My station is a K3S, KPA500, KAT500. The antenna is a 250 ft center
fed wire with 450 window line that runs from the feed point on the
antenna all the way to the operating position where the 450 line
terminates into a 1:1 current balun on the shelf just above the amp and
tuner. I use a common mode choke between the balun and the KAT500.
That common mode choke is a model 8232 purchased from The Wireman. It
is 18" length of coax with about 75 ferrite beads of #43 material.
This provides additional common mode rejection not offered by the
balun. I can work 160M through 6M with this configuration.
The KAT500 is set to automatically switch to BYPASS if the SWR is less
than 1.3:1. And it is set to bypass the amp if the SWR is greater than
1.5:1.
A 10:1 SWR basically says the impedance is somewhere between 5 ohms and
500 ohms. In order to attain this you will need to use both, depending
on band a 1:1 balun or a 4:1 balun as likely with your antenna the
antenna on 40M presents a Z of 3000 ohms or so. Then the length of the
feed line is critical as it becomes part of the impedance acting as a
matching length of line. The "600 ohm" impedance of the line is of
little importance as you are matching the entire complex load and not
just the impedance of the line. Many hams seem to think, incorrectly,
they need to match the impedance of the feed line.
If your showing a Bypass SWR of 12:1 then you are outside of the range
of the KAT500. You are using the wrong balun or you need to change the
600 ohm feed line length to attain a better / lower SWR.
The keying line between the KAT500 and KPA500 should interrupt the PTT
line if the matched SWR exceeds 1.5:1. This is a setting defined in the
KAT500 configuration by the user and the KAT500 Utility.
The best suggestion, make changes to the antenna such that the SWR
falls within the range of the tuner. As to the amp, connect a 50 dummy
load to one output of the tuner {you do have one?} and then see how the
combination of amp and tuner behave.
I'd say the matching range of the KAT500 is the same at 100 watts. The
KAT500 manual {page 2} clearly defines the matching ranges and power
ratings.
73
Bob, K4TAX
On 1/25/2019 10:47 PM, Kevin der Kinderen wrote:
I'm reading the specifications for the KAT500. Typical matching range from
3-30 MHz is 10:1 SWR for 600 watts.
This means that if the KAT500 utility reports "Bypass VSWR" in excess of
10:1 then the KPA500 should not be set to operate.
I'm running a dipole cut for 80 and fed with 600 ohm ladder line as a
multiband antenna. The BALUN is right outside my window. I have the option
of 1:1, 4:1, 9:1 and 12:1 I think. They are DXE brand. My job then is to
pick the right BALUN to provide <10:1 SWR on the bands of interest. I hoped
this would be at least 80-20 if not 80-10.
Not sure which BALUN is plugged in right now but on 80 meters I'm showing a
bypass VSWR of 12.00 and VSWR of 1.6:1. This means I cannot use the KPA500
on 80 regardless of the good match the KAT500 provided.
Should the key line cables from the KAT500 to the KPA500 and the rig (using
a Flex) prevent keying the amp if the SWR exceeds 10:1 automatically?
If I want better than that then I have to find another antenna tuner with a
wider SWR range at 600 watts or a different antenna?
Can anyone guess at the matching range of the KAT500 at 100W?
The thing is... I think I have a dead amp.
Kev K4VD
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to rmcg...@blomand.net
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
