it by 4, meaning just a tad above 1 ohm. It is also very reactive.
>>
>> If you really want to use it on 160, try shorting the ladder line at the feed end, remove the transformer, and connect the shorted end to the coax through a variable cap. Run 1 or 2 wires on the ground from the coax shield and see if you can feed it as a Marconi-T.
>>
>> If your ladder line is 60 ft long, feed Z at the shorted end of the ladder line will be about 110+j1400 and an Xc of 1400 ohms will probably work fine for the KAT500.
>>>
>>> So, as I expected, the tuning never closed in on a descent SWR, the
>>> best I saw on one test only was SWR about 49:1 as reported by the
>>> KAT500 utility. But, the BYPASS SWR reported was about 11:1.
>>
>> SWR meters, which usually measure VSWR are fairly unreliable at high values of mismatch.
>>
>> 73,
>>
>> Fred K6DGW
>> - Northern California Contest Club
>> - CU in the Cal QSO Party 1-2 Oct 2016
>> - www.cqp.org
>>
>> Message delivered to [hidden email]
>
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Jim Brown-10

Re: KAT500 and KAT500 Utility Question

In reply to this post by Wes (N7WS)

On Wed,11/4/2015 3:04 PM, Wes (N7WS) wrote:
> If he wants that he can read my paper here:
> http://k6mhe.com/n7ws/Ladder_Line.pdf

By all means DO read and STUDY it -- it's a GREAT piece of work.

73, Jim K9YC
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