Elecraft

Re: More KAT500

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Jim Wiley

Re: More KAT500

Ed -

According to Elecraft, the KAT500 can match 10:1 SWR at 500 watts, on
any band 80 to 10 meters. It can also match 3:1 SWR at 1000 watts on
those same bands. The 160 meter and 6 meter capabilities are a bit
more limited, but it will still match a fairly wide range of loads. By
inference, 10:1 SWR at 500 watts between 3 and 30 MHz could result in
peak voltages in the range of 2250 volts and peak currents of 42 amperes
RF (one or the other, not simultaneously). This is pretty impressive
for a box that size.

Using those voltages as limits, that indicates that the KAT500 could
handle power levels of about 250 watts at a 14:1 SWR. Any more could
result in damage. I would suggest replacing the 300-ohm line on the
antenna with 450-ohm ladder line, and inserting a 4:1 balun between the
antenna and the KAT500. I suspect that this will reduce the SWR
excursions, and may get you "inside the envelope" for what the KAT500
can handle.

A commonly used antenna is a doublet (dipole) fed with open wire, a 4:1
balun, and a coupler. Most installations use a length of RG-8 coaxial
cable (typically 10 to 20 feet, but no longer than necessary) to "get
through the wall" - or from the coupler to the balun immediately outside
the building, then the open wire line connects to the balun at that
point and continues to the antenna. 450-ohm ladder line is usually a
better choice because it is designed for transmitting use, where 300-ohm
line is usually "TV lead-in" and not particularly suited for use at
higher power. Some transmitter rated 300 ohm line exists, and if you
have that type, it may work for you. As with all open-wire type lines,
keep the line at least 8" to 12" from metal objects if possible, more is
better, and avoid abrupt right angle turns.

- Jim, KL7CC

On 11/15/2012 2:41 AM, Goss, Ed wrote:

> Hi Jim,
> Thanks for the info. I am at work now and unable to post back to
> the group, but I appreciate the explanation. For the low bands, I use
> a 135 ft inv vee center fed with 300 ohm line, with a 1:1 balun near
> the shack. When my KAT500 starts to tune itself, I am seeing high
> SWRs, such as 14:1. After the auto tune cycle, it's 1:1. Perhaps I
> should be concerned that even with 100 watts, there would be
> conditions that overstress KAT500 internal parts with this type of
> antenna, but I want to be very careful about not damaging the tuner.
> I'm not quite sure how a user would know these limits, or if the
> KAT500 protects itself in any way. Perhaps the KAT500 is meant to work
> with antennas that present a somewhat better match to start with, like
> a typical 80 meter dipole which is cut for CW but the user wants to
> use all the way up to 4.0 MHz...
> --Ed---
>

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alsopb

Re: More KAT500

This seems so in many cases but it is very doublet length dependent.

I ran one case in TLW with 45' of 450 ohm line that came out as 13 ohms.
With a 4:1 balun you'd probably be dropping this further. High
current and most likely not a match.

The best suggestion is to model the antenna at height, get it's
feedpoint impedances at bands of interest. Then go into a program like
TLW with the 450 ohm line length and see what impedance results at the
shack end.

Adjusting 450 ohm length or doublet length may be required for an
adequate compromise on the bands of interest.

Without some analysis (or a proven design) it will be a crap shoot.

73 de Brian/K3KO

On 11/15/2012 12:31, Jim Wiley wrote:

