http://elecraft.85.s1.nabble.com/KAT500-KPA500-Sanity-Check-Please-tp7648517p7648539.html
Why do you think there is a problem with the KPA500? I haven’t seen anything so far that explains that.
In addition to the protections the KAT500 provides, the KPA500 has its own set of protections that keep
it going or place it into a safe state. The KPA can take a lot of abuse before it faults, and it does quite a bit
As someone has suggested (I think it was Bob), you should test the KPA500 into a dummy load to make sure if there is an issue.
If something shows up in that situation, then please do raise the issue with support. If you have questions about the KPA500’s
operation, I should be able not answer them. I suspect your issues are with the setup of the KAT500 and perhaps an understanding
of its protection mechanisms. Answering those questions should do a lot to get you going.
One thing of note - the KPA and the KAT do not communicate with each other. If the Key signal is routed through the KAT to the KPA,
then the KAT will protect the amplifier by disabling the key line into the KPA. Thus it is very important to connect this mechanism (as
There is some very good expertise on the reflector. I believe that collectively they will be able to get you going.
By the way, my own setup is similar - the antenna is a 250 foot loop at 35 feet fed with about 15 feet of ladder line. The ladder line connects
to a 1:1balanced to unbalanced transformer (aka balun) that feeds eight feet of RG-213 into the KAT500. It tunes on every HF band
except 160 meters. NEC analysis and real measurements show that the impedance on 160 is way too low for any match.
> On Jan 26, 2019, at 10:22 AM, Kevin der Kinderen <
[hidden email]> wrote:
>
> Hi Bob:
>
> I'm using a very similar setup and forgot to mention the 1:1 current BALUN.
> The 4:1 is outside. There's about 2 feet of coax to a window feedthrough.
> Then from the feedthrough to the tuner is the 1:1 BALUN. The antenna is the
> 80 - 10 from trueladderline.com. Been using this model for years now.
>
> You say "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."
>
> Maybe I'm confused with the settings. In the KAT500 configuration under
> VSWR thresholds I have:
> Band: All
> Amp Key Interrupt: 5.00
> Autotune: 1.80
> Bypass: 1.3
>
> I think this should mean that the amplifier would not be permitted to
> operate (key interrupt) if the tuner shows 5:1 or greater SWR. I think it
> means that once the *tuned* SWR drops below 5 the amp will be keyed. Should
> this be set to 1.5:1? If I really did blow the amp (I'm pretty convinced)
> then, over time, this possibly was the contributing factor.
>
> It is my amp that I think has gone bad, not the tuner.
>
> So if the problem were caused because I was regularly running into an
> antenna with >10:1 SWR (as noted by bypass SWR on the Operate tab) then I
> think the problem would have been with the KAT and not the KPA. Still, I am
> surprised there isn't a setting in the configuration tab that would prevent
> keying the amp when a certain value of bypass VSWR was exceeded. It could
> have a user setting similar to Amplifier Key Interrupt so that, as someone
> else mentioned, a person could elect to operate in less than ideal
> conditions while a person like me could still have some protection of
> pretty expensive equipment.
>
> I still think my amp is bad. Once out of the loop everything works well
> barefoot from my rig. The KPA500 tunes just about anything I throw at it
> and I'm hoping at 100 watt or less the 12:1 safety limit is not applicable.
>
> "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." Here's where my
> misunderstand probably trips me up again. The ladder line fed dipole cut
> for 80 meters should be an all-band antenna as long as I can match the load
> impedance of the antenna to the radio. For the KAT500, this is a max of
> 10:1 at 600 watts. For maybe another manufacturer's tuner (auto or manual)
> higher specs might be available? Or is there a certain point where the
> antenna is just not an antenna? I've got about 10K contacts on this antenna
> along with some DXCC and WAS accomplishments. It also seems to do OK in
> contests.
>
> The KPA shows the following bypass VSWRs for my antenna:
> 80 12.00
> 40 7.46
> 20 1.63
> 15 4.61
> 10 2.33
>
> Changing the BALUN to a different ration would probably shift the numbers
> around a bit but not necessarily improve the situation. From these reading,
> technically my 80 meter band (for which the antenna is cut) is unusable
> with the KAT/KPA at full power but the other bands should be fine. As long
> as I fix the setting for the amplifier key interrupt then I should be able
> to reduce the risk to the amp on other bands. I have no clue why it was set
> to 5.
>
> Thanks for your explanation. It helps a lot.
>
> 73,
> Kev K4VD
>
> On Sat, Jan 26, 2019 at 10:16 AM Bob McGraw K4TAX <
[hidden email]>
> wrote:
>
>> 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
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>>
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