> Ed -
>
> According to Elecraft, the KAT500 can match 10:1 SWR at 500 watts, on
> any band 80 to 10 meters. It can also match 3:1 SWR at 1000 watts on
> those same bands. The 160 meter and 6 meter capabilities are a bit
> more limited, but it will still match a fairly wide range of loads. By
> inference, 10:1 SWR at 500 watts between 3 and 30 MHz could result in
> peak voltages in the range of 2250 volts and peak currents of 42 amperes
> RF (one or the other, not simultaneously). This is pretty impressive
> for a box that size.
>
> Using those voltages as limits, that indicates that the KAT500 could
> handle power levels of about 250 watts at a 14:1 SWR. Any more could
> result in damage. I would suggest replacing the 300-ohm line on the
> antenna with 450-ohm ladder line, and inserting a 4:1 balun between the
> antenna and the KAT500. I suspect that this will reduce the SWR
> excursions, and may get you "inside the envelope" for what the KAT500
> can handle.
>
> A commonly used antenna is a doublet (dipole) fed with open wire, a 4:1
> balun, and a coupler. Most installations use a length of RG-8 coaxial
> cable (typically 10 to 20 feet, but no longer than necessary) to "get
> through the wall" - or from the coupler to the balun immediately outside
> the building, then the open wire line connects to the balun at that
> point and continues to the antenna. 450-ohm ladder line is usually a
> better choice because it is designed for transmitting use, where 300-ohm
> line is usually "TV lead-in" and not particularly suited for use at
> higher power. Some transmitter rated 300 ohm line exists, and if you
> have that type, it may work for you. As with all open-wire type lines,
> keep the line at least 8" to 12" from metal objects if possible, more is
> better, and avoid abrupt right angle turns.
>
> - Jim, KL7CC
>
>
>
>
>
> On 11/15/2012 2:41 AM, Goss, Ed wrote:
>> Hi Jim,
>> Thanks for the info. I am at work now and unable to post back to
>> the group, but I appreciate the explanation. For the low bands, I use
>> a 135 ft inv vee center fed with 300 ohm line, with a 1:1 balun near
>> the shack. When my KAT500 starts to tune itself, I am seeing high
>> SWRs, such as 14:1. After the auto tune cycle, it's 1:1. Perhaps I
>> should be concerned that even with 100 watts, there would be
>> conditions that overstress KAT500 internal parts with this type of
>> antenna, but I want to be very careful about not damaging the tuner.
>> I'm not quite sure how a user would know these limits, or if the
>> KAT500 protects itself in any way. Perhaps the KAT500 is meant to work
>> with antennas that present a somewhat better match to start with, like
>> a typical 80 meter dipole which is cut for CW but the user wants to
>> use all the way up to 4.0 MHz...
>> --Ed---
>>
>
> ______________________________________________________________
> 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
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2012.0.2221 / Virus Database: 2441/5394 - Release Date: 11/14/12
>
>

ke9uw

Re: More KAT500

I use a 1:1 balun at 450 ohm ladder line to get thru the attic and then 4 inch open wire outside to the dipole.

Chuck, KE9UW
Lionel Trains, TCA, LCCA, LRRC
aka Jack, BMW Motorcycles BMWMOA #224

________________________________________
From: [hidden email] [[hidden email]] on behalf of Brian Alsop [[hidden email]]
Sent: Thursday, November 15, 2012 7:02 AM
To: [hidden email]
Subject: Re: [Elecraft] More KAT500

This seems so in many cases but it is very doublet length dependent.

I ran one case in TLW with 45' of 450 ohm line that came out as 13 ohms.
With a 4:1 balun you'd probably be dropping this further. High
current and most likely not a match.

The best suggestion is to model the antenna at height, get it's
feedpoint impedances at bands of interest. Then go into a program like
TLW with the 450 ohm line length and see what impedance results at the
shack end.

Adjusting 450 ohm length or doublet length may be required for an
adequate compromise on the bands of interest.

Without some analysis (or a proven design) it will be a crap shoot.

73 de Brian/K3KO

On 11/15/2012 12:31, Jim Wiley wrote:

-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2221 / Virus Database: 2441/5396 - Release Date: 11/15/12

______________________________________________________________
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______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Chuck, KE9UW

Don Wilhelm-4

Re: More KAT500

In reply to this post by Jim Wiley

There is a common error in assuming that a 4:1 balun should be used with
450 ohm (or 300 ohm) transmission line.

The impedance at the shack end of the line has nothing to do with the
characteristic impedance of the line, and the feedpoint impedance may
actually be quite low. If you have a 5 ohm feedpoint impedance, a 4:1
balun will bring that down further to 1.25 ohms producing an impedance
that most any tuner will find difficult to match.

Bottom line - do some analysis to see what feedpoint impedance you are
really dealing with. If you cannot model the antenna or if you did not
measure the length of the feedline, you can at least measure what you
have with an antenna analyzer. If the impedance on all bands of
interest is high, then a 4:1 balun may be appropriate, but if the
impedance is lower than 100 ohms, then a 1:1 balun will produce an
easier load for the tuner.

73,
Don W3FPR

On 11/15/2012 7:31 AM, Jim Wiley wrote:
> Using those voltages as limits, that indicates that the KAT500 could
> handle power levels of about 250 watts at a 14:1 SWR. Any more could
> result in damage. I would suggest replacing the 300-ohm line on the
> antenna with 450-ohm ladder line, and inserting a 4:1 balun between the
> antenna and the KAT500. I suspect that this will reduce the SWR
> excursions, and may get you "inside the envelope" for what the KAT500
> can handle.
>

______________________________________________________________
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N5GE-2

Re: More KAT500

In reply to this post by ke9uw

I hope you have the ladder-line supported by fire-proof (ceramic)
insulators in the attic.

Letting ladder-line touch anything combustible can start a fire.

Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member

On Thu, 15 Nov 2012 13:22:55 +0000, "hawley, charles j jr"
<[hidden email]> wrote:

>I use a 1:1 balun at 450 ohm ladder line to get thru the attic and then 4 inch open wire outside to the dipole.
>
>Chuck, KE9UW
>Lionel Trains, TCA, LCCA, LRRC
>aka Jack, BMW Motorcycles BMWMOA #224
>
>________________________________________
>From: [hidden email] [[hidden email]] on behalf of Brian Alsop [[hidden email]]
>Sent: Thursday, November 15, 2012 7:02 AM
>To: [hidden email]
>Subject: Re: [Elecraft] More KAT500
>
>This seems so in many cases but it is very doublet length dependent.
>
>I ran one case in TLW with 45' of 450 ohm line that came out as 13 ohms.
> With a 4:1 balun you'd probably be dropping this further. High
>current and most likely not a match.
>
>The best suggestion is to model the antenna at height, get it's
>feedpoint impedances at bands of interest. Then go into a program like
>TLW with the 450 ohm line length and see what impedance results at the
>shack end.
>
>Adjusting 450 ohm length or doublet length may be required for an
>adequate compromise on the bands of interest.
>
>Without some analysis (or a proven design) it will be a crap shoot.
>
>73 de Brian/K3KO
>
>On 11/15/2012 12:31, Jim Wiley wrote:
>> Ed -
>>
>> According to Elecraft, the KAT500 can match 10:1 SWR at 500 watts, on
>> any band 80 to 10 meters. It can also match 3:1 SWR at 1000 watts on
>> those same bands. The 160 meter and 6 meter capabilities are a bit
>> more limited, but it will still match a fairly wide range of loads. By
>> inference, 10:1 SWR at 500 watts between 3 and 30 MHz could result in
>> peak voltages in the range of 2250 volts and peak currents of 42 amperes
>> RF (one or the other, not simultaneously). This is pretty impressive
>> for a box that size.
>>
>> Using those voltages as limits, that indicates that the KAT500 could
>> handle power levels of about 250 watts at a 14:1 SWR. Any more could
>> result in damage. I would suggest replacing the 300-ohm line on the
>> antenna with 450-ohm ladder line, and inserting a 4:1 balun between the
>> antenna and the KAT500. I suspect that this will reduce the SWR
>> excursions, and may get you "inside the envelope" for what the KAT500
>> can handle.
>>
>> A commonly used antenna is a doublet (dipole) fed with open wire, a 4:1
>> balun, and a coupler. Most installations use a length of RG-8 coaxial
>> cable (typically 10 to 20 feet, but no longer than necessary) to "get
>> through the wall" - or from the coupler to the balun immediately outside
>> the building, then the open wire line connects to the balun at that
>> point and continues to the antenna. 450-ohm ladder line is usually a
>> better choice because it is designed for transmitting use, where 300-ohm
>> line is usually "TV lead-in" and not particularly suited for use at
>> higher power. Some transmitter rated 300 ohm line exists, and if you
>> have that type, it may work for you. As with all open-wire type lines,
>> keep the line at least 8" to 12" from metal objects if possible, more is
>> better, and avoid abrupt right angle turns.
>>
>> - Jim, KL7CC
>>
>>
>>
>>
>>
>> On 11/15/2012 2:41 AM, Goss, Ed wrote:
>>> Hi Jim,
>>> Thanks for the info. I am at work now and unable to post back to
>>> the group, but I appreciate the explanation. For the low bands, I use
>>> a 135 ft inv vee center fed with 300 ohm line, with a 1:1 balun near
>>> the shack. When my KAT500 starts to tune itself, I am seeing high
>>> SWRs, such as 14:1. After the auto tune cycle, it's 1:1. Perhaps I
>>> should be concerned that even with 100 watts, there would be
>>> conditions that overstress KAT500 internal parts with this type of
>>> antenna, but I want to be very careful about not damaging the tuner.
>>> I'm not quite sure how a user would know these limits, or if the
>>> KAT500 protects itself in any way. Perhaps the KAT500 is meant to work
>>> with antennas that present a somewhat better match to start with, like
>>> a typical 80 meter dipole which is cut for CW but the user wants to
>>> use all the way up to 4.0 MHz...
>>> --Ed---
>>>
>>
>> ______________________________________________________________
>> 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
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 2012.0.2221 / Virus Database: 2441/5394 - Release Date: 11/14/12
>>
>>
>
>
>
>-----
>No virus found in this message.
>Checked by AVG - www.avg.com
>Version: 2012.0.2221 / Virus Database: 2441/5396 - Release Date: 11/15/12
>
>______________________________________________________________
>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
>______________________________________________________________
>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
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ke9uw

Re: More KAT500

It's supported by electric fence insulators.

Sent from my iPad
Chuck, KE9UW
(Jack for BMW motorcycles)

On Nov 15, 2012, at 2:00 PM, "N5GE" <[hidden email]> wrote:

>
> I hope you have the ladder-line supported by fire-proof (ceramic)
> insulators in the attic.
>
> Letting ladder-line touch anything combustible can start a fire.
>
> Amateur Radio Operator N5GE
> ARRL Lifetime Member
> QCWA Lifetime Member
>
> On Thu, 15 Nov 2012 13:22:55 +0000, "hawley, charles j jr"
> <[hidden email]> wrote:
>
>> I use a 1:1 balun at 450 ohm ladder line to get thru the attic and then 4 inch open wire outside to the dipole.
>>
>> Chuck, KE9UW
>> Lionel Trains, TCA, LCCA, LRRC
>> aka Jack, BMW Motorcycles BMWMOA #224
>>
>> ________________________________________
>> From: [hidden email] [[hidden email]] on behalf of Brian Alsop [[hidden email]]
>> Sent: Thursday, November 15, 2012 7:02 AM
>> To: [hidden email]
>> Subject: Re: [Elecraft] More KAT500
>>
>> This seems so in many cases but it is very doublet length dependent.
>>
>> I ran one case in TLW with 45' of 450 ohm line that came out as 13 ohms.
>> With a 4:1 balun you'd probably be dropping this further. High
>> current and most likely not a match.
>>
>> The best suggestion is to model the antenna at height, get it's
>> feedpoint impedances at bands of interest. Then go into a program like
>> TLW with the 450 ohm line length and see what impedance results at the
>> shack end.
>>
>> Adjusting 450 ohm length or doublet length may be required for an
>> adequate compromise on the bands of interest.
>>
>> Without some analysis (or a proven design) it will be a crap shoot.
>>
>> 73 de Brian/K3KO
>>
>> On 11/15/2012 12:31, Jim Wiley wrote:
>>> Ed -
>>>
>>> According to Elecraft, the KAT500 can match 10:1 SWR at 500 watts, on
>>> any band 80 to 10 meters. It can also match 3:1 SWR at 1000 watts on
>>> those same bands. The 160 meter and 6 meter capabilities are a bit
>>> more limited, but it will still match a fairly wide range of loads. By
>>> inference, 10:1 SWR at 500 watts between 3 and 30 MHz could result in
>>> peak voltages in the range of 2250 volts and peak currents of 42 amperes
>>> RF (one or the other, not simultaneously). This is pretty impressive
>>> for a box that size.
>>>
>>> Using those voltages as limits, that indicates that the KAT500 could
>>> handle power levels of about 250 watts at a 14:1 SWR. Any more could
>>> result in damage. I would suggest replacing the 300-ohm line on the
>>> antenna with 450-ohm ladder line, and inserting a 4:1 balun between the
>>> antenna and the KAT500. I suspect that this will reduce the SWR
>>> excursions, and may get you "inside the envelope" for what the KAT500
>>> can handle.
>>>
>>> A commonly used antenna is a doublet (dipole) fed with open wire, a 4:1
>>> balun, and a coupler. Most installations use a length of RG-8 coaxial
>>> cable (typically 10 to 20 feet, but no longer than necessary) to "get
>>> through the wall" - or from the coupler to the balun immediately outside
>>> the building, then the open wire line connects to the balun at that
>>> point and continues to the antenna. 450-ohm ladder line is usually a
>>> better choice because it is designed for transmitting use, where 300-ohm
>>> line is usually "TV lead-in" and not particularly suited for use at
>>> higher power. Some transmitter rated 300 ohm line exists, and if you
>>> have that type, it may work for you. As with all open-wire type lines,
>>> keep the line at least 8" to 12" from metal objects if possible, more is
>>> better, and avoid abrupt right angle turns.
>>>
>>> - Jim, KL7CC
>>>
>>>
>>>
>>>
>>>
>>> On 11/15/2012 2:41 AM, Goss, Ed wrote:
>>>> Hi Jim,
>>>> Thanks for the info. I am at work now and unable to post back to
>>>> the group, but I appreciate the explanation. For the low bands, I use
>>>> a 135 ft inv vee center fed with 300 ohm line, with a 1:1 balun near
>>>> the shack. When my KAT500 starts to tune itself, I am seeing high
>>>> SWRs, such as 14:1. After the auto tune cycle, it's 1:1. Perhaps I
>>>> should be concerned that even with 100 watts, there would be
>>>> conditions that overstress KAT500 internal parts with this type of
>>>> antenna, but I want to be very careful about not damaging the tuner.
>>>> I'm not quite sure how a user would know these limits, or if the
>>>> KAT500 protects itself in any way. Perhaps the KAT500 is meant to work
>>>> with antennas that present a somewhat better match to start with, like
>>>> a typical 80 meter dipole which is cut for CW but the user wants to
>>>> use all the way up to 4.0 MHz...
>>>> --Ed---
>>>>
>>>
>>> ______________________________________________________________
>>> 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
>>>
>>>
>>> -----
>>> No virus found in this message.
>>> Checked by AVG - www.avg.com
>>> Version: 2012.0.2221 / Virus Database: 2441/5394 - Release Date: 11/14/12
>>>
>>>
>>
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 2012.0.2221 / Virus Database: 2441/5396 - Release Date: 11/15/12
>>
>> ______________________________________________________________
>> 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
>> ______________________________________________________________
>> 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
>

Chuck, KE9UW

N5GE-2

Re: More KAT500

If they are the kind sold by Lowes, Home Depot or Tractor Supply,
they may not catch fire, but may melt. Ceramic is best for avoiding
fire caused by heat...

I have seen Alpha Delta insulators that are plastic catch fire and
melt at the ends of half sloper's fed with RG213 and 9913.

Regards,
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member

On Thu, 15 Nov 2012 21:17:41 +0000, "hawley, charles j jr"
<[hidden email]> wrote:

>It's supported by electric fence insulators.
>
>Sent from my iPad
>Chuck, KE9UW
>(Jack for BMW motorcycles)
>
>On Nov 15, 2012, at 2:00 PM, "N5GE" <[hidden email]> wrote:
>
>>
>> I hope you have the ladder-line supported by fire-proof (ceramic)
>> insulators in the attic.
>>
>> Letting ladder-line touch anything combustible can start a fire.
>>
>> Amateur Radio Operator N5GE
>> ARRL Lifetime Member
>> QCWA Lifetime Member
>>
>> On Thu, 15 Nov 2012 13:22:55 +0000, "hawley, charles j jr"
>> <[hidden email]> wrote:
>>
>>> I use a 1:1 balun at 450 ohm ladder line to get thru the attic and then 4 inch open wire outside to the dipole.
>>>
>>> Chuck, KE9UW
>>> Lionel Trains, TCA, LCCA, LRRC
>>> aka Jack, BMW Motorcycles BMWMOA #224
>>>
>>> ________________________________________
>>> From: [hidden email] [[hidden email]] on behalf of Brian Alsop [[hidden email]]
>>> Sent: Thursday, November 15, 2012 7:02 AM
>>> To: [hidden email]
>>> Subject: Re: [Elecraft] More KAT500
>>>
>>> This seems so in many cases but it is very doublet length dependent.
>>>
>>> I ran one case in TLW with 45' of 450 ohm line that came out as 13 ohms.
>>> With a 4:1 balun you'd probably be dropping this further. High
>>> current and most likely not a match.
>>>
>>> The best suggestion is to model the antenna at height, get it's
>>> feedpoint impedances at bands of interest. Then go into a program like
>>> TLW with the 450 ohm line length and see what impedance results at the
>>> shack end.
>>>
>>> Adjusting 450 ohm length or doublet length may be required for an
>>> adequate compromise on the bands of interest.
>>>
>>> Without some analysis (or a proven design) it will be a crap shoot.
>>>
>>> 73 de Brian/K3KO
>>>
>>> On 11/15/2012 12:31, Jim Wiley wrote:
>>>> Ed -
>>>>
>>>> According to Elecraft, the KAT500 can match 10:1 SWR at 500 watts, on
>>>> any band 80 to 10 meters. It can also match 3:1 SWR at 1000 watts on
>>>> those same bands. The 160 meter and 6 meter capabilities are a bit
>>>> more limited, but it will still match a fairly wide range of loads. By
>>>> inference, 10:1 SWR at 500 watts between 3 and 30 MHz could result in
>>>> peak voltages in the range of 2250 volts and peak currents of 42 amperes
>>>> RF (one or the other, not simultaneously). This is pretty impressive
>>>> for a box that size.
>>>>
>>>> Using those voltages as limits, that indicates that the KAT500 could
>>>> handle power levels of about 250 watts at a 14:1 SWR. Any more could
>>>> result in damage. I would suggest replacing the 300-ohm line on the
>>>> antenna with 450-ohm ladder line, and inserting a 4:1 balun between the
>>>> antenna and the KAT500. I suspect that this will reduce the SWR
>>>> excursions, and may get you "inside the envelope" for what the KAT500
>>>> can handle.
>>>>
>>>> A commonly used antenna is a doublet (dipole) fed with open wire, a 4:1
>>>> balun, and a coupler. Most installations use a length of RG-8 coaxial
>>>> cable (typically 10 to 20 feet, but no longer than necessary) to "get
>>>> through the wall" - or from the coupler to the balun immediately outside
>>>> the building, then the open wire line connects to the balun at that
>>>> point and continues to the antenna. 450-ohm ladder line is usually a
>>>> better choice because it is designed for transmitting use, where 300-ohm
>>>> line is usually "TV lead-in" and not particularly suited for use at
>>>> higher power. Some transmitter rated 300 ohm line exists, and if you
>>>> have that type, it may work for you. As with all open-wire type lines,
>>>> keep the line at least 8" to 12" from metal objects if possible, more is
>>>> better, and avoid abrupt right angle turns.
>>>>
>>>> - Jim, KL7CC
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On 11/15/2012 2:41 AM, Goss, Ed wrote:
>>>>> Hi Jim,
>>>>> Thanks for the info. I am at work now and unable to post back to
>>>>> the group, but I appreciate the explanation. For the low bands, I use
>>>>> a 135 ft inv vee center fed with 300 ohm line, with a 1:1 balun near
>>>>> the shack. When my KAT500 starts to tune itself, I am seeing high
>>>>> SWRs, such as 14:1. After the auto tune cycle, it's 1:1. Perhaps I
>>>>> should be concerned that even with 100 watts, there would be
>>>>> conditions that overstress KAT500 internal parts with this type of
>>>>> antenna, but I want to be very careful about not damaging the tuner.
>>>>> I'm not quite sure how a user would know these limits, or if the
>>>>> KAT500 protects itself in any way. Perhaps the KAT500 is meant to work
>>>>> with antennas that present a somewhat better match to start with, like
>>>>> a typical 80 meter dipole which is cut for CW but the user wants to
>>>>> use all the way up to 4.0 MHz...
>>>>> --Ed---
>>>>>
>>>>
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>>>>
>>>
>>>
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